Preface

"There are no constraints on the human mind, no walls around the human spirit, no barriers to our progress except those we ourselves erect." (Ronald Reagan)

The history of neurosurgery is characterized by a strong relationship with technology. From the introduction of the operating microscope to the development of endoscopes or exoscopes; from the CT scan to the new 3T MRI; from standard ultrasounds to modern high-definition navigated ultrasounds; from intraoperative DSA to new indocyanine video-angiography; and from custom bone reconstruction to 3D printed skull protheses.

Surgery needs technologies to improve its results and the clinical outcome of patients. New generations of surgeons should be trained in the use of new technologies and be open minded towards what tools biomedical engineering or basic science could offer to improve surgical practice.

This book is designed to be a comprehensive introduction to new developments and techniques in neurosurgery and to their application in clinical practice.

Appreciation is due to Prof. Pasquale De Bonis for helping me in this enjoyable task, to Dr. Flavia Dones for her unfailing support and wise counsel, and to Prof. Michele A. Cavallo for his tireless commitment to making me a better surgeon.

> **Dr. Alba Scerrati** Department of Morphology, Experimental Medicine and Surgery, Department of Neurosurgery, University of Ferrara, Italy

> > **Pasquale De Bonis** Professor, University of Ferrara, Italy

**1**

Section 1

Surgery

Section 1 Surgery

**3**

**Chapter 1**

**Abstract**

CT scans, fluoroscopy

**1. Introduction**

Spinal Surgery

Robotic-Assisted Systems for

*Mayank Kaushal, Shekar Kurpad and Hoon Choi*

concludes with future applications of robotics in spinal surgery.

Robotic-assisted spinal surgery is in its infancy. It aims to improve the accuracy of screw placement, lower the risk of surgical complications, and reduce radiation exposure to the patient and the surgical team. The present chapter attempts to provide an overview of the evolution of robotic-assisted spinal surgery and highlights different commercially available spine robotic systems in present use. The review

**Keywords:** robotics, spine surgery, pedicle screws, radiation, shared-control system,

Stereotaxy was coined by Victor Horsley and Robert Clarke in 1908 to describe a method of locating points within the brain by using the Cartesian coordinate system that measures distance from a fixed reference point derived from external cranial landmarks [1]. This was followed by the development of image guidance in 1986, which integrated stereotaxy with computed tomography [2]. The development happened in the backdrop of transition from frame-based to frameless stereotaxy based on enhancements in spatial fidelity of imaging data, computational power, and 3-D digitizers [3]. However, spinal surgery applications of the image guidance systems arising from these refinements carry limitations. These include dependence on a direct line of sight between the optical tracking system and navigated instruments for ensuring screw insertion accuracy and a learning curve for using the navigation system. The learning curve comes from the fact that the surgeon now has to redirect his or her eyes from the patient to the navigation screen in order to follow the planned trajectory for screw placement. This can result in surgical errors since attention is taken away from the patient at the point of screw insertion. An attempt to address this shortcoming has led to the development of robotic systems that utilize similar image guidance platforms while physically guid-

ing the surgeon to the preplanned trajectory for screw placement [4, 5].

The field of spinal surgery is characterized by a unique set of defining features such as the need for high order of surgical precision as several critical structures are located in close proximity of the vertebral column. Injury to these structures, which include blood vessels and nerves, can lead to a wide spectrum of consequences ranging from pain to paralysis. The close association of critical structures is compounded by the narrow operating corridors for doing surgeries involving the spinal column. This set of challenging circumstances strengthens the case for robots as surgical assistants due to the lack of fatigability while undertaking tasks repeatedly

#### **Chapter 1**

## Robotic-Assisted Systems for Spinal Surgery

*Mayank Kaushal, Shekar Kurpad and Hoon Choi*

#### **Abstract**

Robotic-assisted spinal surgery is in its infancy. It aims to improve the accuracy of screw placement, lower the risk of surgical complications, and reduce radiation exposure to the patient and the surgical team. The present chapter attempts to provide an overview of the evolution of robotic-assisted spinal surgery and highlights different commercially available spine robotic systems in present use. The review concludes with future applications of robotics in spinal surgery.

**Keywords:** robotics, spine surgery, pedicle screws, radiation, shared-control system, CT scans, fluoroscopy

#### **1. Introduction**

Stereotaxy was coined by Victor Horsley and Robert Clarke in 1908 to describe a method of locating points within the brain by using the Cartesian coordinate system that measures distance from a fixed reference point derived from external cranial landmarks [1]. This was followed by the development of image guidance in 1986, which integrated stereotaxy with computed tomography [2]. The development happened in the backdrop of transition from frame-based to frameless stereotaxy based on enhancements in spatial fidelity of imaging data, computational power, and 3-D digitizers [3]. However, spinal surgery applications of the image guidance systems arising from these refinements carry limitations. These include dependence on a direct line of sight between the optical tracking system and navigated instruments for ensuring screw insertion accuracy and a learning curve for using the navigation system. The learning curve comes from the fact that the surgeon now has to redirect his or her eyes from the patient to the navigation screen in order to follow the planned trajectory for screw placement. This can result in surgical errors since attention is taken away from the patient at the point of screw insertion. An attempt to address this shortcoming has led to the development of robotic systems that utilize similar image guidance platforms while physically guiding the surgeon to the preplanned trajectory for screw placement [4, 5].

The field of spinal surgery is characterized by a unique set of defining features such as the need for high order of surgical precision as several critical structures are located in close proximity of the vertebral column. Injury to these structures, which include blood vessels and nerves, can lead to a wide spectrum of consequences ranging from pain to paralysis. The close association of critical structures is compounded by the narrow operating corridors for doing surgeries involving the spinal column. This set of challenging circumstances strengthens the case for robots as surgical assistants due to the lack of fatigability while undertaking tasks repeatedly

and without showing a reduction in performance. Since the introduction of da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA), cleared for use by the Food and Drug Administration (FDA) in 2000, the field of robotic surgery has continued to mature and gain more widespread acceptance. However, the field of neurosurgery has seen growing interest only in recent times for the use of surgical robotic systems to assist the surgeon in operative procedures.

With surgical robots becoming more visible in a number of surgical disciplines, the various systems in use can be broadly classified into three main categories depending on the interaction of the surgeon with the robot [3]. The first category is supervisory-controlled systems where the actions carried out by the robot are preprogrammed by the surgeon who then monitors the robot performing the specified steps autonomously. The second type is the telesurgical systems where the surgical manipulator follows the movements of an input device directly manipulated by the surgeon in a master-slave manner. The third type is the shared-control models where the motions are concurrently controlled by both the surgeon and the robot via shared control of the surgical instruments. Despite the shared control, the surgeon remains in charge of the decision-making related to the procedure with the robot providing steady-hand manipulation of the instruments [3]. All the surgical robots approved by the FDA for spinal procedures fall under the third category of shared-control systems.

To this point, robotics have largely been utilized in placement of pedicle screws and shown comparable and/or superior accuracy of screw placement compared to conventional, freehand technique of screw placement [6–8]. Despite the initial encouraging findings, the adoption of surgical robots has been relatively slow among the spine surgical community with robots not yet considered as part of the routine standard operative procedure for spinal indications. A major concern for the tepid response to robots is the significant capital investments required for the surgical robot and the associated navigation equipment. The use of navigation systems irrespective of surgical robots is still not commonplace across the surgical suites, which places training requirements on top of the added cost. Further compounding the situation is the perception that adding steps to the operation workflow would lead to increased operation time and decreased efficiency. Given the limited scientific literature on operative and clinical outcomes, there is skepticism toward robots by the surgical community. In the present article, we attempt to explore the evolution of robotic-assisted spinal surgery to where the field stands now and conclude with future applications.

#### **2. Commercial surgical robotic systems in current use**

The last two decades have seen the introduction of several robotic systems in spinal surgery but the Food and Drug Administration approval has been granted to three of these systems (**Figure 1**). These include SpineAssist® (Medtronic Inc., Dublin, Ireland), ROSA® (Medtech S.A., Montpellier, France), and ExcelsiusGPS® (Globus Medical Inc., Audubon, PA). SpineAssist®, which received both FDA clearance and European CE Mark of approval in 2004, was the first robotic assistance system to be used in the spinal surgery. Subsequent iterations of SpineAssist®, Renaissance®, and Mazor X™ were released to address some of the limitations of SpineAssist® and received both FDA and CE approval in 2011 and 2017, respectively. The most recent follow-up of SpineAssist® is Mazor X™ Stealth Edition, which received FDA clearance in 2018. The second system approved for commercial use, ROSA®, obtained CE Mark of approval in 2014 FDA clearance in 2016, while the most recent surgical robot system, ExcelsiusGPS®, received both FDA and CE approvals in 2017.

**5**

**2.1 SpineAssist®**

*ExcelsiusGPS® (D).*

**Figure 1.**

**2.2 ROSA®**

screw depth.

**2.3 ExcelsiusGPS®**

SpineAssist® was the first commercially available system for robotic-assisted spinal surgery. It comprises a cylindrical device mounted to a patient-specific anatomical landmark, which relies on pre- and/or intraoperative CT imaging to allow trajectory planning for screw insertion. Subsequent iterations of SpineAssist® include Renaissance® followed by Mazor X™ (list price ~US\$1.2 M) with the latter consisting of an independent robotic arm where the attachment to the patient is done using a single pin in place of a robot-mounted platform as is the case with the former. Medtronic Stealth System is used concurrently to provide navigation. Recently, Mazor X™ Stealth Edition has been released, which also obviates the need for K-wires and a separate navigation system. Like the previous versions, it requires the robotic arm to be mounted to the bedframe.

*Systems for robotic-assisted spine surgery: Mazor Renaissance® (A), Mazor X™ (B), ROSA® (C), and* 

The second system approved by the FDA is the ROSA®, which works similar to the SpineAssist® in using pre- or intraoperative CT imaging to plan screw trajectory but provides the additional convenience of built-in navigation for determination of

ExcelsiusGPS®, the third and most recently approved commercial robotic system (list price ~US\$1.2 M), has a built-in navigation system similar to ROSA® but does not require attachment to the patient or the operating table. In addition, it removes the need for a K-wire by providing an end effector for the passage of instruments and detecting "skiving" of instruments. There is also a secondary passive reflective marker to monitor the accuracy of robotic navigation system.

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730* *Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

#### **Figure 1.**

*Neurosurgical Procedures - Innovative Approaches*

systems to assist the surgeon in operative procedures.

and without showing a reduction in performance. Since the introduction of da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA), cleared for use by the Food and Drug Administration (FDA) in 2000, the field of robotic surgery has continued to mature and gain more widespread acceptance. However, the field of neurosurgery has seen growing interest only in recent times for the use of surgical robotic

With surgical robots becoming more visible in a number of surgical disciplines,

the various systems in use can be broadly classified into three main categories depending on the interaction of the surgeon with the robot [3]. The first category is supervisory-controlled systems where the actions carried out by the robot are preprogrammed by the surgeon who then monitors the robot performing the specified steps autonomously. The second type is the telesurgical systems where the surgical manipulator follows the movements of an input device directly manipulated by the surgeon in a master-slave manner. The third type is the shared-control models where the motions are concurrently controlled by both the surgeon and the robot via shared control of the surgical instruments. Despite the shared control, the surgeon remains in charge of the decision-making related to the procedure with the robot providing steady-hand manipulation of the instruments [3]. All the surgical robots approved by the FDA for

spinal procedures fall under the third category of shared-control systems.

**2. Commercial surgical robotic systems in current use**

The last two decades have seen the introduction of several robotic systems in spinal surgery but the Food and Drug Administration approval has been granted to three of these systems (**Figure 1**). These include SpineAssist® (Medtronic Inc., Dublin, Ireland), ROSA® (Medtech S.A., Montpellier, France), and ExcelsiusGPS® (Globus Medical Inc., Audubon, PA). SpineAssist®, which received both FDA clearance and European CE Mark of approval in 2004, was the first robotic assistance system to be used in the spinal surgery. Subsequent iterations of SpineAssist®, Renaissance®, and Mazor X™ were released to address some of the limitations of SpineAssist® and received both FDA and CE approval in 2011 and 2017, respectively. The most recent follow-up of SpineAssist® is Mazor X™ Stealth Edition, which received FDA clearance in 2018. The second system approved for commercial use, ROSA®, obtained CE Mark of approval in 2014 FDA clearance in 2016, while the most recent surgical robot system, ExcelsiusGPS®, received both FDA and CE

To this point, robotics have largely been utilized in placement of pedicle screws and shown comparable and/or superior accuracy of screw placement compared to conventional, freehand technique of screw placement [6–8]. Despite the initial encouraging findings, the adoption of surgical robots has been relatively slow among the spine surgical community with robots not yet considered as part of the routine standard operative procedure for spinal indications. A major concern for the tepid response to robots is the significant capital investments required for the surgical robot and the associated navigation equipment. The use of navigation systems irrespective of surgical robots is still not commonplace across the surgical suites, which places training requirements on top of the added cost. Further compounding the situation is the perception that adding steps to the operation workflow would lead to increased operation time and decreased efficiency. Given the limited scientific literature on operative and clinical outcomes, there is skepticism toward robots by the surgical community. In the present article, we attempt to explore the evolution of robotic-assisted spinal surgery to where the field stands now and conclude

**4**

approvals in 2017.

with future applications.

*Systems for robotic-assisted spine surgery: Mazor Renaissance® (A), Mazor X™ (B), ROSA® (C), and ExcelsiusGPS® (D).*

#### **2.1 SpineAssist®**

SpineAssist® was the first commercially available system for robotic-assisted spinal surgery. It comprises a cylindrical device mounted to a patient-specific anatomical landmark, which relies on pre- and/or intraoperative CT imaging to allow trajectory planning for screw insertion. Subsequent iterations of SpineAssist® include Renaissance® followed by Mazor X™ (list price ~US\$1.2 M) with the latter consisting of an independent robotic arm where the attachment to the patient is done using a single pin in place of a robot-mounted platform as is the case with the former. Medtronic Stealth System is used concurrently to provide navigation. Recently, Mazor X™ Stealth Edition has been released, which also obviates the need for K-wires and a separate navigation system. Like the previous versions, it requires the robotic arm to be mounted to the bedframe.

#### **2.2 ROSA®**

The second system approved by the FDA is the ROSA®, which works similar to the SpineAssist® in using pre- or intraoperative CT imaging to plan screw trajectory but provides the additional convenience of built-in navigation for determination of screw depth.

#### **2.3 ExcelsiusGPS®**

ExcelsiusGPS®, the third and most recently approved commercial robotic system (list price ~US\$1.2 M), has a built-in navigation system similar to ROSA® but does not require attachment to the patient or the operating table. In addition, it removes the need for a K-wire by providing an end effector for the passage of instruments and detecting "skiving" of instruments. There is also a secondary passive reflective marker to monitor the accuracy of robotic navigation system.


#### **Table 1.**

*Comparison of commercially available spine robotic systems.*

**Table 1** highlights salient features of each of the surgical robotic systems. In the subsequent section, the experience with the use of these systems is described followed by an appraisal of the limitations of the present systems and avenues for future research. Due to relative longevity of SpineAssist® availability for commercial application, a significant portion of the published literature is based on the experience of using SpineAssist® and its subsequent iterations, Renaissance® and Mazor X™.

#### **3. Applications of robotics in spinal surgery**

#### **3.1 Pedicle screw instrumentation**

Despite being the most commonly performed procedure related to the thoracolumbar spine, a steep learning curve is associated with transpedicular fixation. Subsequently, the primary application of surgical robots in spinal surgery has been transpedicular fixation. The use of robotic surgical assistants in transpedicular fixation arose from the wide variability of findings about accuracy of screw placements reported for various versions of conventional, fluoroscopic-dependent techniques. The results on the accuracy of pedicle screw instrumentation using surgical robotic assistants have been largely superior to the manual screw insertion using fluoroscopy. The commonly accepted method of determining insertion accuracy involves the use of postoperative CT scans, which despite providing radiographic confirmation of screw placement is limited in divulging the clinical implications of the radiographic findings. This limits the inferences that can be drawn to some extent, but given the popularity of this method of comparison, the various robotic systems are discussed with respect to screw insertion accuracy.

A detailed evaluation of the scientific literature highlights that a significant share of studies document results from SpineAssist® and its iterations, namely, Renaissance® and Mazor X™. The first account on the use of robotics was provided by Sukovich et al. in a 2006 retrospective analysis, which used SpineAssist® in 14 patients for the placement of 98 pedicle screws through a combination of open and minimally invasive techniques. The authors showed that 96% of the screws were within 1–2 mm of the planned trajectory with no cases of pedicle breach [9]. In another study, Pechlivanis et al. looked at the screw insertion accuracy of SpineAssist® during minimally invasive posterior lumbar interbody fusion (PLIF). The accuracy was determined on postoperative CT scans using the Gertzbein and Robbins system (GRS) for evaluating the

**7**

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

accuracy of pedicle screw insertion [10, 11]. The GRS grades the screws into four categories based on the location of the screw within the pedicle: Grade A, screw is completely within the pedicle; Grade B, screw breach is <2 mm; Grade C, screw breach is >2 and <4 mm; Grade D, screw breach is >4 and <6 mm; and Grade E, screw breach is >6 mm. Grades A and B are considered acceptable for screw accuracy. Of the 122 screws inserted, with the exception of one screw that was Grade D, the remaining screws were either GRS Grade A (108) or GRS Grade B [13]. Devito et al. performed a multicenter, retrospective review comprising of 3271 pedicle screws placed with SpineAssist® and showed 98% of the screw insertions to be acceptable when assessed by intraoperative fluoroscopy. Further, accuracy measurements done on postoperative CT scans in a subset of these screws (646) showed over 98% of the screws fell within the safe zone (GRS Grades A and B) [12]. In a study involving 112 patients and 494 screws using SpineAssist®, van Dijk and colleagues found a 97.9% rate of clinically acceptable screw insertion [13]. Hu et al. evaluated 960 pedicle screws placed with Renaissance® and found that 949 screws (98.9%) were placed accurately [14]. A separate study by the same group showed successful screw placement in nine patients with spinal column tumors [15]. In a review of 50 patients with adolescent idiopathic scoliosis (AIS) that underwent robotic MIS posterior spinal fusion, Macke et al. evaluated a total of 662 pedicle screws inserted using Renaissance®. The authors observed a 92.7% acceptable placement rate. Lower rates of screw malpositioning were noted with robotic MIS than prior published data, and improved accuracy of screw insertion was observed when

using preoperative CT obtained in the prone position [16].

A number of studies have compared accuracy between conventional freehand and robotic-assisted procedures. In a retrospective analysis, Kantelhardt et al. used SpineAssist® and performed pedicle screw placement accuracy comparisons between three groups, namely, conventional freehand versus open robotic-assisted versus percutaneous robotic-assisted, and showed comparable accuracy rates for the combined robotic-assisted groups (94.5%) and the freehand group (91.4%) for screw insertion [17]. Schatlo and colleagues used SpineAssist® and demonstrated similar rates of clinically acceptable screw placement between open fluoroscopyguided and robotic-assisted placement (open and percutaneous) groups [18]. In a separate analysis by the same group, the impact of experience of surgeon on screw insertion accuracy was evaluated for 1265 pedicle screws. The authors showed 1217 (96.2%) screw placements were of an acceptable grade with screw misplacement peaking between the first 10 and 20 surgeries and declining as more surgeries were performed by the surgeon [19]. The same group followed this up with an analysis involving 169 patients that underwent posterior instrumentation for spinal instability and showed a higher proportion of non-misplaced screws in the robot (93.4%) than the freehand fluoroscopy-guided cohort (88.9%), which was statistically significant [20]. Schizas et al. evaluated robot-assisted (open or percutaneous) versus fluoroscopy cohort and showed comparable accuracy rates with 95.3% for the robotics group and 92.2% for the freehand group [21]. The accuracy of screw insertion was assessed using the Rampersaud scale, which describes the relative position of the screw to the pedicle and comprises the following four grades: Grade A, completely in; Grade B, <2 mm breach; Grade C, 2–4 mm breach; and Grade D, >4 mm breach [22]. Solomiichuk and colleagues performed a retrospective matched cohort study in 70 patients diagnosed with metastatic spine disease and showed grade A or B screw placement in 162 of 192 (84.4%) in the robotic-assisted group and in 179 of 214 (83.6%) in the conventional group with no differences in screw accuracy between the groups. Further, no differences were found between the cohorts for accuracy, duration of surgery, radiation exposure, or surgical site infection with the

#### *Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

*Neurosurgical Procedures - Innovative Approaches*

**implant placement**

**Robotic system Navigation Direct** 

**Table 1** highlights salient features of each of the surgical robotic systems. In the subsequent section, the experience with the use of these systems is described followed by an appraisal of the limitations of the present systems and avenues for future research. Due to relative longevity of SpineAssist® availability for commercial application, a significant portion of the published literature is based on the experience of using SpineAssist® and its subsequent iterations, Renaissance®

**K-wire required**

Renaissance Separate No Yes ✓ Patient

Mazor X Separate No Yes ✓ ✓ Bed mounted

ROSA Integrated No Yes ✓ Free standing ExcelsiusGPS Integrated Yes No ✓ ✓ ✓ Free standing

Integrated Yes No ✓ ✓ Bed mounted

**Imaging Portability**

mounted

**Intra-op Pre-op Fluoroscopy**

Despite being the most commonly performed procedure related to the thoracolumbar spine, a steep learning curve is associated with transpedicular fixation. Subsequently, the primary application of surgical robots in spinal surgery has been transpedicular fixation. The use of robotic surgical assistants in transpedicular fixation arose from the wide variability of findings about accuracy of screw placements reported for various versions of conventional, fluoroscopic-dependent techniques. The results on the accuracy of pedicle screw instrumentation using surgical robotic assistants have been largely superior to the manual screw insertion using fluoroscopy. The commonly accepted method of determining insertion accuracy involves the use of postoperative CT scans, which despite providing radiographic confirmation of screw placement is limited in divulging the clinical implications of the radiographic findings. This limits the inferences that can be drawn to some extent, but given the popularity of this method of comparison, the various robotic systems

A detailed evaluation of the scientific literature highlights that a significant share of studies document results from SpineAssist® and its iterations, namely, Renaissance® and Mazor X™. The first account on the use of robotics was provided by Sukovich et al. in a 2006 retrospective analysis, which used SpineAssist® in 14 patients for the placement of 98 pedicle screws through a combination of open and minimally invasive techniques. The authors showed that 96% of the screws were within 1–2 mm of the planned trajectory with no cases of pedicle breach [9]. In another study, Pechlivanis et al. looked at the screw insertion accuracy of SpineAssist® during minimally invasive posterior lumbar interbody fusion (PLIF). The accuracy was determined on postoperative CT scans using the Gertzbein and Robbins system (GRS) for evaluating the

**6**

and Mazor X™.

Mazor X Stealth Edition

**Table 1.**

**3. Applications of robotics in spinal surgery**

*Comparison of commercially available spine robotic systems.*

are discussed with respect to screw insertion accuracy.

**3.1 Pedicle screw instrumentation**

accuracy of pedicle screw insertion [10, 11]. The GRS grades the screws into four categories based on the location of the screw within the pedicle: Grade A, screw is completely within the pedicle; Grade B, screw breach is <2 mm; Grade C, screw breach is >2 and <4 mm; Grade D, screw breach is >4 and <6 mm; and Grade E, screw breach is >6 mm. Grades A and B are considered acceptable for screw accuracy. Of the 122 screws inserted, with the exception of one screw that was Grade D, the remaining screws were either GRS Grade A (108) or GRS Grade B [13]. Devito et al. performed a multicenter, retrospective review comprising of 3271 pedicle screws placed with SpineAssist® and showed 98% of the screw insertions to be acceptable when assessed by intraoperative fluoroscopy. Further, accuracy measurements done on postoperative CT scans in a subset of these screws (646) showed over 98% of the screws fell within the safe zone (GRS Grades A and B) [12]. In a study involving 112 patients and 494 screws using SpineAssist®, van Dijk and colleagues found a 97.9% rate of clinically acceptable screw insertion [13]. Hu et al. evaluated 960 pedicle screws placed with Renaissance® and found that 949 screws (98.9%) were placed accurately [14]. A separate study by the same group showed successful screw placement in nine patients with spinal column tumors [15]. In a review of 50 patients with adolescent idiopathic scoliosis (AIS) that underwent robotic MIS posterior spinal fusion, Macke et al. evaluated a total of 662 pedicle screws inserted using Renaissance®. The authors observed a 92.7% acceptable placement rate. Lower rates of screw malpositioning were noted with robotic MIS than prior published data, and improved accuracy of screw insertion was observed when using preoperative CT obtained in the prone position [16].

A number of studies have compared accuracy between conventional freehand and robotic-assisted procedures. In a retrospective analysis, Kantelhardt et al. used SpineAssist® and performed pedicle screw placement accuracy comparisons between three groups, namely, conventional freehand versus open robotic-assisted versus percutaneous robotic-assisted, and showed comparable accuracy rates for the combined robotic-assisted groups (94.5%) and the freehand group (91.4%) for screw insertion [17]. Schatlo and colleagues used SpineAssist® and demonstrated similar rates of clinically acceptable screw placement between open fluoroscopyguided and robotic-assisted placement (open and percutaneous) groups [18]. In a separate analysis by the same group, the impact of experience of surgeon on screw insertion accuracy was evaluated for 1265 pedicle screws. The authors showed 1217 (96.2%) screw placements were of an acceptable grade with screw misplacement peaking between the first 10 and 20 surgeries and declining as more surgeries were performed by the surgeon [19]. The same group followed this up with an analysis involving 169 patients that underwent posterior instrumentation for spinal instability and showed a higher proportion of non-misplaced screws in the robot (93.4%) than the freehand fluoroscopy-guided cohort (88.9%), which was statistically significant [20]. Schizas et al. evaluated robot-assisted (open or percutaneous) versus fluoroscopy cohort and showed comparable accuracy rates with 95.3% for the robotics group and 92.2% for the freehand group [21]. The accuracy of screw insertion was assessed using the Rampersaud scale, which describes the relative position of the screw to the pedicle and comprises the following four grades: Grade A, completely in; Grade B, <2 mm breach; Grade C, 2–4 mm breach; and Grade D, >4 mm breach [22]. Solomiichuk and colleagues performed a retrospective matched cohort study in 70 patients diagnosed with metastatic spine disease and showed grade A or B screw placement in 162 of 192 (84.4%) in the robotic-assisted group and in 179 of 214 (83.6%) in the conventional group with no differences in screw accuracy between the groups. Further, no differences were found between the cohorts for accuracy, duration of surgery, radiation exposure, or surgical site infection with the exception of intensity of radiation [23]. Keric et al. evaluated 90 patients treated for spondylodiscitis with posterior spinal fusion via either conventional, open freehand, or percutaneous robot-assisted spinal instrumentation using Renaissance®. Their findings revealed robotic cohort was associated with higher accuracy and lower likelihood for revision procedures for improper screw placement. Further, the robotic-assisted MIS cohort had lower intraoperative fluoroscopy and shorter postoperative stay [24]. In a separate review of 1857 implanted screws, Keric and colleagues showed increased rates of screw deviation in clinical diagnosis such as tumor, infection, and osteoporotic fractures [25]. In another review of 206 patients with spondylodiscitis that underwent posterior spinal fusion, Alaid et al. observed a lower rate of revision for wound breakdown in the robotic MIS group using SpineAssist® than the open, freehand group [26].

The comparison of screw accuracy between freehand and robotic-guided screw insertion has also been analyzed through a number of randomized controlled trials. Kim et al. compared the accuracy and safety of screw insertion between roboticassisted minimally invasive PLIF using Renaissance® (37 patients) and conventional, freehand technique for PLIF (41 patients). For intrapedicular accuracy, no significant differences were observed between the groups. Of the 74 screws in the robotic cohort, none breached the proximal facet joint, while 13 of the 82 screws in the freehand group violated the proximal facet joint (*P* < 0.001). Further, the average distance of the screws from the left and right facets was significantly smaller in the freehand group [27]. Roser et al. used SpineAssist® to compare screw accuracy between fluoroscopic-guided freehand, navigation-guided, and robotic-assisted screw instrumentation. The authors found no significant differences for screw accuracy between the different techniques, but the conclusion was not backed by statistical analysis due to small study size [28]. Ringel et al. compared an equal number of patients randomly assigned to either percutaneous screw placement using SpineAssist® or conventional, open freehand technique. The results of their RCT differ from the large majority of studies in that a lower rate (85%) of clinically acceptable screw placement was reported for robotic-guided technique than the freehand technique (93%) for screw insertion [29]. Hyun and colleagues performed a prospective study comparing fluoroscopy-guided approach with MIS screw insertion using Renaissance® in lumbar fusions. The authors observed all screws in the robotic group were placed accurately, while in the freehand group, the accuracy rate was 98.6% [30]. In a prospective analysis, Park and colleagues compared 37 patients with MIS screw insertion using Renaissance® and 41 patients that underwent freehand technique for pedicle screw insertion during posterior interbody fusion surgery. They showed both groups had similar improvement in clinical outcomes at 2-year follow-up [31].

Aside from studies on SpineAssist® and its iterations, only a small number of publications have explored other surgical systems. Lonjon et al. compared screw placement using the ROSA® with freehand technique of screw insertion. The authors found a 97.2% accuracy rate in the robotic group and a 92% accuracy rate in the freehand group [32]. In a study by Huntsman et al., MIS screw placement using ExcelsiusGPS® showed 99% of screw placed successfully based on the surgeon's interpretation of intraoperative plain film radiographs, with no cases of screw malposition requiring revision surgery [33].

#### **3.2 Other applications**

Bederman et al. evaluated the utility of SpineAssist® or Renaissance® robotic system in the placement of S2-alar-iliac screws and found all screws are placed accurately with no breach of the anterior sacrum [34]. Hu et al. performed a retrospective analysis of 18 patients who underwent S2AI fixation with assistance from Renaissance® robotic system and found accurate screw trajectory on postoperative CT scans without any

**9**

**Figure 2.**

*ligamentous complex (red circles).*

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

**4. Illustrative case examples**

violations of iliac cortex or breaches of the anterior sacrum [35]. In another study comprising of four adult spinal deformity patients who underwent minimally invasive robotic-guided insertion of S2-alar-iliac (S2AI) screws using Renaissance® robotic system, Hyun et al. observed all the screw trajectories were positioned accurately based on postoperative X-rays and CT scans [36]. Laratta and colleagues evaluated S2AI screw insertion in 23 consecutive patients who underwent spinopelvic fixation with Renaissance® robotic system and noted two violations of iliac cortex but no neurologic, vascular, or visceral complications among the 46 S2AI screws that were inserted [37]. In a retrospective matched cohort analysis, Shillingford et al. compared robotic-assisted using Renaissance® robotic system (23 patients, 46 screws) and conventional, freehand (28 patients, 59 screws) S2AI screw placement in 68 consecutive patients with spinal deformity. The authors observed no differences between the

groups for screw insertion accuracy or intraoperative complications [38].

T11-L3 fixation and fusion (**Figure 3**). The patient had complete recovery.

**4.2 Case 2: open robotic-assisted thoracolumbar fusion for pediatric trauma**

*Case 1: Preoperative CT (A and B) and MRI (C) showing L1 burst fracture with injury to the posterior* 

A 13-year-old boy presented to the hospital after landing on his upper back while attempting to jump out of a swinging hammock. He reported thoracolumbar pain, which was located in the hip region but had no radicular pain into the lower abdomen

**4.1 Case 1: MIS robotic-assisted thoracolumbar instrumentation for adult trauma**

A 44-year-old healthy man presented to the hospital following a 12-ft fall from the roof of a house while repairing it. He complained of severe back pain with right-sided leg numbness. Physical examination demonstrated severe pain and numbness in the lower limbs. On CT, a burst fracture at L1 was observed with MRI showing injury to the posterior ligamentous complex (PLC) (**Figure 2**). The decision-making for the clinical management for the patient was evaluated using the thoracolumbar injury classification and severity score (TLICS), a classification system for thoracolumbar injuries that predicts the need for surgery [39]. It comprises three independent predictors, which are morphology, integrity of PLC, and neurological status. The patient presentation was given a TLICS score of 7, and consequently the patient underwent robotic-assisted MIS

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

*Neurosurgical Procedures - Innovative Approaches*

SpineAssist® than the open, freehand group [26].

similar improvement in clinical outcomes at 2-year follow-up [31].

Aside from studies on SpineAssist® and its iterations, only a small number of publica-

Bederman et al. evaluated the utility of SpineAssist® or Renaissance® robotic system in the placement of S2-alar-iliac screws and found all screws are placed accurately with no breach of the anterior sacrum [34]. Hu et al. performed a retrospective analysis of 18 patients who underwent S2AI fixation with assistance from Renaissance® robotic system and found accurate screw trajectory on postoperative CT scans without any

tions have explored other surgical systems. Lonjon et al. compared screw placement using the ROSA® with freehand technique of screw insertion. The authors found a 97.2% accuracy rate in the robotic group and a 92% accuracy rate in the freehand group [32]. In a study by Huntsman et al., MIS screw placement using ExcelsiusGPS® showed 99% of screw placed successfully based on the surgeon's interpretation of intraoperative plain film radiographs, with no cases of screw malposition requiring revision surgery [33].

exception of intensity of radiation [23]. Keric et al. evaluated 90 patients treated for spondylodiscitis with posterior spinal fusion via either conventional, open freehand, or percutaneous robot-assisted spinal instrumentation using Renaissance®. Their findings revealed robotic cohort was associated with higher accuracy and lower likelihood for revision procedures for improper screw placement. Further, the robotic-assisted MIS cohort had lower intraoperative fluoroscopy and shorter postoperative stay [24]. In a separate review of 1857 implanted screws, Keric and colleagues showed increased rates of screw deviation in clinical diagnosis such as tumor, infection, and osteoporotic fractures [25]. In another review of 206 patients with spondylodiscitis that underwent posterior spinal fusion, Alaid et al. observed a lower rate of revision for wound breakdown in the robotic MIS group using

The comparison of screw accuracy between freehand and robotic-guided screw insertion has also been analyzed through a number of randomized controlled trials. Kim et al. compared the accuracy and safety of screw insertion between roboticassisted minimally invasive PLIF using Renaissance® (37 patients) and conventional, freehand technique for PLIF (41 patients). For intrapedicular accuracy, no significant differences were observed between the groups. Of the 74 screws in the robotic cohort, none breached the proximal facet joint, while 13 of the 82 screws in the freehand group violated the proximal facet joint (*P* < 0.001). Further, the average distance of the screws from the left and right facets was significantly smaller in the freehand group [27]. Roser et al. used SpineAssist® to compare screw accuracy between fluoroscopic-guided freehand, navigation-guided, and robotic-assisted screw instrumentation. The authors found no significant differences for screw accuracy between the different techniques, but the conclusion was not backed by statistical analysis due to small study size [28]. Ringel et al. compared an equal number of patients randomly assigned to either percutaneous screw placement using SpineAssist® or conventional, open freehand technique. The results of their RCT differ from the large majority of studies in that a lower rate (85%) of clinically acceptable screw placement was reported for robotic-guided technique than the freehand technique (93%) for screw insertion [29]. Hyun and colleagues performed a prospective study comparing fluoroscopy-guided approach with MIS screw insertion using Renaissance® in lumbar fusions. The authors observed all screws in the robotic group were placed accurately, while in the freehand group, the accuracy rate was 98.6% [30]. In a prospective analysis, Park and colleagues compared 37 patients with MIS screw insertion using Renaissance® and 41 patients that underwent freehand technique for pedicle screw insertion during posterior interbody fusion surgery. They showed both groups had

**8**

**3.2 Other applications**

violations of iliac cortex or breaches of the anterior sacrum [35]. In another study comprising of four adult spinal deformity patients who underwent minimally invasive robotic-guided insertion of S2-alar-iliac (S2AI) screws using Renaissance® robotic system, Hyun et al. observed all the screw trajectories were positioned accurately based on postoperative X-rays and CT scans [36]. Laratta and colleagues evaluated S2AI screw insertion in 23 consecutive patients who underwent spinopelvic fixation with Renaissance® robotic system and noted two violations of iliac cortex but no neurologic, vascular, or visceral complications among the 46 S2AI screws that were inserted [37]. In a retrospective matched cohort analysis, Shillingford et al. compared robotic-assisted using Renaissance® robotic system (23 patients, 46 screws) and conventional, freehand (28 patients, 59 screws) S2AI screw placement in 68 consecutive patients with spinal deformity. The authors observed no differences between the groups for screw insertion accuracy or intraoperative complications [38].

#### **4. Illustrative case examples**

#### **4.1 Case 1: MIS robotic-assisted thoracolumbar instrumentation for adult trauma**

A 44-year-old healthy man presented to the hospital following a 12-ft fall from the roof of a house while repairing it. He complained of severe back pain with right-sided leg numbness. Physical examination demonstrated severe pain and numbness in the lower limbs. On CT, a burst fracture at L1 was observed with MRI showing injury to the posterior ligamentous complex (PLC) (**Figure 2**). The decision-making for the clinical management for the patient was evaluated using the thoracolumbar injury classification and severity score (TLICS), a classification system for thoracolumbar injuries that predicts the need for surgery [39]. It comprises three independent predictors, which are morphology, integrity of PLC, and neurological status. The patient presentation was given a TLICS score of 7, and consequently the patient underwent robotic-assisted MIS T11-L3 fixation and fusion (**Figure 3**). The patient had complete recovery.

#### **4.2 Case 2: open robotic-assisted thoracolumbar fusion for pediatric trauma**

A 13-year-old boy presented to the hospital after landing on his upper back while attempting to jump out of a swinging hammock. He reported thoracolumbar pain, which was located in the hip region but had no radicular pain into the lower abdomen

#### **Figure 2.**

*Case 1: Preoperative CT (A and B) and MRI (C) showing L1 burst fracture with injury to the posterior ligamentous complex (red circles).*

#### **Figure 4.**

*Case 2: Preoperative MRI showing T11–T12 anterolisthesis, T12 wedge fracture with T11–T12 facet dislocation, and posterior ligamentous injury with small dorsal epidural hematoma (red circle).*

or legs. MRI revealed T11/T12 anterolisthesis, T12 wedge fracture with T11–T12 facet dislocation, and posterior ligamentous injury with small dorsal epidural hematoma (**Figure 4**). CT thoracic spine showed fracture and subluxation at T11–T12 with bilateral perched T11 facets, right pedicle fracture of T12 extending into the superior end plate of the vertebral body with wedging of T12 along with anterior and inferior displacement of the anterior ring apophysis, and spinous process fractures of T11 and to a lesser extent T10 (**Figure 5**). Based on the clinical presentation and imaging findings, a decision to operate was made. The patient underwent robotic-assisted T10-L1 fixation and fusion, T11/T12 open reduction and internal fixation at T11–T12, and T11 laminotomy for epidural hematoma evacuation (**Figure 6**). The patient had complete recovery and subsequently underwent removal of the hardware at 1 year.

**11**

**Figure 6.**

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

*facets, and T10 spinous process fracture (red circles).*

**Figure 5.**

**4.3 Case 3: MIS robotic-assisted TLIF for degenerative spine**

A 58-year-old female presented to the hospital with back and leg pain. The leg pain was on the left side and radiating to the left foot. The patient mentioned the back pain was worse than the left lower extremity (LLE) pain with duration of pain progressing over the last 2 years. Additionally, she complained of LLE weakness and numbness as well as cramping in bilateral calf muscles. Imaging showed 11 mm L4/5 anterolisthesis on standing XR (**Figure 7**) and severe spinal stenosis at L4/5 on MRI (**Figure 8**). Her medication history included hydrocodone, meloxicam, and tizanidine. Due to the long duration of the pain, the patient had tried a number of conservative treatments such as chiropractic, transcutaneous electrical nerve stimulation (TENS), and heat/ice packs but mentioned that none of these treatments had

*Case 2: Postoperative X-ray showing T10–L1 transpedicular fixation and restoration of spinal alignment.*

*Case 2: Preoperative CT thoracic spine (A–D) showing bilateral T11–T12 facet dislocation, bilateral perched* 

**Figure 5.**

*Neurosurgical Procedures - Innovative Approaches*

or legs. MRI revealed T11/T12 anterolisthesis, T12 wedge fracture with T11–T12 facet dislocation, and posterior ligamentous injury with small dorsal epidural hematoma (**Figure 4**). CT thoracic spine showed fracture and subluxation at T11–T12 with bilateral perched T11 facets, right pedicle fracture of T12 extending into the superior end plate of the vertebral body with wedging of T12 along with anterior and inferior displacement of the anterior ring apophysis, and spinous process fractures of T11 and to a lesser extent T10 (**Figure 5**). Based on the clinical presentation and imaging findings, a decision to operate was made. The patient underwent robotic-assisted T10-L1 fixation and fusion, T11/T12 open reduction and internal fixation at T11–T12, and T11 laminotomy for epidural hematoma evacuation (**Figure 6**). The patient had complete recovery and subsequently underwent removal of the hardware at 1 year.

*Case 2: Preoperative MRI showing T11–T12 anterolisthesis, T12 wedge fracture with T11–T12 facet dislocation,* 

*and posterior ligamentous injury with small dorsal epidural hematoma (red circle).*

*Case 1: Intraoperative X-rays showing MIS T11–L3 transpedicular fixation (A and B).*

**10**

**Figure 4.**

**Figure 3.**

*Case 2: Preoperative CT thoracic spine (A–D) showing bilateral T11–T12 facet dislocation, bilateral perched facets, and T10 spinous process fracture (red circles).*

#### **4.3 Case 3: MIS robotic-assisted TLIF for degenerative spine**

A 58-year-old female presented to the hospital with back and leg pain. The leg pain was on the left side and radiating to the left foot. The patient mentioned the back pain was worse than the left lower extremity (LLE) pain with duration of pain progressing over the last 2 years. Additionally, she complained of LLE weakness and numbness as well as cramping in bilateral calf muscles. Imaging showed 11 mm L4/5 anterolisthesis on standing XR (**Figure 7**) and severe spinal stenosis at L4/5 on MRI (**Figure 8**). Her medication history included hydrocodone, meloxicam, and tizanidine. Due to the long duration of the pain, the patient had tried a number of conservative treatments such as chiropractic, transcutaneous electrical nerve stimulation (TENS), and heat/ice packs but mentioned that none of these treatments had

**Figure 6.** *Case 2: Postoperative X-ray showing T10–L1 transpedicular fixation and restoration of spinal alignment.*

**Figure 7.** *Case 3: Preoperative standing X-ray showing 11 mm L4/5 anterolisthesis.*

**Figure 8.**

*Case 3: Preoperative MRI in axial (A and B) and sagittal (C) planes showing severe spinal canal, lateral recess, and foraminal stenoses at L4–5.*

worked for her. Based on the clinical presentation and imaging findings, a decision to surgical operation was made, and the patient underwent an MIS robotic-assisted transforaminal lumbar interbody fusion (TLIF, **Figure 9**). The patient was discharged within a day and had resolution of back and leg symptoms on follow-up.

#### **4.4 Case 4: hybrid MIS robotic-assisted cervicothoracic fusion for adult trauma**

A 30-year-old female presented to the hospital after being involved in a rollover motor vehicle accident. Physical examination demonstrated severe neck pain and tingling in the left arm. On imaging, she had left C5–C6 facet fracture dislocation

**13**

**Figure 10.**

*and gray circles).*

**Figure 9.**

*Case 3: Postoperative standing X-ray showing L4–5 transforaminal lumbar interbody fusion with* 

*Case 4: Preoperative CT showing C5–C6 facet fracture dislocation and bilateral C5–C6 facet distraction (red* 

*spondylolisthesis reduction and disc height restoration.*

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730* *Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

#### **Figure 9.**

*Neurosurgical Procedures - Innovative Approaches*

*Case 3: Preoperative standing X-ray showing 11 mm L4/5 anterolisthesis.*

**12**

**Figure 8.**

**Figure 7.**

*recess, and foraminal stenoses at L4–5.*

*Case 3: Preoperative MRI in axial (A and B) and sagittal (C) planes showing severe spinal canal, lateral* 

worked for her. Based on the clinical presentation and imaging findings, a decision to surgical operation was made, and the patient underwent an MIS robotic-assisted transforaminal lumbar interbody fusion (TLIF, **Figure 9**). The patient was discharged within a day and had resolution of back and leg symptoms on follow-up.

**4.4 Case 4: hybrid MIS robotic-assisted cervicothoracic fusion for adult trauma**

A 30-year-old female presented to the hospital after being involved in a rollover motor vehicle accident. Physical examination demonstrated severe neck pain and tingling in the left arm. On imaging, she had left C5–C6 facet fracture dislocation

*Case 3: Postoperative standing X-ray showing L4–5 transforaminal lumbar interbody fusion with spondylolisthesis reduction and disc height restoration.*

#### **Figure 10.**

*Case 4: Preoperative CT showing C5–C6 facet fracture dislocation and bilateral C5–C6 facet distraction (red and gray circles).*

**Figure 11.** *Case 4: Intraoperative CT showing percutaneous robotic-assisted T1 pedicle screws.*

and bilateral C5–C6 facet distraction (**Figure 10**). The patient underwent C4-T1 fixation and fusion with percutaneous MIS robotic-assisted T1 pedicle screws (**Figure 11**). Her midline incision could be minimized to approximately 3 inches. She had complete recovery and was discharged to the rehabilitation unit.

#### **5. Discussion and future directions**

Radiation exposure is an important consideration when comparing the utility of robotics in spinal surgery to conventional, fluoroscopic techniques. With expanding indications for the use of MIS in more complex spinal cases, the concern about radiation is a major factor in technology adoption going forward. Recognizing the impact of this issue on increased adoption of robotics, a number of studies have looked at the radiation exposure in patients operated with the assistance from surgical robotics vis-à-vis patients treated with conventional, fluoroscopic techniques. Based on the limited literature on this topic, it appears the incorporation of robots in the operating workflow is associated with reduction in both the time and the levels of radiation exposure [40]. In a prospective randomized controlled trial, Hyun et al. observed shorter radiation times and output in the robotic group, which was statistically significant [30]. Kim and colleagues noted a significant reduction in fluoroscopy duration in later cases when compared to the early cases [41]. In a study comparing different guiding methods for pedicle screw insertion, Fan et al. showed that robotic-assisted technique was associated with shorter fluoroscopic time than conventional, freehand technique or O-arm-based navigation but longer time than patient-specific navigational template technique [42]. Another study looking at different screw insertion guiding techniques showed the lowest dose of radiation in the standard navigation group, which was followed by the robotic group and then the conventional, freehand group [28]. Kantelhardt et al. found that robotic-assisted screw insertion had statistically significant lower radiation exposure than conventional, freehand technique. However, the authors found no difference between percutaneous and open robotic-assisted pedicle screw insertion [17]. Similarly, Keric and colleagues noted lower fluoroscopy time in the robotic-assisted

**15**

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

screw insertion cohort [24]. In contrast, Ringel et al. and Schizas et al. found no differences in radiation exposure between the robotic and the freehand groups [21, 29]. Based on published data, it appears that robotic-assisted procedures lead to reduction in radiation exposure with the greatest value addition of robots being in percutaneous screw insertion. The use of robots in this case has the potential to reduce the radiation exposure, which tends to increase dramatically for conventional screw insertion techniques. The end result of incorporating robotics could

When compared with navigation, the use of robotics allows for preplanning of screws. This saves operative time and allows the operating room staff to prepare implants ahead of time. By preparing for any anatomical variations that the surgeon might encounter (such as in deformity, trauma, and previously arthrodesed spines), the robot can be deployed for spinal procedures that involve more complex anatomical relationships. Over time, enhancements to graphical user interface have simplified the screw trajectory planning. By allowing the superimposition of intraoperative scans over preoperative imaging, the robots help the surgeon to take into consideration patient movement to more accurately plan the procedure while also providing the surgeon with the ability to select optimal screw dimensions. By taking into account patient immobilization, a robotic surgical assistant can lead to a diminished operating time while reducing pedicle and vertebral body violations. Further, the visualization provided by the robotic software platform can aid in rod contouring/placement through optimized screw cadence and skin incision optimi-

The experience with the use of surgical robots in spine surgery has been positive so far with a large majority of studies documenting outcomes observed with robots that are equal or superior to the findings observed with conventional, openhand technique. This is on account of the reduction of human manual error as the robot provides a stable, rigid channel for guiding surgical instruments by the surgeon. The same advantage holds true when compared to navigation-assisted screw placement, which is more prone to deviations due to lack of a stable conduit for maneuvering instruments. Further, the ability to lock trajectories allows for repeatability during surgical procedures by limiting the influence of physiological hand tremor, which allows for efficiency gains over time. This element of repeatability has the added benefit of providing the surgeon the ability to better plan skin incisions. Despite the possible advantages of robots, the capabilities of the present robotic systems are fairly limited, which only favors their role in a narrow, specific set of indications as evident from most of the present literature being on the use of robots for primarily pedicle screw fixation. However, it is crucial to acknowledge the results by Ringel et al. that noted lower screw insertion accuracy with the use of surgical robotic system. A number of possible reasons could have led to these findings including lateral skidding of the cannula at the entrance point caused by the steep slope of the lateral aspect of the facet joint or using a platform fixed to a cranial spinal process with a K-wire and attached to the operating table by a bed mount, which meant the

With robotics continuing to become more visible in the spinal surgery, a discussion of future areas of developments is warranted. A major thrust for moving the field of robotics forward would involve arriving at reproducible definitions of screw trajectory that mitigate the interruptions to the surgical workflow caused by the present manual method of trajectory planning. Knez and colleagues employed nonparametric models of vertebral bodies and pedicles registered to the patient CT while also accounting for spinal curvature to calculate automatic trajectories that showed close agreement with manually defined plans [44, 45]. In a study based on an atlas-based method that incorporated patterns of biomechanically optimal

obviate the need for lead apron by the operating room staff.

zation for MIS procedures in obese patients.

robot was only attached to the patient via a single K-wire [43].

#### *Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

*Neurosurgical Procedures - Innovative Approaches*

*Case 4: Intraoperative CT showing percutaneous robotic-assisted T1 pedicle screws.*

**5. Discussion and future directions**

and bilateral C5–C6 facet distraction (**Figure 10**). The patient underwent C4-T1 fixation and fusion with percutaneous MIS robotic-assisted T1 pedicle screws (**Figure 11**). Her midline incision could be minimized to approximately 3 inches.

Radiation exposure is an important consideration when comparing the utility of robotics in spinal surgery to conventional, fluoroscopic techniques. With expanding indications for the use of MIS in more complex spinal cases, the concern about radiation is a major factor in technology adoption going forward. Recognizing the impact of this issue on increased adoption of robotics, a number of studies have looked at the radiation exposure in patients operated with the assistance from surgical robotics vis-à-vis patients treated with conventional, fluoroscopic techniques. Based on the limited literature on this topic, it appears the incorporation of robots in the operating workflow is associated with reduction in both the time and the levels of radiation exposure [40]. In a prospective randomized controlled trial, Hyun et al. observed shorter radiation times and output in the robotic group, which was statistically significant [30]. Kim and colleagues noted a significant reduction in fluoroscopy duration in later cases when compared to the early cases [41]. In a study comparing different guiding methods for pedicle screw insertion, Fan et al. showed that robotic-assisted technique was associated with shorter fluoroscopic time than conventional, freehand technique or O-arm-based navigation but longer time than patient-specific navigational template technique [42]. Another study looking at different screw insertion guiding techniques showed the lowest dose of radiation in the standard navigation group, which was followed by the robotic group and then the conventional, freehand group [28]. Kantelhardt et al. found that robotic-assisted screw insertion had statistically significant lower radiation exposure than conventional, freehand technique. However, the authors found no difference between percutaneous and open robotic-assisted pedicle screw insertion [17]. Similarly, Keric and colleagues noted lower fluoroscopy time in the robotic-assisted

She had complete recovery and was discharged to the rehabilitation unit.

**14**

**Figure 11.**

screw insertion cohort [24]. In contrast, Ringel et al. and Schizas et al. found no differences in radiation exposure between the robotic and the freehand groups [21, 29]. Based on published data, it appears that robotic-assisted procedures lead to reduction in radiation exposure with the greatest value addition of robots being in percutaneous screw insertion. The use of robots in this case has the potential to reduce the radiation exposure, which tends to increase dramatically for conventional screw insertion techniques. The end result of incorporating robotics could obviate the need for lead apron by the operating room staff.

When compared with navigation, the use of robotics allows for preplanning of screws. This saves operative time and allows the operating room staff to prepare implants ahead of time. By preparing for any anatomical variations that the surgeon might encounter (such as in deformity, trauma, and previously arthrodesed spines), the robot can be deployed for spinal procedures that involve more complex anatomical relationships. Over time, enhancements to graphical user interface have simplified the screw trajectory planning. By allowing the superimposition of intraoperative scans over preoperative imaging, the robots help the surgeon to take into consideration patient movement to more accurately plan the procedure while also providing the surgeon with the ability to select optimal screw dimensions. By taking into account patient immobilization, a robotic surgical assistant can lead to a diminished operating time while reducing pedicle and vertebral body violations. Further, the visualization provided by the robotic software platform can aid in rod contouring/placement through optimized screw cadence and skin incision optimization for MIS procedures in obese patients.

The experience with the use of surgical robots in spine surgery has been positive so far with a large majority of studies documenting outcomes observed with robots that are equal or superior to the findings observed with conventional, openhand technique. This is on account of the reduction of human manual error as the robot provides a stable, rigid channel for guiding surgical instruments by the surgeon. The same advantage holds true when compared to navigation-assisted screw placement, which is more prone to deviations due to lack of a stable conduit for maneuvering instruments. Further, the ability to lock trajectories allows for repeatability during surgical procedures by limiting the influence of physiological hand tremor, which allows for efficiency gains over time. This element of repeatability has the added benefit of providing the surgeon the ability to better plan skin incisions. Despite the possible advantages of robots, the capabilities of the present robotic systems are fairly limited, which only favors their role in a narrow, specific set of indications as evident from most of the present literature being on the use of robots for primarily pedicle screw fixation. However, it is crucial to acknowledge the results by Ringel et al. that noted lower screw insertion accuracy with the use of surgical robotic system. A number of possible reasons could have led to these findings including lateral skidding of the cannula at the entrance point caused by the steep slope of the lateral aspect of the facet joint or using a platform fixed to a cranial spinal process with a K-wire and attached to the operating table by a bed mount, which meant the robot was only attached to the patient via a single K-wire [43].

With robotics continuing to become more visible in the spinal surgery, a discussion of future areas of developments is warranted. A major thrust for moving the field of robotics forward would involve arriving at reproducible definitions of screw trajectory that mitigate the interruptions to the surgical workflow caused by the present manual method of trajectory planning. Knez and colleagues employed nonparametric models of vertebral bodies and pedicles registered to the patient CT while also accounting for spinal curvature to calculate automatic trajectories that showed close agreement with manually defined plans [44, 45]. In a study based on an atlas-based method that incorporated patterns of biomechanically optimal

constructs and a surgeon's own planning preferences, Vijayan et al. highlighted a method that is generalizable to other surgical planning applications [46]. The abovementioned methods are not only built on the premise of introducing consistency to screw trajectories but also hold potential for the estimation of screw diameter(s) and length(s) to be used in a given operation.

Perhaps the greatest challenge impeding the growth of robotic systems stems from the inability of present systems to utilize visual cues from the surroundings to identify objects both accurately and automatically. Therefore, the functionality of a robot is completely modeled by the humans, and accordingly robots are only able to perform tasks for which they are preconfigured. The present state of affairs shows the path forward, which in all likelihood will see robotics integrating with artificial intelligence (AI) to confer robots with increased accuracy in visual identification and autonomous decision-making capacity. This would entail competing with visual systems seen in humans where two-dimensional inputs from the environment are collected by the human eye and converted into three-dimensional interpreted by the brain. Further, the surgical environment is a dynamic one and responding in such a way an environment would need sequential processing of external stimuli in real time. This is necessary for the robots to transition from mere translators of preprogrammed structured scenarios to dynamic adaptors in the external world. The enhancements to spatial and temporal visual information processing capabilities bring to attention the central role of neural networks in bringing these capabilities online. Modeled on the parallel processing structure of the human brain, an artificial neural network is composed of interconnected processing elements. Neural network learning is driven by the training algorithm autonomously and continually adjusting the connection weights based on exposure to input/output data. By being exposed to the surgeon's screw planning preferences, the robot would over time be able to automatically plan the screws for the surgeon. Further, machine learning could be utilized to pool data from several surgeons and make use of their combined expertise to suggest optimized screw trajectories over the cloud, irrespective of the geographical location of the surgeon.

As technological adoption increases among the younger generations of surgeons, virtual reality (VR) platforms for skills acquisition and operative planning among other function would grow in demand. While a virtual depiction of the operating environment is imperative from an educational point of view, the superimposition of virtual objects over real-world environment via hybrid systems known as augmented reality (AR) is needed for enhanced manipulation. An example of such a scenario would perhaps include head-mounted visor that projects screw trajectory in front of the surgeon on a virtual display with the surgeon not located in the immediate vicinity of the patient. This would demand capabilities for seamless, real-time transmission and integration of stereoscopic images defining the operative field and imaging data defining the patient anatomy. The rise of AR could also be instrumental in ushering remote collaboration between surgeons located at distant geographic locations. This would need improvements in information transmission capabilities to allow for real-time collaboration, an area where fifth generation (5G) network technology might be of assistance. However, these developments speak to a more distant future, and in the more immediate time frame, robotics in spinal surgery might come to resemble the da Vinci Surgical System, a slave master system, where the surgeon sits at a console and controls the robot.

Of note, the enhanced capabilities would need to be designed in a manner that makes the robot a hand dexterity enhancer for the surgeon while still being in full control by the surgeon. As robotic technology becomes more sophisticated, the move toward autonomous robots will raise concerns about the transfer of control from the surgeon to the robot and the growing dependence of the surgeon on the

**17**

**Author details**

Mayank Kaushal, Shekar Kurpad and Hoon Choi\*

\*Address all correspondence to: hchoi@mcw.edu

provided the original work is properly cited.

Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, USA

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

**6. Conclusions**

in-built systems of the robot. Further, the possibility for real-time collaboration among physicians for screw planning recommendation as well doing the actual screw placement will raise concerns about patient consent, medical liability, and data confidentiality, among others. These are relevant ethical challenges of our time that demand more research into crucial areas of robotic design related to both software and hardware as well as the medicolegal requirements protecting the patient

such as the Health Insurance Portability and Accountability Act (HIPAA).

expected to benefit from further technological developments.

The current state of robotics in spinal surgery is comprised of a limited range of clinical indications related to screw placement. With emerging data showing acceptable rates for screw insertion and radiation exposure, the field of robotics is *Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

in-built systems of the robot. Further, the possibility for real-time collaboration among physicians for screw planning recommendation as well doing the actual screw placement will raise concerns about patient consent, medical liability, and data confidentiality, among others. These are relevant ethical challenges of our time that demand more research into crucial areas of robotic design related to both software and hardware as well as the medicolegal requirements protecting the patient such as the Health Insurance Portability and Accountability Act (HIPAA).

### **6. Conclusions**

*Neurosurgical Procedures - Innovative Approaches*

diameter(s) and length(s) to be used in a given operation.

the cloud, irrespective of the geographical location of the surgeon.

system, where the surgeon sits at a console and controls the robot.

Of note, the enhanced capabilities would need to be designed in a manner that makes the robot a hand dexterity enhancer for the surgeon while still being in full control by the surgeon. As robotic technology becomes more sophisticated, the move toward autonomous robots will raise concerns about the transfer of control from the surgeon to the robot and the growing dependence of the surgeon on the

As technological adoption increases among the younger generations of surgeons, virtual reality (VR) platforms for skills acquisition and operative planning among other function would grow in demand. While a virtual depiction of the operating environment is imperative from an educational point of view, the superimposition of virtual objects over real-world environment via hybrid systems known as augmented reality (AR) is needed for enhanced manipulation. An example of such a scenario would perhaps include head-mounted visor that projects screw trajectory in front of the surgeon on a virtual display with the surgeon not located in the immediate vicinity of the patient. This would demand capabilities for seamless, real-time transmission and integration of stereoscopic images defining the operative field and imaging data defining the patient anatomy. The rise of AR could also be instrumental in ushering remote collaboration between surgeons located at distant geographic locations. This would need improvements in information transmission capabilities to allow for real-time collaboration, an area where fifth generation (5G) network technology might be of assistance. However, these developments speak to a more distant future, and in the more immediate time frame, robotics in spinal surgery might come to resemble the da Vinci Surgical System, a slave master

constructs and a surgeon's own planning preferences, Vijayan et al. highlighted a method that is generalizable to other surgical planning applications [46]. The abovementioned methods are not only built on the premise of introducing consistency to screw trajectories but also hold potential for the estimation of screw

Perhaps the greatest challenge impeding the growth of robotic systems stems from the inability of present systems to utilize visual cues from the surroundings to identify objects both accurately and automatically. Therefore, the functionality of a robot is completely modeled by the humans, and accordingly robots are only able to perform tasks for which they are preconfigured. The present state of affairs shows the path forward, which in all likelihood will see robotics integrating with artificial intelligence (AI) to confer robots with increased accuracy in visual identification and autonomous decision-making capacity. This would entail competing with visual systems seen in humans where two-dimensional inputs from the environment are collected by the human eye and converted into three-dimensional interpreted by the brain. Further, the surgical environment is a dynamic one and responding in such a way an environment would need sequential processing of external stimuli in real time. This is necessary for the robots to transition from mere translators of preprogrammed structured scenarios to dynamic adaptors in the external world. The enhancements to spatial and temporal visual information processing capabilities bring to attention the central role of neural networks in bringing these capabilities online. Modeled on the parallel processing structure of the human brain, an artificial neural network is composed of interconnected processing elements. Neural network learning is driven by the training algorithm autonomously and continually adjusting the connection weights based on exposure to input/output data. By being exposed to the surgeon's screw planning preferences, the robot would over time be able to automatically plan the screws for the surgeon. Further, machine learning could be utilized to pool data from several surgeons and make use of their combined expertise to suggest optimized screw trajectories over

**16**

The current state of robotics in spinal surgery is comprised of a limited range of clinical indications related to screw placement. With emerging data showing acceptable rates for screw insertion and radiation exposure, the field of robotics is expected to benefit from further technological developments.

#### **Author details**

Mayank Kaushal, Shekar Kurpad and Hoon Choi\* Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, USA

\*Address all correspondence to: hchoi@mcw.edu

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

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[2] Roberts DW, Strohbehn JW, Hatch JF, Murray W, Kettenberger H. A frameless stereotaxic integration of computerized tomographic imaging and the operating microscope. Journal of Neurosurgery. 1986;**65**(4):545-549

[3] Nathoo N, Cavusoglu MC, Vogelbaum MA, Barnett GH, et al. Neurosurgery. 2005;**56**(3):421-433. Discussion 33

[4] Overley SC, Cho SK, Mehta AI, Arnold PM. Navigation and robotics in spinal surgery: Where are we now? Neurosurgery. 2017;**80**(3S):S86-S99

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[10] Pechlivanis I, Kiriyanthan G, Engelhardt M, Scholz M, Lucke S, arders A, et al. Percutaneous placement of pedicle screws in the lumbar spine using a bone mounted miniature robotic system: First experiences and accuracy of screw placement. Spine. 2009;**34**(4):392-398

[11] Gertzbein SD, Robbins SE. Accuracy of pedicular screw placement in vivo. Spine. 1990;**15**(1):11-14

[12] Devito DP, Kaplan L, Dietl R, Pfeiffer M, Horne D, Silberstein B, et al. Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: Retrospective study. Spine. 2010;**35**(24):2109-2115

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[14] Hu X, Ohnmeiss DD, Lieberman IH. Robotic-assisted pedicle screw placement: Lessons learned from the first 102 patients. European Spine Journal. 2013;**22**(3):661-666

[15] Hu X, Scharschmidt TJ, Ohnmeiss DD, Lieberman IH. Robotic assisted surgeries for the treatment of spine tumors. International Journal of Spine Surgery. 2015;**9**:1

[16] Macke JJ, Woo R, Varich L. Accuracy of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population.

**19**

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

> [24] Keric N, Eum DJ, Afghanyar F, Rachwal-Czyzewicz I, Renovanz M, Conrad J, et al. Evaluation of surgical strategy of conventional vs. percutaneous robot-assisted spinal trans-pedicular instrumentation in spondylodiscitis.

Journal of Robotic Surgery.

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Surgery. 2017;**13**(e1779)

2013;**72**(Suppl 1):12-18

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freehand screw implantation. Spine.

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of lumbar and sacral pedicle screws: A prospective randomized comparison to conventional

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2017;**11**(1):17-25

Focus. 2017;**42**(5):E11

Journal of Robotic Surgery.

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2014;**20**(6):636-643

2017;**42**(5):E14

Cuvinciuc V, Kotowski M, Schaller K, Tessitore E. Safety and accuracy of robot-assisted versus fluoroscopyguided pedicle screw insertion for degenerative diseases of the lumbar spine: A matched cohort comparison. Journal of Neurosurgery. Spine.

[19] Schatlo B, Martinez R, Alaid A, von Eckardstein K, Akhavan-Sigari R, Hahn A, et al. Acta Neurochirurgica. 2015;**157**(10):1819-1823. Discussion 23

[20] Molliqaj G, Schatlo B, Alaid A, Solomiichuk V, Rohde V, Schaller K, et al. Accuracy of robot-guided versus freehand fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery. Neurosurgical Focus.

[21] Schizas C, Thein E, Kwiatkowski B, Kulik G. Pedicle screw insertion: Robotic assistance versus conventional C-arm fluoroscopy. Acta Orthopaedica

Salonen D, Farooq S. Clinical accuracy of fluoroscopic computer-assisted pedicle screw fixation: A CT analysis.

[23] Solomiichuk V, Fleischhammer J, Molliqaj G, Warda J, Alaid A, von Eckardstein K, et al. Robotic versus fluoroscopy-guided pedicle screw insertion for metastatic spinal disease: A matched-cohort comparison. Neurosurgical Focus. 2017;**42**(5):E13

Belgica. 2012;**78**(2):240-245

[22] Rampersaud YR, Pik JH,

Spine. 2005;**30**(7):E183-E190

[17] Kantelhardt SR, Martinez R, Baerwinkel S, Burger R, Giese A, Rohde V. Perioperative course and accuracy of screw positioning in conventional, open robotic-guided and percutaneous robotic-guided, pedicle screw placement. European Spine Journal. 2011;**20**(6):860-868

2016;**10**(2):145-150

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

Journal of Robotic Surgery. 2016;**10**(2):145-150

[17] Kantelhardt SR, Martinez R, Baerwinkel S, Burger R, Giese A, Rohde V. Perioperative course and accuracy of screw positioning in conventional, open robotic-guided and percutaneous robotic-guided, pedicle screw placement. European Spine Journal. 2011;**20**(6):860-868

[18] Schatlo B, Molliqaj G, Cuvinciuc V, Kotowski M, Schaller K, Tessitore E. Safety and accuracy of robot-assisted versus fluoroscopyguided pedicle screw insertion for degenerative diseases of the lumbar spine: A matched cohort comparison. Journal of Neurosurgery. Spine. 2014;**20**(6):636-643

[19] Schatlo B, Martinez R, Alaid A, von Eckardstein K, Akhavan-Sigari R, Hahn A, et al. Acta Neurochirurgica. 2015;**157**(10):1819-1823. Discussion 23

[20] Molliqaj G, Schatlo B, Alaid A, Solomiichuk V, Rohde V, Schaller K, et al. Accuracy of robot-guided versus freehand fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery. Neurosurgical Focus. 2017;**42**(5):E14

[21] Schizas C, Thein E, Kwiatkowski B, Kulik G. Pedicle screw insertion: Robotic assistance versus conventional C-arm fluoroscopy. Acta Orthopaedica Belgica. 2012;**78**(2):240-245

[22] Rampersaud YR, Pik JH, Salonen D, Farooq S. Clinical accuracy of fluoroscopic computer-assisted pedicle screw fixation: A CT analysis. Spine. 2005;**30**(7):E183-E190

[23] Solomiichuk V, Fleischhammer J, Molliqaj G, Warda J, Alaid A, von Eckardstein K, et al. Robotic versus fluoroscopy-guided pedicle screw insertion for metastatic spinal disease: A matched-cohort comparison. Neurosurgical Focus. 2017;**42**(5):E13

[24] Keric N, Eum DJ, Afghanyar F, Rachwal-Czyzewicz I, Renovanz M, Conrad J, et al. Evaluation of surgical strategy of conventional vs. percutaneous robot-assisted spinal trans-pedicular instrumentation in spondylodiscitis. Journal of Robotic Surgery. 2017;**11**(1):17-25

[25] Keric N, Doenitz C, Haj A, Rachwal-Czyzewicz I, Renovanz M, Wesp DMA, et al. Evaluation of robotguided minimally invasive implantation of 2067 pedicle screws. Neurosurgical Focus. 2017;**42**(5):E11

[26] Alaid A, von Eckardstein K, Smoll NR, Solomiichuk V, Rohde V, Martinez R, et al. Robot guidance for percutaneous minimally invasive placement of pedicle screws for pyogenic spondylodiscitis is associated with lower rates of wound breakdown compared to conventional fluoroscopyguided instrumentation. Neurosurgical Review. 2018;**41**(2):489-496

[27] Kim HJ, Jung WI, Chang BS, Lee CK, Kang KT, Yeom JS. A prospective, randomized, controlled trial of robot-assisted vs freehand pedicle screw fixation in spine surgery. International Journal of Medical Robotics and Computer Assisted Surgery. 2017;**13**(e1779)

[28] Roser F, Tatagiba M, Maier G. Spinal robotics: Current applications and future perspectives. Neurosurgery. 2013;**72**(Suppl 1):12-18

[29] Ringel F, Stuer C, Reinke A, Preuss A, Behr M, Auer F, et al. Accuracy of robot-assisted placement of lumbar and sacral pedicle screws: A prospective randomized comparison to conventional freehand screw implantation. Spine. 2012;**37**(8):E496-E501

[30] Hyun SJ, Kim KJ, Jahng TA, Kim HJ. Minimally invasive robotic versus open fluoroscopic-guided

**18**

*Neurosurgical Procedures - Innovative Approaches*

[1] Schurr PH, Merrington WR. The Horsley-Clarke stereotaxic apparatus. The British Journal of Surgery.

in posterior spinal fusion: Early clinical experience with the SpineAssist. International Journal of Medical Robotics and Computer Assisted Surgery. 2006;**2**(2):114-122

[10] Pechlivanis I, Kiriyanthan G, Engelhardt M, Scholz M, Lucke S, arders A, et al. Percutaneous placement of pedicle screws in the lumbar spine using a bone mounted miniature robotic system: First experiences and accuracy of screw placement. Spine.

[11] Gertzbein SD, Robbins SE. Accuracy of pedicular screw placement in vivo.

[12] Devito DP, Kaplan L, Dietl R, Pfeiffer M, Horne D, Silberstein B, et al. Clinical acceptance and accuracy

[13] van Dijk JD, van den Ende RP, Stramigioli S, Kochling M, Hoss N. Clinical pedicle screw accuracy and deviation from planning in robotguided spine surgery: Robot-guided pedicle screw accuracy. Spine. 2015;**40**(17):E986-E991

[14] Hu X, Ohnmeiss DD, Lieberman IH.

Ohnmeiss DD, Lieberman IH. Robotic assisted surgeries for the treatment of spine tumors. International Journal of

[16] Macke JJ, Woo R, Varich L. Accuracy

of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population.

Robotic-assisted pedicle screw placement: Lessons learned from the first 102 patients. European Spine Journal. 2013;**22**(3):661-666

[15] Hu X, Scharschmidt TJ,

Spine Surgery. 2015;**9**:1

assessment of spinal implants guided with SpineAssist surgical robot: Retrospective study. Spine.

2009;**34**(4):392-398

Spine. 1990;**15**(1):11-14

2010;**35**(24):2109-2115

[2] Roberts DW, Strohbehn JW, Hatch JF, Murray W, Kettenberger H. A frameless stereotaxic integration of computerized tomographic imaging and the operating microscope. Journal of Neurosurgery.

**References**

1978;**65**(1):33-36

1986;**65**(4):545-549

Discussion 33

[3] Nathoo N, Cavusoglu MC, Vogelbaum MA, Barnett GH, et al. Neurosurgery. 2005;**56**(3):421-433.

[4] Overley SC, Cho SK, Mehta AI, Arnold PM. Navigation and robotics in spinal surgery: Where are we now? Neurosurgery. 2017;**80**(3S):S86-S99

[5] Theodore N, Arnold PM, Mehta AI. Introduction: The rise of the robots in spinal surgery. Neurosurgical Focus.

[6] Gao S, Lv Z, Fang H. Robot-assisted and conventional freehand pedicle screw placement: A systematic review and meta-analysis of randomized controlled trials. European Spine Journal. 2018;**27**(4):921-930

[7] Ghasem A, Sharma A, Greif DN, Alam M, Maaieh MA. The arrival of robotics in spine surgery: A review of the literature. Spine.

[8] Fan Y, Du JP, Liu JJ, Zhang JN, Qiao HH, Liu SC, et al. Accuracy of pedicle screw placement comparing robot-assisted technology and the freehand with fluoroscopy-guided method in spine surgery: An updated metaanalysis. Medicine. 2018;**97**(22):e10970

[9] Sukovich W, Brink-Danan S, Hardenbrook M. Miniature robotic guidance for pedicle screw placement

2018;**43**(23):1670-1677

2018;**45**(VideoSuppl1):Intro

spinal instrumented fusions: A randomized controlled trial. Spine. 2017;**42**(6):353-358

[31] Park SM, Kim HJ, Lee SY, Chang BS, Lee CK, Yeom JS. Radiographic and clinical outcomes of robot-assisted posterior pedicle screw fixation: Two-year results from a randomized controlled trial. Yonsei Medical Journal. 2018;**59**(3):438-444

[32] Lonjon N, Chan-Seng E, Costalat V, Bonnafoux B, Vassal M, Boetto J. Robotassisted spine surgery: Feasibility study through a prospective case-matched analysis. European Spine Journal. 2016;**25**(3):947-955

[33] Huntsman KT, Ahrendtsen LA, Riggleman JR, Ledonio CG. Roboticassisted navigated minimally invasive pedicle screw placement in the first 100 cases at a single institution. Journal of Robotic Surgery. 2019

[34] Bederman SS, Hahn P, Colin V, Kiester PD, Bhatia NN. Robotic guidance for S2-alar-iliac screws in spinal deformity correction. Clinical Spine Surgery. 2017;**30**(1):E49-E53

[35] Hu X, Lieberman IH. Roboticguided sacro-pelvic fixation using S2 alar-iliac screws: Feasibility and accuracy. European Spine Journal. 2017;**26**(3):720-725

[36] Hyun SJ, Kim KJ, Jahng TA. S2 alar iliac screw placement under robotic guidance for adult spinal deformity patients: Technical note. European Spine Journal. 2017;**26**(8):2198-2203

[37] Laratta JL, Shillingford JN, Lombardi JM, Alrabaa RG, Benkli B, Fischer C, et al. Accuracy of S2 alariliac screw placement under robotic guidance. Spine Deformity. 2018;**6**(2):130-136

[38] Shillingford JN, Laratta JL, Park PJ, Lombardi JM, Tuchman A, Saifi C, et al. Human versus robot: A propensitymatched analysis of the accuracy of free hand versus robotic guidance for placement of S2 alar-iliac (S2AI) screws. Spine. 2018;**43**(21):E1297-EE304

[39] Vaccaro AR, Zeiller SC, Hulbert RJ, Anderson PA, Harris M, Hedlund R, et al. The thoracolumbar injury severity score: A proposed treatment algorithm. Journal of Spinal Disorders & Techniques. 2005;**18**(3):209-215

[40] Stull JD, Mangan JJ, Vaccaro AR, Schroeder GD. Robotic guidance in minimally invasive spine surgery: A review of recent literature and commentary on a developing technology. Current Reviews in Musculoskeletal Medicine. 2019;**12**(2):245-251

[41] Kim HJ, Lee SH, Chang BS, Lee CK, Lim TO, Hoo LP, et al. Monitoring the quality of robot-assisted pedicle screw fixation in the lumbar spine by using a cumulative summation test. Spine. 2015;**40**(2):87-94

[42] Fan Y, Du J, Zhang J, Liu S, Xue X, Huang Y, et al. Comparison of accuracy of pedicle screw insertion among 4 guided technologies in spine surgery. Medical Science Monitor. 2017;**23**:5960-5968

[43] Marcus HJ, Cundy TP, Nandi D, Yang GZ, Darzi A. Robotassisted and fluoroscopy-guided pedicle screw placement: A systematic review. European Spine Journal. 2014;**23**(2):291-297

[44] Knez D, Likar B, Pernus F, Vrtovec T. Computer-assisted screw size and insertion trajectory planning for pedicle screw placement surgery. IEEE Transactions on Medical Imaging. 2016;**35**(6):1420-1430

[45] Knez D, Nahle IS, Vrtovec T, Parent S, Kadoury S, editors. Computerassisted pedicle screw placement

**21**

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

planning: Towards clinical practice. In: 2018 IEEE 15th International Symposium on Biomedical Imaging

[46] Vijayan R, De Silva T, Han R, Zhang X, Uneri A, Doerr S, et al. Automatic pedicle screw planning using atlas-based registration of anatomy and reference trajectories. Physics in

(ISBI 2018); 4-7 April 2018

Medicine and Biology. 2019

*Robotic-Assisted Systems for Spinal Surgery DOI: http://dx.doi.org/10.5772/intechopen.88730*

planning: Towards clinical practice. In: 2018 IEEE 15th International Symposium on Biomedical Imaging (ISBI 2018); 4-7 April 2018

*Neurosurgical Procedures - Innovative Approaches*

Human versus robot: A propensitymatched analysis of the accuracy of free hand versus robotic guidance for placement of S2 alar-iliac (S2AI) screws.

Spine. 2018;**43**(21):E1297-EE304

Journal of Spinal Disorders & Techniques. 2005;**18**(3):209-215

2019;**12**(2):245-251

2015;**40**(2):87-94

2017;**23**:5960-5968

2014;**23**(2):291-297

2016;**35**(6):1420-1430

[43] Marcus HJ, Cundy TP,

Nandi D, Yang GZ, Darzi A. Robotassisted and fluoroscopy-guided pedicle screw placement: A systematic review. European Spine Journal.

[44] Knez D, Likar B, Pernus F, Vrtovec T. Computer-assisted screw size and insertion trajectory planning for pedicle screw placement surgery. IEEE Transactions on Medical Imaging.

[45] Knez D, Nahle IS, Vrtovec T,

Parent S, Kadoury S, editors. Computerassisted pedicle screw placement

[42] Fan Y, Du J, Zhang J, Liu S, Xue X, Huang Y, et al. Comparison of accuracy of pedicle screw insertion among 4 guided technologies in spine surgery. Medical Science Monitor.

[40] Stull JD, Mangan JJ, Vaccaro AR, Schroeder GD. Robotic guidance in minimally invasive spine surgery: A review of recent literature and commentary on a developing technology. Current Reviews in Musculoskeletal Medicine.

[41] Kim HJ, Lee SH, Chang BS, Lee CK, Lim TO, Hoo LP, et al. Monitoring the quality of robot-assisted pedicle screw fixation in the lumbar spine by using a cumulative summation test. Spine.

[39] Vaccaro AR, Zeiller SC, Hulbert RJ, Anderson PA, Harris M, Hedlund R, et al. The thoracolumbar injury severity score: A proposed treatment algorithm.

[31] Park SM, Kim HJ, Lee SY, Chang BS, Lee CK, Yeom JS. Radiographic and clinical outcomes of robot-assisted posterior pedicle screw fixation: Two-year results from a randomized controlled trial. Yonsei Medical Journal.

[32] Lonjon N, Chan-Seng E, Costalat V, Bonnafoux B, Vassal M, Boetto J. Robotassisted spine surgery: Feasibility study through a prospective case-matched analysis. European Spine Journal.

[33] Huntsman KT, Ahrendtsen LA, Riggleman JR, Ledonio CG. Roboticassisted navigated minimally invasive pedicle screw placement in the first 100 cases at a single institution. Journal of

[34] Bederman SS, Hahn P, Colin V, Kiester PD, Bhatia NN. Robotic guidance

for S2-alar-iliac screws in spinal deformity correction. Clinical Spine

[35] Hu X, Lieberman IH. Roboticguided sacro-pelvic fixation using S2 alar-iliac screws: Feasibility and accuracy. European Spine Journal.

[36] Hyun SJ, Kim KJ, Jahng TA. S2 alar iliac screw placement under robotic guidance for adult spinal deformity patients: Technical note. European Spine

[38] Shillingford JN, Laratta JL, Park PJ, Lombardi JM, Tuchman A, Saifi C, et al.

Journal. 2017;**26**(8):2198-2203

[37] Laratta JL, Shillingford JN, Lombardi JM, Alrabaa RG, Benkli B, Fischer C, et al. Accuracy of S2 alariliac screw placement under robotic

guidance. Spine Deformity.

2018;**6**(2):130-136

Surgery. 2017;**30**(1):E49-E53

spinal instrumented fusions: A randomized controlled trial. Spine.

2017;**42**(6):353-358

2018;**59**(3):438-444

2016;**25**(3):947-955

Robotic Surgery. 2019

2017;**26**(3):720-725

**20**

[46] Vijayan R, De Silva T, Han R, Zhang X, Uneri A, Doerr S, et al. Automatic pedicle screw planning using atlas-based registration of anatomy and reference trajectories. Physics in Medicine and Biology. 2019

**23**

**Chapter 2**

**Abstract**

**1. Introduction**

Innovations in the Surgery of

Visualization, Perfusion, and

Function Monitoring

paradigms of cerebral aneurysm treatment.

monitoring, perivascular flow probe, endoscope

Cerebral Aneurysms: Enhanced

*Oriela Rustemi, Alessandro Della Puppa and Alba Scerrati*

Surgery of cerebral aneurysms has evolved over the years. Advances regard enhanced intraoperative visualization and monitoring of both function and perfusion. Technological assistance used in oncological or skull base surgery, such as intraoperative neurophysiological monitoring (IONM) or endoscopy, now adopt to vascular surgery. Intraoperative indocyanine green video angiography (ICG-VA) and techniques for its interpretation (squeezing maneuver; entrapment sign), endoscopes, and exoscopes increase visualization. Flow evaluation by microflow probe permits perfusion monitoring; IONM allows functional monitoring. Bypasses replace flow in complex aneurysm cases. Pre-, intra-, and postoperative imaging and flow measurement techniques help in donor selection and follow-up. Despite some progression in the aneurysm clips, the principle has not changed. Innovation and even change of principle in aneurysm exclusion might be desirable. Basic research in aneurysm wall and flow dynamics might in the future change the

**Keywords:** aneurysm surgery, cerebral aneurysm, bypass, clipping, vascular surgery, indocyanine green video angiography, flow measurement, neurophysiological

The advent of endovascular treatment determined the crisis of cerebral aneurysm surgery. Endovascular therapy is less invasive and its progression is rapid. Industries' interests and investments potentiate the technological endovascular advancements. Surgical treatment by clipping of intracranial aneurysms is durable and stable in time. There are advances in making surgical treatment safer and offering treatment to the more complicated cases, not amenable to endovascular therapy. Advances and investments in the surgery of cerebral aneurysms are less deafening in the last decade. However, some silent innovative advances are made over the years. Here we present innovations in cerebral aneurysm surgery.

#### **Chapter 2**

## Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion, and Function Monitoring

*Oriela Rustemi, Alessandro Della Puppa and Alba Scerrati*

#### **Abstract**

Surgery of cerebral aneurysms has evolved over the years. Advances regard enhanced intraoperative visualization and monitoring of both function and perfusion. Technological assistance used in oncological or skull base surgery, such as intraoperative neurophysiological monitoring (IONM) or endoscopy, now adopt to vascular surgery. Intraoperative indocyanine green video angiography (ICG-VA) and techniques for its interpretation (squeezing maneuver; entrapment sign), endoscopes, and exoscopes increase visualization. Flow evaluation by microflow probe permits perfusion monitoring; IONM allows functional monitoring. Bypasses replace flow in complex aneurysm cases. Pre-, intra-, and postoperative imaging and flow measurement techniques help in donor selection and follow-up. Despite some progression in the aneurysm clips, the principle has not changed. Innovation and even change of principle in aneurysm exclusion might be desirable. Basic research in aneurysm wall and flow dynamics might in the future change the paradigms of cerebral aneurysm treatment.

**Keywords:** aneurysm surgery, cerebral aneurysm, bypass, clipping, vascular surgery, indocyanine green video angiography, flow measurement, neurophysiological monitoring, perivascular flow probe, endoscope

#### **1. Introduction**

The advent of endovascular treatment determined the crisis of cerebral aneurysm surgery. Endovascular therapy is less invasive and its progression is rapid. Industries' interests and investments potentiate the technological endovascular advancements. Surgical treatment by clipping of intracranial aneurysms is durable and stable in time. There are advances in making surgical treatment safer and offering treatment to the more complicated cases, not amenable to endovascular therapy. Advances and investments in the surgery of cerebral aneurysms are less deafening in the last decade. However, some silent innovative advances are made over the years. Here we present innovations in cerebral aneurysm surgery.

#### **2. Enhanced intraoperative visualization: intraoperative indocyanine green video angiography (ICG-VA) principle and implantation in vascular neurosurgery**

Indocyanine green (ICG) is a near-infrared (NIR) fluorescent dye initially approved by the Food and Drug Administration (FDA) in 1956 for the evaluation of the cardiocirculatory and liver function. FDA extended the approval for ophthalmic angiography in 1975. Nowadays, ICG fluorescence is routinely used in ophthalmology for the visualization of the retinal microcirculation. A specific optical setup for near-infrared (NIR) light is necessary for the visualization of the ICG fluorescence. The development of an ICG angiography new system allowed further implementation for the intraoperative visualization of the tissue perfusion in general surgery.

Raabe et al. gave a substantial contribution by implementing ICG angiography use in vascular neurosurgery [1].

The absorption peak of ICG is 805 nm, while the emission peak is 835 nm. Within these two peaks, the endogenous tissue chromophore absorption is low.

NIR light penetrates the tissue from several millimeters to a few centimeters. ICG is injected intravenously, and it bounds in 1–2 s predominantly to globulins (α1-lipoproteins). In the absence of vascular permeability damage, ICG bound to globulins remains intravascular. ICG has a plasma half-life of 3–4 min. It is only excreted by the liver with no metabolization.

Raabe et al. used a laser-fluorescence imaging device (IC-View; Pulsion Medical Systems AG, Munich, Germany), consisting of a NIR laser light source (0.16 W, λ = 780 nm) and a NIR-sensitive digital camcorder.

ICG was injected intravenously in a bolus (standard dose of 25 mg dissolved in 5 ml of water). ICG fluorescence was induced by the NIR light emitted by the laser light source. The digital video camera with optical filtering recorded only the ICGinduced fluorescence signal.

The near-infrared filter was commercially available for surgical microscopes routinely used in neurosurgery, and ICG-VA could be applied in vascular neurosurgery.

For example, intraoperative ICG-VA could be performed using a surgical microscope (OPMI® PenteroTM, The Carl Zeiss Co., Oberkochen, Germany) equipped with a microscope-integrated near-infrared ICG-VA (Carl Zeiss, Infrared 800TM, Meditec, Germany). ICG is injected intravenously in a bolus of 25 mg dissolved in 5 ml of water, and the operating field is illuminated with near-infrared light. Realtime angiographic images are visualized on a video screen and recorded. The images can be replayed. Only the illuminated field is recorded. ICG can be injected multiple times during surgery; thus ICG-VA is repeatable.

#### **3. ICG-VA for accessing aneurysm occlusion after clipping**

After Raabe's first report [1], ICG-VA gradually became routinely used in aneurysm surgery. It is used after aneurysm clipping to access whether the aneurysm occlusion is complete. Catheter angiography is the gold standard for cerebral aneurysm diagnosis [2] and for confirming aneurysm occlusion. However, intraoperative catheter angiography requires a programmed setup; is invasive, expensive, and time-consuming, and requires a well-trained staff. It is reserved to particular complicated cases, and it is not intraoperatively routinely used in the surgery of intracranial aneurysms. Furthermore, the time required for an intraoperative angiogram may be sufficient for the establishment of irreversible ischemia. Postoperative residual aneurysms after clipping are reported in a variable range from 4 to 19%

**25**

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion...*

of cases [3–10]. ICG-VA is fast, easily used, and not invasive. It allows immediate assessment of the aneurysm occlusion after clipping, and permits whether necessary clip repositioning or further clip positioning. Although, ICG-VA is inferior to catheter angiography in assessing aneurysm complete occlusion, it is intraoperatively easily used in the cases where intraoperative catheter angiography would not be used routinely. It does not substitute postoperative neuroradiological control of aneurysm complete occlusion but allows to have higher postoperative occlusion rates. Postoperative catheter angiography remains the gold standard for assessment of aneurysm occlusion. Generally, intraoperative ICG-VA is used to access clipping after apparent complete occlusion under the microscope light. Della Puppa et al. showed that despite apparent complete occlusion under microscope visualization, ICG-VA revealed unexpected residual aneurysms in 9% [11]. Roessler et al. in a study of 295 aneurysms clipped with the use of ICG-VA showed an intraoperative clip modification rate of 15% based on ICG-VA data [12]. Thus, ICG-VA is a complementary tool that increases aneurysm occlusion rate, but it does not substitute postoperative digital subtraction angiography (DSA) for the detection of aneurysm remnants [13]. Intraoperative aneurysm puncture, or opening whenever possible, remains the most reliable intraoperative measure to assess complete occlusion.

Different factors can determine false-negative or false-positive ICG-VA findings.

ICG-VA despite improvement of aneurysm occlusions rate can also show deceptive false-negative results. Della Puppa et al. described a surgical simple maneuver to detect false-negative ICG-VA results after clipping of a cerebral aneurysm [15]. The squeezing maneuver consists of a gentle pinch with bipolar/Cushing bayonet forceps of the dome of a clipped aneurysm when ICG-VA documents its apparent exclusion. The maneuver is performed during the same ICG injection to confirm the aneurysm exclusion. It is considered positive when, after an initial ICG-VA shows the aneurysm exclusion, a gentle pinch of the slack aneurysm dome with a bipolar or Cushing bayonet forceps under ICG-VA visualization causes the prompt dyeing of the sac, suggesting that the aneurysm is still filling up. The maneuver is considered negative when, after pinching of the clipped dome, the sac does not fill up. The puncture and opening of the sac can confirm whether a flow is still filling the aneurysm. The squeezing maneuver can depict ICG-VA false-negative results.

This permits to readjust the clip or position a second clip to completely exclude the aneurysm during the same procedure. Calcification/atheroma of the wall/neck was predictive of a positive maneuver (*P* = 0.001). This is consistent with Gekka et al. findings several years later, which report false-negative ICG-VA results in

ICG-VA can also show false-positive results, if misinterpreted. When ICG is injected before the final aneurysm clipping, the dye might be entrapped within

atherosclerosis and wall thickening at the clipping site [14].

Arteriosclerosis and wall thickening at the clipping site influence false-negative ICG-VA findings [14]. Repeated ICG can determine false-positive results. Also, a small remnant detected in ICG can undergo spontaneous thrombosis and thus may

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

**4. Tools to improve ICG-VA interpretation**

not present a real residual.

**4.1 Squeezing maneuver**

**4.2 ICG entrapment sign**

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion... DOI: http://dx.doi.org/10.5772/intechopen.91030*

of cases [3–10]. ICG-VA is fast, easily used, and not invasive. It allows immediate assessment of the aneurysm occlusion after clipping, and permits whether necessary clip repositioning or further clip positioning. Although, ICG-VA is inferior to catheter angiography in assessing aneurysm complete occlusion, it is intraoperatively easily used in the cases where intraoperative catheter angiography would not be used routinely. It does not substitute postoperative neuroradiological control of aneurysm complete occlusion but allows to have higher postoperative occlusion rates. Postoperative catheter angiography remains the gold standard for assessment of aneurysm occlusion. Generally, intraoperative ICG-VA is used to access clipping after apparent complete occlusion under the microscope light. Della Puppa et al. showed that despite apparent complete occlusion under microscope visualization, ICG-VA revealed unexpected residual aneurysms in 9% [11]. Roessler et al. in a study of 295 aneurysms clipped with the use of ICG-VA showed an intraoperative clip modification rate of 15% based on ICG-VA data [12]. Thus, ICG-VA is a complementary tool that increases aneurysm occlusion rate, but it does not substitute postoperative digital subtraction angiography (DSA) for the detection of aneurysm remnants [13]. Intraoperative aneurysm puncture, or opening whenever possible, remains the most reliable intraoperative measure to assess complete occlusion.

#### **4. Tools to improve ICG-VA interpretation**

Different factors can determine false-negative or false-positive ICG-VA findings. Arteriosclerosis and wall thickening at the clipping site influence false-negative ICG-VA findings [14]. Repeated ICG can determine false-positive results. Also, a small remnant detected in ICG can undergo spontaneous thrombosis and thus may not present a real residual.

#### **4.1 Squeezing maneuver**

*Neurosurgical Procedures - Innovative Approaches*

**vascular neurosurgery**

use in vascular neurosurgery [1].

induced fluorescence signal.

neurosurgery.

excreted by the liver with no metabolization.

λ = 780 nm) and a NIR-sensitive digital camcorder.

times during surgery; thus ICG-VA is repeatable.

**3. ICG-VA for accessing aneurysm occlusion after clipping**

After Raabe's first report [1], ICG-VA gradually became routinely used in aneurysm surgery. It is used after aneurysm clipping to access whether the aneurysm occlusion is complete. Catheter angiography is the gold standard for cerebral aneurysm diagnosis [2] and for confirming aneurysm occlusion. However, intraoperative catheter angiography requires a programmed setup; is invasive, expensive, and time-consuming, and requires a well-trained staff. It is reserved to particular complicated cases, and it is not intraoperatively routinely used in the surgery of intracranial aneurysms. Furthermore, the time required for an intraoperative angiogram may be sufficient for the establishment of irreversible ischemia. Postoperative residual aneurysms after clipping are reported in a variable range from 4 to 19%

**2. Enhanced intraoperative visualization: intraoperative indocyanine green video angiography (ICG-VA) principle and implantation in** 

Indocyanine green (ICG) is a near-infrared (NIR) fluorescent dye initially approved by the Food and Drug Administration (FDA) in 1956 for the evaluation of the cardiocirculatory and liver function. FDA extended the approval for ophthalmic angiography in 1975. Nowadays, ICG fluorescence is routinely used in ophthalmology for the visualization of the retinal microcirculation. A specific optical setup for near-infrared (NIR) light is necessary for the visualization of the ICG fluorescence. The development of an ICG angiography new system allowed further implementation for the intraoperative visualization of the tissue perfusion in general surgery. Raabe et al. gave a substantial contribution by implementing ICG angiography

The absorption peak of ICG is 805 nm, while the emission peak is 835 nm. Within these two peaks, the endogenous tissue chromophore absorption is low. NIR light penetrates the tissue from several millimeters to a few centimeters. ICG is injected intravenously, and it bounds in 1–2 s predominantly to globulins (α1-lipoproteins). In the absence of vascular permeability damage, ICG bound to globulins remains intravascular. ICG has a plasma half-life of 3–4 min. It is only

Raabe et al. used a laser-fluorescence imaging device (IC-View; Pulsion Medical Systems AG, Munich, Germany), consisting of a NIR laser light source (0.16 W,

ICG was injected intravenously in a bolus (standard dose of 25 mg dissolved in 5 ml of water). ICG fluorescence was induced by the NIR light emitted by the laser light source. The digital video camera with optical filtering recorded only the ICG-

For example, intraoperative ICG-VA could be performed using a surgical microscope (OPMI® PenteroTM, The Carl Zeiss Co., Oberkochen, Germany) equipped with a microscope-integrated near-infrared ICG-VA (Carl Zeiss, Infrared 800TM, Meditec, Germany). ICG is injected intravenously in a bolus of 25 mg dissolved in 5 ml of water, and the operating field is illuminated with near-infrared light. Realtime angiographic images are visualized on a video screen and recorded. The images can be replayed. Only the illuminated field is recorded. ICG can be injected multiple

The near-infrared filter was commercially available for surgical microscopes routinely used in neurosurgery, and ICG-VA could be applied in vascular

**24**

ICG-VA despite improvement of aneurysm occlusions rate can also show deceptive false-negative results. Della Puppa et al. described a surgical simple maneuver to detect false-negative ICG-VA results after clipping of a cerebral aneurysm [15]. The squeezing maneuver consists of a gentle pinch with bipolar/Cushing bayonet forceps of the dome of a clipped aneurysm when ICG-VA documents its apparent exclusion.

The maneuver is performed during the same ICG injection to confirm the aneurysm exclusion. It is considered positive when, after an initial ICG-VA shows the aneurysm exclusion, a gentle pinch of the slack aneurysm dome with a bipolar or Cushing bayonet forceps under ICG-VA visualization causes the prompt dyeing of the sac, suggesting that the aneurysm is still filling up. The maneuver is considered negative when, after pinching of the clipped dome, the sac does not fill up. The puncture and opening of the sac can confirm whether a flow is still filling the aneurysm. The squeezing maneuver can depict ICG-VA false-negative results.

This permits to readjust the clip or position a second clip to completely exclude the aneurysm during the same procedure. Calcification/atheroma of the wall/neck was predictive of a positive maneuver (*P* = 0.001). This is consistent with Gekka et al. findings several years later, which report false-negative ICG-VA results in atherosclerosis and wall thickening at the clipping site [14].

#### **4.2 ICG entrapment sign**

ICG-VA can also show false-positive results, if misinterpreted. When ICG is injected before the final aneurysm clipping, the dye might be entrapped within the sac by the clip's blades, which would obstacle the dye washout. ICG-VA would show the dye entrapped in the sac. An erroneous interpretation of the data would be to consider the aneurysm unsecured. Della Puppa et al. introduced the ICG entrapment sign as the detection under infrared light of ICG remnants sequestered in the dome [16]. ICG entrapment sign detects dye stasis, and not active filling. It is considered a sign of aneurysm occlusion in the setting of ICG injection prior to final clipping. This may happen if ICG is injected prior to clipping for visualization of perforating arteries near to the sac or detection of atheromas of the neck/dome. This happens more commonly after clip repositioning based on ICG indication.

The squeezing maneuver can detect a false-negative ICG-VA (an unsecured aneurysm despite apparent occlusion after ICG), whereas the ICG entrapment sign can detect a false-positive ICV-VA result (a secured aneurysm under infrared light, despite ICG-VA showing dye).

#### **5. Other ICG-VA uses**

#### **5.1 Transdural application**

ICG-VA can be used before dural opening in vascular arteriovenous malformations or fistulas to optimize the exposure of the malformation, perform a safe dural opening, and identify dural vascular connections of the lesion [17]. The cases where transdural ICG can help in aneurysm surgery are very rare. These are the cases of distal cortical, generally distal middle cerebral artery (M4) aneurysms. In a case of M4 ruptured aneurysm, ICG-VA allowed transdural aneurysm visualization [18]. This is particularly helpful in an emergency setting, when neuronavigation is not available, to localize the aneurysm and avoid damage while opening the dura.

#### **5.2 Transoptic aneurysm visualization**

Other exceptional ICG-VA applications reported are the transoptic aneurysm visualization and occlusion confirmation in a case of an optic splitting aneurysm [19]. An ophthalmic artery aneurysm medially and superiorly projecting, suspicious for an under optic growth, underwent surgery. Initially the aneurysm was not visible. ICG-VA permitted the transoptic aneurysm visualization and after clipping final occlusion.

ICG-VA application was extended in other pathologies [20–26].

#### **5.3 Flow measurement by microflow probe: principle and implementation in neurosurgery**

Vascular micro-Dopplers are used in cerebral aneurysm surgery to indicate the flow velocity. They are easy to use and give the surgeon an acoustic signal feedback. The flow velocity is used as a surrogate of the flow quantity. Flow velocity is not the most reliable indicator for flow. Flow quantity is the most reliable flow measure.

Till the 1990s, the intraoperative ultrasonic blood flow probes have been used to quantitatively measure flow only in cardiac, vascular, and transplant surgery. Charbel et al. in the University of Illinois at Chicago first reported in 1997 the implantation of the ultrasonic perivascular micro blood flow probes in the clipping of cerebral aneurysms [27–31].

The first transit time flowmeters were described in 1962 and 1964 [32, 33]. Limitations in estimating vessel diameter, vessel misalignment, and an unstable zero calibration prevented medical applications [34]. In 1978 Drost et al. presented

**27**

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion...*

the theoretical basis for a flowmeter based on the transit time technique [35, 36].

The transit time blood volume flowmeter gives a direct measurement of volume flow through the acoustic window of its implanted sensor, independent of flow profile. In contrast, earlier Doppler and transit time ultrasonic flowmeters sense blood velocity, which makes volume flow measurements critically dependent on

The transonic perivascular flow-measuring device includes an electronic flow detection unit with enhanced frequency resolution and volume flow-sensing perivascular probes (Transonic Medical Flowmeter; Transonic Systems, Inc., Ithaca, NY, USA). The perivascular flow probes are manufactured in 1.5, 2, and 3 mm diameter and can be used to measure the average flow volume (mL/min) instanta-

The flowmeter uses ultrasonic transit time principle to sense liquid volume flow

The ultrasonic transducers transmit ultrasound which helps to sense the volume

The flow probe consists of a probe body which houses two ultrasonic transducers and a fixed acoustic reflector. The transducer is positioned around the blood vessel, and then the flow in that vessel is displayed in the digital form. The flowmeter derives an accurate measure of the "transit time," which is the time the wave of

Practically, a portion of the vessel of interest is dissected from the arachnoid,

The flow appears as a digital display on the detection unit and is registered as positive or negative dependent on the direction of flow in relation to the orientation of the probe. The flow is detected as the volume (mL/min), and the flow volume

**5.4 Flow measurement by microflow probe: application in aneurysm surgery**

Quantitative blood flow measurement became essential in blood flow preservation to avoid postoperative ischemic complication in cerebral aneurysm surgery. Amin-Hanjani et al. proposed a baseline evaluation of blood flow in the vessels at risk of flow compromise after clipping (generally the efferent arteries, distal to the aneurysm) and a second flow evaluation of the same vessels after clipping [31]. A reduction of the flow greater than 25% of baseline was considered at risk for ischemic complications, and the clip was repositioned. The data was reproduced by other studies [11, 37, 38]. Flow measurement by microflow probe was also used in

IONM routinely used in oncological surgery, over the years, has become essential also in vascular surgery to avoid ischemic complications. Monitoring includes bilateral upper and lower limb motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs). Generally, in aneurysm surgery, MEPs are monitored by transcranial electric stimulation, rather than by direct cortical mapping, because

The electronic flow-detecting unit is a line-powered flowmeter that automatically identifies the scaling factor and individual calibration factor of the flow probe connected to it. The flow sensors are connected to the flow-detecting unit via a

in vessels independent of flow velocity, hematocrit, and turbulence.

of blood flowing through the blood vessel in which the sensor is applied.

ultrasound has taken to travel from one transducer to the other [28].

and the probe is hooked around the vessel under saline irrigation.

**6. Intraoperative neurophysiological monitoring IONM**

over time of recording diagram can be printed.

other cerebrovascular diseases [39–42].

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

vessel diameter [35, 36].

neously in cerebral vessels.

flexible cable.

The transit time flowmeter was introduced in 1983 [36].

#### *Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion... DOI: http://dx.doi.org/10.5772/intechopen.91030*

the theoretical basis for a flowmeter based on the transit time technique [35, 36]. The transit time flowmeter was introduced in 1983 [36].

The transit time blood volume flowmeter gives a direct measurement of volume flow through the acoustic window of its implanted sensor, independent of flow profile. In contrast, earlier Doppler and transit time ultrasonic flowmeters sense blood velocity, which makes volume flow measurements critically dependent on vessel diameter [35, 36].

The transonic perivascular flow-measuring device includes an electronic flow detection unit with enhanced frequency resolution and volume flow-sensing perivascular probes (Transonic Medical Flowmeter; Transonic Systems, Inc., Ithaca, NY, USA). The perivascular flow probes are manufactured in 1.5, 2, and 3 mm diameter and can be used to measure the average flow volume (mL/min) instantaneously in cerebral vessels.

The flowmeter uses ultrasonic transit time principle to sense liquid volume flow in vessels independent of flow velocity, hematocrit, and turbulence.

The electronic flow-detecting unit is a line-powered flowmeter that automatically identifies the scaling factor and individual calibration factor of the flow probe connected to it. The flow sensors are connected to the flow-detecting unit via a flexible cable.

The ultrasonic transducers transmit ultrasound which helps to sense the volume of blood flowing through the blood vessel in which the sensor is applied.

The flow probe consists of a probe body which houses two ultrasonic transducers and a fixed acoustic reflector. The transducer is positioned around the blood vessel, and then the flow in that vessel is displayed in the digital form. The flowmeter derives an accurate measure of the "transit time," which is the time the wave of ultrasound has taken to travel from one transducer to the other [28].

Practically, a portion of the vessel of interest is dissected from the arachnoid, and the probe is hooked around the vessel under saline irrigation.

The flow appears as a digital display on the detection unit and is registered as positive or negative dependent on the direction of flow in relation to the orientation of the probe. The flow is detected as the volume (mL/min), and the flow volume over time of recording diagram can be printed.

#### **5.4 Flow measurement by microflow probe: application in aneurysm surgery**

Quantitative blood flow measurement became essential in blood flow preservation to avoid postoperative ischemic complication in cerebral aneurysm surgery. Amin-Hanjani et al. proposed a baseline evaluation of blood flow in the vessels at risk of flow compromise after clipping (generally the efferent arteries, distal to the aneurysm) and a second flow evaluation of the same vessels after clipping [31]. A reduction of the flow greater than 25% of baseline was considered at risk for ischemic complications, and the clip was repositioned. The data was reproduced by other studies [11, 37, 38]. Flow measurement by microflow probe was also used in other cerebrovascular diseases [39–42].

#### **6. Intraoperative neurophysiological monitoring IONM**

IONM routinely used in oncological surgery, over the years, has become essential also in vascular surgery to avoid ischemic complications. Monitoring includes bilateral upper and lower limb motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs). Generally, in aneurysm surgery, MEPs are monitored by transcranial electric stimulation, rather than by direct cortical mapping, because

*Neurosurgical Procedures - Innovative Approaches*

despite ICG-VA showing dye).

**5. Other ICG-VA uses**

final occlusion.

**neurosurgery**

of cerebral aneurysms [27–31].

**5.1 Transdural application**

**5.2 Transoptic aneurysm visualization**

the sac by the clip's blades, which would obstacle the dye washout. ICG-VA would show the dye entrapped in the sac. An erroneous interpretation of the data would be to consider the aneurysm unsecured. Della Puppa et al. introduced the ICG entrapment sign as the detection under infrared light of ICG remnants sequestered in the dome [16]. ICG entrapment sign detects dye stasis, and not active filling. It is considered a sign of aneurysm occlusion in the setting of ICG injection prior to final clipping. This may happen if ICG is injected prior to clipping for visualization of perforating arteries near to the sac or detection of atheromas of the neck/dome. This happens more commonly after clip repositioning based on ICG indication. The squeezing maneuver can detect a false-negative ICG-VA (an unsecured aneurysm despite apparent occlusion after ICG), whereas the ICG entrapment sign can detect a false-positive ICV-VA result (a secured aneurysm under infrared light,

ICG-VA can be used before dural opening in vascular arteriovenous malformations or fistulas to optimize the exposure of the malformation, perform a safe dural opening, and identify dural vascular connections of the lesion [17]. The cases where transdural ICG can help in aneurysm surgery are very rare. These are the cases of distal cortical, generally distal middle cerebral artery (M4) aneurysms. In a case of M4 ruptured aneurysm, ICG-VA allowed transdural aneurysm visualization [18]. This is particularly helpful in an emergency setting, when neuronavigation is not available, to localize the aneurysm and avoid damage while opening the dura.

Other exceptional ICG-VA applications reported are the transoptic aneurysm visualization and occlusion confirmation in a case of an optic splitting aneurysm [19]. An ophthalmic artery aneurysm medially and superiorly projecting, suspicious for an under optic growth, underwent surgery. Initially the aneurysm was not visible. ICG-VA permitted the transoptic aneurysm visualization and after clipping

**5.3 Flow measurement by microflow probe: principle and implementation in** 

Vascular micro-Dopplers are used in cerebral aneurysm surgery to indicate the flow velocity. They are easy to use and give the surgeon an acoustic signal feedback. The flow velocity is used as a surrogate of the flow quantity. Flow velocity is not the most reliable indicator for flow. Flow quantity is the most reliable flow measure. Till the 1990s, the intraoperative ultrasonic blood flow probes have been used to quantitatively measure flow only in cardiac, vascular, and transplant surgery. Charbel et al. in the University of Illinois at Chicago first reported in 1997 the implantation of the ultrasonic perivascular micro blood flow probes in the clipping

The first transit time flowmeters were described in 1962 and 1964 [32, 33]. Limitations in estimating vessel diameter, vessel misalignment, and an unstable zero calibration prevented medical applications [34]. In 1978 Drost et al. presented

ICG-VA application was extended in other pathologies [20–26].

**26**

the motor area is not routinely exposed during standard pterional approaches for anterior circulation aneurysms, and it is never exposed with mini invasive approaches. Direct electrical cortical stimulation might also increase the risk of epileptic seizures. For MEP monitoring transcranial electric stimulation is made by electrodes positioned at C1 and C2 according to the 10–20 International System (IS). These electrodes continuously stimulate the motor area during surgery by train stimuli (the pulse trains used are different according to the users; there are reported 4–8 pulse trains) [37, 43]. MEPs are recorded by subcutaneous needle electrodes from the abductor pollicis brevis and abductor hallucis muscles. The baseline MEPs are recorded at the beginning of the surgery, and it is found a compromise with the surgeon between continuous MEP recording and the movements caused by the stimuli tolerated by the surgeon for the dissection and clipping procedure. To avoid false-negative results on MEPs, the stimulus applied for MEP acquisition should be minimal not to activate the distal motor pathways [44]. To avoid false-positive results, brain shift due to the cerebrospinal loss after cisternal opening should be considered.

The reduction of 50% in MEP amplitude or MEP disappearance is considered as an alarm criterion. The surgeon changes the strategy to tempt to recover the MEPs. Temporary clipping is interrupted, or the definitive clip is released. The arterial blood pressure may be increased; local irrigation with saline and papaverine may be tempted. The surgical procedure is temporarily stopped, whenever it is possible (the aneurysm is not intraoperatively ruptured, or it is not opened by the surgeon) to permit the MEPs to recover. The MEP deterioration can be reversible, when the MEPs return to more than 50% of baseline amplitude.

Another methodology of MEP monitoring is by direct cortical stimulation.

Upper limb SSEPs are recorded from C3 and C4 by electrically stimulating the contralateral median nerve at the wrist. Lower limbs are recorded by electric stimulation of the contralateral tibial nerve at the medial malleolus. Recordings from Cz′ and Fz are made according to the 10–20 International System [37].

A total intravenous anesthesia (TIVA) is used. Neuromuscular blockers are not used during surgery, unless extremely necessary. Muscle relaxants are used only for endotracheal intubation.

An early experimental study by Branston et al. in 1974 showed that there is a failure of neuronal function in the cortex when the local blood flow falls below about 16 ml/100 g/min. This failure becomes manifest as a progressive reduction in the amplitude of the surface recorded SSEP, and this results in the abolition of the SSEPs if the flow is below about 12 ml/l00 g/min. There is a close relationship between reduced cerebral blood flow (CBF: 12–16 ml/100 g/min) and a reduction in SSEP amplitude or SSEP abolition [45].

MEP monitoring has higher diagnostic accuracy than SSEPs in predicting the occurrence of a postoperative neurological deficit [46].

Li et al. analyzed 92 patients operated for cerebral aneurysms that showed intraoperative MEP deterioration. They found that a MEP deterioration duration greater than or equal to 13 min in intracranial aneurysm surgery was significantly associated with postoperative motor deficits [43].

#### **7. Awake surgery in the surgery of intracranial aneurysms**

The principles of neuro-oncological monitoring are being gradually transferred to cerebral aneurysm surgery. In neuro-oncological surgery, the best way to monitor

**29**

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion...*

the neurological and neurophysiological function is by awake surgery. Awake surgery of cerebral aneurysms is controversial for the potential consequences of intraoperative aneurysm rupture. Intraoperative aneurysm rupture does not impact the clinical outcome. This would not be true if the clipping was performed in awake surgery. However, in selected case of clipping of the aneurysms of the dominant hemisphere, the monitoring of the language function and thus awake surgery would be useful. Abdulrauf et al. reported awake surgery in 30 unruptured cerebral aneurysms [47]. In three patients the strategy affected the outcome, since the removal of the temporary clipping determined the reversal of the clinical neurological and neurophysiological changes. One patient developed a neurological damage depending on the clipping, but that could not be reversed by the clip repositioning. Three patients developed hemiparesis without changes in MEPs; thus they were false negatives. The important was the visual testing after final clipping in four patients with internal carotid artery ophthalmic segment aneurysms, and one of these patients required repositioning of the clip. Three patients underwent an intraoperative vessel occlusion test, since the vessel occlusion was part of the

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

permanent treatment of the aneurysm.

**8.1 Endoscopic-assisted clipping**

**8.2 Endoscopic ICG-VA**

**8. Blind spot avoidance and mini invasive approaches**

endoscope use, not to cause iatrogenic damage [50].

perforating arteries hidden in blind spots.

endoscopic transcranial pure approaches.

**8.3 Pure endoscopic transcranial or endonasal**

The endoscope is mainly used as assistance during microsurgical clipping of intracranial aneurysms. The endoscopic-assisted microsurgery has been promoted by the father of the keyhole approaches Perneczky and by Fries [48]. The endoscope can be used for inspection before clipping; also clipping under endoscopic view and post clipping evaluation to observe the perforator integrity can be performed [49]. The endoscope allows the visualization of the blind spots to the microscope, allows thus the vision around corners, and enhances the visualization. It can potentially ameliorate the quality of treatment. The microscope enables vision in a straight line, while the endoscope enables the visualization of angles. The endoscope can be complementary to the microscope. However, the surgeon must be familiar with the

Endoscopic ICG-VA is an important development that combines the benefits of the vision behind the corners of endoscopy and the vessel visualization of ICG-VA [51]. The combination of both is particularly important for the visualization of the

Purely endoscopic approach to cerebral aneurysms is a potential method in its very beginning. There are case reports of endonasal clipping of aneurysms and of

Radovanovic reports a cadaveric study of a purely endoscopic transpterional port craniotomy to access lesions involving the cavernous sinus and the anterolateral skull base [52]. In the illustration videos, the author includes clipping of a middle cerebral artery aneurysm through this approach. There are also strictly selected case reports or small series of endoscopic endonasal clipping of anterior *Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion... DOI: http://dx.doi.org/10.5772/intechopen.91030*

the neurological and neurophysiological function is by awake surgery. Awake surgery of cerebral aneurysms is controversial for the potential consequences of intraoperative aneurysm rupture. Intraoperative aneurysm rupture does not impact the clinical outcome. This would not be true if the clipping was performed in awake surgery. However, in selected case of clipping of the aneurysms of the dominant hemisphere, the monitoring of the language function and thus awake surgery would be useful. Abdulrauf et al. reported awake surgery in 30 unruptured cerebral aneurysms [47]. In three patients the strategy affected the outcome, since the removal of the temporary clipping determined the reversal of the clinical neurological and neurophysiological changes. One patient developed a neurological damage depending on the clipping, but that could not be reversed by the clip repositioning. Three patients developed hemiparesis without changes in MEPs; thus they were false negatives. The important was the visual testing after final clipping in four patients with internal carotid artery ophthalmic segment aneurysms, and one of these patients required repositioning of the clip. Three patients underwent an intraoperative vessel occlusion test, since the vessel occlusion was part of the permanent treatment of the aneurysm.

#### **8. Blind spot avoidance and mini invasive approaches**

#### **8.1 Endoscopic-assisted clipping**

*Neurosurgical Procedures - Innovative Approaches*

opening should be considered.

endotracheal intubation.

SSEP amplitude or SSEP abolition [45].

occurrence of a postoperative neurological deficit [46].

**7. Awake surgery in the surgery of intracranial aneurysms**

associated with postoperative motor deficits [43].

MEPs return to more than 50% of baseline amplitude.

and Fz are made according to the 10–20 International System [37].

the motor area is not routinely exposed during standard pterional approaches for anterior circulation aneurysms, and it is never exposed with mini invasive approaches. Direct electrical cortical stimulation might also increase the risk of epileptic seizures. For MEP monitoring transcranial electric stimulation is made by electrodes positioned at C1 and C2 according to the 10–20 International System (IS). These electrodes continuously stimulate the motor area during surgery by train stimuli (the pulse trains used are different according to the users; there are reported 4–8 pulse trains) [37, 43]. MEPs are recorded by subcutaneous needle electrodes from the abductor pollicis brevis and abductor hallucis muscles. The baseline MEPs are recorded at the beginning of the surgery, and it is found a compromise with the surgeon between continuous MEP recording and the movements caused by the stimuli tolerated by the surgeon for the dissection and clipping procedure. To avoid false-negative results on MEPs, the stimulus applied for MEP acquisition should be minimal not to activate the distal motor pathways [44]. To avoid false-positive results, brain shift due to the cerebrospinal loss after cisternal

The reduction of 50% in MEP amplitude or MEP disappearance is considered as an alarm criterion. The surgeon changes the strategy to tempt to recover the MEPs. Temporary clipping is interrupted, or the definitive clip is released. The arterial blood pressure may be increased; local irrigation with saline and papaverine may be tempted. The surgical procedure is temporarily stopped, whenever it is possible (the aneurysm is not intraoperatively ruptured, or it is not opened by the surgeon) to permit the MEPs to recover. The MEP deterioration can be reversible, when the

Another methodology of MEP monitoring is by direct cortical stimulation. Upper limb SSEPs are recorded from C3 and C4 by electrically stimulating the contralateral median nerve at the wrist. Lower limbs are recorded by electric stimulation of the contralateral tibial nerve at the medial malleolus. Recordings from Cz′

A total intravenous anesthesia (TIVA) is used. Neuromuscular blockers are not used during surgery, unless extremely necessary. Muscle relaxants are used only for

An early experimental study by Branston et al. in 1974 showed that there is a failure of neuronal function in the cortex when the local blood flow falls below about 16 ml/100 g/min. This failure becomes manifest as a progressive reduction in the amplitude of the surface recorded SSEP, and this results in the abolition of the SSEPs if the flow is below about 12 ml/l00 g/min. There is a close relationship between reduced cerebral blood flow (CBF: 12–16 ml/100 g/min) and a reduction in

MEP monitoring has higher diagnostic accuracy than SSEPs in predicting the

The principles of neuro-oncological monitoring are being gradually transferred to cerebral aneurysm surgery. In neuro-oncological surgery, the best way to monitor

Li et al. analyzed 92 patients operated for cerebral aneurysms that showed intraoperative MEP deterioration. They found that a MEP deterioration duration greater than or equal to 13 min in intracranial aneurysm surgery was significantly

**28**

The endoscope is mainly used as assistance during microsurgical clipping of intracranial aneurysms. The endoscopic-assisted microsurgery has been promoted by the father of the keyhole approaches Perneczky and by Fries [48]. The endoscope can be used for inspection before clipping; also clipping under endoscopic view and post clipping evaluation to observe the perforator integrity can be performed [49]. The endoscope allows the visualization of the blind spots to the microscope, allows thus the vision around corners, and enhances the visualization. It can potentially ameliorate the quality of treatment. The microscope enables vision in a straight line, while the endoscope enables the visualization of angles. The endoscope can be complementary to the microscope. However, the surgeon must be familiar with the endoscope use, not to cause iatrogenic damage [50].

#### **8.2 Endoscopic ICG-VA**

Endoscopic ICG-VA is an important development that combines the benefits of the vision behind the corners of endoscopy and the vessel visualization of ICG-VA [51]. The combination of both is particularly important for the visualization of the perforating arteries hidden in blind spots.

#### **8.3 Pure endoscopic transcranial or endonasal**

Purely endoscopic approach to cerebral aneurysms is a potential method in its very beginning. There are case reports of endonasal clipping of aneurysms and of endoscopic transcranial pure approaches.

Radovanovic reports a cadaveric study of a purely endoscopic transpterional port craniotomy to access lesions involving the cavernous sinus and the anterolateral skull base [52]. In the illustration videos, the author includes clipping of a middle cerebral artery aneurysm through this approach. There are also strictly selected case reports or small series of endoscopic endonasal clipping of anterior circulation aneurysms [53]. Other case reports regard the pure endoscopic endonasal transclival approach for clipping of posterior circulation aneurysms [54]. These minimally invasive approaches constitute very limited experiences, and they need very deep expertise; otherwise they become dangerous. Safety must never be sacrificed for achieving minimal invasiveness.

#### **8.4 Exoscope**

Exoscopes are projected to combine the benefits of neurosurgical microscopes and endoscopes. With the exoscope, the surgeon looks at the monitor while operating, and the entire surgical team has the same view as the primary surgeon. The 3D 4K-HD exoscopes have favorable ergonomics to visualize angles maintaining the surgeon's comfort, maneuverability, and immersive visual experience. The assistant positioning relative to the surgeon can be problematic during surgery. ORBEYE (Olympus, Tokyo, Japan) exoscope has been used in aneurysm surgery with reported excellent visualization of the arterial tree [55], but with a subjective disadvantage in the visualization of bleeding tissue particularly in the muscle or white matter [56]. This new technology is proposed with advantages and limits, and time will tell its exact role in the future.

#### **9. Perforating artery evaluation**

The perforating arteries are small twigs of the main cerebral arteries that irrorate the paramedian region of the brainstem, the diencephalon, the basal ganglia, and the internal capsule [57]. Commonly, the perforators are small vessels of less than 1 mm in diameter, except for some lenticulostriate arteries (LSAs) and Heubner arteries larger than 1 mm. They may be multiple and sometimes anastomose. Although the same territory can be supplied by multiple perforators, the consequence of the occlusion of a perforator is unpredictable and more often than not results in a neurological deficit. Perforator infarction was shown as an independent risk factor of poor functional outcome in a series of anterior communicating aneurysms [58]. In the surgery of cerebral aneurysms, it is essential to preserve the perforating arteries. While the flow preservation of a larger artery is easier and eventually the flow can be replaced by revascularization, the perforator damage is more feared and less predictable. The monitoring of the perforators is fundamental. ICG-VA has the advantage of being able to visualize the perforating arteries. As a speculation, it is assumed that flowmetry and SSEPs account for the cortical gray matter function while the MEPs for the subcortical white matter function. Thus, MEPs can be used to evaluate the perforating artery function, and ICG-VA allows their visualization along with endoscopes, exoscopes, and endoscopic ICG-VA that permit the vision behind blind points.

#### **10. Complementary tools**

None of the tools described is superior to the others, and their role in improving clinical results in aneurysm surgery is complementary. Della Puppa et al. have described the complementary role of enhanced visualization with ICG-VA and maneuvers and signs to better interpret the data, along with monitoring of function (IONM) and perfusion (flowmetry) [37].

**31**

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion...*

**11. Quantitative magnetic resonance angiography and donor selection in** 

Quantitative magnetic resonance angiography (QMRA) is an MRA that permits blood flow quantification of the major cerebral vessels [59, 60]. QMRA is implemented with a commercially available software called Noninvasive Optimal Vessel Analysis (NOVA) (VasSol, Inc., Chicago, Illinois). MRA creates the cerebral vascular tree. A double-oblique scan is performed using a gated two-dimensional phase-contrast MRA imaged perpendicular to the vessel of interest axis. The software generates a flow report with the mean volumetric flow rate (mL/min) of the vessels of interest. QMRA data have been validated in vivo and have shown proportional differences, around 10% to direct transit time flow measurements [60]. QMRA is reported to be used preoperatively to evaluate the flow of the major vessels in patients with cerebral aneurysm that would require a bypass, when vessel sacrifice is needed to treat the aneurysm [42]. Intraoperatively a flow-based algorithm can be used to determine the flow needed to replace the flow sacrificed. Transit time flow measurements are used for intraoperative measurements. These measurements indicate which is the more appropriate donor graft to be used for the anastomosis. This methodology has shown that superficial temporal artery is often sufficient to replace flow, which renders the surgery easier than using vein or radial artery grafts. QMRA is used in follow-up to detect the bypass flow. The hemisphere flows are calculated and are maintained over time. Details of the algorithm used for calculation of the flow needed to be replaced and the donor flow potential can be

Lawton has rendered popular the intracranial-intracranial (IC-IC) bypass for flow replacement in complex aneurysms [61]. This type of bypass, although more elegant, has several pitfalls and requires very experienced surgeons. IC-IC bypass puts at dangers both the donor and receiving territories. The anastomosis is deep and more difficult to be performed. However, in selected cases and experienced

The ELANA has been developed for intracranial bypass without the need for temporary recipient occlusion. A sutureless variant of the ELANA—the SELANA slide—showed a preclinical success and clinical application started. Unfortunately,

Many technological innovations now assist the surgeon in the treatment of cerebral aneurysms. Also, different clips are used over the years. However, the clip principle has not changed. A change in occlusion strategy, based on principles other than clipping, might be desirable for the future. There is space for new ideas and new principles. The basic research studies for cerebral aneurysms are focused

**13. Sutureless excimer laser-assisted nonocclusive anastomosis** 

it was not shown suitable for clinical applications [62].

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

found in the paper by Rustemi et al. [42].

**12. Intracranial-intracranial bypass**

hands, it represents an advancement.

**(SELANA)**

**14. Future prospective**

**bypass surgery for flow replacement**

#### **11. Quantitative magnetic resonance angiography and donor selection in bypass surgery for flow replacement**

Quantitative magnetic resonance angiography (QMRA) is an MRA that permits blood flow quantification of the major cerebral vessels [59, 60]. QMRA is implemented with a commercially available software called Noninvasive Optimal Vessel Analysis (NOVA) (VasSol, Inc., Chicago, Illinois). MRA creates the cerebral vascular tree. A double-oblique scan is performed using a gated two-dimensional phase-contrast MRA imaged perpendicular to the vessel of interest axis. The software generates a flow report with the mean volumetric flow rate (mL/min) of the vessels of interest. QMRA data have been validated in vivo and have shown proportional differences, around 10% to direct transit time flow measurements [60]. QMRA is reported to be used preoperatively to evaluate the flow of the major vessels in patients with cerebral aneurysm that would require a bypass, when vessel sacrifice is needed to treat the aneurysm [42]. Intraoperatively a flow-based algorithm can be used to determine the flow needed to replace the flow sacrificed. Transit time flow measurements are used for intraoperative measurements. These measurements indicate which is the more appropriate donor graft to be used for the anastomosis. This methodology has shown that superficial temporal artery is often sufficient to replace flow, which renders the surgery easier than using vein or radial artery grafts. QMRA is used in follow-up to detect the bypass flow. The hemisphere flows are calculated and are maintained over time. Details of the algorithm used for calculation of the flow needed to be replaced and the donor flow potential can be found in the paper by Rustemi et al. [42].

#### **12. Intracranial-intracranial bypass**

Lawton has rendered popular the intracranial-intracranial (IC-IC) bypass for flow replacement in complex aneurysms [61]. This type of bypass, although more elegant, has several pitfalls and requires very experienced surgeons. IC-IC bypass puts at dangers both the donor and receiving territories. The anastomosis is deep and more difficult to be performed. However, in selected cases and experienced hands, it represents an advancement.

#### **13. Sutureless excimer laser-assisted nonocclusive anastomosis (SELANA)**

The ELANA has been developed for intracranial bypass without the need for temporary recipient occlusion. A sutureless variant of the ELANA—the SELANA slide—showed a preclinical success and clinical application started. Unfortunately, it was not shown suitable for clinical applications [62].

#### **14. Future prospective**

Many technological innovations now assist the surgeon in the treatment of cerebral aneurysms. Also, different clips are used over the years. However, the clip principle has not changed. A change in occlusion strategy, based on principles other than clipping, might be desirable for the future. There is space for new ideas and new principles. The basic research studies for cerebral aneurysms are focused

*Neurosurgical Procedures - Innovative Approaches*

sacrificed for achieving minimal invasiveness.

time will tell its exact role in the future.

**9. Perforating artery evaluation**

**8.4 Exoscope**

circulation aneurysms [53]. Other case reports regard the pure endoscopic endonasal transclival approach for clipping of posterior circulation aneurysms [54]. These minimally invasive approaches constitute very limited experiences, and they need very deep expertise; otherwise they become dangerous. Safety must never be

Exoscopes are projected to combine the benefits of neurosurgical microscopes and endoscopes. With the exoscope, the surgeon looks at the monitor while operating, and the entire surgical team has the same view as the primary surgeon. The 3D 4K-HD exoscopes have favorable ergonomics to visualize angles maintaining the surgeon's comfort, maneuverability, and immersive visual experience. The assistant positioning relative to the surgeon can be problematic during surgery. ORBEYE (Olympus, Tokyo, Japan) exoscope has been used in aneurysm surgery with reported excellent visualization of the arterial tree [55], but with a subjective disadvantage in the visualization of bleeding tissue particularly in the muscle or white matter [56]. This new technology is proposed with advantages and limits, and

The perforating arteries are small twigs of the main cerebral arteries that irrorate the paramedian region of the brainstem, the diencephalon, the basal ganglia, and the internal capsule [57]. Commonly, the perforators are small vessels of less than 1 mm in diameter, except for some lenticulostriate arteries (LSAs) and Heubner arteries larger than 1 mm. They may be multiple and sometimes anastomose. Although the same territory can be supplied by multiple perforators, the consequence of the occlusion of a perforator is unpredictable and more often than not results in a neurological deficit. Perforator infarction was shown as an independent risk factor of poor functional outcome in a series of anterior communicating aneurysms [58]. In the surgery of cerebral aneurysms, it is essential to preserve the perforating arteries. While the flow preservation of a larger artery is easier and eventually the flow can be replaced by revascularization, the perforator damage is more feared and less predictable. The monitoring of the perforators is fundamental. ICG-VA has the advantage of being able to visualize the perforating arteries. As a speculation, it is assumed that flowmetry and SSEPs account for the cortical gray matter function while the MEPs for the subcortical white matter function. Thus, MEPs can be used to evaluate the perforating artery function, and ICG-VA allows their visualization along with endoscopes, exoscopes, and endoscopic ICG-VA that permit the vision behind

None of the tools described is superior to the others, and their role in improving clinical results in aneurysm surgery is complementary. Della Puppa et al. have described the complementary role of enhanced visualization with ICG-VA and maneuvers and signs to better interpret the data, along with monitoring of function

**30**

blind points.

**10. Complementary tools**

(IONM) and perfusion (flowmetry) [37].

on wall analysis and flow stimulations. If advances will become more solid, in the future, cerebral aneurysms will not need neurosurgeons or neuroendovascular radiologists.

#### **15. Conclusions**

Surgery of cerebral aneurysms has advanced over the years. Innovations are rapid in this technological era. Many innovations are now routinely used in the clinical practice; others will be soon implemented. The technological innovations currently used in the surgery of cerebral aneurysms are summarized in this chapter. The comprehension of the biology and pathology might in the future render the aneurysm a medical disease.

#### **Conflict of interest**

Nothing to declare.

#### **Acronyms and abbreviations**


**33**

**Author details**

Oriela Rustemi1

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion…*

\*, Alessandro Della Puppa2,3 and Alba Scerrati4

3 Department of Neurosurgery, Neuroscience, Psychology, Pharmacology, and

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

4 Department of Neurosurgery, S. Anna University Hospital, Ferrara, Italy

1 Department of Neurosurgery, San Bortolo Hospital, Vicenza, Italy

Child Health, University of Florence, Careggi, Florence, Italy

\*Address all correspondence to: orielarustemi@libero.it

provided the original work is properly cited.

2 Department of Neurosurgery, University of Florence, Florence, Italy

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion… DOI: http://dx.doi.org/10.5772/intechopen.91030*

#### **Author details**

*Neurosurgical Procedures - Innovative Approaches*

radiologists.

**15. Conclusions**

aneurysm a medical disease.

**Conflict of interest**

Nothing to declare.

**Acronyms and abbreviations**

ICG indocyanine green NIR near-infrared

IS International System TIVA total intravenous anesthesia

CBF cerebral blood flow LSAs lenticulostriate arteries

SELANA sutureless ELANA

IC-IC intracranial-intracranial

IONM intraoperative neurophysiological monitoring

QMRA quantitative magnetic resonance angiography

ELANA excimer laser-assisted nonocclusive anastomosis

NOVA Noninvasive Optimal Vessel Analysis

ICG-VA indocyanine green video angiography

FDA Food and Drug Administration M4 distal middle cerebral artery MEPs motor evoked potentials

SSEPs somatosensory evoked potentials

on wall analysis and flow stimulations. If advances will become more solid, in the future, cerebral aneurysms will not need neurosurgeons or neuroendovascular

Surgery of cerebral aneurysms has advanced over the years. Innovations are rapid in this technological era. Many innovations are now routinely used in the clinical practice; others will be soon implemented. The technological innovations currently used in the surgery of cerebral aneurysms are summarized in this chapter. The comprehension of the biology and pathology might in the future render the

**32**

Oriela Rustemi1 \*, Alessandro Della Puppa2,3 and Alba Scerrati4

1 Department of Neurosurgery, San Bortolo Hospital, Vicenza, Italy

2 Department of Neurosurgery, University of Florence, Florence, Italy

3 Department of Neurosurgery, Neuroscience, Psychology, Pharmacology, and Child Health, University of Florence, Careggi, Florence, Italy

4 Department of Neurosurgery, S. Anna University Hospital, Ferrara, Italy

\*Address all correspondence to: orielarustemi@libero.it

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Raabe A, Beck J, Gerlach R, Zimmermann M, Seifert V. Nearinfrared indocyanine green video angiography: A new method for intraoperative assessment of vascular flow. Neurosurgery. 2003;**52**:132-139; discussion 139

[2] Rustemi O, Alaraj A, Shakur SF, Orning JL, Du X, Aletich VA, et al. Detection of unruptured intracranial aneurysms on noninvasive imaging. Is there still a role for digital subtraction angiography? Surgical Neurology International. 2015;**6**:175. DOI: 10.4103/2152-7806.170029

[3] Alexander TD, Macdonald RL, Weir B, Kowalczuk A. Intraoperative angiography in cerebral aneurysm surgery: A prospective study of 100 craniotomies. Neurosurgery. 1996;**39**:10-18

[4] Drake C, Allcock J. Postoperative angiography and the slipped clip. Journal of Neurosurgery. 1973;**39**:683-689

[5] Feuerberg I, Lindquist C, Lindqvist M, Steiner L. Natural history of postoperative aneurysm rests. Journal of Neurosurgery. 1987;**66**:30-34

[6] Macdonald RL, Wallace MC, Kestle JR. Role of angiography following aneurysm surgery. Journal of Neurosurgery. 1993;**79**:826-832

[7] Proust F, Hannequin D, Langlois O, Freger P, Creissard P. Causes of morbidity and mortality after ruptured aneurysm surgery in a series of 230 patients. The importance of control angiography. Stroke. 1995;**26**:1553-1557

[8] Rauzzino MJ, Quinn CM, Fisher WS. Angiography after aneurysm surgery: Indications for selective angiography. Surgical Neurology. 1998;**49**:32-40

[9] Samson D, Hodosh R, Reid W, Beyer CW, Clark WK. Risk of intracranial aneurysm surgery in the good grade patient: Early versus late operation. Neurosurgery. 1979;**5**:422-426

[10] Suzuki J, Kwak R, Katakura R. Review of incompletely occluded surgically treated cerebral aneurysms. Surgical Neurology. 1980;**13**:306-310

[11] Della Puppa A, Volpin F, Gioffre G, Rustemi O, Troncon I, Scienza R. Microsurgical clipping of intracranial aneurysms assisted by green indocyanine videoangiography (ICG-VA) and ultrasonic perivascular microflow probe measurement. Clinical Neurology and Neurosurgery. 2014;**116**:35-40. DOI: 10.1016/j. clineuro.2013.11.004

[12] Roessler K, Krawagna M, Dörfler A, Buchfelder M, Ganslandt O. Essentials in intraoperative indocyanine green videoangiography assessment for intracranial aneurysm surgery: Conclusions from 295 consecutively clipped aneurysms and review of the literature. Neurosurgical Focus. 2014;**36**:E7. DOI: 10.3171/2013.11. FOCUS13475

[13] Riva M, Amin-Hanjani S, Giussani C, De Witte O, Bruneau M. Indocyanine green videoangiography in aneurysm surgery: Systematic review and metaanalysis. Neurosurgery. 2018;**83**:166- 180. DOI: 10.1093/neuros/nyx387

[14] Gekka M, Nakayama N, Uchino H, Houkin K. Factors influencing cerebral aneurysm obliteration and reliability of indocyanine green video-angiography. Acta Neurochirurgica. 2018;**160**:269- 276. DOI: 10.1007/s00701-017-3379-6

[15] Della Puppa A, Rustemi O, Rossetto M, Gioffrè G, Munari M, Charbel FT, et al. The "squeezing

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*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion…*

Neurochirurgica. 2014;**156**:1419-1420. DOI: 10.1007/s00701-014-2001-4

[22] Della Puppa A, Rustemi O, Gioffrè G, Rolma G, Grandis M, Munari M, et al. Application of indocyanine green video angiography in parasagittal meningioma surgery. Neurosurgical Focus. 2014;**36**:E13. DOI:

10.3171/2013.12.FOCUS13385

s00701-016-2704-9

[25] Rustemi O, Scienza R, Della Puppa A. Utility of indocyanine green videoangiography in subcortical arteriovenous malformation resection. Neurosurgical Focus. 2017;**43**(Video Suppl 1):V10. DOI: 10.3171/2017.7.FocusVid.1774

[26] Scerrati A, Della Pepa GM, Conforti G, Sabatino G, Puca A, Albanese A, et al. Indocyanine green video-angiography in neurosurgery: A glance beyond vascular applications. Clinical Neurology and Neurosurgery. 2014;**124**:106-113. DOI: 10.1016/j.

[27] Hoffman WE, Charbel FT, Ausman JI. Cerebral blood flow and metabolic response to etomidate and ischemia. Neurological Research.

[28] Charbel FT, Hoffman WE, Misra M, Hannigan K, Ausman JI. Role of a perivascular ultrasonic micro-flow

clineuro.2014.06.032

1997;**19**:41-44

[23] Rustemi O, Scienza R, Della Puppa A. ICG-VA application in subtemporal transtentorial treatment of a Cognard V dural

arteriovenous fistula. Neurosurg Focus. 2016;**40**(Video Suppl 1):V7. DOI: 10.3171/2016.1.FocusVid.15423

[24] Rustemi O, Scienza R, Della Puppa A. Intra-operative devascularization of petroclival meningiomas by ICG-VAguided Bernasconi & Cassinari artery identification. Acta Neurochirurgica. 2016;**158**:427-428. DOI: 10.1007/

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

maneuver" in microsurgical clipping of intracranial aneurysms assisted by indocyanine green videoangiography. Neurosurgery. 2014;**10**:208-212; discussion 212-203. DOI: 10.1227/ NEU.0000000000000334

[16] Della Puppa A, Rustemi O,

[17] Della Puppa A, Rustemi O, Gioffrè G, Causin F, Scienza R. Transdural indocyanine green videoangiography of vascular malformations. Acta Neurochirurgica. 2014;**156**:1761- 1767. DOI: 10.1007/s00701-014-2164-z

[18] Rustemi O, Scienza R, Della Puppa A. Indocyanine green

videoangiography application in distal (M4) middle cerebral artery aneurysm surgery. Journal of Neurosurgical Sciences. 2017;**61**:351-354. DOI: 10.23736/S0390-5616.16.03271-9

[19] Rustemi O, Cester G, Causin F, Scienza R, Della Puppa A. Indocyanine green videoangiography transoptic visualization and clipping confirmation of an optic splitting ophthalmic artery aneurysm. World Neurosurgery. 2016;**90**:705.e5-705.e8. DOI: 10.1016/j.

[20] Della Puppa A, d'Avella E, Volpin F, Rustemi O, Gioffre' G, Scienza R. Indocyanine green videoangiography (ICG-VA) in parasagittal meningiomas surgery. Considerations on veins management and brain function preservation. Acta Neurochirurgica. 2013;**155**:1475-1476. DOI: 10.1007/s00701-013-1784-z

[21] Della Puppa A, Rustemi O, Gioffrè G. Is the intra-operative application of indocyanine green effective in retro-orbital surgery? Acta

wneu.2016.03.010

Scienza R. The "ICG Entrapment Sign" in cerebral aneurysm surgery assisted by indocyanine green videoangiography. World Neurosurgery. 2017;**97**:287-291. DOI: 10.1016/j.wneu.2016.10.011

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion… DOI: http://dx.doi.org/10.5772/intechopen.91030*

maneuver" in microsurgical clipping of intracranial aneurysms assisted by indocyanine green videoangiography. Neurosurgery. 2014;**10**:208-212; discussion 212-203. DOI: 10.1227/ NEU.0000000000000334

[16] Della Puppa A, Rustemi O, Scienza R. The "ICG Entrapment Sign" in cerebral aneurysm surgery assisted by indocyanine green videoangiography. World Neurosurgery. 2017;**97**:287-291. DOI: 10.1016/j.wneu.2016.10.011

[17] Della Puppa A, Rustemi O, Gioffrè G, Causin F, Scienza R. Transdural indocyanine green videoangiography of vascular malformations. Acta Neurochirurgica. 2014;**156**:1761- 1767. DOI: 10.1007/s00701-014-2164-z

[18] Rustemi O, Scienza R, Della Puppa A. Indocyanine green videoangiography application in distal (M4) middle cerebral artery aneurysm surgery. Journal of Neurosurgical Sciences. 2017;**61**:351-354. DOI: 10.23736/S0390-5616.16.03271-9

[19] Rustemi O, Cester G, Causin F, Scienza R, Della Puppa A. Indocyanine green videoangiography transoptic visualization and clipping confirmation of an optic splitting ophthalmic artery aneurysm. World Neurosurgery. 2016;**90**:705.e5-705.e8. DOI: 10.1016/j. wneu.2016.03.010

[20] Della Puppa A, d'Avella E, Volpin F, Rustemi O, Gioffre' G, Scienza R. Indocyanine green videoangiography (ICG-VA) in parasagittal meningiomas surgery. Considerations on veins management and brain function preservation. Acta Neurochirurgica. 2013;**155**:1475-1476. DOI: 10.1007/s00701-013-1784-z

[21] Della Puppa A, Rustemi O, Gioffrè G. Is the intra-operative application of indocyanine green effective in retro-orbital surgery? Acta Neurochirurgica. 2014;**156**:1419-1420. DOI: 10.1007/s00701-014-2001-4

[22] Della Puppa A, Rustemi O, Gioffrè G, Rolma G, Grandis M, Munari M, et al. Application of indocyanine green video angiography in parasagittal meningioma surgery. Neurosurgical Focus. 2014;**36**:E13. DOI: 10.3171/2013.12.FOCUS13385

[23] Rustemi O, Scienza R, Della Puppa A. ICG-VA application in subtemporal transtentorial treatment of a Cognard V dural arteriovenous fistula. Neurosurg Focus. 2016;**40**(Video Suppl 1):V7. DOI: 10.3171/2016.1.FocusVid.15423

[24] Rustemi O, Scienza R, Della Puppa A. Intra-operative devascularization of petroclival meningiomas by ICG-VAguided Bernasconi & Cassinari artery identification. Acta Neurochirurgica. 2016;**158**:427-428. DOI: 10.1007/ s00701-016-2704-9

[25] Rustemi O, Scienza R, Della Puppa A. Utility of indocyanine green videoangiography in subcortical arteriovenous malformation resection. Neurosurgical Focus. 2017;**43**(Video Suppl 1):V10. DOI: 10.3171/2017.7.FocusVid.1774

[26] Scerrati A, Della Pepa GM, Conforti G, Sabatino G, Puca A, Albanese A, et al. Indocyanine green video-angiography in neurosurgery: A glance beyond vascular applications. Clinical Neurology and Neurosurgery. 2014;**124**:106-113. DOI: 10.1016/j. clineuro.2014.06.032

[27] Hoffman WE, Charbel FT, Ausman JI. Cerebral blood flow and metabolic response to etomidate and ischemia. Neurological Research. 1997;**19**:41-44

[28] Charbel FT, Hoffman WE, Misra M, Hannigan K, Ausman JI. Role of a perivascular ultrasonic micro-flow

**34**

*Neurosurgical Procedures - Innovative Approaches*

[9] Samson D, Hodosh R, Reid W, Beyer CW, Clark WK. Risk of intracranial aneurysm surgery in the good grade patient: Early versus late operation. Neurosurgery.

[10] Suzuki J, Kwak R, Katakura R. Review of incompletely occluded surgically treated cerebral aneurysms. Surgical Neurology. 1980;**13**:306-310

[11] Della Puppa A, Volpin F, Gioffre G, Rustemi O, Troncon I, Scienza R. Microsurgical clipping of intracranial aneurysms assisted by green indocyanine videoangiography (ICG-VA) and ultrasonic perivascular microflow probe measurement. Clinical Neurology and Neurosurgery. 2014;**116**:35-40. DOI: 10.1016/j.

clineuro.2013.11.004

FOCUS13475

[12] Roessler K, Krawagna M, Dörfler A, Buchfelder M, Ganslandt O. Essentials in intraoperative indocyanine green videoangiography assessment for intracranial aneurysm surgery: Conclusions from 295 consecutively clipped aneurysms and review of the literature. Neurosurgical Focus. 2014;**36**:E7. DOI: 10.3171/2013.11.

[13] Riva M, Amin-Hanjani S, Giussani C, De Witte O, Bruneau M. Indocyanine green videoangiography in aneurysm surgery: Systematic review and metaanalysis. Neurosurgery. 2018;**83**:166- 180. DOI: 10.1093/neuros/nyx387

[14] Gekka M, Nakayama N, Uchino H, Houkin K. Factors influencing cerebral aneurysm obliteration and reliability of indocyanine green video-angiography. Acta Neurochirurgica. 2018;**160**:269- 276. DOI: 10.1007/s00701-017-3379-6

[15] Della Puppa A, Rustemi O, Rossetto M, Gioffrè G, Munari M, Charbel FT, et al. The "squeezing

1979;**5**:422-426

[1] Raabe A, Beck J, Gerlach R, Zimmermann M, Seifert V. Nearinfrared indocyanine green video angiography: A new method for intraoperative assessment of vascular flow. Neurosurgery. 2003;**52**:132-139;

[2] Rustemi O, Alaraj A, Shakur SF, Orning JL, Du X, Aletich VA, et al. Detection of unruptured intracranial aneurysms on noninvasive imaging. Is there still a role for digital subtraction angiography? Surgical Neurology International. 2015;**6**:175. DOI: 10.4103/2152-7806.170029

[3] Alexander TD, Macdonald RL, Weir B, Kowalczuk A. Intraoperative angiography in cerebral aneurysm surgery: A prospective study of 100 craniotomies. Neurosurgery.

[4] Drake C, Allcock J. Postoperative

Lindqvist M, Steiner L. Natural history of postoperative aneurysm rests. Journal

Kestle JR. Role of angiography following

[7] Proust F, Hannequin D, Langlois O,

ruptured aneurysm surgery in a series of 230 patients. The importance of control angiography. Stroke.

[8] Rauzzino MJ, Quinn CM, Fisher WS. Angiography after aneurysm surgery: Indications for selective angiography. Surgical Neurology. 1998;**49**:32-40

angiography and the slipped clip. Journal of Neurosurgery.

[5] Feuerberg I, Lindquist C,

of Neurosurgery. 1987;**66**:30-34

[6] Macdonald RL, Wallace MC,

Freger P, Creissard P. Causes of morbidity and mortality after

1995;**26**:1553-1557

aneurysm surgery. Journal of Neurosurgery. 1993;**79**:826-832

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1973;**39**:683-689

probe in aneurysm surgery. Neurologia Medico-Chirurgica (Tokyo). 1998;**38**(Suppl):35-38

[29] Charbel FT, Hoffman WE, Misra M, Ostergren L. Ultrasonic perivascular flow probe: Technique and application in neurosurgery. Neurological Research. 1998;**20**:439-442

[30] Charbel FT, Gonzales-Portillo G, Hoffman WE, Ostergren LA, Misra M. Quantitative assessment of vessel flow integrity for aneurysm surgery. Technical note. Journal of Neurosurgery. 1999;**91**:1050-1054

[31] Amin-Hanjani S, Meglio G, Gatto R, Bauer A, Charbel FT. The utility of intraoperative blood flow measurement during aneurysm surgery using an ultrasonic perivascular flow probe. Neurosurgery. 2006;**58**:ONS-305- ONS-312; discussion ONS-312

[32] Franklin DL, Ellis RS, Rushmer RF. Ultrasonic transit time flowmeter. IRE Trans Biomed Eng. 1962:44-49

[33] Plass KG. A new ultrasonic flowmeter for intravascular application. IEEE Transactions on Biomedical Engineering. 1964;**BME-ll**:154-156

[34] Lundell A, Bergqvist D, Mattsson E, Nilsson B. Volume blood flow measurements with a transit time flowmeter: An in vivo and in vitro variability and validation study. Clinical Physiology. 1993;**13**:547-557

[35] Drost CJ. Vessel diameterindependent volume flow measurements using ultrasound. Proceedings of San Diego Biomedical Symposium. 1978;**17**:299

[36] Barnes RJ, Comline RS, Dobson A, Drost CJ. An implantable transit-time ultrasonic blood flow-meter. The Journal of Physiology. 1983;**34**:2

[37] Della Puppa A, Rossetto M, Volpin F, Rustemi O, Grego A, Gerardi A, et al.

Microsurgical clipping of intracranial aneurysms assisted by neurophysiological monitoring, microvascular flow probe, and ICG-VA: Outcomes and intraoperative data on a multimodal strategy. World Neurosurgery. 2018;**113**:e336-e344. DOI: 10.1016/j. wneu.2018.02.029

[38] Pasqualin A, Meneghelli P, Musumeci A, Della Puppa A, Pavesi G, Pinna G, et al. Intraoperative measurement of arterial blood flow in aneurysm surgery. Acta Neurochirurgica. Supplement. 2018;**129**:43-52. DOI: 10.1007/978-3-319-73739-3\_7

[39] Della Puppa A, Scienza R, Rustemi O, Gioffré G. Can the efficacy of indocyanine green videoangiography in cerebral arterio-venous malformations surgery be further improved? Neurosurgery. 2014;**75**:E732-E734. DOI: 10.1227/ NEU.0000000000000531

[40] Della Puppa A, Rustemi O, Scienza R. Intraoperative flow measurement by microflow probe during surgery for brain arteriovenous malformations. Neurosurgery. 2015;**11**:268-273. DOI: 10.1227/ NEU.0000000000000741

[41] Della Puppa A, Rustemi O, Scienza R. Intraoperative flow measurement by microflow probe during spinal dural arteriovenous fistula surgery. World Neurosurgery. 2016;**89**:413-419. DOI: 10.1016/j. wneu.2016.02.043

[42] Rustemi O, Amin-Hanjani S, Shakur SF, Du X, Charbel FT. Donor selection in flow replacement bypass surgery for cerebral aneurysms: Quantitative analysis of long-term native donor flow sufficiency. Neurosurgery. 2016;**78**:332-341; discussion 341-342. DOI: 10.1227/ NEU.0000000000001074

**37**

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion…*

[50] Taniguchi M, Takimoto H, Yoshimine T, Shimada N, Miyao Y, Hirata M, et al. Application of a rigid endoscope to the microsurgical management of 54 cerebral aneurysms: Results in 48 patients. Journal of Neurosurgery. 1999;**91**:231-237

[51] Nishiyama Y, Kinouchi H, Senbokuya N, Kato T, Kanemaru K, Yoshioka H, et al. Endoscopic

10.3171/2012.5.JNS112300

JNS171898

[52] Andrade-Barazarte H, Patel K, Turel MK, Doglietto F, Agur A, Gentili F, et al. The endoscopic transpterional port approach:

[53] Xiao LM, Tang B, Xie SH, Huang GL, Wang ZG, Zeng EM, et al. Endoscopic endonasal clipping of anterior circulation aneurysm: Surgical techniques and results. World Neurosurgery. 2018;**115**:e33-e44. DOI:

10.1016/j.wneu.2018.03.093

onsE127-128. DOI: 10.1227/ NEU.0b013e318223b637

[54] Enseñat J, Alobid I, de Notaris M, Sanchez M, Valero R, Prats-Galino A, et al. Endoscopic endonasal clipping of a ruptured vertebral-posterior inferior cerebellar artery aneurysm: Technical case report. Neurosurgery. 2011;**69**:onsE121-onsE127; discussion

[55] Khalessi AA, Rahme R, Rennert RC, Borgas P, Steinberg JA, White TG, et al. First-in-man clinical experience using a high-definition 3-dimensional exoscope system for microneurosurgery. Operative Neurosurgery (Hagerstown).

Anatomy, technique, and initial clinical experience. Journal of Neurosurgery. 2019;**22**:1-11. DOI: 10.3171/2018.10.

indocyanine green video angiography in aneurysm surgery: An innovative method for intraoperative assessment of blood flow in vasculature hidden from microscopic view. Journal of Neurosurgery. 2012;**117**:302-308. DOI:

*DOI: http://dx.doi.org/10.5772/intechopen.91030*

[44] Guo L, Gelb AW. The use of motor evoked potential monitoring during cerebral aneurysm surgery to predict pure motor deficits due to subcortical ischemia. Clinical Neurophysiology.

Crockard HA, Pasztor E. Relationship between the cortical evoked potential and local cortical blood flow following acute middle cerebral artery occlusion

[46] Thomas B, Guo D. The diagnostic accuracy of evoked potential monitoring

[47] Abdulrauf SI, Vuong P, Patel R, Sampath R, Ashour AM, Germany LM, et al. "Awake" clipping of cerebral aneurysms: Report of initial series. Journal of Neurosurgery. 2017;**127**:311- 318. DOI: 10.3171/2015.12.JNS152140 Erratum in: J Neurosurg. 2017;127:445

[48] Perneczky A, Fries G. Endoscopeassisted brain surgery: Part 1— Evolution, basic concept, and current technique. Neurosurgery. 1998;**42**:219-

[49] Fischer G, Oertel J, Perneczky A. Endoscopy in aneurysm surgery. Neurosurgery. 2012;**70**:184-190; discussion 190-191. DOI: 10.1227/

224; discussion 224

NEU.0b013e3182376a36

[43] Li Z, Fan X, Wang M, Tao X, Qi L, Ling M, et al. Prediction of postoperative motor deficits using motor evoked potential deterioration duration in intracranial aneurysm surgery. Clinical Neurophysiology. 2019;**130**:707-713. DOI: 10.1016/j.

clinph.2019.02.010

2011;**122**:648-655

[45] Branston NM, Symon L,

in the baboon. Experimental Neurology. 1974;**45**:195-208. DOI: 10.1016/0014-4886(74)90112-5

techniques during intracranial aneurysm surgery for predicting postoperative ischemic damage: A systematic review and meta-analysis. World Neurosurgery. 2017;**103**:829-840. e3. DOI: 10.1016/j.wneu.2017.04.071

*Innovations in the Surgery of Cerebral Aneurysms: Enhanced Visualization, Perfusion… DOI: http://dx.doi.org/10.5772/intechopen.91030*

[43] Li Z, Fan X, Wang M, Tao X, Qi L, Ling M, et al. Prediction of postoperative motor deficits using motor evoked potential deterioration duration in intracranial aneurysm surgery. Clinical Neurophysiology. 2019;**130**:707-713. DOI: 10.1016/j. clinph.2019.02.010

*Neurosurgical Procedures - Innovative Approaches*

probe in aneurysm surgery. Neurologia

Microsurgical clipping of intracranial aneurysms assisted by neurophysiological

monitoring, microvascular flow probe, and ICG-VA: Outcomes and intraoperative data on a multimodal strategy. World Neurosurgery. 2018;**113**:e336-e344. DOI: 10.1016/j.

[38] Pasqualin A, Meneghelli P, Musumeci A, Della Puppa A, Pavesi G, Pinna G, et al. Intraoperative measurement of arterial blood flow in aneurysm surgery. Acta Neurochirurgica. Supplement. 2018;**129**:43-52. DOI: 10.1007/978-3-319-73739-3\_7

[39] Della Puppa A, Scienza R,

further improved? Neurosurgery. 2014;**75**:E732-E734. DOI: 10.1227/ NEU.0000000000000531

[40] Della Puppa A, Rustemi O, Scienza R. Intraoperative flow measurement by microflow probe during surgery for brain arteriovenous

malformations. Neurosurgery. 2015;**11**:268-273. DOI: 10.1227/ NEU.0000000000000741

[41] Della Puppa A, Rustemi O, Scienza R. Intraoperative flow measurement by microflow probe during spinal dural arteriovenous fistula surgery. World Neurosurgery. 2016;**89**:413-419. DOI: 10.1016/j.

[42] Rustemi O, Amin-Hanjani S, Shakur SF, Du X, Charbel FT. Donor selection in flow replacement bypass surgery for cerebral aneurysms: Quantitative analysis of long-term native donor flow sufficiency. Neurosurgery. 2016;**78**:332-341; discussion 341-342. DOI: 10.1227/ NEU.0000000000001074

wneu.2016.02.043

in cerebral arterio-venous malformations surgery be

Rustemi O, Gioffré G. Can the efficacy of indocyanine green videoangiography

wneu.2018.02.029

[29] Charbel FT, Hoffman WE, Misra M, Ostergren L. Ultrasonic perivascular flow probe: Technique and application in neurosurgery. Neurological Research.

[30] Charbel FT, Gonzales-Portillo G,

[31] Amin-Hanjani S, Meglio G, Gatto R, Bauer A, Charbel FT. The utility of intraoperative blood flow measurement during aneurysm surgery using an ultrasonic perivascular flow probe. Neurosurgery. 2006;**58**:ONS-305- ONS-312; discussion ONS-312

[32] Franklin DL, Ellis RS, Rushmer RF. Ultrasonic transit time flowmeter. IRE

flowmeter for intravascular application. IEEE Transactions on Biomedical Engineering. 1964;**BME-ll**:154-156

Mattsson E, Nilsson B. Volume blood flow measurements with a transit time flowmeter: An in vivo and in vitro variability and validation study. Clinical

[36] Barnes RJ, Comline RS, Dobson A, Drost CJ. An implantable transit-time ultrasonic blood flow-meter. The Journal of Physiology. 1983;**34**:2

[37] Della Puppa A, Rossetto M, Volpin F, Rustemi O, Grego A, Gerardi A, et al.

Trans Biomed Eng. 1962:44-49

[33] Plass KG. A new ultrasonic

[34] Lundell A, Bergqvist D,

Physiology. 1993;**13**:547-557

Symposium. 1978;**17**:299

[35] Drost CJ. Vessel diameterindependent volume flow measurements using ultrasound. Proceedings of San Diego Biomedical

Hoffman WE, Ostergren LA, Misra M. Quantitative assessment of vessel flow integrity for aneurysm surgery. Technical note. Journal of Neurosurgery. 1999;**91**:1050-1054

Medico-Chirurgica (Tokyo). 1998;**38**(Suppl):35-38

1998;**20**:439-442

**36**

[44] Guo L, Gelb AW. The use of motor evoked potential monitoring during cerebral aneurysm surgery to predict pure motor deficits due to subcortical ischemia. Clinical Neurophysiology. 2011;**122**:648-655

[45] Branston NM, Symon L, Crockard HA, Pasztor E. Relationship between the cortical evoked potential and local cortical blood flow following acute middle cerebral artery occlusion in the baboon. Experimental Neurology. 1974;**45**:195-208. DOI: 10.1016/0014-4886(74)90112-5

[46] Thomas B, Guo D. The diagnostic accuracy of evoked potential monitoring techniques during intracranial aneurysm surgery for predicting postoperative ischemic damage: A systematic review and meta-analysis. World Neurosurgery. 2017;**103**:829-840. e3. DOI: 10.1016/j.wneu.2017.04.071

[47] Abdulrauf SI, Vuong P, Patel R, Sampath R, Ashour AM, Germany LM, et al. "Awake" clipping of cerebral aneurysms: Report of initial series. Journal of Neurosurgery. 2017;**127**:311- 318. DOI: 10.3171/2015.12.JNS152140 Erratum in: J Neurosurg. 2017;127:445

[48] Perneczky A, Fries G. Endoscopeassisted brain surgery: Part 1— Evolution, basic concept, and current technique. Neurosurgery. 1998;**42**:219- 224; discussion 224

[49] Fischer G, Oertel J, Perneczky A. Endoscopy in aneurysm surgery. Neurosurgery. 2012;**70**:184-190; discussion 190-191. DOI: 10.1227/ NEU.0b013e3182376a36

[50] Taniguchi M, Takimoto H, Yoshimine T, Shimada N, Miyao Y, Hirata M, et al. Application of a rigid endoscope to the microsurgical management of 54 cerebral aneurysms: Results in 48 patients. Journal of Neurosurgery. 1999;**91**:231-237

[51] Nishiyama Y, Kinouchi H, Senbokuya N, Kato T, Kanemaru K, Yoshioka H, et al. Endoscopic indocyanine green video angiography in aneurysm surgery: An innovative method for intraoperative assessment of blood flow in vasculature hidden from microscopic view. Journal of Neurosurgery. 2012;**117**:302-308. DOI: 10.3171/2012.5.JNS112300

[52] Andrade-Barazarte H, Patel K, Turel MK, Doglietto F, Agur A, Gentili F, et al. The endoscopic transpterional port approach: Anatomy, technique, and initial clinical experience. Journal of Neurosurgery. 2019;**22**:1-11. DOI: 10.3171/2018.10. JNS171898

[53] Xiao LM, Tang B, Xie SH, Huang GL, Wang ZG, Zeng EM, et al. Endoscopic endonasal clipping of anterior circulation aneurysm: Surgical techniques and results. World Neurosurgery. 2018;**115**:e33-e44. DOI: 10.1016/j.wneu.2018.03.093

[54] Enseñat J, Alobid I, de Notaris M, Sanchez M, Valero R, Prats-Galino A, et al. Endoscopic endonasal clipping of a ruptured vertebral-posterior inferior cerebellar artery aneurysm: Technical case report. Neurosurgery. 2011;**69**:onsE121-onsE127; discussion onsE127-128. DOI: 10.1227/ NEU.0b013e318223b637

[55] Khalessi AA, Rahme R, Rennert RC, Borgas P, Steinberg JA, White TG, et al. First-in-man clinical experience using a high-definition 3-dimensional exoscope system for microneurosurgery. Operative Neurosurgery (Hagerstown).

2019;**16**:717-725. DOI: 10.1093/ons/ opy320

[56] Langer DJ, White TG, Schulder M, Boockvar JA, Labib M, Lawton MT. Advances in intraoperative optics: A brief review of current exoscope platforms. Operative Neurosurgery (Hagerstown). 2019. pii: opz276. DOI: 10.1093/ons/opz276

[57] Djulejić V, Marinković S, Milić V, Georgievski B, Rašić M, Aksić M, et al. Common features of the cerebral perforating arteries and their clinical significance. Acta Neurochirurgica. 2015;**157**:743-754; discussion 754. DOI: 10.1007/s00701-015-2378-8

[58] Yamamoto Y, Fukuda H, Yamada D, Kurosaki Y, Handa A, Lo B, et al. Association of perforator infarction with clinical courses and outcomes following surgical clipping of ruptured anterior communicating artery aneurysms. World Neurosurgery. 2017;**107**:724-731. DOI: 10.1016/j. wneu.2017.08.086

[59] Zhao M, Charbel FT, Alperin N, Loth F, Clark ME. Improved phasecontrast flow quantification by three-dimensional vessel localization. Magnetic Resonance Imaging. 2000;**18**:697-706

[60] Calderon-Arnulphi M, Amin-Hanjani S, Alaraj A, Zhao M, Du X, Ruland S, et al. In vivo evaluation of quantitative MR angiography in a canine carotid artery stenosis model. AJNR. American Journal of Neuroradiology. 2011;**32**:1552-1559. DOI: 10.3174/ajnr.A2546

[61] Abla AA, Lawton MT. Anterior cerebral artery bypass for complex aneurysms: An experience with intracranial-intracranial reconstruction and review of bypass options. Journal of Neurosurgery. 2014;**120**:1364-1377. DOI: 10.3171/2014.3.JNS132219

[62] van Doormaal TPC, de Boer B, Redegeld S, van Thoor S, Tulleken CAF, van der Zwan A. Preclinical success but clinical failure of the sutureless excimer laser-assisted non-occlusive anastomosis (SELANA) slide. Acta Neurochirurgica. 2018;**160**:2159-2167. DOI: 10.1007/s00701-018-3686-6

**39**

**Chapter 3**

Role of Cranioplasty in

Management of Chiari

Chiari malformations (CM) are a set of enigmatic congenital anomalies, owing

to their complex pathology, varied presentations and management dilemma. Because of the daunting nature of this disease, a universal definitive treatment protocol is yet to be established. Diverse surgical procedures are in practice with various philosophies, aiming to resolve different sections of the pathologies of this disorder, either singly or in combination. However, outcomes are quite variable. Though not a well-recognized and commonly practiced paradigm of managing CM, different techniques of cranioplasty for CM has been described by many authors with variable rates of success. Cranioplasty for Chiari has been found to be helpful in different circumstances with the objective to address different predicaments. Initially, it has been exercised as one of the modalities to manage some particular situations, mostly in cases to solve complications following surgery. Now in some centers, different types of methods of cranioplasty are practiced routinely to treat particular set of Chiari patients with specifically set criteria and some have shown success in those certain scenarios. In this chapter, different methods of cranioplasty for Chiari malformation by different authors, strategies behind the techniques and their results are described in brief. "Stealth cranioplasty", a technique devised by

**Keywords:** Chiari malformation, posterior fossa volume, posterior fossa

Hans Chiari analytically described his eponymous subset of patients of Chiari malformation (CM) first in 1891. In his subsequent article on CM in 1896, he elaborated the entity and added a new type to his previously described three types. He only described his findings and gave two theories to relate the findings to probable pathogenesis. He thought that the herniation is a result of congenital hydrocephalus, which is a chronic one with early onset that displaces the neural structures through the foramen magnum (FM) into the spinal canal [1]. But that is actually not the case always. The other possibility that he thought of was inadequate bone growth and insufficient enlargement of skull triggering raised intracranial pressure (ICP) leading to force down the hindbrain. Later, with advancements of technologies and further research, Chiari's latter hypothesis appears to be impressively a precise one [1–4]. Some other scientists around that period of Chiari, like Cleland

Malformation

*Asifur Rahman*

our team is also portrayed.

decompression, cranioplasty

**1. Introduction**

**Abstract**

#### **Chapter 3**

*Neurosurgical Procedures - Innovative Approaches*

[62] van Doormaal TPC, de Boer B, Redegeld S, van Thoor S, Tulleken CAF, van der Zwan A. Preclinical success but clinical failure of the sutureless excimer laser-assisted non-occlusive anastomosis (SELANA) slide. Acta Neurochirurgica. 2018;**160**:2159-2167. DOI: 10.1007/s00701-018-3686-6

2019;**16**:717-725. DOI: 10.1093/ons/

[56] Langer DJ, White TG, Schulder M, Boockvar JA, Labib M, Lawton MT. Advances in intraoperative optics: A brief review of current exoscope platforms. Operative Neurosurgery (Hagerstown). 2019. pii: opz276. DOI:

[57] Djulejić V, Marinković S, Milić V, Georgievski B, Rašić M, Aksić M, et al. Common features of the cerebral perforating arteries and their clinical significance. Acta Neurochirurgica. 2015;**157**:743-754; discussion 754. DOI:

[58] Yamamoto Y, Fukuda H, Yamada D, Kurosaki Y, Handa A, Lo B, et al. Association of perforator infarction with clinical courses and outcomes following surgical clipping of ruptured

10.1007/s00701-015-2378-8

anterior communicating artery aneurysms. World Neurosurgery. 2017;**107**:724-731. DOI: 10.1016/j.

[59] Zhao M, Charbel FT, Alperin N, Loth F, Clark ME. Improved phasecontrast flow quantification by three-dimensional vessel localization.

Magnetic Resonance Imaging.

DOI: 10.3174/ajnr.A2546

10.3171/2014.3.JNS132219

[60] Calderon-Arnulphi M, Amin-Hanjani S, Alaraj A, Zhao M, Du X, Ruland S, et al. In vivo evaluation of quantitative MR angiography in a canine carotid artery stenosis model. AJNR. American Journal of Neuroradiology. 2011;**32**:1552-1559.

[61] Abla AA, Lawton MT. Anterior cerebral artery bypass for complex aneurysms: An experience with

intracranial-intracranial reconstruction and review of bypass options. Journal of Neurosurgery. 2014;**120**:1364-1377. DOI:

wneu.2017.08.086

2000;**18**:697-706

opy320

10.1093/ons/opz276

**38**

## Role of Cranioplasty in Management of Chiari Malformation

*Asifur Rahman*

#### **Abstract**

Chiari malformations (CM) are a set of enigmatic congenital anomalies, owing to their complex pathology, varied presentations and management dilemma. Because of the daunting nature of this disease, a universal definitive treatment protocol is yet to be established. Diverse surgical procedures are in practice with various philosophies, aiming to resolve different sections of the pathologies of this disorder, either singly or in combination. However, outcomes are quite variable. Though not a well-recognized and commonly practiced paradigm of managing CM, different techniques of cranioplasty for CM has been described by many authors with variable rates of success. Cranioplasty for Chiari has been found to be helpful in different circumstances with the objective to address different predicaments. Initially, it has been exercised as one of the modalities to manage some particular situations, mostly in cases to solve complications following surgery. Now in some centers, different types of methods of cranioplasty are practiced routinely to treat particular set of Chiari patients with specifically set criteria and some have shown success in those certain scenarios. In this chapter, different methods of cranioplasty for Chiari malformation by different authors, strategies behind the techniques and their results are described in brief. "Stealth cranioplasty", a technique devised by our team is also portrayed.

**Keywords:** Chiari malformation, posterior fossa volume, posterior fossa decompression, cranioplasty

#### **1. Introduction**

Hans Chiari analytically described his eponymous subset of patients of Chiari malformation (CM) first in 1891. In his subsequent article on CM in 1896, he elaborated the entity and added a new type to his previously described three types. He only described his findings and gave two theories to relate the findings to probable pathogenesis. He thought that the herniation is a result of congenital hydrocephalus, which is a chronic one with early onset that displaces the neural structures through the foramen magnum (FM) into the spinal canal [1]. But that is actually not the case always. The other possibility that he thought of was inadequate bone growth and insufficient enlargement of skull triggering raised intracranial pressure (ICP) leading to force down the hindbrain. Later, with advancements of technologies and further research, Chiari's latter hypothesis appears to be impressively a precise one [1–4]. Some other scientists around that period of Chiari, like Cleland

in 1883 and Mennicke in 1891 described about hindbrain herniation and also advocated that the pathology lies in the defective bone around the foramen magnum, which supports the theory of the pathogenesis originating from the small posterior cranial fossa (PCF) [5, 6]. Though, these earlier studies were based on observations of autopsy findings, these theories still are very much contemporary, as verified by the findings of the modern technologies of recent times. However, Chiari or other researchers of his time did not think of solving the problem.

For this puzzling condition, surgery was not contemplated till 1930, when Cornelis Joachimus Van Houweninge Graftdijk, first attempted surgery for CM on a patient with myelomeningocele and ventriculogram-proven hindbrain herniation. He tried to restore better flow of cerebrospinal fluid (CSF) around the craniovertebral junction (CVJ) by widening the space through which the redundant cerebellar tissue had herniated [7]. Since then, attempts to solve the problem of CM by surgery are being practiced and many procedures have been devised and various modifications have been made.

From the very beginning of surgical endeavors, disputes regarding management of CM are a continuing issue of debate because of its intricate and perplexing character. The pathophysiology of syringomyelia (SM) that often exist with CM, seems to be identical and gives the opportunity to solve both with a common procedure, as both CM and SM share the common pathology [8]. The commonest surgical practice for Chiari malformation type 1 (CM1), the commonest of the Chiari malformations, and SM is a simple posterior fossa decompression with the removal of part of posterior arch of C1 combined with variations in the next steps. Reconstruction of the posterior fossa (PF) by cranioplasty is not a routine procedure following posterior fossa decompression (PFD) for the CM1. Many authors described posterior fossa reconstruction with cranioplasty following PFD in many ways with different philosophies. In this chapter, we will discuss the different procedures of cranioplasties performed in surgery for CM1 along with the concepts behind those with elaboration of our thoughts while we do cranioplasty in our technique.

#### **2. Common surgical approaches for Chiari malformation**

Development of CM results from developmental anomaly of the occipital bone, rendering the posterior fossa small and shallow, which, along with other factors, leads to herniation of the normal neural elements through the foramen magnum. To reach a unanimous management protocol for CM is challenging owing to the nature of the disorder, its diverse clinical presentations and inexplicable image findings. Depending on presentation in milder forms of symptoms, some authors have advocated conservative management. Nonetheless, surgical intervention remains the gold standard for most of the symptomatic CMs, both in reduction of tonsilar herniation and reestablishment of CSF dynamics around the CVJ; and ultimately in overall outcome. Surgical procedures are many for CM, but no definite single procedure is accepted universally. Keeping the basic techniques identical, many forms and variations are adopted in the procedures and are practiced in different combinations. For many years after Van Houweninge Graftdijk first attempted to treat CM surgically, surgery carried a grave prognosis. At present, with better understanding of the pathology and advances in technology, most patients with CM1 can be benefited by surgical procedures.

The common practice in all surgical approaches is a suboccipital craniectomy with removal of posterior arch of C1. However, there are disagreements and wide range of variations regarding the extent of bone removal and different additional measures taken along with. For management of CM1, dura can be addressed in different ways like leaving the dura intact with removal of the constricting bands only [9], scoring of

**41**

*Role of Cranioplasty in Management of Chiari Malformation*

**3. An overview of cranioplasties for Chiari malformation**

for CM with philosophies behind those are portrayed here.

maintain normal CSF flow around the foramen magnum.

**3.1 "Expansive suboccipital cranioplasty" by Tokuno et al.**

The very first portrayal of cranioplasty designed for surgery of Chiari malformation found in English literature is by Tokuno et al. in 1987, when they described their technique for treating patients of CM with SM [39]. Till then, the commonest and most popular operative technique of surgery for Chiari was based on the theories of Gardner and William. Tokuno et al. operated on 38 patients over 10 years between 1976 and 1986. A total of 31 out of 38 patients of their series had syringomyelia. In the last 2 years of their study, they carried out an "expansive suboccipital cranioplasty" on their last 17 patients, in addition to Gardner's operation. With the goal of expanding the posterior fossa, they did cranioplasty with autologous suboccipital bone and an iliac bone graft, creating a larger suboccipital bone flap measuring about 5 × 3 × 0.5 cm in size. They followed up all the 38 patients for 1–10 years post-operatively. The addition of "expansive suboccipital cranioplasty" to Gardner's operation resulted in substantially better result in comparison to Gardner's operation alone, with 82% and 67% of good recovery, respectively. Following expansive suboccipital cranioplasty, symptoms of the patients also seemed to improve more rapidly, though a very few patients had transient worsening. By their new operative method, they wanted to obtain a full decompression of the posterior fossa to

As there was no regular use of MRI for screening or diagnosing CM or SM at that time, they could not measure the volume of the posterior fossa in all of their patients.

the dura [10, 11], resection of the outer layer of the dura [12–14], opening the dura and keeping it remain open [15–17], and performing duraplasty with different materials, both natural and artificial [13, 18–24]. The arachnoid manipulation equally differs from leaving it intact by doing an arachnoid preserving durotomy or arachnoid preserving duraplasty [9, 25–27], to opening and resecting it to remove adhesions [8, 19, 23, 28–30]. Dealing the cerebellar tonsils also vary like not touching them [27, 31], separating them by dissection [28, 32], shrinking by bipolar coagulation [13, 19, 23, 33, 34] or carrying out a subpial resection [8, 19, 35, 36]. Recently, minimal invasive endoscopy assisted decompression at the foramen magnum for CM have also been reported [37, 38].

Cranioplasty is not an uncommon procedure in neurosurgery for different conditions. In CM1 surgery, cranioplasty is not a generally prescribed regular technique and thus is not practiced frequently. Most of the times, this is done to manage complications related to routine surgeries for CM1 and sometimes for other types of CM. Whatever the reason is, those who do cranioplasty during CM1 surgery have their own philosophies and the techniques have evolved around the basic pathology of development of CM1 or the complications following regular surgery. Various operative methods for CM and SM have been reported and their efficacy either singly or in combinations in management of CM is still debatable. Most of the authors who practice cranioplasty for the treatment of CM have the theory in their minds that the basic pathology lays in the erroneous architecture of the posterior fossa. Most believe that the posterior fossa is less roomy than the volume of normal neural structures which attributes to herniation of the tonsils through the foramen magnum as well as resulting in disequilibrium of the CSF flow and dynamics between the cranial and the spinal CSF compartments. In some instances, cranioplasty is done routinely in selected cases of CM1. A chronology of cranioplasty procedures

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Neurosurgical Procedures - Innovative Approaches*

modifications have been made.

researchers of his time did not think of solving the problem.

**2. Common surgical approaches for Chiari malformation**

Development of CM results from developmental anomaly of the occipital bone, rendering the posterior fossa small and shallow, which, along with other factors, leads to herniation of the normal neural elements through the foramen magnum. To reach a unanimous management protocol for CM is challenging owing to the nature of the disorder, its diverse clinical presentations and inexplicable image findings. Depending on presentation in milder forms of symptoms, some authors have advocated conservative management. Nonetheless, surgical intervention remains the gold standard for most of the symptomatic CMs, both in reduction of tonsilar herniation and reestablishment of CSF dynamics around the CVJ; and ultimately in overall outcome. Surgical procedures are many for CM, but no definite single procedure is accepted universally. Keeping the basic techniques identical, many forms and variations are adopted in the procedures and are practiced in different combinations. For many years after Van Houweninge Graftdijk first attempted to treat CM surgically, surgery carried a grave prognosis. At present, with better understanding of the pathology and advances in technology, most patients with CM1 can be benefited by surgical procedures.

The common practice in all surgical approaches is a suboccipital craniectomy with removal of posterior arch of C1. However, there are disagreements and wide range of variations regarding the extent of bone removal and different additional measures taken along with. For management of CM1, dura can be addressed in different ways like leaving the dura intact with removal of the constricting bands only [9], scoring of

in 1883 and Mennicke in 1891 described about hindbrain herniation and also advocated that the pathology lies in the defective bone around the foramen magnum, which supports the theory of the pathogenesis originating from the small posterior cranial fossa (PCF) [5, 6]. Though, these earlier studies were based on observations of autopsy findings, these theories still are very much contemporary, as verified by the findings of the modern technologies of recent times. However, Chiari or other

For this puzzling condition, surgery was not contemplated till 1930, when Cornelis Joachimus Van Houweninge Graftdijk, first attempted surgery for CM on a patient with myelomeningocele and ventriculogram-proven hindbrain herniation. He tried to restore better flow of cerebrospinal fluid (CSF) around the craniovertebral junction (CVJ) by widening the space through which the redundant cerebellar tissue had herniated [7]. Since then, attempts to solve the problem of CM by surgery are being practiced and many procedures have been devised and various

From the very beginning of surgical endeavors, disputes regarding management of CM are a continuing issue of debate because of its intricate and perplexing character. The pathophysiology of syringomyelia (SM) that often exist with CM, seems to be identical and gives the opportunity to solve both with a common procedure, as both CM and SM share the common pathology [8]. The commonest surgical practice for Chiari malformation type 1 (CM1), the commonest of the Chiari malformations, and SM is a simple posterior fossa decompression with the removal of part of posterior arch of C1 combined with variations in the next steps. Reconstruction of the posterior fossa (PF) by cranioplasty is not a routine procedure following posterior fossa decompression (PFD) for the CM1. Many authors described posterior fossa reconstruction with cranioplasty following PFD in many ways with different philosophies. In this chapter, we will discuss the different procedures of cranioplasties performed in surgery for CM1 along with the concepts behind those with elaboration of our thoughts while we do cranioplasty in our technique.

**40**

the dura [10, 11], resection of the outer layer of the dura [12–14], opening the dura and keeping it remain open [15–17], and performing duraplasty with different materials, both natural and artificial [13, 18–24]. The arachnoid manipulation equally differs from leaving it intact by doing an arachnoid preserving durotomy or arachnoid preserving duraplasty [9, 25–27], to opening and resecting it to remove adhesions [8, 19, 23, 28–30]. Dealing the cerebellar tonsils also vary like not touching them [27, 31], separating them by dissection [28, 32], shrinking by bipolar coagulation [13, 19, 23, 33, 34] or carrying out a subpial resection [8, 19, 35, 36]. Recently, minimal invasive endoscopy assisted decompression at the foramen magnum for CM have also been reported [37, 38].

#### **3. An overview of cranioplasties for Chiari malformation**

Cranioplasty is not an uncommon procedure in neurosurgery for different conditions. In CM1 surgery, cranioplasty is not a generally prescribed regular technique and thus is not practiced frequently. Most of the times, this is done to manage complications related to routine surgeries for CM1 and sometimes for other types of CM. Whatever the reason is, those who do cranioplasty during CM1 surgery have their own philosophies and the techniques have evolved around the basic pathology of development of CM1 or the complications following regular surgery. Various operative methods for CM and SM have been reported and their efficacy either singly or in combinations in management of CM is still debatable. Most of the authors who practice cranioplasty for the treatment of CM have the theory in their minds that the basic pathology lays in the erroneous architecture of the posterior fossa. Most believe that the posterior fossa is less roomy than the volume of normal neural structures which attributes to herniation of the tonsils through the foramen magnum as well as resulting in disequilibrium of the CSF flow and dynamics between the cranial and the spinal CSF compartments. In some instances, cranioplasty is done routinely in selected cases of CM1. A chronology of cranioplasty procedures for CM with philosophies behind those are portrayed here.

#### **3.1 "Expansive suboccipital cranioplasty" by Tokuno et al.**

The very first portrayal of cranioplasty designed for surgery of Chiari malformation found in English literature is by Tokuno et al. in 1987, when they described their technique for treating patients of CM with SM [39]. Till then, the commonest and most popular operative technique of surgery for Chiari was based on the theories of Gardner and William. Tokuno et al. operated on 38 patients over 10 years between 1976 and 1986. A total of 31 out of 38 patients of their series had syringomyelia. In the last 2 years of their study, they carried out an "expansive suboccipital cranioplasty" on their last 17 patients, in addition to Gardner's operation. With the goal of expanding the posterior fossa, they did cranioplasty with autologous suboccipital bone and an iliac bone graft, creating a larger suboccipital bone flap measuring about 5 × 3 × 0.5 cm in size. They followed up all the 38 patients for 1–10 years post-operatively. The addition of "expansive suboccipital cranioplasty" to Gardner's operation resulted in substantially better result in comparison to Gardner's operation alone, with 82% and 67% of good recovery, respectively. Following expansive suboccipital cranioplasty, symptoms of the patients also seemed to improve more rapidly, though a very few patients had transient worsening. By their new operative method, they wanted to obtain a full decompression of the posterior fossa to maintain normal CSF flow around the foramen magnum.

As there was no regular use of MRI for screening or diagnosing CM or SM at that time, they could not measure the volume of the posterior fossa in all of their patients. However, based on radiological and intra-operative observations of 32% of their patients having narrow posterior fossa, they came to a conclusion that there is disproportion between the suboccipital cavity and the infratentorial content. They also had the premonition that, even if the suboccipital space seems to be normal, the infratentorial component might be relatively too large for that. They devised their procedure with the intention to remodel the neural structures back to a normal physiology by enlarging the posterior fossa through "expansive suboccipital cranioplasty".

#### **3.2 "Expansive suboccipital cranioplasty" by Sakamoto et al.**

In 1999, after 12 years of the first report of cranioplasty for Chiari by Tokuno et al., Sakamoto et al. from the same university hospital of Osaka City reported a procedure of cranioplasty for surgery of CM1 associated with SM with some modifications of the procedure of their predecessors. They also termed their technique "expansive suboccipital cranioplasty" (ESC) [40]. Relatively high incidence of postoperative complications and deterioration following the most practiced Gardner's operation, instigated them to devise their technique. During the period between 1985 and 1996, they divided their patients into 2 groups with 20 patients in each group. One group consisted of the patients who underwent ESC together with opening of the foramen of Magendie and plugging of the obex (ESC + PO) from 1985 to 1990 and the other consisted of another 20 patients who underwent ESC but without any intra-arachnoidal procedures between 1991 and 1996.

Their technique of ESC comprised of a large suboccipital osteoplastic craniotomy extending from the FM inferiorly to the margin of the transverse sinus superiorly and 5 cm from the midline laterally on each side along with an osteoplastic laminotomy of the atlas. The FM was enlarged and arachnoid preserving dural opening was carried out ensuring absence of any arachnoid adhesion at the major cistern by intra-operative ultrasound. Duraplasty was done with pericranium. For enlargement of the posterior fossa, the harvested occipital bone flap was fashioned to be expanded by joining the preserved part of the atlas and graft harvested from the outer layer of the cranium at the external protuberance or from the iliac bone. The newly crafted bone flap was then restored and fixed over the craniotomy gap to cover the major cistern. Dural tacking with the bone flap was done to widen the CSF space around the major cistern.

Post-operative MRI revealed enlargement of the major cistern and the whole subarachnoid space of the posterior fossa and reduction of the syrinx size and length in all 40 patients irrespective of clinical improvement. All the 20 patients who underwent ESC, had neurological improvement after surgery without recurrence, while 17 patients improved neurologically and 3 remained unchanged in the ESC + PO group. Based on the theory of a small posterior fossa that may trigger CM and SM, they developed the ESC, targeting to enlarge the small posterior fossa and to obtain a sufficient flow of CSF. They postulated that intra-arachnoid procedures are not necessary to facilitate restoration of CSF flow as by expanding the posterior cranial fossa, the CSF spaces are enlarged and the craniospinal pressure dissociation is also reduced. They also had the impression that the major cistern can be effectively kept open by tacking the dura to the overlying bone flap. They furthermore postulated that ESC can prevent cerebellar slump despite a large craniotomy by avoiding adhesion of the caudal surface of the cerebellum to the dura.

#### **3.3 "Partial suboccipital cranioplasty" by Holly and Batzdorf**

Cerebellar ptosis (CP) is not an uncommon occurrence that usually results from too large a craniectomy for CM, which often can potentially refute the desired

**43**

extrathecal CSF shunts.

their devised technique successfully.

*Role of Cranioplasty in Management of Chiari Malformation*

outcome of the surgery. In 2001, Holly and Batzdorf reported partial suboccipital cranioplasty with or without intradural exploration for cerebellar ptosis following

Aiming to treat CP following PFD for CM1 effectively, they developed their technique and implemented that on four of the seven symptomatic CP patients. These patients presented with symptoms from 9 months to 17 years following initial surgery. Of the four patients, two patients underwent re-exploration with reduction of the tonsils, pericranial duraplasty and partial suboccipital cranioplasty with hydroxyapatite (HA) in one and with methylmethacrylate (MMA) in the other. Rest of the two patients underwent extradural exploration of the suboccipital craniectomy and partial suboccipital cranioplasty with MMA. All the four patients, who had partial suboccipital cranioplasty with or without intradural exploration produced rewarding results. With their crescent-shaped partial suboccipital cranioplasty the previous 4 × 4 cm suboccipital craniectomies were transformed into approximately 2 × 2 cm ones. To secure the prosthesis, they grooved the contiguous

Most of these patients of cerebellar sag present with headache and neurological deficits due to persistent obstruction of CSF flow around the CVJ leading to disturbance in CSF flow dynamics. Usually, too large a craniectomy leads to CP, and from that they philosophized that decompression of the posterior fossa extensively is unnecessary to treat a pathology that is primarily around the level of the foramen magnum. They felt that the initial craniectomies were nearly twice as large as necessary and lessened the opening to approximately 2 × 2 cm in all. They basically had the aim to make the posterior fossa as roomy as possible to reestablish the CSF flow dynamics around the FM back to normal without hampering the support for the cerebellum and suggested that enough bone should be left to support the greatest diameter of the cerebellum as a bony supportive shelf. The use of MMA or HA for the cranioplasty was chosen as prosthesis as because these materials can be fixed in place without any additional hardware. Partial suboccipital cranioplasty was successful in treating the headache by supporting the cerebellum and alleviating

bone edges with high speed drill and injected MMA into the grooves.

stretching the dura mater with reversal of the CSF flow obstruction.

**3.4 "Supratentorial cranial enlargement" by Di Rocco and Velardi**

Chiari malformation is generally a congenital anomaly, but CM can be an acquired event as well. Some literatures in recent time have highlighted the role of the cranio-spinal pressure differential across the foramen magnum in pathogenesis of Acquired Chiari type-1 malformation (ACM1). In 2003, Di Rocco and Velardi drew attention to a different dimension in development of acquired ACM1 in patients that had surgery for raised ICP resulting from causes other than congenital HCP and they treated these patients in their technique [42]. They described two cases of symptomatic ACM1 following lumbo-peritoneal shunt and cystoventriculo-peritoneal shunt for pseudotumor cerebri and suprasellar arachnoid cyst, respectively, in two adolescents. They hypothesized that secondary craniocephalic disproportion plays a substantial role in the genesis of ACM1 in patients having

Both of their patients remained asymptomatic following the initial shunting procedures. However, both became symptomatic after a long interval and MRI revealed ACM1 in both the patients. Di Rocco and Velardi did surgery upon them in

They devised a method of supratentorial cranial decompression by expansive cranioplasty with autologous bone. In their procedure, two parietal bone flaps were made on each side of the sagittal suture. The bone flaps were then raised to augment

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

suboccipital craniectomy for CM [41].

#### *Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Neurosurgical Procedures - Innovative Approaches*

space around the major cistern.

However, based on radiological and intra-operative observations of 32% of their patients having narrow posterior fossa, they came to a conclusion that there is disproportion between the suboccipital cavity and the infratentorial content. They also had the premonition that, even if the suboccipital space seems to be normal, the infratentorial component might be relatively too large for that. They devised their procedure with the intention to remodel the neural structures back to a normal physiology by

enlarging the posterior fossa through "expansive suboccipital cranioplasty".

but without any intra-arachnoidal procedures between 1991 and 1996.

Their technique of ESC comprised of a large suboccipital osteoplastic craniotomy extending from the FM inferiorly to the margin of the transverse sinus superiorly and 5 cm from the midline laterally on each side along with an osteoplastic laminotomy of the atlas. The FM was enlarged and arachnoid preserving dural opening was carried out ensuring absence of any arachnoid adhesion at the major cistern by intra-operative ultrasound. Duraplasty was done with pericranium. For enlargement of the posterior fossa, the harvested occipital bone flap was fashioned to be expanded by joining the preserved part of the atlas and graft harvested from the outer layer of the cranium at the external protuberance or from the iliac bone. The newly crafted bone flap was then restored and fixed over the craniotomy gap to cover the major cistern. Dural tacking with the bone flap was done to widen the CSF

Post-operative MRI revealed enlargement of the major cistern and the whole subarachnoid space of the posterior fossa and reduction of the syrinx size and length in all 40 patients irrespective of clinical improvement. All the 20 patients who underwent ESC, had neurological improvement after surgery without recurrence, while 17 patients improved neurologically and 3 remained unchanged in the ESC + PO group. Based on the theory of a small posterior fossa that may trigger CM and SM, they developed the ESC, targeting to enlarge the small posterior fossa and to obtain a sufficient flow of CSF. They postulated that intra-arachnoid procedures are not necessary to facilitate restoration of CSF flow as by expanding the posterior cranial fossa, the CSF spaces are enlarged and the craniospinal pressure dissociation is also reduced. They also had the impression that the major cistern can be effectively kept open by tacking the dura to the overlying bone flap. They furthermore postulated that ESC can prevent cerebellar slump despite a large craniotomy by

avoiding adhesion of the caudal surface of the cerebellum to the dura.

Cerebellar ptosis (CP) is not an uncommon occurrence that usually results from

too large a craniectomy for CM, which often can potentially refute the desired

**3.3 "Partial suboccipital cranioplasty" by Holly and Batzdorf**

In 1999, after 12 years of the first report of cranioplasty for Chiari by Tokuno et al., Sakamoto et al. from the same university hospital of Osaka City reported a procedure of cranioplasty for surgery of CM1 associated with SM with some modifications of the procedure of their predecessors. They also termed their technique "expansive suboccipital cranioplasty" (ESC) [40]. Relatively high incidence of postoperative complications and deterioration following the most practiced Gardner's operation, instigated them to devise their technique. During the period between 1985 and 1996, they divided their patients into 2 groups with 20 patients in each group. One group consisted of the patients who underwent ESC together with opening of the foramen of Magendie and plugging of the obex (ESC + PO) from 1985 to 1990 and the other consisted of another 20 patients who underwent ESC

**3.2 "Expansive suboccipital cranioplasty" by Sakamoto et al.**

**42**

outcome of the surgery. In 2001, Holly and Batzdorf reported partial suboccipital cranioplasty with or without intradural exploration for cerebellar ptosis following suboccipital craniectomy for CM [41].

Aiming to treat CP following PFD for CM1 effectively, they developed their technique and implemented that on four of the seven symptomatic CP patients. These patients presented with symptoms from 9 months to 17 years following initial surgery. Of the four patients, two patients underwent re-exploration with reduction of the tonsils, pericranial duraplasty and partial suboccipital cranioplasty with hydroxyapatite (HA) in one and with methylmethacrylate (MMA) in the other. Rest of the two patients underwent extradural exploration of the suboccipital craniectomy and partial suboccipital cranioplasty with MMA. All the four patients, who had partial suboccipital cranioplasty with or without intradural exploration produced rewarding results. With their crescent-shaped partial suboccipital cranioplasty the previous 4 × 4 cm suboccipital craniectomies were transformed into approximately 2 × 2 cm ones. To secure the prosthesis, they grooved the contiguous bone edges with high speed drill and injected MMA into the grooves.

Most of these patients of cerebellar sag present with headache and neurological deficits due to persistent obstruction of CSF flow around the CVJ leading to disturbance in CSF flow dynamics. Usually, too large a craniectomy leads to CP, and from that they philosophized that decompression of the posterior fossa extensively is unnecessary to treat a pathology that is primarily around the level of the foramen magnum. They felt that the initial craniectomies were nearly twice as large as necessary and lessened the opening to approximately 2 × 2 cm in all. They basically had the aim to make the posterior fossa as roomy as possible to reestablish the CSF flow dynamics around the FM back to normal without hampering the support for the cerebellum and suggested that enough bone should be left to support the greatest diameter of the cerebellum as a bony supportive shelf. The use of MMA or HA for the cranioplasty was chosen as prosthesis as because these materials can be fixed in place without any additional hardware. Partial suboccipital cranioplasty was successful in treating the headache by supporting the cerebellum and alleviating stretching the dura mater with reversal of the CSF flow obstruction.

#### **3.4 "Supratentorial cranial enlargement" by Di Rocco and Velardi**

Chiari malformation is generally a congenital anomaly, but CM can be an acquired event as well. Some literatures in recent time have highlighted the role of the cranio-spinal pressure differential across the foramen magnum in pathogenesis of Acquired Chiari type-1 malformation (ACM1). In 2003, Di Rocco and Velardi drew attention to a different dimension in development of acquired ACM1 in patients that had surgery for raised ICP resulting from causes other than congenital HCP and they treated these patients in their technique [42]. They described two cases of symptomatic ACM1 following lumbo-peritoneal shunt and cystoventriculo-peritoneal shunt for pseudotumor cerebri and suprasellar arachnoid cyst, respectively, in two adolescents. They hypothesized that secondary craniocephalic disproportion plays a substantial role in the genesis of ACM1 in patients having extrathecal CSF shunts.

Both of their patients remained asymptomatic following the initial shunting procedures. However, both became symptomatic after a long interval and MRI revealed ACM1 in both the patients. Di Rocco and Velardi did surgery upon them in their devised technique successfully.

They devised a method of supratentorial cranial decompression by expansive cranioplasty with autologous bone. In their procedure, two parietal bone flaps were made on each side of the sagittal suture. The bone flaps were then raised to augment the supratentorial cranial volume. For sustained elevated position of the bone flaps in order to maintain the enlarged cranial dimension, two small blocks of bone harvested from the posterior parietal margin of the bone flaps were placed between the bone flap and the margin of the craniotomy adjacent to the medial border. Cosmetic aspect of the expanding craniotomy to maintain precise contour of the calvarial surface was meticulously taken care of.

There were marked improvements of the symptoms of both the patients. Headache and papilledema in the first patient and diplopia, papilledema, retinal hemorrhage, headache, mild right hemiparesis and mild dysmetria of the left upper limb in the second patient—all subsided. Post-operative MRI showed significant regression of tonsillar caudal descent in both the patients.

Pathogenesis of ACM1 is most likely multifactorial and its development following extrathecal shunts can be explained by the "craniospinal pressure gradient" theory and the "cephalocranial disproportion" theory. They theorized from their observations that placement of the extrathecal shunt in children leads to cessation of cranial growth as well as results in progressive thickening of the cranial vault by inner apposition of bone, which spans for years. Further observation of upward displacement of the upper cerebellar vermis to lodge upward into the quadrigeminal cistern along with the caudal herniation of the cerebellar tonsils, firmly establishes the fact of overcrowding of the neural structures within the posterior cranial fossa. When cephalocranial disproportion is the main factor responsible for ACM1 in these cases, it was logical for them to go for the cranial expansion as a whole to create more supratentorial intracranial space by autologous bone cranioplasty to dismiss the cephalocranial disproportion, which yielded satisfactory result. This alleviated the need for manipulation of the shunts as well.

#### **3.5 "One-stage posterior decompression and fusion" by Nishikwawa et al.**

In 2004, Nishikwawa et al. came with their method of one stage expansive cranioplasty with autologous bone and rigid occipitocervical fixation for CM1 associated with various degrees of other anomalies in two patients [43]. Their patients presented with various symptoms like occipitalgia, chest pain and numbness from face to both hands. Radiologically, there were occipitalization of the atlas, mild form of AAD, ventral compression of the cervicomedullary junction by the basilar invagination, Chiari malformation and syringomyelia Additionally, the second patient had possible slump of the cerebellum following foramen magnum decompression with small craniectomy and splitting the dura elsewhere 12 years previously.

A large suboccipital osteoplastic craniotomy in the first case and extension of the previous suboccipital craniectomy in the second case was performed. Ultasonographic confirmation of pulsation of the tonsils was done to ensure adequate decompression. Safety of the screw insertion was verified from preoperative and peroperative simulation by computerized navigation system for two cervical transarticular screws through the lateral mass of the axis into the lateral mass of the occipitalized atlas in patient 1 and into the pedicle of the axis in patient 2. Guide holes along the diploic space on the margin of the craniotomy in the 1st patient and oblique burr hole at the margin of the craniotomy on each side in the 2nd patient were made. Rigid occipitoaxial fixation was accomplished by connecting the diploic screws to the pedicle or transarticular screws with a rod on each side. The autologous bone flap was secured with titanium wires. Finally, dural tacking sutures connecting the dura to the overlying bone were done.

Both the patients had remarkable recovery of their symptoms with notable expansion of the posterior fossa with an enlarged CSF space in MRI and good fusion

**45**

*Role of Cranioplasty in Management of Chiari Malformation*

reduced position is mandatory for successful fusion.

**3.6 "Simple technique for expansive suboccipital cranioplasty"** 

reinforced with fibrin glue, was done to complete the cranioplasty.

**3.7 "Cranioplasty using hydroxyapatite implants" by Itoh et al.**

Itoh et al. described a procedure of cranioplasty with a curved plate of Hydroxyapatite for Treatment of Syringomyelia associated with Chiari I

Malformation, in 2001 [46]. They applied their method on eight patients diagnosed on basis of clinical examinations and neuroradiological findings of MRI and 3D-CT over a period of 19 months. All patients had varying degrees of sensory discomfort of the extremities with the mean duration of symptoms for 40 months. The most frequent complaint was unilateral dysesthesia in the upper extremity. MRI revealed

of the bone flap on the bony defect.

of the grafted bones in 3D CT scan. They innovated the technique of simultaneous occipitocervical fusion in addition to their regularly practiced method of posterior fossa decompression and expansive cranioplasty for implantation of screw in the occipital diploic space for stabilization and fusion of occipitocervical instability in Chiari patients with syrinx, basilar invagination and AAD. They opined that diploic screws can be used safely for occipital fixation irrespective of the size of the suboccipital craniectomy and in cases of mobile and partially or completely reducible atlantoaxial dislocation. However, a synchronized stabilization in the optimally

Takayasu et al. made posterior fossa reconstruction simpler and easier by autologous cranioplasty for CM with SM and described this procedure on 14 patients in 2001 and on 16 patients in 2004 [44, 45]. The basic idea of this method was also to expand the volume of the PCF, thus they too call it expansive suboccipital cranioplasty like their preceding Japanese colleagues. They performed their procedures on patients of syringomyelia associated with Chiari I malformation since 1992. Different symptoms and signs in their patients included sensory disturbances, motor weakness, brainstem and/or cerebellar signs and intractable pain.

In their simpler procedure, they first did an en bloc upper suboccipital craniotomy, keeping the foramen magnum margin intact. Under the microscope with the help of air drill, Kerrison punches and rongeurs, the posterior bony margin of the FM is removed. The C1 posterior arch is removed to the maximum along with the upper part of the C2 lamina if the tonsils extended beyond C2. Arachnoid preserving duraplasty with fascia lata was done. The thick internal crista of the occipital bone flap is removed and the flap is shaped to fit the lower portion of the craniectomy gap to cover the FM. Expansive cranioplasty is accomplished by fixing the tailored bone flap with titanium miniplates. In some cases, the flap was replaced inside-out to buy more space and to have a better fit. Tacking of the dural graft with the bone graft and packing of bone chips into the upper craniectomy defect,

All the patients improved clinically significantly within a few weeks of surgery, except 2. Both had persistent dysesthetic pain, one of whom improved within several months. In follow-up of more than 1 year most of the patients showed marked improvement in terms of ascent of tonsils and resolution of size of syringes. They did the cranioplasty with the intension to prevent complications like pseudomeningocele and CSF leakage by providing support for the dural closure. Furthermore, posterior fossa reconstruction has the potential to prevent relapse of symptoms from restenosis of the cisterna magna, cerebellar ptosis and wound depression. Their method is simpler than the others as this only needs repositioning

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

**by Takayasu et al.**

#### *Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Neurosurgical Procedures - Innovative Approaches*

surface was meticulously taken care of.

regression of tonsillar caudal descent in both the patients.

alleviated the need for manipulation of the shunts as well.

sutures connecting the dura to the overlying bone were done.

**3.5 "One-stage posterior decompression and fusion" by Nishikwawa et al.**

In 2004, Nishikwawa et al. came with their method of one stage expansive cranioplasty with autologous bone and rigid occipitocervical fixation for CM1 associated with various degrees of other anomalies in two patients [43]. Their patients presented with various symptoms like occipitalgia, chest pain and numbness from face to both hands. Radiologically, there were occipitalization of the atlas, mild form of AAD, ventral compression of the cervicomedullary junction by the basilar invagination, Chiari malformation and syringomyelia Additionally, the second patient had possible slump of the cerebellum following foramen magnum decompression with small craniectomy and splitting the dura elsewhere

A large suboccipital osteoplastic craniotomy in the first case and extension of the previous suboccipital craniectomy in the second case was performed. Ultasonographic confirmation of pulsation of the tonsils was done to ensure adequate decompression. Safety of the screw insertion was verified from preoperative and peroperative simulation by computerized navigation system for two cervical transarticular screws through the lateral mass of the axis into the lateral mass of the occipitalized atlas in patient 1 and into the pedicle of the axis in patient 2. Guide holes along the diploic space on the margin of the craniotomy in the 1st patient and oblique burr hole at the margin of the craniotomy on each side in the 2nd patient were made. Rigid occipitoaxial fixation was accomplished by connecting the diploic screws to the pedicle or transarticular screws with a rod on each side. The autologous bone flap was secured with titanium wires. Finally, dural tacking

Both the patients had remarkable recovery of their symptoms with notable expansion of the posterior fossa with an enlarged CSF space in MRI and good fusion

the supratentorial cranial volume. For sustained elevated position of the bone flaps in order to maintain the enlarged cranial dimension, two small blocks of bone harvested from the posterior parietal margin of the bone flaps were placed between the bone flap and the margin of the craniotomy adjacent to the medial border. Cosmetic aspect of the expanding craniotomy to maintain precise contour of the calvarial

There were marked improvements of the symptoms of both the patients. Headache and papilledema in the first patient and diplopia, papilledema, retinal hemorrhage, headache, mild right hemiparesis and mild dysmetria of the left upper limb in the second patient—all subsided. Post-operative MRI showed significant

Pathogenesis of ACM1 is most likely multifactorial and its development following extrathecal shunts can be explained by the "craniospinal pressure gradient" theory and the "cephalocranial disproportion" theory. They theorized from their observations that placement of the extrathecal shunt in children leads to cessation of cranial growth as well as results in progressive thickening of the cranial vault by inner apposition of bone, which spans for years. Further observation of upward displacement of the upper cerebellar vermis to lodge upward into the quadrigeminal cistern along with the caudal herniation of the cerebellar tonsils, firmly establishes the fact of overcrowding of the neural structures within the posterior cranial fossa. When cephalocranial disproportion is the main factor responsible for ACM1 in these cases, it was logical for them to go for the cranial expansion as a whole to create more supratentorial intracranial space by autologous bone cranioplasty to dismiss the cephalocranial disproportion, which yielded satisfactory result. This

**44**

12 years previously.

of the grafted bones in 3D CT scan. They innovated the technique of simultaneous occipitocervical fusion in addition to their regularly practiced method of posterior fossa decompression and expansive cranioplasty for implantation of screw in the occipital diploic space for stabilization and fusion of occipitocervical instability in Chiari patients with syrinx, basilar invagination and AAD. They opined that diploic screws can be used safely for occipital fixation irrespective of the size of the suboccipital craniectomy and in cases of mobile and partially or completely reducible atlantoaxial dislocation. However, a synchronized stabilization in the optimally reduced position is mandatory for successful fusion.

#### **3.6 "Simple technique for expansive suboccipital cranioplasty" by Takayasu et al.**

Takayasu et al. made posterior fossa reconstruction simpler and easier by autologous cranioplasty for CM with SM and described this procedure on 14 patients in 2001 and on 16 patients in 2004 [44, 45]. The basic idea of this method was also to expand the volume of the PCF, thus they too call it expansive suboccipital cranioplasty like their preceding Japanese colleagues. They performed their procedures on patients of syringomyelia associated with Chiari I malformation since 1992. Different symptoms and signs in their patients included sensory disturbances, motor weakness, brainstem and/or cerebellar signs and intractable pain.

In their simpler procedure, they first did an en bloc upper suboccipital craniotomy, keeping the foramen magnum margin intact. Under the microscope with the help of air drill, Kerrison punches and rongeurs, the posterior bony margin of the FM is removed. The C1 posterior arch is removed to the maximum along with the upper part of the C2 lamina if the tonsils extended beyond C2. Arachnoid preserving duraplasty with fascia lata was done. The thick internal crista of the occipital bone flap is removed and the flap is shaped to fit the lower portion of the craniectomy gap to cover the FM. Expansive cranioplasty is accomplished by fixing the tailored bone flap with titanium miniplates. In some cases, the flap was replaced inside-out to buy more space and to have a better fit. Tacking of the dural graft with the bone graft and packing of bone chips into the upper craniectomy defect, reinforced with fibrin glue, was done to complete the cranioplasty.

All the patients improved clinically significantly within a few weeks of surgery, except 2. Both had persistent dysesthetic pain, one of whom improved within several months. In follow-up of more than 1 year most of the patients showed marked improvement in terms of ascent of tonsils and resolution of size of syringes.

They did the cranioplasty with the intension to prevent complications like pseudomeningocele and CSF leakage by providing support for the dural closure. Furthermore, posterior fossa reconstruction has the potential to prevent relapse of symptoms from restenosis of the cisterna magna, cerebellar ptosis and wound depression. Their method is simpler than the others as this only needs repositioning of the bone flap on the bony defect.

#### **3.7 "Cranioplasty using hydroxyapatite implants" by Itoh et al.**

Itoh et al. described a procedure of cranioplasty with a curved plate of Hydroxyapatite for Treatment of Syringomyelia associated with Chiari I Malformation, in 2001 [46]. They applied their method on eight patients diagnosed on basis of clinical examinations and neuroradiological findings of MRI and 3D-CT over a period of 19 months. All patients had varying degrees of sensory discomfort of the extremities with the mean duration of symptoms for 40 months. The most frequent complaint was unilateral dysesthesia in the upper extremity. MRI revealed

tonsillar herniation and syrinx of various degrees and extents. Phase-contrast cine-MRI displayed absence of CSF flow in the retrotonsillar subarachnoid space and to-and-fro drift within the syrinx.

In their technique, they first did foramen magnum decompression by a suboccipital craniectomy as in other procedures along with C1 laminectomy in seven cases and did C1 and C2 upper dome laminectomies in one case. In three cases, they did duraplasty with Gore-Tex membrane and resected the outer layer of the dura in five cases. Cranioplasty to cover the craniectomy gap as well as to expand the posterior fossa was performed using HA implants in all cases. They did tenting of the dura or the duraplasty with the implants in all cases.

In a mean follow-up period of 13.3-months, five patients improved and three patients remained unchanged. Postoperative syrinx resolution was seen in seven patients on MRI. HA cranioplasty had to be removed in one patient because of development of an epidural abscess, but this patient had no further neurological deterioration. Six months after surgery, 3D-CT revealed the HA implant to be integrated with the adjacent occipital bone. They used HA, as a substitute for autologous bone grafts, for expansive cranioplasty to enlarge small posterior fossa to establish better CSF flow at the major cistern. The use of HA was to reduce the chance of absorption of the autologous bone in the long run if used for cranioplasty. Moreover, it is technically easy to use the HA implants. The idea of tenting the dura with the cranioplasty was to inhibit the retention of CSF at epidural space following surgery.

#### **3.8 "Simple and safe method of cranial reconstruction" by Sheikh et al.**

In 2006, Sheikh et al. described a simple method of cranioplasty that they applied for posterior fossa reconstruction for many procedures including Chiari malformation [47]. They depicted their easy modified procedure of cranioplasty utilizing patient's own bone dust, tissue glue and gel foam sheets. Ten patients underwent posterior fossa reconstruction between the period of 2000 and 2004 for different pathologies including CM.

After exposure of the suboccipital bone, craniectomy is done by doing multiple burr holes and connecting them with a high-speed drill. Produced bone dust is meticulously collected, preserved and kept wet in a container with small amount of antibiotic treated saline. Following craniectomy and water tight dural closure, a layer of tissue glue is applied over the dura. Two sheets of gel foam are fashioned to fit the craniectomy defect. The bone dust is dried to make dough and is spread between the 2 layers of the gel foam sheets and is held together with tissue glue. The bone dust sandwich is placed over the craniectomy defect separated from the overlying muscle layer by another sheet of gel foam to complete the cranioplasty.

Post-operative plain and 3D CT scan in follow-up of 11–36 months showed excellent reconstruction of the posterior fossa bony contour with the cranioplasty. Two patients needed redo surgery after 6 weeks of cranioplasty which revealed interesting findings. In both the patients, the cranioplasty was totally separated from the suboccipital musculature and the dura. No other complication was noted.

They devised this quick and safe reconstruction technique to prevent the persistent post craniectomy headache due to dural stretching from musculo-fibrous adhesion with the dura as well as to give a better cosmetic result by preventing depression at the craniectomy site. Their procedure of making a bone dust sandwich was better than putting the bone dust directly on the craniectomy gap as the dust is not dispersed. The gel foam used for the cranioplasty also hold some blood which help in ingrowth of osteoblasts to form new bone. This simple and easy procedure had a satisfactory and effective result both clinically and radiologically.

**47**

cerebellar ptosis on MRI.

*Role of Cranioplasty in Management of Chiari Malformation*

**3.9 "Posterior cranial fossa box expansion" by Heller et al.**

syrinx in five of the seven patients were confirmed by MRI.

**3.10 "Partial suboccipital cranioplasty" by Di et al.**

They felt that the cerebellar ptosis is a combination of lack of mechanical support from PFD and pressure-dissociation of CSF causing a sucking effect. As they acknowledged the need of cerebellar support, with their procedure they reduced previous craniectomy gap around the foramen magnum to 2 × 3 cm from over 4 × 4 cm. As a whole their box reconstruction cranioplasty resulted in expansion of the posterior cranial fossa with support to prevent cerebellar ptosis and preservation of pressure dissociation equilibrium around the cisterna magna with the added benefit of maintenance of separation between the neck musculature and soft tissues from the neural tissue. They infer that posterior fossa box reconstruction can resolve symptomatology of cerebellar sag without any intradural manipulation.

Di et al. described cranioplasty related to surgery for CM in 2008 [49]. They reported about critical complication of respiratory arrest in 2 patients following partial cranioplasty for cerebellar ptosis subsequent to PFD for CM. One patient developed symptoms like recurrent and intractable headache and gait disturbance for 1 year following surgery for CM 2 years previously, while the other had developed mild headache, dizziness, difficulty in swallowing, gait imbalance, progressive numbness in the face and upper extremities and occasional urinary incontinence for 4 years following PFD 7 years back. Both the patients had severe

Both the patients underwent a partial suboccipital cranioplasty. Per-operatively large suboccipital craniectomy gaps were identified in both where the cerebellar hemispheres protruded out of the previous craniectomy gap. Only duraplasty was done in one while tonsillar cautery and duraplasty was done in the other. Partial suboccipital cranioplasty with titanium mesh and MMA in one and only with MMA in other was accomplished to reduce the previous craniectomy gap to approximately 2 × 2 cm in size.

Heller et al. portrayed a new method of "posterior cranial fossa box expansion" for MRI confirmed symptomatic cerebellar ptosis following cranial vault decompression for Chiari I malformations in 2007 [48]. They operated on seven patients, who had undergone posterior fossa decompression for CM and developed symptomatic cerebellar ptosis for 12 ± 1 months from the initial surgery at other institutions. Their patients presented with headache, upper extremity numbness, paresthesia, respiratory disturbance and walking difficulty from cerebellar ptosis. Through the previous incision, the previous suboccipital craniectomy was delineated. In the next steps of the procedure, a split thickness square calvarial bone graft, approximately 2–3 cm larger than the width of foramen magnum is harvested from the occipital bone, just below the lambdoid suture. With the help of reciprocating saw and bone cutter, the bone graft is fashioned for the box reconstruction by trisecting the approximately 1 cm wide upper and lower margins into equal 3 segments which leaves six split-thickness pieces and one large rectangular graft. The smaller grafts are stacked into three stacks of two grafts each and fixed with screw at the upper and the two lateral margins of the foramen magnum in an inverted "U" manner. The rectangular bone graft is placed and fixed with the three legs of the bone graft stacks to create a concave dome of bone over the foramen magnum. The box cranioplasty is then completed to cover the cerebellum, separating the surrounding soft tissues and reducing the foramen magnum defect significantly. All their patients were symptom free in a follow-up period of more than 12 months and resolution of cerebellar ptosis in all seven patients and collapse of

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Neurosurgical Procedures - Innovative Approaches*

the dura or the duraplasty with the implants in all cases.

to-and-fro drift within the syrinx.

following surgery.

different pathologies including CM.

tonsillar herniation and syrinx of various degrees and extents. Phase-contrast cine-MRI displayed absence of CSF flow in the retrotonsillar subarachnoid space and

In their technique, they first did foramen magnum decompression by a suboccipital craniectomy as in other procedures along with C1 laminectomy in seven cases and did C1 and C2 upper dome laminectomies in one case. In three cases, they did duraplasty with Gore-Tex membrane and resected the outer layer of the dura in five cases. Cranioplasty to cover the craniectomy gap as well as to expand the posterior fossa was performed using HA implants in all cases. They did tenting of

In a mean follow-up period of 13.3-months, five patients improved and three patients remained unchanged. Postoperative syrinx resolution was seen in seven patients on MRI. HA cranioplasty had to be removed in one patient because of development of an epidural abscess, but this patient had no further neurological deterioration. Six months after surgery, 3D-CT revealed the HA implant to be integrated with the adjacent occipital bone. They used HA, as a substitute for autologous bone grafts, for expansive cranioplasty to enlarge small posterior fossa to establish better CSF flow at the major cistern. The use of HA was to reduce the chance of absorption of the autologous bone in the long run if used for cranioplasty. Moreover, it is technically easy to use the HA implants. The idea of tenting the dura with the cranioplasty was to inhibit the retention of CSF at epidural space

**3.8 "Simple and safe method of cranial reconstruction" by Sheikh et al.**

had a satisfactory and effective result both clinically and radiologically.

In 2006, Sheikh et al. described a simple method of cranioplasty that they applied for posterior fossa reconstruction for many procedures including Chiari malformation [47]. They depicted their easy modified procedure of cranioplasty utilizing patient's own bone dust, tissue glue and gel foam sheets. Ten patients underwent posterior fossa reconstruction between the period of 2000 and 2004 for

After exposure of the suboccipital bone, craniectomy is done by doing multiple burr holes and connecting them with a high-speed drill. Produced bone dust is meticulously collected, preserved and kept wet in a container with small amount of antibiotic treated saline. Following craniectomy and water tight dural closure, a layer of tissue glue is applied over the dura. Two sheets of gel foam are fashioned to fit the craniectomy defect. The bone dust is dried to make dough and is spread between the 2 layers of the gel foam sheets and is held together with tissue glue. The bone dust sandwich is placed over the craniectomy defect separated from the overlying muscle layer by another sheet of gel foam to complete the cranioplasty. Post-operative plain and 3D CT scan in follow-up of 11–36 months showed excellent reconstruction of the posterior fossa bony contour with the cranioplasty. Two patients needed redo surgery after 6 weeks of cranioplasty which revealed interesting findings. In both the patients, the cranioplasty was totally separated from the suboccipital musculature and the dura. No other complication was noted. They devised this quick and safe reconstruction technique to prevent the persistent post craniectomy headache due to dural stretching from musculo-fibrous adhesion with the dura as well as to give a better cosmetic result by preventing depression at the craniectomy site. Their procedure of making a bone dust sandwich was better than putting the bone dust directly on the craniectomy gap as the dust is not dispersed. The gel foam used for the cranioplasty also hold some blood which help in ingrowth of osteoblasts to form new bone. This simple and easy procedure

**46**

#### **3.9 "Posterior cranial fossa box expansion" by Heller et al.**

Heller et al. portrayed a new method of "posterior cranial fossa box expansion" for MRI confirmed symptomatic cerebellar ptosis following cranial vault decompression for Chiari I malformations in 2007 [48]. They operated on seven patients, who had undergone posterior fossa decompression for CM and developed symptomatic cerebellar ptosis for 12 ± 1 months from the initial surgery at other institutions. Their patients presented with headache, upper extremity numbness, paresthesia, respiratory disturbance and walking difficulty from cerebellar ptosis.

Through the previous incision, the previous suboccipital craniectomy was delineated. In the next steps of the procedure, a split thickness square calvarial bone graft, approximately 2–3 cm larger than the width of foramen magnum is harvested from the occipital bone, just below the lambdoid suture. With the help of reciprocating saw and bone cutter, the bone graft is fashioned for the box reconstruction by trisecting the approximately 1 cm wide upper and lower margins into equal 3 segments which leaves six split-thickness pieces and one large rectangular graft. The smaller grafts are stacked into three stacks of two grafts each and fixed with screw at the upper and the two lateral margins of the foramen magnum in an inverted "U" manner. The rectangular bone graft is placed and fixed with the three legs of the bone graft stacks to create a concave dome of bone over the foramen magnum. The box cranioplasty is then completed to cover the cerebellum, separating the surrounding soft tissues and reducing the foramen magnum defect significantly.

All their patients were symptom free in a follow-up period of more than 12 months and resolution of cerebellar ptosis in all seven patients and collapse of syrinx in five of the seven patients were confirmed by MRI.

They felt that the cerebellar ptosis is a combination of lack of mechanical support from PFD and pressure-dissociation of CSF causing a sucking effect. As they acknowledged the need of cerebellar support, with their procedure they reduced previous craniectomy gap around the foramen magnum to 2 × 3 cm from over 4 × 4 cm. As a whole their box reconstruction cranioplasty resulted in expansion of the posterior cranial fossa with support to prevent cerebellar ptosis and preservation of pressure dissociation equilibrium around the cisterna magna with the added benefit of maintenance of separation between the neck musculature and soft tissues from the neural tissue. They infer that posterior fossa box reconstruction can resolve symptomatology of cerebellar sag without any intradural manipulation.

#### **3.10 "Partial suboccipital cranioplasty" by Di et al.**

Di et al. described cranioplasty related to surgery for CM in 2008 [49]. They reported about critical complication of respiratory arrest in 2 patients following partial cranioplasty for cerebellar ptosis subsequent to PFD for CM. One patient developed symptoms like recurrent and intractable headache and gait disturbance for 1 year following surgery for CM 2 years previously, while the other had developed mild headache, dizziness, difficulty in swallowing, gait imbalance, progressive numbness in the face and upper extremities and occasional urinary incontinence for 4 years following PFD 7 years back. Both the patients had severe cerebellar ptosis on MRI.

Both the patients underwent a partial suboccipital cranioplasty. Per-operatively large suboccipital craniectomy gaps were identified in both where the cerebellar hemispheres protruded out of the previous craniectomy gap. Only duraplasty was done in one while tonsillar cautery and duraplasty was done in the other. Partial suboccipital cranioplasty with titanium mesh and MMA in one and only with MMA in other was accomplished to reduce the previous craniectomy gap to approximately 2 × 2 cm in size.

Both the patients suffered from similar episodes of apnea and subsequent respiratory arrest, 15 h and 72 h post-operatively, respectively. No bleeding, infarct and blockage of the CSF pathway was seen in the post-operative MRI or CT scan. Chest radiographs were also normal. Both were reintubated and monitored in an intensive care unit. One of them was extubated within 24 h and was discharged home 1 week after, while, extubation failed twice in the other and recovery to a near independent state was achieved after a prolonged mechanical ventilation, with tracheostomy.

Among various post-operative complications, cerebellar ptosis, which usually results from a large craniectomy, has a potentially severe consequence, and its incidence is possibly underestimated. Partial suboccipital cranioplasty has been used to treat the cerebellar ptosis to minimize the large craniectomy gap and to support the cerebellum. The respiratory arrest in these patients is thought to be from stretching on the vulnerable and damaged brainstem by the elevation of the cerebellum during the cerebellar shelving process. There might have been some compromised vasculature too, which surely could play a role.

#### **3.11 "Autologous cranioplasty" by Chou et al.**

In 2009, Chou et al. published a technical note on a cranioplasty technique that they devised for treatment for CM [50]. They believed that adherence between muscle and dura, together with the development of occipital neuromas, are the factors of common postoperative complaint of headache. They made some modifications to the conventional craniectomy with the aim to expansion of the posterior fossa. They performed suboccipital craniotomy in their technique on six patients with CM1.

They performed a rectangular craniotomy extending from just below the nuchal line down to the foramen magnum. Following duraplasty, with the help of a Leibinger plate attached to the inner table, the craniotomy flap was fixed to the outer table of the skull with 2 mm screws to elevate the bone flap and to expand the posterior fossa volume as well.

They followed-up the patients for 7 months on average. Post-operative headaches in all the patients improved within 3–4 weeks and there had been no complication. Patients with syringomyelia had complete resolution of syringes. Improvement was seen in overall quality of life of the patients. Three-dimensional analysis of posterior fossa volume revealed effective increase in posterior fossa volume on average, from pre-operative 168 cc to post-operative 192 cc.

Small and shallow posterior fossa is recognized to be the prime factor in development of CM. The authors felt the need of the posterior fossa to be expanded. Consequently, they devised their technique of decompression and expansion of the posterior fossa. With their procedure they also eliminated the possibility of fibrous adhesion between nuchal musculature and the exposed dura to reduce the chance of post-operative headache and neckache during motion from dural stretching. Cranioplasty with autologous bone has the added advantage of reducing local tissue reaction and edema by artificial grafts.

#### **3.12 "Cranioplasty" by Furtado et al.**

Furtado et al. reported the management of rare entity of Chiari 3 malformation (CM3) by cranioplasty among other measures in 2009 [51]. Their patient, a 15 months old girl was presented with titubation and occipito-cervical encephalocele since birth. She also had downbeat nystigmus. MRI revealed an occipito-cervical encephalocele containing cerebellum, brainstem and both the occipital poles,

**49**

to the area.

adults and in children.

*Role of Cranioplasty in Management of Chiari Malformation*

mal-development of the C1 and C2 posterior arches.

**3.13 "Expansile suboccipital cranioplasty" by Oro et al.**

Chiari malformation or on recurrent CM patients.

in a shallow posterior fossa. 3D CT scan showed a big gap in the occipital bone with

the cranioplasty. Wound was covered with an occipital rotation skin flap.

On surgery, after excising the gliotic cerebellum and the occipital lobes, a meticulous watertight dural closure was accomplished. The large bony gap in the occipital bone was covered with a 5 × 5 cm methylmethacrylate cranioplasty that was fixed with the margin of the occipital bone with steel wire. The remaining occipital lobe, transverse sinus and the upper part of the cerebellum were well contained within

Recovery was uneventful and the baby was discharged home after 5 days. Her lower cranial nerves were intact and there was no HCP. Follow-up CT scan at 3 year showed no bone growth along the cranioplasty margin and she had retarded physi-

They introduced a variant of cranioplasty procedure to cover and support the transverse sinus and the occipital lobe in a case of CM3. They did cranioplasty with the goal to prevent further herniation of the remaining cerebellar tissue by reducing the gap down to half. Though the functional outcome of CM3 is grave most of the

Oro et al. in 2011 reported the largest series of expansile cranioplasty for CM1 [52]. They described their technique that they applied on 241 patients of fresh

In 2004, they developed a preformed crescent shaped titanium plate to treat CM1 patients by expansile suboccipital cranioplasty. Their titanium plate was designed to cover a craniectomy defect measuring 3 cm wide. Larger crescent plates that can cover 4 cm craniectomies also exist and plates to cover wider decompressions for post-surgical patients can also be customized. Besides, they developed a triangular plate for smaller triangular-shaped craniectomies. After the desired craniectomy, once the suitable plate is selected, it is manually bent into a curved arch and fixed to cover the upper two-thirds to three-fourths of the craniectomy with five to six small screws. No plate dislodgements have been detected in followup MRI. The use of the plate is straightforward and they are redesigning the plate to

The goals of surgery are to achieve dorsal and dorsolateral decompression with restoration of normal CSF dynamics at the CVJ and reduction of the surgical risks. The expected extent of craniectomy, which varies from 2.7 to 3 cm and the size of the duraplasty, approximately 1.5–2 cm less than the base length, are planned from the T2 sagittal MRI of the CVJ. Planning for inclusion of a C1 laminectomy, and on rare occasions a partial C2 laminectomy, depends on the extent of tonsillar

They designed their cranioplasty with the goal to provide a rigid surface for attachment of the suboccipital muscles to prevent formation of scar to dura. This process can also prevent "soft spot" headache and reduce the possibility of injury

In 2012, Rekate and Bristol described their method of cranioplasty following foramen magnum decompression for CM1 [53]. They only described their procedure, but did not provide any patient data. They applied their technique both in

herniation, and the degree of tonsillar and brainstem compression.

**3.14 "Cranioplasty with titanium plate" by Rekate and Bristol**

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

cal and mental development.

times, surgery is recommended.

provide more coverage.

#### *Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Neurosurgical Procedures - Innovative Approaches*

ture too, which surely could play a role.

with CM1.

posterior fossa volume as well.

reaction and edema by artificial grafts.

**3.12 "Cranioplasty" by Furtado et al.**

**3.11 "Autologous cranioplasty" by Chou et al.**

Both the patients suffered from similar episodes of apnea and subsequent respiratory arrest, 15 h and 72 h post-operatively, respectively. No bleeding, infarct and blockage of the CSF pathway was seen in the post-operative MRI or CT scan. Chest radiographs were also normal. Both were reintubated and monitored in an intensive care unit. One of them was extubated within 24 h and was discharged home 1 week after, while, extubation failed twice in the other and recovery to a near independent state was achieved after a prolonged mechanical ventilation, with tracheostomy. Among various post-operative complications, cerebellar ptosis, which usually results from a large craniectomy, has a potentially severe consequence, and its incidence is possibly underestimated. Partial suboccipital cranioplasty has been used to treat the cerebellar ptosis to minimize the large craniectomy gap and to support the cerebellum. The respiratory arrest in these patients is thought to be from stretching on the vulnerable and damaged brainstem by the elevation of the cerebellum during the cerebellar shelving process. There might have been some compromised vascula-

In 2009, Chou et al. published a technical note on a cranioplasty technique that they devised for treatment for CM [50]. They believed that adherence between muscle and dura, together with the development of occipital neuromas, are the factors of common postoperative complaint of headache. They made some modifications to the conventional craniectomy with the aim to expansion of the posterior fossa. They performed suboccipital craniotomy in their technique on six patients

They performed a rectangular craniotomy extending from just below the nuchal line down to the foramen magnum. Following duraplasty, with the help of a Leibinger plate attached to the inner table, the craniotomy flap was fixed to the outer table of the skull with 2 mm screws to elevate the bone flap and to expand the

They followed-up the patients for 7 months on average. Post-operative headaches in all the patients improved within 3–4 weeks and there had been no complication. Patients with syringomyelia had complete resolution of syringes. Improvement was seen in overall quality of life of the patients. Three-dimensional analysis of posterior fossa volume revealed effective increase in posterior fossa

Small and shallow posterior fossa is recognized to be the prime factor in development of CM. The authors felt the need of the posterior fossa to be expanded. Consequently, they devised their technique of decompression and expansion of the posterior fossa. With their procedure they also eliminated the possibility of fibrous adhesion between nuchal musculature and the exposed dura to reduce the chance of post-operative headache and neckache during motion from dural stretching. Cranioplasty with autologous bone has the added advantage of reducing local tissue

Furtado et al. reported the management of rare entity of Chiari 3 malformation (CM3) by cranioplasty among other measures in 2009 [51]. Their patient, a 15 months old girl was presented with titubation and occipito-cervical encephalocele since birth. She also had downbeat nystigmus. MRI revealed an occipito-cervical encephalocele containing cerebellum, brainstem and both the occipital poles,

volume on average, from pre-operative 168 cc to post-operative 192 cc.

**48**

in a shallow posterior fossa. 3D CT scan showed a big gap in the occipital bone with mal-development of the C1 and C2 posterior arches.

On surgery, after excising the gliotic cerebellum and the occipital lobes, a meticulous watertight dural closure was accomplished. The large bony gap in the occipital bone was covered with a 5 × 5 cm methylmethacrylate cranioplasty that was fixed with the margin of the occipital bone with steel wire. The remaining occipital lobe, transverse sinus and the upper part of the cerebellum were well contained within the cranioplasty. Wound was covered with an occipital rotation skin flap.

Recovery was uneventful and the baby was discharged home after 5 days. Her lower cranial nerves were intact and there was no HCP. Follow-up CT scan at 3 year showed no bone growth along the cranioplasty margin and she had retarded physical and mental development.

They introduced a variant of cranioplasty procedure to cover and support the transverse sinus and the occipital lobe in a case of CM3. They did cranioplasty with the goal to prevent further herniation of the remaining cerebellar tissue by reducing the gap down to half. Though the functional outcome of CM3 is grave most of the times, surgery is recommended.

#### **3.13 "Expansile suboccipital cranioplasty" by Oro et al.**

Oro et al. in 2011 reported the largest series of expansile cranioplasty for CM1 [52]. They described their technique that they applied on 241 patients of fresh Chiari malformation or on recurrent CM patients.

In 2004, they developed a preformed crescent shaped titanium plate to treat CM1 patients by expansile suboccipital cranioplasty. Their titanium plate was designed to cover a craniectomy defect measuring 3 cm wide. Larger crescent plates that can cover 4 cm craniectomies also exist and plates to cover wider decompressions for post-surgical patients can also be customized. Besides, they developed a triangular plate for smaller triangular-shaped craniectomies. After the desired craniectomy, once the suitable plate is selected, it is manually bent into a curved arch and fixed to cover the upper two-thirds to three-fourths of the craniectomy with five to six small screws. No plate dislodgements have been detected in followup MRI. The use of the plate is straightforward and they are redesigning the plate to provide more coverage.

The goals of surgery are to achieve dorsal and dorsolateral decompression with restoration of normal CSF dynamics at the CVJ and reduction of the surgical risks.

The expected extent of craniectomy, which varies from 2.7 to 3 cm and the size of the duraplasty, approximately 1.5–2 cm less than the base length, are planned from the T2 sagittal MRI of the CVJ. Planning for inclusion of a C1 laminectomy, and on rare occasions a partial C2 laminectomy, depends on the extent of tonsillar herniation, and the degree of tonsillar and brainstem compression.

They designed their cranioplasty with the goal to provide a rigid surface for attachment of the suboccipital muscles to prevent formation of scar to dura. This process can also prevent "soft spot" headache and reduce the possibility of injury to the area.

#### **3.14 "Cranioplasty with titanium plate" by Rekate and Bristol**

In 2012, Rekate and Bristol described their method of cranioplasty following foramen magnum decompression for CM1 [53]. They only described their procedure, but did not provide any patient data. They applied their technique both in adults and in children.

In their method, the rim of the foramen magnum is removed to a distance of 1.5– 2.0 cm. The posterior arch of C1 and the laminae and spinous process of C2, when felt necessary, are removed along with the ligamentum flavum. Dura is opened in a linear fashion starting from the spinal dura and then extending upwards upto the bone margin. The fourth ventricle is entered into, to see and lyse the veil, which the authors claim to be typically present and advocates that the veil must be opened to visualize the porcelain white floor of the fourth ventricle. Duraplasty is performed with pericranium, which is sewn in place with absorbable or nonabsorbable suture. Cranioplasty is done with a titanium plate that has been developed only to extend over the craniectomy gap around the foramen magnum and fixed with screws on both sides. The preformed plate allows for custom fitting depending on the patient's anatomy and the extent of the bony opening. A tenting is taken from the center of the graft to the titanium plate.

They set their goals of surgery to remove the compression from the brainstem and reestablish normal CSF dynamics at the CVJ. The dura was opened and the arachnoid around the tonsils was dissected to see the floor of the fourth ventricle with the theory in mind that this maneuver does not add morbidity to the procedure. The aim of dural closure with a patch graft is to create a larger CSF space around the CVJ. The cranioplasty is done mainly to prevent the scarring of the graft to the underlying tonsils.

#### **3.15 "Expansile suboccipital cranioplasty with titanium mesh-assisted dural tenting" by Assina**

Assina et al. in 2014 described their process of titanium mesh-assisted dural tenting and expansile suboccipital cranioplasty for preventing cerebellar ptosis following posterior fossa decompression for CM1 [54]. Cerebellar ptosis and dural prolapse or collapse of the cisterna magna are well-recognized complications following PFD. Almost one-third of the operated patients come back with recurrence in their lifetime, often from ptosis and dural prolapse.

They developed their method to prevent cerebellar ptosis and dural prolapse by the technique of titanium mesh-assisted dural tenting and expansile suboccipital cranioplasty. They performed surgery by this procedure on four patients of CM1, three of whom had associated syrinx. All presented with suboccipital headache.

Their craniectomy was extended to the posterior aspect of the occipital condyles laterally. A partial laminectomy of the C2 was done sometimes when the tonsils were extended down to C2. Arachnoid preserving dural opening was performed in a "Y"-shaped fashion superiorly and upside down "T" fashion inferiorly to have a larger dural opening. After watertight duraplasty, a titanium mesh cranioplasty, covering the superior aspect of the craniectomy was done and 2-3 dural tentings were tied with the cranioplasty.

All the patients had uneventful post-operative course without any complication in mean follow-up period of 19 months. In follow-up MRI at 1 year no cerebellar ptosis, collapse or restenosis of cisterna magna, obstruction of CSF pathway requiring re-do surgery was evident. All the patients had improvement of their symptoms and radiographic resolution of syrinx. By this expansile titanium mesh cranioplasty, in addition to expanding the volume of the posterior fossa, they also had the aim to prevent the cerebellar sag by the support of the cranioplast and dural prolapse and the collapse of the cisterna magna by the dural tenting with the cranioplasty. The titanium mesh also has the extra preventive accomplishment against re-stenosis at the CVJ by creating a barrier between the musculature and the dura.

**51**

*Role of Cranioplasty in Management of Chiari Malformation*

**3.16 "Modified pi-technique of reduction cranioplasty" by Choi et al.**

Choi et al. in 2014 described reduction cranioplasty in an infant of congenital HCP, occipital encephalocele with CM1 [55]. Though it was not a conventional posterior fossa decompression surgery the presence of CM1 carries the merit to be

They reported a baby of occipital encephalocele diagnosed antenatally by USG. MRI at the age of 1 day revealed severe hydrocephalus, occipital encephalocele and herniation of the lower brainstem and cerebellum into the cervical defect. The baby underwent multiple surgeries from the age of day 1, like repair of the encephalocele, VP shunt, foramen magnum decompression, ETV and EVD for multiple times. Despite all these measures, macrocephaly persisted and anterior fontanelle

The cranial vault was reshaped by modified pi-procedure of reduction cranioplasty. The gap at the anterior fontanalle was covered with two paired sagittal-parietal bone flaps and the coronal bone flap was advanced to the midline to cover the bone defect. To allow the brain to expand laterally, multiple barrel stave osteotomy

Postoperatively, the skull defect at the non-fused fontanelle was closed. The skull vault circumference decreased from 58 to 53 cm and correction of macrocephally was seen. There were no postoperative complications. However, they did not mention about the post-operative status of the CM1. Early in infancy, the patient had considerable developmental delays in early infancy. Nevertheless, slow neurological improvement was witnessed during the overall course of development

The Chiari malformations are a complex of hindbrain deformities associated hydrocephalus in a minority of patients that need to be managed during the initial stages, which can be cumbersome. Different CSF diversion procedures, even with multiple attempts can lead to craniocerebral disproportion due to discrepancy between the volume of the brain and the volume of the cranium. They recommended that patients of CM1 with other congenital anomalies and HCP can be satisfactorily managed by reduction cranioplasty utilizing the modified pi-technique.

**3.17 "Posterior fossa reconstruction using titanium plate" by Udani et al.**

In 2014, Udani et al. described their technique of partial posterior fossa cranioplasty using perforated titanium plate for treating cerebellar ptosis and dural ectasia

They described 12 patients, who previously had undergone PFD for CM1. The interval ranged from 2 to 12 years between the initial surgery and the cranioplasty. First surgery consisted of different combinations of procedures like durapasty, tonsillar shrinkage or syrinx shunting in addition to PFD. Patients presented with headache, neck and back pain, gait ataxia, limb weakness, sensory changes and nystagmus. Imaging revealed persistent tonsillar descent. Four patients had bulging dural ectasia and eight patients had ptosis. Three of the patients had recurrent syrinx. Five patients, including the three with syrinx, had a 1- to 2-week trial of suboccipital counter pressure with a soft foam rubber pad against the decompression site that was held in place with an elastic bandage, prior to partial titanium cranioplasty and had symptomatic improvement with this trial. Prior craniectomy defects were defined in all the patients per-operatively. A suboccipital perforated titanium plate was shaped to make it slightly convex in the midline and flat on the sides to merge with the bone. It was placed along the inferior edge of the craniectomy to support the dura over the cerebellar hemispheres but not extending down to the foramen

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

was open and bulged at 32 months postnatally.

following posterior fossa decompression [56].

was done at the level of the squamosal suture bilaterally.

mentioned here.

of the baby.

*Neurosurgical Procedures - Innovative Approaches*

the graft to the titanium plate.

to the underlying tonsils.

**tenting" by Assina**

were tied with the cranioplasty.

musculature and the dura.

in their lifetime, often from ptosis and dural prolapse.

In their method, the rim of the foramen magnum is removed to a distance of 1.5– 2.0 cm. The posterior arch of C1 and the laminae and spinous process of C2, when felt necessary, are removed along with the ligamentum flavum. Dura is opened in a linear fashion starting from the spinal dura and then extending upwards upto the bone margin. The fourth ventricle is entered into, to see and lyse the veil, which the authors claim to be typically present and advocates that the veil must be opened to visualize the porcelain white floor of the fourth ventricle. Duraplasty is performed with pericranium, which is sewn in place with absorbable or nonabsorbable suture. Cranioplasty is done with a titanium plate that has been developed only to extend over the craniectomy gap around the foramen magnum and fixed with screws on both sides. The preformed plate allows for custom fitting depending on the patient's anatomy and the extent of the bony opening. A tenting is taken from the center of

They set their goals of surgery to remove the compression from the brainstem and reestablish normal CSF dynamics at the CVJ. The dura was opened and the arachnoid around the tonsils was dissected to see the floor of the fourth ventricle with the theory in mind that this maneuver does not add morbidity to the procedure. The aim of dural closure with a patch graft is to create a larger CSF space around the CVJ. The cranioplasty is done mainly to prevent the scarring of the graft

**3.15 "Expansile suboccipital cranioplasty with titanium mesh-assisted dural** 

Assina et al. in 2014 described their process of titanium mesh-assisted dural tenting and expansile suboccipital cranioplasty for preventing cerebellar ptosis following posterior fossa decompression for CM1 [54]. Cerebellar ptosis and dural prolapse or collapse of the cisterna magna are well-recognized complications following PFD. Almost one-third of the operated patients come back with recurrence

They developed their method to prevent cerebellar ptosis and dural prolapse by the technique of titanium mesh-assisted dural tenting and expansile suboccipital cranioplasty. They performed surgery by this procedure on four patients of CM1, three of whom had associated syrinx. All presented with suboccipital

Their craniectomy was extended to the posterior aspect of the occipital condyles

laterally. A partial laminectomy of the C2 was done sometimes when the tonsils were extended down to C2. Arachnoid preserving dural opening was performed in a "Y"-shaped fashion superiorly and upside down "T" fashion inferiorly to have a larger dural opening. After watertight duraplasty, a titanium mesh cranioplasty, covering the superior aspect of the craniectomy was done and 2-3 dural tentings

All the patients had uneventful post-operative course without any complication in mean follow-up period of 19 months. In follow-up MRI at 1 year no cerebellar ptosis, collapse or restenosis of cisterna magna, obstruction of CSF pathway requiring re-do surgery was evident. All the patients had improvement of their symptoms and radiographic resolution of syrinx. By this expansile titanium mesh cranioplasty, in addition to expanding the volume of the posterior fossa, they also had the aim to prevent the cerebellar sag by the support of the cranioplast and dural prolapse and the collapse of the cisterna magna by the dural tenting with the cranioplasty. The titanium mesh also has the extra preventive accomplishment against re-stenosis at the CVJ by creating a barrier between the

**50**

headache.

#### **3.16 "Modified pi-technique of reduction cranioplasty" by Choi et al.**

Choi et al. in 2014 described reduction cranioplasty in an infant of congenital HCP, occipital encephalocele with CM1 [55]. Though it was not a conventional posterior fossa decompression surgery the presence of CM1 carries the merit to be mentioned here.

They reported a baby of occipital encephalocele diagnosed antenatally by USG. MRI at the age of 1 day revealed severe hydrocephalus, occipital encephalocele and herniation of the lower brainstem and cerebellum into the cervical defect. The baby underwent multiple surgeries from the age of day 1, like repair of the encephalocele, VP shunt, foramen magnum decompression, ETV and EVD for multiple times. Despite all these measures, macrocephaly persisted and anterior fontanelle was open and bulged at 32 months postnatally.

The cranial vault was reshaped by modified pi-procedure of reduction cranioplasty. The gap at the anterior fontanalle was covered with two paired sagittal-parietal bone flaps and the coronal bone flap was advanced to the midline to cover the bone defect. To allow the brain to expand laterally, multiple barrel stave osteotomy was done at the level of the squamosal suture bilaterally.

Postoperatively, the skull defect at the non-fused fontanelle was closed. The skull vault circumference decreased from 58 to 53 cm and correction of macrocephally was seen. There were no postoperative complications. However, they did not mention about the post-operative status of the CM1. Early in infancy, the patient had considerable developmental delays in early infancy. Nevertheless, slow neurological improvement was witnessed during the overall course of development of the baby.

The Chiari malformations are a complex of hindbrain deformities associated hydrocephalus in a minority of patients that need to be managed during the initial stages, which can be cumbersome. Different CSF diversion procedures, even with multiple attempts can lead to craniocerebral disproportion due to discrepancy between the volume of the brain and the volume of the cranium. They recommended that patients of CM1 with other congenital anomalies and HCP can be satisfactorily managed by reduction cranioplasty utilizing the modified pi-technique.

#### **3.17 "Posterior fossa reconstruction using titanium plate" by Udani et al.**

In 2014, Udani et al. described their technique of partial posterior fossa cranioplasty using perforated titanium plate for treating cerebellar ptosis and dural ectasia following posterior fossa decompression [56].

They described 12 patients, who previously had undergone PFD for CM1. The interval ranged from 2 to 12 years between the initial surgery and the cranioplasty. First surgery consisted of different combinations of procedures like durapasty, tonsillar shrinkage or syrinx shunting in addition to PFD. Patients presented with headache, neck and back pain, gait ataxia, limb weakness, sensory changes and nystagmus. Imaging revealed persistent tonsillar descent. Four patients had bulging dural ectasia and eight patients had ptosis. Three of the patients had recurrent syrinx.

Five patients, including the three with syrinx, had a 1- to 2-week trial of suboccipital counter pressure with a soft foam rubber pad against the decompression site that was held in place with an elastic bandage, prior to partial titanium cranioplasty and had symptomatic improvement with this trial. Prior craniectomy defects were defined in all the patients per-operatively. A suboccipital perforated titanium plate was shaped to make it slightly convex in the midline and flat on the sides to merge with the bone. It was placed along the inferior edge of the craniectomy to support the dura over the cerebellar hemispheres but not extending down to the foramen

magnum and was fixed with the bone using four 4-mm mini screws. Seven patients had intradural exploration with duraplasty with a composite dural graft.

In the mean follow-up period of 18 months, symptoms of four patients with dural ectasia improved significantly. Syrinx improved in two of the three patients. Overall, 10 out of 12 patients responded favorably to the partial titanium cranioplasty.

The cerebellar ptosis, which may develop as a delayed and potentially serious complication, has the potential to reestablish contact with the brainstem, recreating partial obstruction of CSF flow. This in turn may re-establish conditions for filling of a syrinx cavity which is usually a consequence of large craniectomies. They theorized that larger craniectomies are not necessary to accomplish tonsillar decompression.

#### **3.18 "Hemicranioplasty for osteopetrosis and CM1" by Alsahlawi et al.**

Alsahlawi et al. reported a case of autosomal-dominant type of osteopetrosis with concomitant CM1, who had headache and severe visual deterioration, all attributing to increased ICP [57]. Osteopetrosis, a disease of abnormal bone density and volume, resulting from imbalance between osteoblastic formation and osteoclastic resorption, usually presents to a neurosurgeon with features of raised ICP. However, association of osteopetrosis and Chiari malformation is rare.

Their patient presented with gradual deteriorating vision, generalized pain in back, limbs and face, and occasional dizziness and tinnitus. Bone mineral density was high and CT scan revealed generalized diffuse thickening of the skull vault and secondary narrowing of the skull base foramina and internal acoustic meatus. MRI demonstrated crowding at the foramen magnum with bilateral cerebellar tonsillar herniation. There was also severe bilateral compression of the cerebral hemispheres with effacement of the ventricles and the subarachnoid spaces. Medical treatment and left sided optic nerve fenestration failed to resolve the symptoms, rather the patient continued to deteriorate and elective hemicranioplasty was performed after 6 weeks of fenestration.

A right sided fronto-pareital craniotomy flap, measuring 14 × 12 cm, was made with the help of 6 burr holes connected by making grooves with drill first and then with craniotome to cover the thickness of the bone. The inner table of the craniotomy flap was thinned out with saw and drill to reduce the thickness from 30 to 8 mm. The brain under pressure was relieved by duraplasty. Cranioplasty was done with the thinned bone with help of mesh and micro plates. Their plan was to do bilateral decompression, but brain was found to be relaxed after performing the procedure on right side.

Immediately after surgery, the patient noticed significant relief of headache. At 6-month follow-up, headache had resolved completely and vision improved markedly. Postop CT scan showed relief of the brain compression evidenced by enlargement of the ventricles and the subarachnoid spaces. Marked improvement of the cerebellar tonsillar herniation was also observed.

Presently, there exists no medical cure for osteopetrosis. Neurosurgical management evolve around symptom relief mainly. Because of severe headache and progressive visual loss, the authors decided to be aggressive in approach. In absence of osteoclastic activity, thickening of the bones led to raised ICP as well as smaller posterior fossa which ultimately resulted in herniation of the tonsils and following decompressive hemicranioplasty, both the raised ICP and tonsillar herniation were markedly relieved.

#### **3.19 "Expansive suboccipital cranioplasty" by Korshunov**

Korshunov et al. described their method of expansive suboccipital cranioplasty for CM1 in 2017 [58]. Their patient presented with intensive disabling persistent

**53**

*Role of Cranioplasty in Management of Chiari Malformation*

headache and cervico-occipital pain. The patient also had two attacks of generalized tonic seizures with loss of consciousness. Neurological examination revealed horizontal nystagmus. MRI revealed wedge-shaped tonsillar herniation down to

The thickened and deformed margin of the foramen magnum was widely dissected following a posterior fossa midline osteoplastic craniotomy. Posterior arch of the atlas was also resected. Arachnoid preserving duraplasty was performed with collagen matrix patch graft. The thickness of the free bone flap was reduced by grinding and the margin of the foramen magnum on the bone flap was also widened. The upper edge of the bone flap was fixed at the upper margin of the craniectomy defect by silk sutures. The lower part of the flap was pulled outwards and fixed with two resorbable mini-plates to create new space in the lower portion of the PCF. Immediate postop CT scan revealed satisfactory cranioplasty. At 3 months follow-up, the patient was totally free of headache, cervico-occipital pain and seizure and MRI revealed resolution of tonsillar herniation and reformation of the

Posterior decompression of the craniovertebral junction is the most common treatment for CM1. In addition to the conventional procedure, the authors tried to expand the posterior fossa with the aim to normalize CSF circulation at the CVJ with some modification. The whole procedure renders a better dural closure with less chance of complications, less chance of compression from inside and outside because of the bony barrier and better chance of reformation of the occipital cistern.

**3.20 "Upside down-inside out cranioplasty" by Tjokorda and Tjokorda**

or younger had Chiari malformation type I with or without syringomyelia.

Tjokorda and Tjokorda described a method of a less invasive suboccipital decompression-cranioplasty in 2018 [59]. They analyzed retrospectively, 10 patients from 2010 to 2016, on whom they performed their formulated method of upside

Seven patients in their 4th decade or older and three patients in their 3rd decade

With the help of pneumatic perforator and drill, a reverse triangular-shaped craniotomy was done in one piece. Laminectomy of C1 and duraplasty was performed, ensuring normal cerebrospinal fluid flow and dural pulsation. The triangular bone flap harvested from the suboccipital craniotomy was replaced upside down-inside

All patients had improvement of their sensory and motor functions immediately following surgery. Post-operative Japanese Orthopedic Association scoring system (JOA score) scores compared to pre-operative scores were improved in all the patients. Only one patient needed a syringo-subarachnoid shunt for syrinx. No acute or late surgical complications were encountered in a follow-up period of at least 12 months. The philosophy behind putting the bone upside down and inside out was to place the bone graft above the external table of its origin with periosteum inside to increase the posterior fossa volume, prevent re-stenosis and dural scarring. Other benefits of UDIO were thought to be protecting the cerebellum from adhesion or sagging, and this was believed to prevent adhesion, preventing formation of the pseudomeningocele, facilitating the reconstruction of the posterior neck muscles

In 2019, Valentini et al. described cranial vault remodeling of five children in a special subset of CM1 with untreated sagittal stenosis (USS) [60]. Association of

17 mm below the foramen magnum. There was no HCP or syrinx.

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

down-inside out (UDIO) cranioplasty.

out and was fixed with titanium mini plate and screws.

and preventing CSF leak by reducing the suction effect.

**3.21 "Cranial vault remodeling" by Valentini et al.**

occipital cistern.

#### *Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

*Neurosurgical Procedures - Innovative Approaches*

cranioplasty.

magnum and was fixed with the bone using four 4-mm mini screws. Seven patients

The cerebellar ptosis, which may develop as a delayed and potentially serious complication, has the potential to reestablish contact with the brainstem, recreating partial obstruction of CSF flow. This in turn may re-establish conditions for filling of a syrinx cavity which is usually a consequence of large craniectomies. They theorized that larger craniectomies are not necessary to accomplish tonsillar decompression.

Alsahlawi et al. reported a case of autosomal-dominant type of osteopetrosis with concomitant CM1, who had headache and severe visual deterioration, all attributing to increased ICP [57]. Osteopetrosis, a disease of abnormal bone density and volume, resulting from imbalance between osteoblastic formation and osteoclastic resorption, usually presents to a neurosurgeon with features of raised ICP. However, association of osteopetrosis and Chiari malformation is rare.

Their patient presented with gradual deteriorating vision, generalized pain in back, limbs and face, and occasional dizziness and tinnitus. Bone mineral density was high and CT scan revealed generalized diffuse thickening of the skull vault and secondary narrowing of the skull base foramina and internal acoustic meatus. MRI demonstrated crowding at the foramen magnum with bilateral cerebellar tonsillar herniation. There was also severe bilateral compression of the cerebral hemispheres with effacement of the ventricles and the subarachnoid spaces. Medical treatment and left sided optic nerve fenestration failed to resolve the symptoms, rather the patient continued to deteriorate and elective hemicranioplasty was performed after 6 weeks of fenestration. A right sided fronto-pareital craniotomy flap, measuring 14 × 12 cm, was made

with the help of 6 burr holes connected by making grooves with drill first and then with craniotome to cover the thickness of the bone. The inner table of the craniotomy flap was thinned out with saw and drill to reduce the thickness from 30 to 8 mm. The brain under pressure was relieved by duraplasty. Cranioplasty was done with the thinned bone with help of mesh and micro plates. Their plan was to do bilateral decompression, but brain was found to be relaxed after performing the

Immediately after surgery, the patient noticed significant relief of headache. At 6-month follow-up, headache had resolved completely and vision improved markedly. Postop CT scan showed relief of the brain compression evidenced by enlargement of the ventricles and the subarachnoid spaces. Marked improvement of the

Presently, there exists no medical cure for osteopetrosis. Neurosurgical management

Korshunov et al. described their method of expansive suboccipital cranioplasty for CM1 in 2017 [58]. Their patient presented with intensive disabling persistent

evolve around symptom relief mainly. Because of severe headache and progressive visual loss, the authors decided to be aggressive in approach. In absence of osteoclastic activity, thickening of the bones led to raised ICP as well as smaller posterior fossa which ultimately resulted in herniation of the tonsils and following decompressive hemicranioplasty, both the raised ICP and tonsillar herniation were markedly relieved.

had intradural exploration with duraplasty with a composite dural graft. In the mean follow-up period of 18 months, symptoms of four patients with dural ectasia improved significantly. Syrinx improved in two of the three patients. Overall, 10 out of 12 patients responded favorably to the partial titanium

**3.18 "Hemicranioplasty for osteopetrosis and CM1" by Alsahlawi et al.**

**52**

procedure on right side.

cerebellar tonsillar herniation was also observed.

**3.19 "Expansive suboccipital cranioplasty" by Korshunov**

headache and cervico-occipital pain. The patient also had two attacks of generalized tonic seizures with loss of consciousness. Neurological examination revealed horizontal nystagmus. MRI revealed wedge-shaped tonsillar herniation down to 17 mm below the foramen magnum. There was no HCP or syrinx.

The thickened and deformed margin of the foramen magnum was widely dissected following a posterior fossa midline osteoplastic craniotomy. Posterior arch of the atlas was also resected. Arachnoid preserving duraplasty was performed with collagen matrix patch graft. The thickness of the free bone flap was reduced by grinding and the margin of the foramen magnum on the bone flap was also widened. The upper edge of the bone flap was fixed at the upper margin of the craniectomy defect by silk sutures. The lower part of the flap was pulled outwards and fixed with two resorbable mini-plates to create new space in the lower portion of the PCF.

Immediate postop CT scan revealed satisfactory cranioplasty. At 3 months follow-up, the patient was totally free of headache, cervico-occipital pain and seizure and MRI revealed resolution of tonsillar herniation and reformation of the occipital cistern.

Posterior decompression of the craniovertebral junction is the most common treatment for CM1. In addition to the conventional procedure, the authors tried to expand the posterior fossa with the aim to normalize CSF circulation at the CVJ with some modification. The whole procedure renders a better dural closure with less chance of complications, less chance of compression from inside and outside because of the bony barrier and better chance of reformation of the occipital cistern.

#### **3.20 "Upside down-inside out cranioplasty" by Tjokorda and Tjokorda**

Tjokorda and Tjokorda described a method of a less invasive suboccipital decompression-cranioplasty in 2018 [59]. They analyzed retrospectively, 10 patients from 2010 to 2016, on whom they performed their formulated method of upside down-inside out (UDIO) cranioplasty.

Seven patients in their 4th decade or older and three patients in their 3rd decade or younger had Chiari malformation type I with or without syringomyelia.

With the help of pneumatic perforator and drill, a reverse triangular-shaped craniotomy was done in one piece. Laminectomy of C1 and duraplasty was performed, ensuring normal cerebrospinal fluid flow and dural pulsation. The triangular bone flap harvested from the suboccipital craniotomy was replaced upside down-inside out and was fixed with titanium mini plate and screws.

All patients had improvement of their sensory and motor functions immediately following surgery. Post-operative Japanese Orthopedic Association scoring system (JOA score) scores compared to pre-operative scores were improved in all the patients. Only one patient needed a syringo-subarachnoid shunt for syrinx. No acute or late surgical complications were encountered in a follow-up period of at least 12 months.

The philosophy behind putting the bone upside down and inside out was to place the bone graft above the external table of its origin with periosteum inside to increase the posterior fossa volume, prevent re-stenosis and dural scarring. Other benefits of UDIO were thought to be protecting the cerebellum from adhesion or sagging, and this was believed to prevent adhesion, preventing formation of the pseudomeningocele, facilitating the reconstruction of the posterior neck muscles and preventing CSF leak by reducing the suction effect.

#### **3.21 "Cranial vault remodeling" by Valentini et al.**

In 2019, Valentini et al. described cranial vault remodeling of five children in a special subset of CM1 with untreated sagittal stenosis (USS) [60]. Association of

CM1 with craniosynostosis is not uncommon and coexistent low cranial volume, especially the small posterior fossa with venous engorgement and hydrocephalus has the potential to contribute in developing symptomatic CM1 in infants.

From a series of 636 CM1 children, from 1998 to 2018, 48 cases of untreated sagittal synostosis associated with CM1 were analyzed. Of the 48 children, 27 children were operated for different signs and symptoms like headache, intellectual disability, behavioral disorders, visual loss, sleep apneas, raised ICP, papilledema, syringomyelia and scoliosis. Different modalities of surgical procedures were performed and 5 of the children underwent cranial vault remodeling. Three of them had only cranial vault remodeling, while craniovertebral decompression (CVD) was also performed on 1 before and on 1 after the remodeling.

They did a complete cranial vault remodeling, by means of a personal free flaps technique, adopting the osteo-distraction techniques used for complex craniosynostosis. The flaps were extended on the sagittal area also to favor vertical and wide enlargement.

All the patients had improved symptomatically. In postop MRI they had restoration of normal posterior fossa CSF flow with tonsillar ascent or stabilization, and shrinkage or control of the syrinx diameter.

This procedure was aimed to increase the skull volume, both supra and infratentorial, to reduce the struggle for space between cerebrum and cerebellum. The pathogenesis of CM1 in sagittal stenosis (SS) has been explained by the downward compensatory cranial growth. USS causes a constraint to the posterior cranial vault vertical expansion, resulting in a posterior fossa smaller than normal. The reduced supratentorial volume contributes to downward cerebellar migration directly or through the increase of ICP, and probably also related to the venous hypertension due to superior sagittal sinus constriction in the bony groove. They suggested that the double causal factor in SS, the competition for volume between cerebrum and cerebellum; and the small posterior fossa, both need a surgical intervention by cranial vault remodeling and by CVD respectively. The observations suggest, SS carries the risk to develop a symptomatic CM1, when left untreated, is not amenable by CVD alone.

#### **3.22 "Stealth cranioplasty" by Rahman et al.: our technique and thoughts**

In 2017, we described a novel technique of reconstruction of posterior fossa by cranioplasty with the use of pre-shaped titanium mesh for CM1, which we call "Stealth cranioplasty" [27]. In the procedure, we set our goal to address all possible symptoms with maintenance of the surgical modifications continually as well as to prevent complications and recurrence.

We performed surgery in our method on 11 adult patients of CM1 with SM, who presented between 2012 and early 2017. Neurological symptoms of the patients included sensory disturbance, neckache, limb weakness and suboccipital headache for a duration of 6–84 months. MRI of all the patients demonstrated cerebellar tonsillar descent more than 5 mm from the foramen magnum and syringes of different diameters, extending from 3 to more than 10 levels.

A midline posterior fossa craniectomy measuring about 3 × 2.5 cm and laminectomy of the C1 posterior arch about 1 cm on both sides from the midline is done (**Figure 1A**). An arachnoid preserving midline linear durotomy (**Figure 1B**) followed by duraplasty with a patch of investing layer of the deep cervical fascia is performed (**Figure 1C**). Six tacking sutures are taken from the cut margins of the dura; 2 on both sides and 1 each from the upper and lower tips of the opening (**Figure 1B** and **C**).

**55**

cisterna magna.

**Figure 1.**

*Role of Cranioplasty in Management of Chiari Malformation*

*and tenting, (E) stealth cranioplast from front and (F) from rear.*

A titanium mesh measuring about 5 × 5 cm is bent in the middle into a longitudinally half split cone to mimic the cockpit and the flat sides of the mesh are bent outwards to give them the contour of the wings of a Stealth bomber (**Figure 1E** and **F**). The widened part of the cone is cut in a crescent to create more space around the CVJ. The titanium mesh Stealth cranioplast is placed over the craniectomy gap with the wider portion at the lower end over the foramen magnum and is fixed with 6–7 mini screws. The six tackings are now tacked with the cranioplasty giving the duraplasty the shape of a hexagonal tent (**Figure 1D**). The "stealth cranioplasty" augments the posterior fossa volume and maintains that and the tacking of the duraplasty maintains the patency of the newly formed

*Different stages of stealth cranioplasty: (A) craniectomy and C1 posterior arch laminectomy, (B) arachnoid preserving durotomy and 6 tackings from the margin, (C) duraplasty, (D) placing of the stealth cranioplast* 

All the patients of the series were followed up for a period of 7–54 months. Eight patients improved having a Chicago Chiari Outcome Scale (CCOS) score of 13–15, while 3 patients remained unchanged. All the patients had remarkable shape change of the posterior fossa from a flat lower part to a spherical and voluminous lower part on postop CT scan. Diameter of the FM also increased evidently (**Figure 2A** and **B**). On post-operative MRI, good re-establishment of cisterna magna was noted in all the patients. Marked reduction of syrinx was observed in two patients (**Figure 2C** and **D**). Eight patients had moderate to mild reduction of syrinx while one patient had no change. No post-operative complication or worsening of pre-operative

Though our technique is not an all-encompassing one, we developed our novel procedure based on the well-established theory of overcrowded shallow posterior fossa causing herniation of the contents through the foramen magnum. We thought of cranioplasty first to make more space in the posterior fossa, especially around the foramen magnum as well as to prevent recurrence from posterior compression by the muscles and fibrous tissue on the unprotected dura following to the craniectomy. The arachnoid preserving duraplasty was done with the intention to avoid CSF-related complications like CSF leak, pseudomeningocele and meningitis. Later, we thought of maintaining the newly formed CSF space by tenting the duraplasty with the cranioplasty. Initially, we used to put a titanium mesh as it is, but with time we faced some complications and started to shape the titanium mesh into the shape

symptoms were seen and none of the patients needed redo surgery.

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

#### **Figure 1.**

*Neurosurgical Procedures - Innovative Approaches*

enlargement.

by CVD alone.

also performed on 1 before and on 1 after the remodeling.

shrinkage or control of the syrinx diameter.

prevent complications and recurrence.

diameters, extending from 3 to more than 10 levels.

CM1 with craniosynostosis is not uncommon and coexistent low cranial volume, especially the small posterior fossa with venous engorgement and hydrocephalus has the potential to contribute in developing symptomatic CM1 in infants.

From a series of 636 CM1 children, from 1998 to 2018, 48 cases of untreated sagittal synostosis associated with CM1 were analyzed. Of the 48 children, 27 children were operated for different signs and symptoms like headache, intellectual disability, behavioral disorders, visual loss, sleep apneas, raised ICP, papilledema, syringomyelia and scoliosis. Different modalities of surgical procedures were performed and 5 of the children underwent cranial vault remodeling. Three of them had only cranial vault remodeling, while craniovertebral decompression (CVD) was

They did a complete cranial vault remodeling, by means of a personal free flaps technique, adopting the osteo-distraction techniques used for complex craniosynostosis. The flaps were extended on the sagittal area also to favor vertical and wide

All the patients had improved symptomatically. In postop MRI they had restoration of normal posterior fossa CSF flow with tonsillar ascent or stabilization, and

This procedure was aimed to increase the skull volume, both supra and infraten-

torial, to reduce the struggle for space between cerebrum and cerebellum. The pathogenesis of CM1 in sagittal stenosis (SS) has been explained by the downward compensatory cranial growth. USS causes a constraint to the posterior cranial vault vertical expansion, resulting in a posterior fossa smaller than normal. The reduced supratentorial volume contributes to downward cerebellar migration directly or through the increase of ICP, and probably also related to the venous hypertension due to superior sagittal sinus constriction in the bony groove. They suggested that the double causal factor in SS, the competition for volume between cerebrum and cerebellum; and the small posterior fossa, both need a surgical intervention by cranial vault remodeling and by CVD respectively. The observations suggest, SS carries the risk to develop a symptomatic CM1, when left untreated, is not amenable

**3.22 "Stealth cranioplasty" by Rahman et al.: our technique and thoughts**

In 2017, we described a novel technique of reconstruction of posterior fossa by cranioplasty with the use of pre-shaped titanium mesh for CM1, which we call "Stealth cranioplasty" [27]. In the procedure, we set our goal to address all possible symptoms with maintenance of the surgical modifications continually as well as to

We performed surgery in our method on 11 adult patients of CM1 with SM, who

presented between 2012 and early 2017. Neurological symptoms of the patients included sensory disturbance, neckache, limb weakness and suboccipital headache for a duration of 6–84 months. MRI of all the patients demonstrated cerebellar tonsillar descent more than 5 mm from the foramen magnum and syringes of different

A midline posterior fossa craniectomy measuring about 3 × 2.5 cm and laminectomy of the C1 posterior arch about 1 cm on both sides from the midline is done (**Figure 1A**). An arachnoid preserving midline linear durotomy (**Figure 1B**) followed by duraplasty with a patch of investing layer of the deep cervical fascia is performed (**Figure 1C**). Six tacking sutures are taken from the cut margins of the dura; 2 on both sides and 1 each from the upper and lower tips of the opening

**54**

(**Figure 1B** and **C**).

*Different stages of stealth cranioplasty: (A) craniectomy and C1 posterior arch laminectomy, (B) arachnoid preserving durotomy and 6 tackings from the margin, (C) duraplasty, (D) placing of the stealth cranioplast and tenting, (E) stealth cranioplast from front and (F) from rear.*

A titanium mesh measuring about 5 × 5 cm is bent in the middle into a longitudinally half split cone to mimic the cockpit and the flat sides of the mesh are bent outwards to give them the contour of the wings of a Stealth bomber (**Figure 1E** and **F**). The widened part of the cone is cut in a crescent to create more space around the CVJ. The titanium mesh Stealth cranioplast is placed over the craniectomy gap with the wider portion at the lower end over the foramen magnum and is fixed with 6–7 mini screws. The six tackings are now tacked with the cranioplasty giving the duraplasty the shape of a hexagonal tent (**Figure 1D**).

The "stealth cranioplasty" augments the posterior fossa volume and maintains that and the tacking of the duraplasty maintains the patency of the newly formed cisterna magna.

All the patients of the series were followed up for a period of 7–54 months. Eight patients improved having a Chicago Chiari Outcome Scale (CCOS) score of 13–15, while 3 patients remained unchanged. All the patients had remarkable shape change of the posterior fossa from a flat lower part to a spherical and voluminous lower part on postop CT scan. Diameter of the FM also increased evidently (**Figure 2A** and **B**). On post-operative MRI, good re-establishment of cisterna magna was noted in all the patients. Marked reduction of syrinx was observed in two patients (**Figure 2C** and **D**). Eight patients had moderate to mild reduction of syrinx while one patient had no change. No post-operative complication or worsening of pre-operative symptoms were seen and none of the patients needed redo surgery.

Though our technique is not an all-encompassing one, we developed our novel procedure based on the well-established theory of overcrowded shallow posterior fossa causing herniation of the contents through the foramen magnum. We thought of cranioplasty first to make more space in the posterior fossa, especially around the foramen magnum as well as to prevent recurrence from posterior compression by the muscles and fibrous tissue on the unprotected dura following to the craniectomy. The arachnoid preserving duraplasty was done with the intention to avoid CSF-related complications like CSF leak, pseudomeningocele and meningitis. Later, we thought of maintaining the newly formed CSF space by tenting the duraplasty with the cranioplasty. Initially, we used to put a titanium mesh as it is, but with time we faced some complications and started to shape the titanium mesh into the shape

**Figure 2.**

*Pre and postoperative images: (A) preoperative CT scan showing shallow posterior fossa and narrow foramen magnum, (B) postoperatively which has clearly increased in volume and diameter respectively, (C) preoperative MRI shows tonsillar herniation, absence of cisterna magna and big syrinx, and (D) postoperative MRI showing tonsillar ascent, appearance of good retrocerebellar CSF space and obvious resolution of syrinx.*

of a Stealth bomber, thus we call it "Stealth cranioplasty". The Stealth cranioplasty can also prevent cerebellar slump as we flatten the upper portion to support the cerebellum. As a whole, we intended to increase the posterior fossa volume to restore and maintain normal anatomy and physiology around the foramen magnum including the CSF dynamics as well as to prevent cerebellar slump, CSF related complications and recurrence. Reduced financial and psychological burden on the patients came as a byproduct as they did not have complications and did not need any redo surgery so far. As of March 2019, we performed Stealth cranioplasty on 17 symptomatic adults for CM1 with SM and all are doing well without any complication or recurrence.

#### **4. Final remarks and future directions**

It was the Japanese neurosurgeons, who pioneered the cranioplasty for CM1. After that, quite a few attempts have been made to manage CM1 by cranioplasty in different formats. Even though, not a regular practice for CM1 surgery, cranioplasty can successfully be performed in selected cases with good outcome.

Different techniques of cranioplasty have been devised with different concepts. Whatever the strategy is preferred, the ultimate goal is to give CM1 patients the utmost benefit. Cranioplasty was first adopted with the aim to increase the volume of the posterior cranial fossa as most of the surgeons of this genre believe that the shallow posterior fossa is the main pathology behind development of CM1. The next other important pathology related to CM is the aberration of the CSF dynamics around the CVJ, which is also believed to be a consequence of the abnormal physiology resulting from the small posterior fossa. The cranioplasties also aim to manage this problem of CSF dynamics and with most of the cranioplasty procedures, this can be managed successfully. Apart from these two, the other valid objectives to choose cranioplasty in treatment of CM can be, dealing and preventing complications like cerebellar ptosis, dural ectasia, CSF related complications, post-surgery headaches and recurrences.

Till now, there is no common method for managing all cases of CM. Thus, every CM should be dealt with its individuality. The genetics of CM is being revealed now with time and the genetic basis of the pathophysiology of CM may allow scientists to manage all CM patients in a single manner in future. Until then, cranioplasty in different formats may serve as good means of dealing most of the straightforward cases of CM as the primary treatment modality in different combinations.

**57**

**Author details**

Asifur Rahman

Dhaka, Bangladesh

Department of Neurosurgery, Bangabandhu Sheikh Mujib Medical University,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: bijoun14@yahoo.com

provided the original work is properly cited.

*Role of Cranioplasty in Management of Chiari Malformation*

can be adopted as a routine procedure for most of the cases.

Cranioplasty can play effective role in addressing the primary pathology as well as the way to prevent and manage most of the possible complications. In general, this

I am indebted to my colleagues and patients for their enormous support in so

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

**Acknowledgements**

**Conflict of interest**

None.

many ways in writing this chapter.

*Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

Cranioplasty can play effective role in addressing the primary pathology as well as the way to prevent and manage most of the possible complications. In general, this can be adopted as a routine procedure for most of the cases.

### **Acknowledgements**

I am indebted to my colleagues and patients for their enormous support in so many ways in writing this chapter.

### **Conflict of interest**

None.

*Neurosurgical Procedures - Innovative Approaches*

of a Stealth bomber, thus we call it "Stealth cranioplasty". The Stealth cranioplasty can also prevent cerebellar slump as we flatten the upper portion to support the cerebellum. As a whole, we intended to increase the posterior fossa volume to restore and maintain normal anatomy and physiology around the foramen magnum including the CSF dynamics as well as to prevent cerebellar slump, CSF related complications and recurrence. Reduced financial and psychological burden on the patients came as a byproduct as they did not have complications and did not need any redo surgery so far. As of March 2019, we performed Stealth cranioplasty on 17 symptomatic adults for CM1 with SM and all are doing well without any complica-

*Pre and postoperative images: (A) preoperative CT scan showing shallow posterior fossa and narrow foramen magnum, (B) postoperatively which has clearly increased in volume and diameter respectively, (C) preoperative MRI shows tonsillar herniation, absence of cisterna magna and big syrinx, and (D) postoperative MRI showing tonsillar ascent, appearance of good retrocerebellar CSF space and obvious resolution of syrinx.*

It was the Japanese neurosurgeons, who pioneered the cranioplasty for CM1. After that, quite a few attempts have been made to manage CM1 by cranioplasty in different formats. Even though, not a regular practice for CM1 surgery, cranioplasty

Different techniques of cranioplasty have been devised with different concepts. Whatever the strategy is preferred, the ultimate goal is to give CM1 patients the utmost benefit. Cranioplasty was first adopted with the aim to increase the volume of the posterior cranial fossa as most of the surgeons of this genre believe that the shallow posterior fossa is the main pathology behind development of CM1. The next other important pathology related to CM is the aberration of the CSF dynamics around the CVJ, which is also believed to be a consequence of the abnormal physiology resulting from the small posterior fossa. The cranioplasties also aim to manage this problem of CSF dynamics and with most of the cranioplasty procedures, this can be managed successfully. Apart from these two, the other valid objectives to choose cranioplasty in treatment of CM can be, dealing and preventing complications like cerebellar ptosis, dural ectasia, CSF related complications, post-surgery

Till now, there is no common method for managing all cases of CM. Thus, every CM should be dealt with its individuality. The genetics of CM is being revealed now with time and the genetic basis of the pathophysiology of CM may allow scientists to manage all CM patients in a single manner in future. Until then, cranioplasty in different formats may serve as good means of dealing most of the straightforward cases of CM as the primary treatment modality in different combinations.

can successfully be performed in selected cases with good outcome.

**56**

tion or recurrence.

**Figure 2.**

headaches and recurrences.

**4. Final remarks and future directions**

### **Author details**

Asifur Rahman Department of Neurosurgery, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh

\*Address all correspondence to: bijoun14@yahoo.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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2019;**10**(1):85

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*DOI: http://dx.doi.org/10.5772/intechopen.90055*

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with Chiari type I malformation: Relationship between tonsillo-dural distance and syrinx cavity. Turkish Neurosurgery. 2019;**29**(2):229-236

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[18] Badie B, Mendoza D, Batzdorf U. Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery. 1995;**37**(2):214-218

[19] Batzdorf U, McArthur DL, Bentson JR. Surgical treatment of Chiari malformation with and without syringomyelia: Experience with 177 adult patients. Journal of Neurosurgery. 2013;**118**(2):232-242

[20] Bonney PA, Maurer AJ, Cheema AA, Duong Q, Glenn CA, Safavi-Abbasi S, et al. Clinical significance of changes in pB-C2 distance in patients with Chiari type I malformations following posterior fossa decompression: A single-institution experience. Journal of Neurosurgery: Pediatrics. 2016;**17**(3):336-342

[21] Cools MJ, Quinsey CS, Elton SW. Chiari decompression outcomes using ligamentum nuchae harvest and duraplasty in pediatric patients with Chiari malformation type I. Journal of Neurosurgery: Pediatrics. 2018;**22**(1):47-51

[22] Oral S, Yilmaz A, Kucuk A, Tumturk A, Menku A. Comparison of dural splitting and duraplasty in patients with Chiari type I malformation: Relationship between tonsillo-dural distance and syrinx cavity. Turkish Neurosurgery. 2019;**29**(2):229-236

[23] Radmanesh A, Greenberg JK, Chatterjee A, Smyth MD, Limbrick DD, Sharma A. Tonsillar pulsatility before and after surgical decompression for

children with Chiari malformation type 1: An application for true fast imaging with steady state precession. Neuroradiology. 2015;**57**(4):387-393

[24] Singhal GD, Singhal S, Agrawal G, Singhal D, Arora V. Surgical experience in pediatric patients with Chiari-I malformations aged ≤ 18 years. Journal of Neurosciences in Rural Practice. 2019;**10**(1):85

[25] Hida K, Iwasaki Y, Koyanagi I, Sawamura Y, Abe H. Surgical indication and results of foramen magnum decompression versus syringosubarachnoid shunting for syringomyelia associated with Chiari I malformation. Neurosurgery. 1995;**37**(4):673-679

[26] Zhang L, Yi Z, Duan H, Li L. A novel autologous duraplasty in situ technique for the treatment of Chiari malformation type I. Journal of Neurosurgery. 2017;**126**(1):91-97

[27] Rahman A, Rana MS, Bhandari PB, Asif DS, Uddin ANW, Obaida ASMA, et al. "Stealth cranioplasty:" A novel endeavor for symptomatic adult Chiari I patients with syringomyelia: Technical note, appraisal, and philosophical considerations. Journal of Craniovertebral Junction and Spine. 2017;**8**(3):243

[28] Aghakhani N, Parker F, David P, Morar S, Lacroix C, Benoudiba F, et al. Long-term follow-up of Chiari-related syringomyelia in adults: Analysis of 157 surgically treated cases. Neurosurgery. 2009;**64**(2):308-315

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**58**

*Neurosurgical Procedures - Innovative Approaches*

[1] Chiari H. Concerning alterations in the cerebellum resulting from cerebral hydrocephalus. Pediatric Neurosurgery. results of arachnoid-preserving posterior fossa decompression for Chiari I malformation with associated syringomyelia. Journal of Clinical Neuroscience. 2012;**19**(4):557-560

2015;**16**(2):150-158

System. 2004;**20**(5):349-356

[10] Kennedy BC, Kelly KM, Phan MQ, Bruce SS, McDowell MM, Anderson RC, et al. Outcomes after suboccipital decompression without dural opening in children with Chiari malformation type I. Journal of Neurosurgery: Pediatrics.

[11] Navarro R, Olavarria G, Seshadri R, Gonzales-Portillo G, McLone DG, Tomita T. Surgical results of posterior fossa decompression for patients with Chiari I malformation. Child's Nervous

[12] Munshi I, Frim D, Stine-Reyes R, Weir BK, Hekmatpanah J, Brown F. Effects of posterior fossa decompression with and without duraplasty on Chiari malformation-associated hydromyelia. Neurosurgery. 2000;**46**(6):1384-1390

[13] Pomeraniec IJ, Ksendzovsky A, Awad AJ, Fezeu F, Jane JA. Natural and surgical history of Chiari malformation type I in the pediatric population. Journal of Neurosurgery: Pediatrics.

[14] Quon JL, Grant RA, DiLuna ML. Multimodal evaluation of CSF dynamics following extradural decompression for Chiari malformation type I. Journal of Neurosurgery: Spine.

[15] Gardner WJ, Goodall RJ. The surgical treatment of Arnold-Chiari malformation in adults: An explanation of its mechanism and importance of encephalography in diagnosis. Journal of Neurosurgery. 1950;**7**(3):199-206

[16] Krieger MD, McComb JG, Levy ML. Toward a simpler surgical

2016;**17**(3):343-352

2015;**22**(6):622-630

[2] Koehler P. Chiari's description of cerebellar ectopy (1891): With a summary of Cleland's and Arnold's contributions and some early observations on neural-tube defects. Journal of Neurosurgery.

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[7] Tubbs RS, Oakes WJ. The Chiari Malformations: A Historical Context. The Chiari Malformations. New York:

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2017;**108**:991.e1-991.e5

[55] Choi J-I, Dhong ES, Lim D-J, Kim S-D. Reduction cranioplasty for macrocephaly with long-standing hydrocephalus and non-fused Fontanelle in Chiari malformation type I. Child's Nervous System.

[56] Udani V, Holly LT, Chow D, Batzdorf U. Posterior fossa

[57] Alsahlawi A, Ekhzaimy A, Alshowair D, Ajlan A. Decompressive

cranioplasty in a patient with osteopetrosis. World Neurosurgery.

[58] Korshunov A, Kushel Y. Expansive Suboccipital Cranioplasty in Chiari-1 Malformation (a Case Report and Technical Notes). Moscow: Media Sphera Publishing Group; 2017. p. 92

[59] Tjokorda GM, Tjokorda GS. A less invasive suboccipital decompression-

cranioplasty for Chiari type I malformation: Is it beneficial? Interdisciplinary Neurosurgery.

2018;**14**:59-62

reconstruction using titanium plate for the treatment of cerebellar ptosis after decompression for Chiari malformation. World Neurosurgery.

*DOI: http://dx.doi.org/10.5772/intechopen.90055*

Hara M, Anzai M. A simple technique for expansive suboccipital cranioplasty

[46] Itoh Y, Kuwahara N, Hirano Y, Sasajima T, Suzuki A, Mizoi K. Surgical Treatment of Syringomyelia Associated with Chiari I Malformation: Advantage of Cranioplasty Using Hydroxyapatite Implants. Syringomyelia: Springer;

[47] Sheikh BY. Simple and safe method of cranial reconstruction after posterior fossa craniectomy. Surgical Neurology.

[48] Heller JB, Lazareff J, Gabbay JS, Lam S, Kawamoto HK, Bradley JP. Posterior cranial fossa box expansion leads to resolution of symptomatic cerebellar ptosis following Chiari I malformation repair. The Journal of Craniofacial Surgery. 2007;**18**(2):274-280

[49] Di X, Luciano MG, Benzel EC. Acute respiratory arrest following partial suboccipital cranioplasty for cerebellar ptosis from Chiari malformation decompression: Report of 2 cases. Neurosurgical Focus. 2008;**25**(6):E12

[50] Chou Y-C, Sarkar R, Osuagwu FC, Lazareff JA. Suboccipital craniotomy in the surgical treatment of Chiari I malformation. Child's Nervous System.

[51] Furtado SV, Anantharam BA, Reddy K, Hegde AS. Repair of Chiari III malformation using cranioplasty and an occipital rotation flap: Technical note and review of literature. Surgical Neurology. 2009;**72**(4):414-417

2009;**25**(9):1111-1114

Syringomyelia: Springer; 2001.

[45] Takayasu M, Takagi T,

following foramen magnum decompression for the treatment of syringomyelia associated with Chiari I malformation. Neurosurgical Review.

2004;**27**(3):173-177

2001. pp. 188-193

2006;**65**(1):63-66

pp. 159-163

*Role of Cranioplasty in Management of Chiari Malformation DOI: http://dx.doi.org/10.5772/intechopen.90055*

Syringomyelia: Springer; 2001. pp. 159-163

*Neurosurgical Procedures - Innovative Approaches*

Surgery Part A: Central European Neurosurgery. 2018;**79**(01):045-051

[38] Zagzoog N, Reddy KK. Use of minimally invasive tubular retractors for foramen magnum decompression of Chiari malformation: A technical note and case series. World Neurosurgery.

[39] Tokuno H, Suzuki T, Nishimura S, Hakuba A, editors. Operative treatment

of Chiari malformation with syringomyelia. In: Proceedings of the 8th European Congress of Neurosurgery; September 6-11, 1987;

Barcelona. Springer; 1988

[40] Sakamoto H, Nishikawa M, Hakuba A, Yasui T, Kitano S, Nakanishi N, et al. Expansive suboccipital cranioplasty for the treatment of syringomyelia associated with Chiari malformation. Acta Neurochirurgica. 1999;**141**(9):949-961

[41] Holly LT, Batzdorf U. Management

[42] Di Rocco C, Velardi F. Acquired

Baba M, Terakawa Y, Hara M. Chiari I malformation associated with ventral compression and instability: One-stage posterior decompression and fusion with a new instrumentation technique. Neurosurgery. 2004;**54**(6):1430-1435

of cerebellar ptosis following craniovertebral decompression for Chiari I malformation. Journal of Neurosurgery. 2001;**94**(1):21-26

Chiari type I malformation managed by supratentorial cranial enlargement. Child's Nervous System.

[43] Nishikawa M, Ohata K,

[44] Takayasu M, Nishizawa T,

Cranioplasty Following Foramen Magnum Decompression for the Treatment of Syringomyelia

Yoshida J. Simple Expansive Suboccipital

Associated with Chiari I Malformation.

2003;**19**(12):800-807

2019;**128**:248-253

magnetic resonance imaging of Chiari I malformations: An analysis of cerebrospinal fluid dynamics. Neurosurgery. 1994;**35**(2):214-224

2015;**15**(2):178-188

1988;**68**(5):726-730

2001;**11**(1):1-9

2016;**17**(2):174-181

Miller JI, Bergland RM,

Neurosurgery Clinics. 2015;**26**(4):527-531

resonance imaging criteria. Neurosurgery. 1992;**31**(2):231-245

[31] Ladner TR, Dewan MC, Day MA, Shannon CN, Tomycz L, Tulipan N, et al. Evaluating the relationship of the pB-C2 line to clinical outcomes in a 15-year single-center cohort of pediatric Chiari I malformation. Journal of Neurosurgery: Pediatrics.

[32] Batzdorf U. Chiari I malformation with syringomyelia: Evaluation of surgical therapy by magnetic resonance imaging. Journal of Neurosurgery.

[33] Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ. Treatment of Chiari type I malformation in patients with and without syringomyelia: A consecutive series of 66 cases. Neurosurgical Focus.

[34] Stanko KM, Lee YM, Rios J,

[35] Milhorat TH, Johnson WD,

Hollenberg-Sher J. Surgical treatment of syringomyelia based on magnetic

[36] Rocque BG, Oakes WJ. Surgical treatment of Chiari I malformation.

[37] Ratre S, Yadav N, Yadav YR, Parihar VS, Bajaj J, Kher Y. Endoscopic

management of Arnold-Chiari malformation type I with or without syringomyelia. Journal of Neurological

Wu A, Sobrinho GW, Weingart JD, et al. Improvement of syrinx resolution after tonsillar cautery in pediatric patients with Chiari type I malformation. Journal of Neurosurgery: Pediatrics.

**60**

[45] Takayasu M, Takagi T, Hara M, Anzai M. A simple technique for expansive suboccipital cranioplasty following foramen magnum decompression for the treatment of syringomyelia associated with Chiari I malformation. Neurosurgical Review. 2004;**27**(3):173-177

[46] Itoh Y, Kuwahara N, Hirano Y, Sasajima T, Suzuki A, Mizoi K. Surgical Treatment of Syringomyelia Associated with Chiari I Malformation: Advantage of Cranioplasty Using Hydroxyapatite Implants. Syringomyelia: Springer; 2001. pp. 188-193

[47] Sheikh BY. Simple and safe method of cranial reconstruction after posterior fossa craniectomy. Surgical Neurology. 2006;**65**(1):63-66

[48] Heller JB, Lazareff J, Gabbay JS, Lam S, Kawamoto HK, Bradley JP. Posterior cranial fossa box expansion leads to resolution of symptomatic cerebellar ptosis following Chiari I malformation repair. The Journal of Craniofacial Surgery. 2007;**18**(2):274-280

[49] Di X, Luciano MG, Benzel EC. Acute respiratory arrest following partial suboccipital cranioplasty for cerebellar ptosis from Chiari malformation decompression: Report of 2 cases. Neurosurgical Focus. 2008;**25**(6):E12

[50] Chou Y-C, Sarkar R, Osuagwu FC, Lazareff JA. Suboccipital craniotomy in the surgical treatment of Chiari I malformation. Child's Nervous System. 2009;**25**(9):1111-1114

[51] Furtado SV, Anantharam BA, Reddy K, Hegde AS. Repair of Chiari III malformation using cranioplasty and an occipital rotation flap: Technical note and review of literature. Surgical Neurology. 2009;**72**(4):414-417

[52] Oró JJ, Mueller DM. Posterior fossa decompression and reconstruction in adolescents and adults with the Chiari I malformation. Neurological Research. 2011;**33**(3):261-271

[53] Bambakidis NC, Dickman CA. Surgery of the Craniovertebral Junction. New York: Thieme; 2012

[54] Assina R, Meleis AM, Cohen MA, Iqbal MO, Liu JK. Titanium meshassisted dural tenting for an expansile suboccipital cranioplasty in the treatment of Chiari 1 malformation. Journal of Clinical Neuroscience. 2014;**21**(9):1641-1646

[55] Choi J-I, Dhong ES, Lim D-J, Kim S-D. Reduction cranioplasty for macrocephaly with long-standing hydrocephalus and non-fused Fontanelle in Chiari malformation type I. Child's Nervous System. 2014;**30**(10):1763-1766

[56] Udani V, Holly LT, Chow D, Batzdorf U. Posterior fossa reconstruction using titanium plate for the treatment of cerebellar ptosis after decompression for Chiari malformation. World Neurosurgery. 2014;**81**(5-6):836-841

[57] Alsahlawi A, Ekhzaimy A, Alshowair D, Ajlan A. Decompressive cranioplasty in a patient with osteopetrosis. World Neurosurgery. 2017;**108**:991.e1-991.e5

[58] Korshunov A, Kushel Y. Expansive Suboccipital Cranioplasty in Chiari-1 Malformation (a Case Report and Technical Notes). Moscow: Media Sphera Publishing Group; 2017. p. 92

[59] Tjokorda GM, Tjokorda GS. A less invasive suboccipital decompressioncranioplasty for Chiari type I malformation: Is it beneficial? Interdisciplinary Neurosurgery. 2018;**14**:59-62

[60] Valentini LG, Saletti V, Erbetta A, Chiapparini L, Furlanetto M. Chiari 1 malformation and untreated sagittal synostosis: A new subset of complex Chiari? Child's Nervous System. 2019;**35**:1-13

**63**

**Chapter 4**

Evolution

*Asifur Rahman*

**Abstract**

**1. Introduction**

"Stealth Cranioplasty" for Adult

Chiari malformation (CM) and its management are long debated enigmas for neurosurgeons. Many surgical procedures have been innovated and are in practice for this perplexing and daunting entity to give the patients a satisfactory remedy. But, a unanimously accepted surgical procedure is still lacking to achieve gratifying result. We tried to develop a novel technique, which we call the "stealth cranioplasty (SCP)," to help the adult Chiari malformation type 1 (CM1) patients. In this chapter, the philosophy behind developing the technique of "stealth cranioplasty" by reconstruction of posterior fossa (PF) by cranioplasty with pre-shaped titanium mesh is described. Different stages, difficulties, and modifications of the journey

The baffling malady of Chiari malformation (CM) is still an enigma for neurosurgeons for its poorly understood pathophysiology, uncertain natural history, and dilemma concerning management options since Hans Chiari described it first in 1891 and detailed with refinements in 1896. Even being a diverse disease in presentation, Chiari malformation is being detected more often than before because of the advent of magnetic resonance imaging (MRI) and its better delineation of soft tissue especially in the posterior fossa (PF) and the craniovertebral junction (CVJ). Owing to its diverse presentations, varied thoughts on pathophysiology, and numerous philosophies in management, a myriad of surgical options are existent for CM. Better understanding of pathophysiology with technical advancements and better availability of imaging facilities have made CM more treatable with encouraging outcomes, and CM no more remains an unfamiliar entity. In this chapter we will present a novel technique that we developed over years to treat only the adult Chiari malformation type 1 (CM1) patients. We will also discuss about the philosophy behind developing this as well as the evolution process of the procedure

Chiari Malformation Type 1:

Innovation, Adaptation, and

A Philosophical Journey of

toward the present day status are also elaborated graphically.

**Keywords:** Chiari malformation, Chiari malformation type 1, arachnoid-preserving duraplasty, stealth cranioplasty, posterior fossa

#### **Chapter 4**

*Neurosurgical Procedures - Innovative Approaches*

[60] Valentini LG, Saletti V, Erbetta A, Chiapparini L, Furlanetto M. Chiari 1 malformation and untreated sagittal synostosis: A new subset of complex Chiari? Child's Nervous System.

2019;**35**:1-13

**62**

## "Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey of Innovation, Adaptation, and Evolution

*Asifur Rahman*

### **Abstract**

Chiari malformation (CM) and its management are long debated enigmas for neurosurgeons. Many surgical procedures have been innovated and are in practice for this perplexing and daunting entity to give the patients a satisfactory remedy. But, a unanimously accepted surgical procedure is still lacking to achieve gratifying result. We tried to develop a novel technique, which we call the "stealth cranioplasty (SCP)," to help the adult Chiari malformation type 1 (CM1) patients. In this chapter, the philosophy behind developing the technique of "stealth cranioplasty" by reconstruction of posterior fossa (PF) by cranioplasty with pre-shaped titanium mesh is described. Different stages, difficulties, and modifications of the journey toward the present day status are also elaborated graphically.

**Keywords:** Chiari malformation, Chiari malformation type 1, arachnoid-preserving duraplasty, stealth cranioplasty, posterior fossa

#### **1. Introduction**

The baffling malady of Chiari malformation (CM) is still an enigma for neurosurgeons for its poorly understood pathophysiology, uncertain natural history, and dilemma concerning management options since Hans Chiari described it first in 1891 and detailed with refinements in 1896. Even being a diverse disease in presentation, Chiari malformation is being detected more often than before because of the advent of magnetic resonance imaging (MRI) and its better delineation of soft tissue especially in the posterior fossa (PF) and the craniovertebral junction (CVJ). Owing to its diverse presentations, varied thoughts on pathophysiology, and numerous philosophies in management, a myriad of surgical options are existent for CM. Better understanding of pathophysiology with technical advancements and better availability of imaging facilities have made CM more treatable with encouraging outcomes, and CM no more remains an unfamiliar entity. In this chapter we will present a novel technique that we developed over years to treat only the adult Chiari malformation type 1 (CM1) patients. We will also discuss about the philosophy behind developing this as well as the evolution process of the procedure

focusing on the problems that we faced and how we modified our procedure to solve those and finally reached here. With our procedure we tried to address the two most common pathophysiological aspects of CM1 rationally that play the major roles: the shallow posterior fossa and the difference in pressure gradient of cerebrospinal fluid (CSF) between cranial and spinal compartments. With our procedure we also tried to prevent recurrence and avoid complications in a cost-effective way.

#### **2. Pathophysiology**

Any conclusive pathology in development of Chiari malformations is still lacking, and heterogeneity of theories regarding pathogenesis of CM continues to deepen the controversy. The most popular and accepted theory regarding Chiari 1 is that it is a developmental anomaly that causes tonsillar herniation from a discrepancy between the content, the hindbrain and the container, and the posterior fossa [1, 2]. Arguments can be made that this malady entirely is not a malformation. The shallow posterior fossa is an anomaly or deviation from the normal arrangement in its structure, while the herniation of the part of the normal hindbrain is an alteration that the nature makes in an attempt to maintain the homeostasis in the posterior fossa and the CVJ [3]. The origin of shallow PF may have several pathological bases, and our technique is primarily based on the theory of shallow posterior fossa as well as other pathologies that play important role in development of CM.

#### **2.1 Evolution of human skull and brain and CM1**

Studies on human evolution have revealed significant changes in the braincase; the skull, especially in the posterior skull base region; and the brain itself. Analysis on evolution demonstrated the gradual increase in cranial capacity from about 800 cm3 in Homo erectus to 1000–1200 cm3 in the species of the Middle Pleistocene and further to 1500 cm3 in Neanderthals and modern humans [4–6]. But in the process of evolution from Homo neanderthalensis to *Homo sapiens*, both the cranial capacity and basal angle had decreased considerably, while the brain size increased significantly [5]. The posterior cranial fossa of *H. sapiens* has diminished in size, occupying around 26.8% of the available intracranial space, while in CM1 this space is further reduced to around 21.6%, resulting from different factors [7]. Modern human beings may carry some primitive genes of ancient hominins in their genomic code influenced by gene flow interchange, interbreeding, and anatomic reshaping of the skull base during evolution at random in some individuals of CM1 [5]. So, the shallow and small posterior fossa in CM1 may bear an evolutionary imprint.

#### **2.2 Genetics of CM1**

The majority of cases of CM1 are considered as sporadic. However, there are clues that suggest a genetic component playing role in development of Chiari in at least a subset of patients. Evidence of manifestation of CM1 in twins, in siblings, in first-degree relatives, in familial clustering among generations, or in conjunction with some known genetic syndromes supports the genetic origin vigorously. From these, it can be presumed that genetic factors, along with other epigenetic and/or environmental factors, prompt development of a small posterior cranial fossa. Familial aggregation is a representative of traits that hints to an underlying genetic basis [8–19]. Studies of families having Chiari among the members suggest posterior fossa volume (PFV) to be highly heritable, and genetic analysis reveals

**65**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

indicative linkage to regions at chromosomes 1q, 8q, 9q, 12p, 12q, 15q, and 22q. Moreover, disturbance in formation of the basichondrocranium from hyperossification or hypo-ossification has the possibility of having morphometric changes in the posterior cranial fossa in patients with Chiari resulting from the misregulation in

In the development of a shallow and small posterior fossa, embryological derangement is pivotal. Occipitocervical transition develops during the fourth week of embryological life from bilateral four occipital somites (OS1–OS4) and seven cervical somites (CS1–CS7) that form the axial skeleton [25–27]. Different parts of the occipital bone originate from different somites and grow at different paces. This discrepancy in the rate of growth of different parts of the occipital bone during development leads to the typical developmental disorder of CM1 [28]. The supratentorial part of the squamous occipital derives from membranous origin, while the infratentorial part comes from cartilaginous origin. The shallowness of the posterior fossa may result from an abnormality of the lower part of the occipital squamous bone derived from the cartilaginous origin. The chondrified supraocciput, which is vulnerable to regression, theoretically offers an embryological basis

From the thoughtful observations and meticulous analysis, along with his theory of chronically raised intracranial pressure (ICP), Chiari furthermore believed that inadequate bone growth and insufficient enlargement of skull triggered raised ICP which plays a vital role in this condition to force down the hindbrain [30–33]. Cleland in 1883 and Mennicke in 1891 also advocated that the pathology lies in the defective bone around the foramen magnum while describing hindbrain herniation [34, 35]. Many studies in the modern era, with the help of modern technological advancements, have also strongly proven that the posterior fossa is indeed shallow or smaller than the normal hindbrain in Chiari patients. The shallowness of the posterior fossa has been proven in Chiari patients in comparison to controls using X-rays [36, 37]. Ratio of the posterior fossa with supratentorial volumes on MR images between patients with Chiari 1 malformation and controls also demonstrated smaller ratio in Chiari patients who were symptomatic, and most of them

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

**2.3 Embryological basis of CM1**

for the shortening of the supraocciput in CM [29].

**2.4 Posterior fossa volume and development of CM1**

improved following posterior fossa decompression (PFD) [38].

where the PFV is rendered smaller than usual.

Some studies found PFV to be smaller in pediatric CM1 patients also, which matches the studies in adults and aids the theory relating to the pathophysiological mechanism of CM1 resulting from small posterior fossa [7]. Interestingly, in cases of acquired Chiari malformation (ACM), surgical management of only the primary lesion has shown to improve ACM which also supports the discrepancy between the volume of the posterior fossa and its contents [39]. From different studies, it is now proposed that development of Chiari results from multifactorial etiologies, where small PF remains to be the most crucial one [40–52]. The theory of small PF is further strengthened by demonstration of CM by creating smaller basichondrocrania and posterior cranial fossa than controls by producing a state of hypervitaminosis A in experimental models of rodents [53]. Moreover, CM1 has been described in several metabolic disorders also like Paget's disease [54], rickets [55, 56], craniometaphyseal dysplasia [57], acromegaly [58], and growth hormone deficiency [59],

genes [13, 20–24].

#### *"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

indicative linkage to regions at chromosomes 1q, 8q, 9q, 12p, 12q, 15q, and 22q. Moreover, disturbance in formation of the basichondrocranium from hyperossification or hypo-ossification has the possibility of having morphometric changes in the posterior cranial fossa in patients with Chiari resulting from the misregulation in genes [13, 20–24].

#### **2.3 Embryological basis of CM1**

*Neurosurgical Procedures - Innovative Approaches*

**2. Pathophysiology**

focusing on the problems that we faced and how we modified our procedure to solve those and finally reached here. With our procedure we tried to address the two most common pathophysiological aspects of CM1 rationally that play the major roles: the shallow posterior fossa and the difference in pressure gradient of cerebrospinal fluid (CSF) between cranial and spinal compartments. With our procedure we also

tried to prevent recurrence and avoid complications in a cost-effective way.

Any conclusive pathology in development of Chiari malformations is still lacking, and heterogeneity of theories regarding pathogenesis of CM continues to deepen the controversy. The most popular and accepted theory regarding Chiari 1 is that it is a developmental anomaly that causes tonsillar herniation from a discrepancy between the content, the hindbrain and the container, and the posterior fossa [1, 2]. Arguments can be made that this malady entirely is not a malformation. The shallow posterior fossa is an anomaly or deviation from the normal arrangement in its structure, while the herniation of the part of the normal hindbrain is an alteration that the nature makes in an attempt to maintain the homeostasis in the posterior fossa and the CVJ [3]. The origin of shallow PF may have several pathological bases, and our technique is primarily based on the theory of shallow posterior fossa

as well as other pathologies that play important role in development of CM.

Studies on human evolution have revealed significant changes in the braincase; the skull, especially in the posterior skull base region; and the brain itself. Analysis on evolution demonstrated the gradual increase in cranial capacity from about

process of evolution from Homo neanderthalensis to *Homo sapiens*, both the cranial capacity and basal angle had decreased considerably, while the brain size increased significantly [5]. The posterior cranial fossa of *H. sapiens* has diminished in size, occupying around 26.8% of the available intracranial space, while in CM1 this space is further reduced to around 21.6%, resulting from different factors [7]. Modern human beings may carry some primitive genes of ancient hominins in their genomic code influenced by gene flow interchange, interbreeding, and anatomic reshaping of the skull base during evolution at random in some individuals of CM1 [5]. So, the

shallow and small posterior fossa in CM1 may bear an evolutionary imprint.

The majority of cases of CM1 are considered as sporadic. However, there are clues that suggest a genetic component playing role in development of Chiari in at least a subset of patients. Evidence of manifestation of CM1 in twins, in siblings, in first-degree relatives, in familial clustering among generations, or in conjunction with some known genetic syndromes supports the genetic origin vigorously. From these, it can be presumed that genetic factors, along with other epigenetic and/or environmental factors, prompt development of a small posterior cranial fossa. Familial aggregation is a representative of traits that hints to an underlying genetic basis [8–19]. Studies of families having Chiari among the members suggest posterior fossa volume (PFV) to be highly heritable, and genetic analysis reveals

in Neanderthals and modern humans [4–6]. But in the

in the species of the Middle Pleistocene

**2.1 Evolution of human skull and brain and CM1**

in Homo erectus to 1000–1200 cm3

**64**

800 cm3

and further to 1500 cm3

**2.2 Genetics of CM1**

In the development of a shallow and small posterior fossa, embryological derangement is pivotal. Occipitocervical transition develops during the fourth week of embryological life from bilateral four occipital somites (OS1–OS4) and seven cervical somites (CS1–CS7) that form the axial skeleton [25–27]. Different parts of the occipital bone originate from different somites and grow at different paces. This discrepancy in the rate of growth of different parts of the occipital bone during development leads to the typical developmental disorder of CM1 [28]. The supratentorial part of the squamous occipital derives from membranous origin, while the infratentorial part comes from cartilaginous origin. The shallowness of the posterior fossa may result from an abnormality of the lower part of the occipital squamous bone derived from the cartilaginous origin. The chondrified supraocciput, which is vulnerable to regression, theoretically offers an embryological basis for the shortening of the supraocciput in CM [29].

#### **2.4 Posterior fossa volume and development of CM1**

From the thoughtful observations and meticulous analysis, along with his theory of chronically raised intracranial pressure (ICP), Chiari furthermore believed that inadequate bone growth and insufficient enlargement of skull triggered raised ICP which plays a vital role in this condition to force down the hindbrain [30–33]. Cleland in 1883 and Mennicke in 1891 also advocated that the pathology lies in the defective bone around the foramen magnum while describing hindbrain herniation [34, 35]. Many studies in the modern era, with the help of modern technological advancements, have also strongly proven that the posterior fossa is indeed shallow or smaller than the normal hindbrain in Chiari patients. The shallowness of the posterior fossa has been proven in Chiari patients in comparison to controls using X-rays [36, 37]. Ratio of the posterior fossa with supratentorial volumes on MR images between patients with Chiari 1 malformation and controls also demonstrated smaller ratio in Chiari patients who were symptomatic, and most of them improved following posterior fossa decompression (PFD) [38].

Some studies found PFV to be smaller in pediatric CM1 patients also, which matches the studies in adults and aids the theory relating to the pathophysiological mechanism of CM1 resulting from small posterior fossa [7]. Interestingly, in cases of acquired Chiari malformation (ACM), surgical management of only the primary lesion has shown to improve ACM which also supports the discrepancy between the volume of the posterior fossa and its contents [39]. From different studies, it is now proposed that development of Chiari results from multifactorial etiologies, where small PF remains to be the most crucial one [40–52]. The theory of small PF is further strengthened by demonstration of CM by creating smaller basichondrocrania and posterior cranial fossa than controls by producing a state of hypervitaminosis A in experimental models of rodents [53]. Moreover, CM1 has been described in several metabolic disorders also like Paget's disease [54], rickets [55, 56], craniometaphyseal dysplasia [57], acromegaly [58], and growth hormone deficiency [59], where the PFV is rendered smaller than usual.

#### **2.5 Tonsillar descent in CM1**

By definition, radiologically, tonsillar herniation more than 5 mm below the foramen magnum is considered to be CM1. Incidental findings of patients having more than 5 mm descent of tonsil without any recognizable symptoms of Chiari are not uncommon. On the other hand, there are patients who have less than 5 mm descent of the tonsils and yet show pronounced symptoms of CM1. Though the cerebellar tonsillar herniation is the most commonly used radiological measurement to determine the diagnosis of CM1, clinical presentations often pose dilemma in decision making. So, this radiological measurement of degree of tonsillar descent alone may not be reliable enough to ascertain the presence and severity of CM1 and should always be tallied with the clinicopathological setting [1, 60–70].

#### **2.6 Cranial and spinal cerebrospinal fluid pressure gradient difference in pathogenesis of CM1**

Chiari, while describing the hindbrain herniation first, hypothesized the changes to be related to congenital hydrocephalus [30]. Studies later revealed that the malformation is not always accompanied by hydrocephalus; rather the fetal cerebellar herniation is due to the lowered intraspinal pressure owing to leakage of CSF at the myelocele, especially in cases of Chiari type 2 [71–74].

In fact, it is recommended that the pressure difference between the cranial and spinal compartments is the force responsible for the herniation. It is very much feasible as the brain tissue is a thick jelly like substance and acts like a viscoelastic medium to be subjected to deformation in response to stress [75]. Thus, any imbalance between the cranial and spinal CSF compartments leading to reduced CSF pressure in the spinal compartment may result in spontaneous occurrence of a CM1 which is also evidenced by tonsillar herniation following spinal shunting procedure. Conversion of a lumbar shunt to a ventricular shunt has shown to eliminate the downward craniospinal pressure gradient, leading to the reversal of the tonsillar descent or at least arresting further migration amplifying the aptness of this theory [74, 76–81]. This theory of disequilibrium of CSF dynamics might explain the reason of the tonsils to go back to their normal position following PFD which relieves the discrepancy of the pressure gradient between the cranial and spinal compartments, and our procedure is partly based on this theory also.

#### **3. Commonly practiced surgical procedures**

First attempted surgery for CM was in 1930 by a Dutchman Cornelis Joachimus Van Houweninge Graftdijk, on a patient with myelomeningocele and ventriculogram-proven hindbrain herniation. He tried surgically to relieve CSF obstruction at the CVJ by the redundant cerebellar tissue. His thought was to try to restore better flow of CSF by widening the space through which the brain had herniated [82]. For many years after the first attempt by Van Houweninge Graftdijk, surgery of CM carried grave prognosis. Now, with the better understanding of the pathology and improvements in technology, most patients with CM1 can be benefited by different surgical procedures [83].

Owing to the nature of this disorder and its diversity in clinical presentation and image findings, it is difficult to come to a consensus on which is the best way to manage this. Depending on presentation in milder forms of symptoms, some authors have advocated conservative management. However, according to most

**67**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

experts, surgical intervention remains the gold standard, both in reduction of tonsillar herniation, resolution of syrinx, and in overall outcome, in most of the cases [61, 66, 67, 84, 85]. The common procedure in almost all surgical approaches comprise of a suboccipital craniectomy with removal of posterior arch of C1 with the aim of posterior fossa decompression. Nevertheless, there are controversies concerning the extent of bone removal and additional measures taken along with it [86, 87]. Management of the dura includes leaving the dura intact with removal of the constricting band only [88], dural scoring [89, 90], resecting the outer layer of the dura [67, 91–94], opening the dura and leaving it open [95–98], and performing a duraplasty [38, 43, 67, 88, 91, 94, 99–104]. The arachnoid manipulation similarly varies from leaving it intact [88, 91, 105] to opening and resecting it [96, 99–103, 106, 107]. The cerebellar tonsils have been addressed in various ways also like not touching them [108], dissecting to separate them [99, 109], shrinking by bipolar coagulation [43, 67, 100, 102, 103, 110, 111], and subpial resection [38, 43, 67, 106, 107, 110, 112]. Recently, minimal invasive endoscopy-assisted decompression at the

Many authors have postulated many factors to be responsible for development of Chiari malformations, and it seems that there actually are various pathologies in play. As the pathophysiology is multifactorial, it is almost impossible to address all the problems at a time with a single procedure. We tried to address the two basic pathologies that we feel to be of paramount importance in the pathophysiological process in the development of Chiari malformation. Accordingly we developed our technique only for the patients of CM1, which are young adults and do not have any other problem related to or complicating the condition like HCP, basilar invagination, and platybasia. Our patient subset also had syringes of different diameters and extensions. But we feel that it was not a big factor on influencing the result of the surgical technique, as the pathologies of both CM and SM seem to be the same. It was of our interest to see if the procedure addressing the Chiari only can solve syrinx as well, and that would provide some explanation that CM and SM share at least some common etiological factors and pathologies, which can be dealt with a

Whatever theory regarding the pathophysiology is apt, with time and experience, centering on the two basic pathologies of shallow PF and imbalance of CSF dynamics around the CVJ, now the goal of our procedure is a persistent voluminous PF that would reestablish the CSF flow dynamics and would prevent recurrence and

We place the patient prone, in a modified concord position, under general anesthesia (**Figure 1A**). Special attention is given to keep the head in neutral position, and that is not flexed in any way. This gives two benefits. When the head is neutral, it helps the already jeopardized medulla from kinking from flexion as well as keeps it free from further compression by the herniated tonsils, which is already there. During reconstruction of the posterior fossa, neutral position gives better idea about the anatomy of the structures around the foramen magnum. This also gives the additional advantage of facilitation of venous return, by ensuring the jugular veins to be free of compression which helps in avoiding unnecessary oozing. Care of

the airway, pressure points, and the vital monitoring are as usual.

foramen magnum for CM has also been reported [113, 114].

**4. Our technique**

single procedure.

complications cost-effectively.

**4.1 Patient positioning**

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

experts, surgical intervention remains the gold standard, both in reduction of tonsillar herniation, resolution of syrinx, and in overall outcome, in most of the cases [61, 66, 67, 84, 85]. The common procedure in almost all surgical approaches comprise of a suboccipital craniectomy with removal of posterior arch of C1 with the aim of posterior fossa decompression. Nevertheless, there are controversies concerning the extent of bone removal and additional measures taken along with it [86, 87]. Management of the dura includes leaving the dura intact with removal of the constricting band only [88], dural scoring [89, 90], resecting the outer layer of the dura [67, 91–94], opening the dura and leaving it open [95–98], and performing a duraplasty [38, 43, 67, 88, 91, 94, 99–104]. The arachnoid manipulation similarly varies from leaving it intact [88, 91, 105] to opening and resecting it [96, 99–103, 106, 107]. The cerebellar tonsils have been addressed in various ways also like not touching them [108], dissecting to separate them [99, 109], shrinking by bipolar coagulation [43, 67, 100, 102, 103, 110, 111], and subpial resection [38, 43, 67, 106, 107, 110, 112]. Recently, minimal invasive endoscopy-assisted decompression at the foramen magnum for CM has also been reported [113, 114].

#### **4. Our technique**

*Neurosurgical Procedures - Innovative Approaches*

By definition, radiologically, tonsillar herniation more than 5 mm below the foramen magnum is considered to be CM1. Incidental findings of patients having more than 5 mm descent of tonsil without any recognizable symptoms of Chiari are not uncommon. On the other hand, there are patients who have less than 5 mm descent of the tonsils and yet show pronounced symptoms of CM1. Though the cerebellar tonsillar herniation is the most commonly used radiological measurement to determine the diagnosis of CM1, clinical presentations often pose dilemma in decision making. So, this radiological measurement of degree of tonsillar descent alone may not be reliable enough to ascertain the presence and severity of CM1 and

should always be tallied with the clinicopathological setting [1, 60–70].

CSF at the myelocele, especially in cases of Chiari type 2 [71–74].

**2.6 Cranial and spinal cerebrospinal fluid pressure gradient difference in** 

Chiari, while describing the hindbrain herniation first, hypothesized the changes to be related to congenital hydrocephalus [30]. Studies later revealed that the malformation is not always accompanied by hydrocephalus; rather the fetal cerebellar herniation is due to the lowered intraspinal pressure owing to leakage of

In fact, it is recommended that the pressure difference between the cranial and spinal compartments is the force responsible for the herniation. It is very much feasible as the brain tissue is a thick jelly like substance and acts like a viscoelastic medium to be subjected to deformation in response to stress [75]. Thus, any imbalance between the cranial and spinal CSF compartments leading to reduced CSF pressure in the spinal compartment may result in spontaneous occurrence of a CM1 which is also evidenced by tonsillar herniation following spinal shunting procedure. Conversion of a lumbar shunt to a ventricular shunt has shown to eliminate the downward craniospinal pressure gradient, leading to the reversal of the tonsillar descent or at least arresting further migration amplifying the aptness of this theory [74, 76–81]. This theory of disequilibrium of CSF dynamics might explain the reason of the tonsils to go back to their normal position following PFD which relieves the discrepancy of the pressure gradient between the cranial and spinal compartments, and our procedure is partly based

First attempted surgery for CM was in 1930 by a Dutchman Cornelis Joachimus Van Houweninge Graftdijk, on a patient with myelomeningocele and ventriculogram-proven hindbrain herniation. He tried surgically to relieve CSF obstruction at the CVJ by the redundant cerebellar tissue. His thought was to try to restore better flow of CSF by widening the space through which the brain had herniated [82]. For many years after the first attempt by Van Houweninge Graftdijk, surgery of CM carried grave prognosis. Now, with the better understanding of the pathology and improvements in technology, most patients with CM1 can be benefited by different

Owing to the nature of this disorder and its diversity in clinical presentation and image findings, it is difficult to come to a consensus on which is the best way to manage this. Depending on presentation in milder forms of symptoms, some authors have advocated conservative management. However, according to most

**2.5 Tonsillar descent in CM1**

**pathogenesis of CM1**

on this theory also.

surgical procedures [83].

**3. Commonly practiced surgical procedures**

**66**

Many authors have postulated many factors to be responsible for development of Chiari malformations, and it seems that there actually are various pathologies in play. As the pathophysiology is multifactorial, it is almost impossible to address all the problems at a time with a single procedure. We tried to address the two basic pathologies that we feel to be of paramount importance in the pathophysiological process in the development of Chiari malformation. Accordingly we developed our technique only for the patients of CM1, which are young adults and do not have any other problem related to or complicating the condition like HCP, basilar invagination, and platybasia. Our patient subset also had syringes of different diameters and extensions. But we feel that it was not a big factor on influencing the result of the surgical technique, as the pathologies of both CM and SM seem to be the same. It was of our interest to see if the procedure addressing the Chiari only can solve syrinx as well, and that would provide some explanation that CM and SM share at least some common etiological factors and pathologies, which can be dealt with a single procedure.

Whatever theory regarding the pathophysiology is apt, with time and experience, centering on the two basic pathologies of shallow PF and imbalance of CSF dynamics around the CVJ, now the goal of our procedure is a persistent voluminous PF that would reestablish the CSF flow dynamics and would prevent recurrence and complications cost-effectively.

#### **4.1 Patient positioning**

We place the patient prone, in a modified concord position, under general anesthesia (**Figure 1A**). Special attention is given to keep the head in neutral position, and that is not flexed in any way. This gives two benefits. When the head is neutral, it helps the already jeopardized medulla from kinking from flexion as well as keeps it free from further compression by the herniated tonsils, which is already there. During reconstruction of the posterior fossa, neutral position gives better idea about the anatomy of the structures around the foramen magnum. This also gives the additional advantage of facilitation of venous return, by ensuring the jugular veins to be free of compression which helps in avoiding unnecessary oozing. Care of the airway, pressure points, and the vital monitoring are as usual.

#### **4.2 Skin incision, harvesting graft, and exposure of bone**

A midline skin incision is made from just above the external occipital protuberance down to a little below the prominence of the C2 vertebra. After opening the skin, a strip of the investing layer of the deep cervical fascia, measuring about 2 × 5 cm, is harvested for the duraplasty (**Figure 1B**). This strip is an advantageous graft material for duraplasty as it is autologous and hence can avoid foreign body reaction, potential risk of infection, and arachnoiditis. This graft is also flexible and durable. Most importantly, we do not need to make any additional wound to harvest it. Then the bones, up to the inion above and the posterior arch of the atlas below, are exposed by subperiosteal dissection maintaining the avascular plane in the midline along the ligamentum nuchae to reduce bleeding and postoperative pain from muscle injury. Subperiosteal dissection of the squamous occipital bone down to the margin of foramen magnum and the posterior arch of atlas is continued to expose the bones to a width of about 2 cm on each side.

#### **4.3 Craniectomy**

Two burr holes below the inion just lateral to the midline are made, and a 2.5–3 cm wide posterior fossa craniectomy is done in the midline extending from the foramen magnum to 4–5 cm above with the help of bone and Kerrison's rongeurs. Care is taken not to widen the craniectomy more than 1.5 cm beyond the midline on either side. In Chiari patients, often the bone around the inion is very thick. In those cases, the inner surface is undermined with the help of the Kerrison's rongeurs to make more space there. The posterior arch of the atlas is also removed about 1 cm on both sides of the midline (**Figure 1C**).

#### **4.4 Dural opening and grafting**

The dura is opened in the midline with a straight incision, keeping the arachnoid intact. On very rare occasions, there may be dural venous lakes or lacunae,

#### **Figure 1.**

*Per-operative picture of different steps of stealth cranioplasty (SCP). Patient is placed prone with head in neutral position. (A) Harvesting of the cervical fascial graft. (B) Posterior fossa craniectomy is in the midline measuring 2.5–3.0 cm in width and 4–5 cm vertically from the foramen magnum. (C) Arachnoid-preserving midline dural opening and hitches for tenting. (D) Duraplasty with cervical fascial graft. (E) Molding of the titanium "stealth cranioplasty." (F and G) Fixing of the cranioplasty over the craniectomy gap. (H) Tenting of the duraplasty with the cranioplasty mesh (I).*

**69**

**Figure 2.**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

which can be managed by continuous sutures along the cut margins to control the troublesome bleeding. If there is any accidental nick in the arachnoid, that is sealed with a very low bipolar cautery. The dural bands, which are present often, are kept as they are, to facilitate the dural tenting in the later part of the procedure. Two hitches are taken from the topmost and the lowermost points of the dural opening and two each from the free margins on either side. So, a total of six dural hitches are taken from the cut margins to tack those with the cranioplasty mesh later. The dural bands, which are not disturbed, help in strengthening the tenting where we want to pull the dura most, to widen the room in the posterior fossa around the foramen magnum (**Figure 1D**). The deep cervical fascial graft is sewn in the opening of the dura with 5–0 or 6–0 absorbable suture running stitches to complete an arachnoid-preserving duraplasty (APD) in a manner that when the dural tentings are fixed with the cranioplasty mesh, it resembles the roof of a

The 5 × 5 cm titanium mesh (**Figure 2A**), which is malleable but tough enough to support the craniectomy gap after molding, is shaped to fit in the craniectomy gap in such a way that it covers the opening and at the same time increases the volume of the posterior fossa. The mesh is gradually curved in the middle like a longitudinally half-split cone, and the rest is kept flat (**Figures 1F, G** and 2**B–F, H, I**). By this the half cone takes the contour of a cockpit, and the flat parts take the contour of the wings of a "stealth" bomber (**Figure 2G**). That's why we call it a "stealth cranioplasty". The tapered end of the half cone, which almost merges with the flat of the construct, is placed at the upper part of the craniectomy defect to fit with the curvature of the occipital bone near the occipital protuberance. The lower part of the molded mesh having the wider portion of the half cone is placed inferiorly. The margin of this broader edge of the cone is shaped in a manner of a half circle (**Figure 2E, F**), to create more space around the foramen magnum to provide more range of motion during neck extension postoperatively. The lower border of the wings of the cranioplasty is merged with the margin of the foramen magnum. The

*Steps of molding of the titanium mesh to the shape of "stealth cranioplasty". The titanium mesh before molding. (A) The mesh is bent to make a triangular flat part in the middle. (B) The flat triangular part is curved into a longitudinally half split cone to mimic the cockpit and the sides are bent outwards to give them the contour of the wings of a Stealth bomber. (C & D) The widened part of the cone is cut in a crescent. (E & F) The pre-formed titanium mesh from front mimicking the cockpit of the Stealth bomber. (G) The look of the Stealth* 

*cranioplast from the wider part of the cone from rear (H) and below. (I).*

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

hexagonal tent (**Figure 1E**).

**4.5 Crafting of the stealth cranioplasty**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

which can be managed by continuous sutures along the cut margins to control the troublesome bleeding. If there is any accidental nick in the arachnoid, that is sealed with a very low bipolar cautery. The dural bands, which are present often, are kept as they are, to facilitate the dural tenting in the later part of the procedure. Two hitches are taken from the topmost and the lowermost points of the dural opening and two each from the free margins on either side. So, a total of six dural hitches are taken from the cut margins to tack those with the cranioplasty mesh later. The dural bands, which are not disturbed, help in strengthening the tenting where we want to pull the dura most, to widen the room in the posterior fossa around the foramen magnum (**Figure 1D**). The deep cervical fascial graft is sewn in the opening of the dura with 5–0 or 6–0 absorbable suture running stitches to complete an arachnoid-preserving duraplasty (APD) in a manner that when the dural tentings are fixed with the cranioplasty mesh, it resembles the roof of a hexagonal tent (**Figure 1E**).

#### **4.5 Crafting of the stealth cranioplasty**

*Neurosurgical Procedures - Innovative Approaches*

**4.3 Craniectomy**

**4.2 Skin incision, harvesting graft, and exposure of bone**

about 1 cm on both sides of the midline (**Figure 1C**).

**4.4 Dural opening and grafting**

*the duraplasty with the cranioplasty mesh (I).*

A midline skin incision is made from just above the external occipital protuberance down to a little below the prominence of the C2 vertebra. After opening the skin, a strip of the investing layer of the deep cervical fascia, measuring about 2 × 5 cm, is harvested for the duraplasty (**Figure 1B**). This strip is an advantageous graft material for duraplasty as it is autologous and hence can avoid foreign body reaction, potential risk of infection, and arachnoiditis. This graft is also flexible and durable. Most importantly, we do not need to make any additional wound to harvest it. Then the bones, up to the inion above and the posterior arch of the atlas below, are exposed by subperiosteal dissection maintaining the avascular plane in the midline along the ligamentum nuchae to reduce bleeding and postoperative pain from muscle injury. Subperiosteal dissection of the squamous occipital bone down to the margin of foramen magnum and the posterior arch of atlas is continued to expose the bones to a width of about 2 cm on each side.

Two burr holes below the inion just lateral to the midline are made, and a 2.5–3 cm wide posterior fossa craniectomy is done in the midline extending from the foramen magnum to 4–5 cm above with the help of bone and Kerrison's rongeurs. Care is taken not to widen the craniectomy more than 1.5 cm beyond the midline on either side. In Chiari patients, often the bone around the inion is very thick. In those cases, the inner surface is undermined with the help of the Kerrison's rongeurs to make more space there. The posterior arch of the atlas is also removed

The dura is opened in the midline with a straight incision, keeping the arachnoid intact. On very rare occasions, there may be dural venous lakes or lacunae,

*Per-operative picture of different steps of stealth cranioplasty (SCP). Patient is placed prone with head in neutral position. (A) Harvesting of the cervical fascial graft. (B) Posterior fossa craniectomy is in the midline measuring 2.5–3.0 cm in width and 4–5 cm vertically from the foramen magnum. (C) Arachnoid-preserving midline dural opening and hitches for tenting. (D) Duraplasty with cervical fascial graft. (E) Molding of the titanium "stealth cranioplasty." (F and G) Fixing of the cranioplasty over the craniectomy gap. (H) Tenting of* 

**68**

**Figure 1.**

The 5 × 5 cm titanium mesh (**Figure 2A**), which is malleable but tough enough to support the craniectomy gap after molding, is shaped to fit in the craniectomy gap in such a way that it covers the opening and at the same time increases the volume of the posterior fossa. The mesh is gradually curved in the middle like a longitudinally half-split cone, and the rest is kept flat (**Figures 1F, G** and 2**B–F, H, I**). By this the half cone takes the contour of a cockpit, and the flat parts take the contour of the wings of a "stealth" bomber (**Figure 2G**). That's why we call it a "stealth cranioplasty". The tapered end of the half cone, which almost merges with the flat of the construct, is placed at the upper part of the craniectomy defect to fit with the curvature of the occipital bone near the occipital protuberance. The lower part of the molded mesh having the wider portion of the half cone is placed inferiorly. The margin of this broader edge of the cone is shaped in a manner of a half circle (**Figure 2E, F**), to create more space around the foramen magnum to provide more range of motion during neck extension postoperatively. The lower border of the wings of the cranioplasty is merged with the margin of the foramen magnum. The

#### **Figure 2.**

*Steps of molding of the titanium mesh to the shape of "stealth cranioplasty". The titanium mesh before molding. (A) The mesh is bent to make a triangular flat part in the middle. (B) The flat triangular part is curved into a longitudinally half split cone to mimic the cockpit and the sides are bent outwards to give them the contour of the wings of a Stealth bomber. (C & D) The widened part of the cone is cut in a crescent. (E & F) The pre-formed titanium mesh from front mimicking the cockpit of the Stealth bomber. (G) The look of the Stealth cranioplast from the wider part of the cone from rear (H) and below. (I).*

rest of the wings is fixed with the bone at the lateral margins of the craniectomy defect to fit with the contour of the bone (**Figure 1H**).

#### **4.6 Tenting and closure**

The tentings are tied with the cranioplasty mesh to give the dural graft a final shape of the roof of a hexagonal tent (**Figure 1I**). Hemostasis is secured and the wound is closed in usual fashion in layers without any drain. Initially, there is some potential space between the dural graft and the cranioplasty, even after tenting. But this eventually is filled up with time by the pulsation of the brain as the duraplasty merges with the cranioplasty to create space for the CSF and neural structures.

#### **5. Result**

Eleven male and six female symptomatic CM1 adult patients, between age ranges of 22 and 42 years (mean 30.47 years), presented with different neurological symptoms related to CM1 and SM for 6–84 months (mean 27.70 months). The patients had syringes extending from three to more than ten vertebral levels (**Table 1**). All of the patients underwent PFD and arachnoid-preserving duraplasty followed by SCP and dural tenting and were followed up for a period of


**Table 1.**

*Showing distribution of gender, age, clinical symptoms, duration of symptoms, and extent of syrinx.*

**71**

**Figure 3.**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

7–72 months (mean 32.59 months). Of 17 patients, 13 patients improved according to the Chicago Chiari Outcome Scale (CCOS) with score of 13–15, while 4 patients remained unchanged with CCOS of 12, and there was no worsening (**Table 2**). There was no complication related to Chiari surgery in any of the patients. All the patients had reestablishment of cisterna magna to different extents (**Figure 3E, F**). Five patients had marked reduction of syrinx, while 11 patients had moderate to mild reduction, and 1 patient had no change of syrinx. None of the patients needed

**Parameters Number of patients (N = 17)**

Improved 13 Unchanged 4 Worsened 0

13–16 13 9–12 4 <12 0

Marked reduction 5 Moderate reduction 7 Mild reduction 4 No reduction 1 Worsened/enlarged 0

*Showing clinical outcome, outcome according to CCOS, and radiological outcome of syrinx.*

*Postoperative 3D CT scan following "stealth cranioplasty" increase in diameter of foramen magnum (A) and the final contour after fixing the cranioplasty with bone (B). Preoperative and (C) postoperative (D) sagittal reconstruction of bone around the CVJ showing increase in diameter of the foramen magnum and reconstruction of the posterior fossa in a shape of a sphere. Preoperative (E) and postoperative (F) sagittal T2WI ascent of the cerebellar tonsil, reestablishment of cisterna magna, and marked reduction of syrinx.*

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

redo surgery so far.

**Clinical outcome**

**Radiological outcome of syrinx**

**CCOS**

**Table 2.**

#### *"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

7–72 months (mean 32.59 months). Of 17 patients, 13 patients improved according to the Chicago Chiari Outcome Scale (CCOS) with score of 13–15, while 4 patients remained unchanged with CCOS of 12, and there was no worsening (**Table 2**). There was no complication related to Chiari surgery in any of the patients. All the patients had reestablishment of cisterna magna to different extents (**Figure 3E, F**). Five patients had marked reduction of syrinx, while 11 patients had moderate to mild reduction, and 1 patient had no change of syrinx. None of the patients needed redo surgery so far.


#### **Table 2.**

*Neurosurgical Procedures - Innovative Approaches*

**4.6 Tenting and closure**

**5. Result**

**Gender**

**Clinical symptoms**

**Extension of syrinx**

**Duration of symptoms (months)**

defect to fit with the contour of the bone (**Figure 1H**).

rest of the wings is fixed with the bone at the lateral margins of the craniectomy

The tentings are tied with the cranioplasty mesh to give the dural graft a final shape of the roof of a hexagonal tent (**Figure 1I**). Hemostasis is secured and the wound is closed in usual fashion in layers without any drain. Initially, there is some potential space between the dural graft and the cranioplasty, even after tenting. But this eventually is filled up with time by the pulsation of the brain as the duraplasty merges with the cranioplasty to create space for the CSF and neural structures.

Eleven male and six female symptomatic CM1 adult patients, between age ranges of 22 and 42 years (mean 30.47 years), presented with different neurological symptoms related to CM1 and SM for 6–84 months (mean 27.70 months). The patients had syringes extending from three to more than ten vertebral levels (**Table 1**). All of the patients underwent PFD and arachnoid-preserving duraplasty followed by SCP and dural tenting and were followed up for a period of

**Attribute Number of patients (N = 17)**

**Mean age in years (range)** 30.47 (22–42 Years)

Male 11 Female 6

Sensory disturbance 12 Neck ache 10 Upper limb weakness 9 Lower limb weakness 6 Suboccipital headache 5

1–12 3 13–24 4 25–36 3 37–48 4 49–60 2 >60 1

3–6 levels 6 7–10 levels 8 >10 levels 3

*Showing distribution of gender, age, clinical symptoms, duration of symptoms, and extent of syrinx.*

**70**

**Table 1.**

*Showing clinical outcome, outcome according to CCOS, and radiological outcome of syrinx.*

#### **Figure 3.**

*Postoperative 3D CT scan following "stealth cranioplasty" increase in diameter of foramen magnum (A) and the final contour after fixing the cranioplasty with bone (B). Preoperative and (C) postoperative (D) sagittal reconstruction of bone around the CVJ showing increase in diameter of the foramen magnum and reconstruction of the posterior fossa in a shape of a sphere. Preoperative (E) and postoperative (F) sagittal T2WI ascent of the cerebellar tonsil, reestablishment of cisterna magna, and marked reduction of syrinx.*

#### **6. Our philosophy of innovation and evolution**

Reconstruction of the posterior fossa by expansive cranioplasty is not practiced routinely following posterior fossa decompression for the CM1. Many authors have tried posterior fossa reconstruction with cranioplasty after PFD in many ways with different objectives. Cranioplasty as an attempt to treat and prevent further cerebellar subsidence during redo surgery has been described. Many techniques have been described in the literature like partial cranioplasty with methyl methacrylate (MMA) [115, 116], with autologous bone [117–122], and cranioplasty with different varieties of titanium prosthesis [48, 123–126]. Tacking of duraplasty with or without cranioplasty has also been described by some authors with intention to keep the cistern patent and to prevent adhesion [48, 120, 122, 123, 127]. We have tried to blend the procedures in an effective and least invasive way to give the utmost benefit to the patients.

Our journey began with the thought of the big concern of recurrence of symptoms in management of CM1. Postoperative recurrence of compression over the cerebellar tonsils around the foramen magnum and obliteration of CSF flow and dynamics around the CVJ may be caused by compression over the dura through the craniectomy gap by repositioned muscle bulk, fibrosis, and cerebellar sag.

We felt that, in conventional procedures, there is no measure to protect the dura from compression by the muscle bulk postoperatively from the back (**Figure 4A**–**C**). Initially the goal of cranioplasty was to prevent this by covering the craniectomy gap. Eventually, we felt that this cranioplasty can serve as a means to increase the posterior fossa volume as well.

So, we developed the technique based on our observations and thoughts in addition to the initial considerations of merely preventing recurrence and augmenting the posterior fossa volume.

Firstly, many patients come back with recurrences of symptoms from compression of the neuronal elements as well as obliteration of posterior CSF column by muscle bulk and fibrous tissue from posterior aspect around the surgical site as evident in many follow-up MRIs. This seemed to be due to having no protection against

#### **Figure 4.**

*Preoperative sagittal T2WI of a patient with CM1 and syrinx (A) 1 year postoperative sagittal T1WI and T2WI following posterior fossa bony decompression only. Worthy to note the posterior compression on dura by muscle and fibrous tissue and the status of Chiari and syrinx (B and C).*

**73**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

recompression from the posterior aspect. This led us to think about cranioplasty to make a protective safeguard against any compression from posterior aspect to avoid

Secondly, we wanted to augment the PFV so that the herniated contents can come back, can be accommodated with ease in the newly formed abode, and can relieve the compression around the foramen magnum to get the anatomy and physiology including CSF dynamics back to near normal. Any container which is spherical is more voluminous compared to a flat one. The pathology in case of CM1, is the shallow posterior fossa due to flattening of the lower part. Our endeavor is to make the posterior fossa more spherical and voluminous by performing the APD,

Thirdly, cerebellar slump is often encountered when a larger craniectomy is done. This might be due to release of pressure in the posterior fossa creating much space, and the slump can further be aided by gravity. Though we do not make the craniectomy bigger than 2.5 cm wide and 3–4 cm vertically, this cranioplasty helps

Fourthly, arachnoid-preserving duraplasty has the advantage of preventing postoperative arachnoiditis related to surgery which may result from manipulation of the arachnoid and seepage of blood into the subarachnoid space. APD also has the advantage of avoiding CSF-related complications. As the Pascal's law states, any force in a closed fluid filled container is equally distributed to all directions with the same force. Our hypothesis is that the force of CSF in the new space, aided by brain pulsation, is capable of opening up any adhesion of the arachnoid or creating new pathway naturally if ample space can be created. Some reports are there that sometimes there are arachnoid veils over the foramen of Magendie to block the CSF flow, and we are afraid that in this subset of patients, the SCP might not work to reestablish the CSF flow. Possibly there was no patient like this in our series, as we found all our patients to have better CSF flow around the CVJ. Moreover, as the bigger CSF space is molded and maintained around the CVJ by APD and dural tenting, the CSF makes its way to the spinal subarachnoid space to equilibrate the pressure gradient with the cranial CSF. This CSF equilibrium has the potential to push the tonsils up, back to the newly formed space, and keeps it floating with the buoyancy to prevent it from going down again and castoffs the need to handle the tonsils as well. Initially the new space is enlarged moderately to relieve the symptoms. With time and CSF pulsation, the space expands more and takes the contour of the cranioplasty and is maintained very well, making the PFV and CSF dynamics adequate to sustain relief of symptoms. Following PFD, APD, dural tenting, and SCP, with reversal of CSF dynamics to normalcy, the syrinx usually reduces without taking any additional measure. However, in a good number of cases, the syrinx takes a long time to resolve or does not resolve

in preventing the cerebellar ptosis, even if there is any chance at all.

appreciably, and the symptoms related to syrinx resolve markedly.

extra expenses from re-surgery and rehabilitation program.

dural tacking can help in enhancing and maintaining the CSF space also.

Finally, financial and psychological burden other than physical disability takes a heavy toll on the patients of CM1 and their families. These financial and psychological burdens can be avoided as this is well affordable by the patients of a low socioeconomic condition like ours since it costs no more than USD \$50 for the implant. At the same time, with this minimal expense, patients can avoid further

Fifthly, with the APD with autologous fascia and hexagonal tacking of that with the "stealth" cranioplasty, some complications can be prevented effectively. The CSF-related complications like CSF leak, meningitis or pseudomeningocele, inflammation, scarring and adhesion of dural graft, cerebellar sag, and compression from behind can be avoided and prevented efficiently with this combined technique. The

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

recurrence of symptoms.

SCP, and dural tenting.

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

recompression from the posterior aspect. This led us to think about cranioplasty to make a protective safeguard against any compression from posterior aspect to avoid recurrence of symptoms.

Secondly, we wanted to augment the PFV so that the herniated contents can come back, can be accommodated with ease in the newly formed abode, and can relieve the compression around the foramen magnum to get the anatomy and physiology including CSF dynamics back to near normal. Any container which is spherical is more voluminous compared to a flat one. The pathology in case of CM1, is the shallow posterior fossa due to flattening of the lower part. Our endeavor is to make the posterior fossa more spherical and voluminous by performing the APD, SCP, and dural tenting.

Thirdly, cerebellar slump is often encountered when a larger craniectomy is done. This might be due to release of pressure in the posterior fossa creating much space, and the slump can further be aided by gravity. Though we do not make the craniectomy bigger than 2.5 cm wide and 3–4 cm vertically, this cranioplasty helps in preventing the cerebellar ptosis, even if there is any chance at all.

Fourthly, arachnoid-preserving duraplasty has the advantage of preventing postoperative arachnoiditis related to surgery which may result from manipulation of the arachnoid and seepage of blood into the subarachnoid space. APD also has the advantage of avoiding CSF-related complications. As the Pascal's law states, any force in a closed fluid filled container is equally distributed to all directions with the same force. Our hypothesis is that the force of CSF in the new space, aided by brain pulsation, is capable of opening up any adhesion of the arachnoid or creating new pathway naturally if ample space can be created. Some reports are there that sometimes there are arachnoid veils over the foramen of Magendie to block the CSF flow, and we are afraid that in this subset of patients, the SCP might not work to reestablish the CSF flow. Possibly there was no patient like this in our series, as we found all our patients to have better CSF flow around the CVJ. Moreover, as the bigger CSF space is molded and maintained around the CVJ by APD and dural tenting, the CSF makes its way to the spinal subarachnoid space to equilibrate the pressure gradient with the cranial CSF. This CSF equilibrium has the potential to push the tonsils up, back to the newly formed space, and keeps it floating with the buoyancy to prevent it from going down again and castoffs the need to handle the tonsils as well. Initially the new space is enlarged moderately to relieve the symptoms. With time and CSF pulsation, the space expands more and takes the contour of the cranioplasty and is maintained very well, making the PFV and CSF dynamics adequate to sustain relief of symptoms. Following PFD, APD, dural tenting, and SCP, with reversal of CSF dynamics to normalcy, the syrinx usually reduces without taking any additional measure. However, in a good number of cases, the syrinx takes a long time to resolve or does not resolve appreciably, and the symptoms related to syrinx resolve markedly.

Fifthly, with the APD with autologous fascia and hexagonal tacking of that with the "stealth" cranioplasty, some complications can be prevented effectively. The CSF-related complications like CSF leak, meningitis or pseudomeningocele, inflammation, scarring and adhesion of dural graft, cerebellar sag, and compression from behind can be avoided and prevented efficiently with this combined technique. The dural tacking can help in enhancing and maintaining the CSF space also.

Finally, financial and psychological burden other than physical disability takes a heavy toll on the patients of CM1 and their families. These financial and psychological burdens can be avoided as this is well affordable by the patients of a low socioeconomic condition like ours since it costs no more than USD \$50 for the implant. At the same time, with this minimal expense, patients can avoid further extra expenses from re-surgery and rehabilitation program.

*Neurosurgical Procedures - Innovative Approaches*

benefit to the patients.

posterior fossa volume as well.

the posterior fossa volume.

**6. Our philosophy of innovation and evolution**

Reconstruction of the posterior fossa by expansive cranioplasty is not practiced routinely following posterior fossa decompression for the CM1. Many authors have tried posterior fossa reconstruction with cranioplasty after PFD in many ways with different objectives. Cranioplasty as an attempt to treat and prevent further cerebellar subsidence during redo surgery has been described. Many techniques have been described in the literature like partial cranioplasty with methyl methacrylate (MMA) [115, 116], with autologous bone [117–122], and cranioplasty with different varieties of titanium prosthesis [48, 123–126]. Tacking of duraplasty with or without cranioplasty has also been described by some authors with intention to keep the cistern patent and to prevent adhesion [48, 120, 122, 123, 127]. We have tried to blend the procedures in an effective and least invasive way to give the utmost

Our journey began with the thought of the big concern of recurrence of symptoms in management of CM1. Postoperative recurrence of compression over the cerebellar tonsils around the foramen magnum and obliteration of CSF flow and dynamics around the CVJ may be caused by compression over the dura through the

We felt that, in conventional procedures, there is no measure to protect the dura from compression by the muscle bulk postoperatively from the back (**Figure 4A**–**C**). Initially the goal of cranioplasty was to prevent this by covering the craniectomy gap. Eventually, we felt that this cranioplasty can serve as a means to increase the

So, we developed the technique based on our observations and thoughts in addition to the initial considerations of merely preventing recurrence and augmenting

Firstly, many patients come back with recurrences of symptoms from compression of the neuronal elements as well as obliteration of posterior CSF column by muscle bulk and fibrous tissue from posterior aspect around the surgical site as evident in many follow-up MRIs. This seemed to be due to having no protection against

*Preoperative sagittal T2WI of a patient with CM1 and syrinx (A) 1 year postoperative sagittal T1WI and T2WI following posterior fossa bony decompression only. Worthy to note the posterior compression on dura by* 

*muscle and fibrous tissue and the status of Chiari and syrinx (B and C).*

craniectomy gap by repositioned muscle bulk, fibrosis, and cerebellar sag.

**72**

**Figure 4.**

But all these adaptations did not take place straightway. We had to develop it step by step after facing different problems at different stages. Initially we had the considerations in mind that we have mentioned already. We started cranioplasty first with autologous bone with a titanium mesh buttress across the bone margins (**Figure 5A, B**). After few cases, we wanted to make it convenient for us by doing the cranioplasty with bone cement (MMA) with a buttress like the one as in cranioplasty with autologous bone (**Figure 5C, D**). We thought that the procedure can be made easier if we do the cranioplasty straight forward with a titanium mesh (**Figure 5E, F**). We expected that the gap created between the dura and the mesh by removing the bone at the craniectomy would be specious enough to serve the purpose of creating space for the cerebellum and reestablishment of CSF flow. That far we used to remove the dural bands only and did the cranioplasty with mesh and did so with satisfactory results in the next few cases until we faced problem with one patient 3 months postoperatively. This male patient was doing well postoperatively with marked improvement till he sneezed one morning and suddenly became quadriparetic. MRI showed greater herniation of the tonsils again (**Figure 6A, C**), while the immediate postop CT after the first surgery showed some ascent of the tonsil (**Figure 6A, B**). Preoperatively at the second surgery, we found that the dura was severely compressed along the lower margin of the mesh, and it seemed that the mesh margin has trapped the tonsil which was also evident in the MRI (**Figure 6C, D**). We only cut the inferior margin of the mesh in a crescentic shape and resected some fibrous tissue over the dura longitudinally to relieve the tonsils (**Figure 6E, F**), and the patient improved gradually. However the improvement was slow and was never as good as the first postoperative status.

After this, we routinely put the mesh by cutting the lower margin to make more space around the foramen magnum (**Figure 7A, B**). Then we thought that we can make some more space in the midline if we bend the mesh in the middle like a longitudinally half-split tube in the middle (**Figure 7C, D**). At this part of the advance of our journey, we started arachnoid-preserving duraplasty and dural tenting as well, and

#### **Figure 5.**

*Preoperative picture and postoperative 3D CT scan of cranioplasties using different materials. Cranioplasty with autologous bone (A and B), bone cement (MMA) (C and D), and flat titanium mesh (E and F).*

#### **Figure 6.**

*MRI before first surgery of the patient that gave us the impetus to develop this technique, showing tonsillar herniation (A), CT scan after first surgery showing appreciable ascent of the tonsil (B), MRI before second surgery (after clinical deterioration) showing entrapped tonsil by the lower margin of the titanium mesh (C), preoperative picture at second surgery showing the dural compression by the lower margin of the titanium mesh (D), decompressed dura following cutting the lower margin of the titanium mesh and lysis of fibrosis (E), post of 3D CT scan to showing the lower cut margin of the titanium mesh to relieve the compression around the CVJ.*

**75**

gives us satisfactory result.

**Acknowledgements**

**Conflict of interest**

None.

**7. Conclusion**

**Figure 7.**

*protuberance (E and F).*

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

that produced good results. We had to rethink of the shape of the mesh while molding, when some patients complained of some uneasiness from the little swelling under the skin from the bend at the upper part. Though we tried to merge the upper part of the tube-like bending with the external occipital protuberance, in some patients it was little more protruded than the external occipital protuberance (**Figure 7E, F**). We were afraid of skin excoriation in these patients after we were noticed about this problem. However, practically it did not produce any complication in any of the patients. We then changed the molding a little to come to the present day shape to merge the upper part with the bone near the external occipital protuberance by bending it like a longitudinally half split cone instead of a half split tube, which when fixed with the bone becomes flattened to merge with the contour of the occipital bone. Actually that gave us an additional benefit of preventing cerebellar sag also; as the upper part is flatter, this has more chance of supporting the cerebellum from sagging, if there is any chance at all through the narrow craniectomy gap (**Figure 3B**). This also gives the

*Preoperative picture (A) and postoperative 3D CT scan (B) showing the placement of flat titanium mesh by cutting the lower margin to make more space around the foramen magnum. Molding of the titanium mesh in a longitudinally split half tube (C) which gives ample space around the foramen magnum as seen in postoperative CT scan (D). Postoperative 3D CT scan showing the protrusion around the external occipital* 

scope to increase the diameter of the foramen magnum (**Figure 3A, C, D**).

Treatment for CM1 is surgical and success of surgery depends on appropriate patient selection. We consider it a factor of paramount importance while selecting patients for stealth cranioplasty. Our patients are all adults, having no associated complex pathologies like hydrocephalus, platybasia, or basilar invagination, which

The journey to develop "stealth cranioplasty" was not a smooth one. After a lot of trial and error, now it seems to be an effective, fruitful, and cost-effective technique for management of symptomatic adult Chiari malformation type 1 with syringomyelia. This technique has the advantages of preventing complications and recurrences

I am deeply indebted to the members of the team and sincerely thank them all for helping me in developing this technique with their valuable technical advices.

in addition to improvement of symptoms by addressing the basic pathology.

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

#### **Figure 7.**

*Neurosurgical Procedures - Innovative Approaches*

slow and was never as good as the first postoperative status.

After this, we routinely put the mesh by cutting the lower margin to make more space around the foramen magnum (**Figure 7A, B**). Then we thought that we can make some more space in the midline if we bend the mesh in the middle like a longitudinally half-split tube in the middle (**Figure 7C, D**). At this part of the advance of our journey, we started arachnoid-preserving duraplasty and dural tenting as well, and

*MRI before first surgery of the patient that gave us the impetus to develop this technique, showing tonsillar herniation (A), CT scan after first surgery showing appreciable ascent of the tonsil (B), MRI before second surgery (after clinical deterioration) showing entrapped tonsil by the lower margin of the titanium mesh (C), preoperative picture at second surgery showing the dural compression by the lower margin of the titanium mesh (D), decompressed dura following cutting the lower margin of the titanium mesh and lysis of fibrosis (E), post of 3D CT scan to showing the lower cut margin of the titanium mesh to relieve the compression around the CVJ.*

*Preoperative picture and postoperative 3D CT scan of cranioplasties using different materials. Cranioplasty with autologous bone (A and B), bone cement (MMA) (C and D), and flat titanium mesh (E and F).*

But all these adaptations did not take place straightway. We had to develop it step by step after facing different problems at different stages. Initially we had the considerations in mind that we have mentioned already. We started cranioplasty first with autologous bone with a titanium mesh buttress across the bone margins (**Figure 5A, B**). After few cases, we wanted to make it convenient for us by doing the cranioplasty with bone cement (MMA) with a buttress like the one as in cranioplasty with autologous bone (**Figure 5C, D**). We thought that the procedure can be made easier if we do the cranioplasty straight forward with a titanium mesh (**Figure 5E, F**). We expected that the gap created between the dura and the mesh by removing the bone at the craniectomy would be specious enough to serve the purpose of creating space for the cerebellum and reestablishment of CSF flow. That far we used to remove the dural bands only and did the cranioplasty with mesh and did so with satisfactory results in the next few cases until we faced problem with one patient 3 months postoperatively. This male patient was doing well postoperatively with marked improvement till he sneezed one morning and suddenly became quadriparetic. MRI showed greater herniation of the tonsils again (**Figure 6A, C**), while the immediate postop CT after the first surgery showed some ascent of the tonsil (**Figure 6A, B**). Preoperatively at the second surgery, we found that the dura was severely compressed along the lower margin of the mesh, and it seemed that the mesh margin has trapped the tonsil which was also evident in the MRI (**Figure 6C, D**). We only cut the inferior margin of the mesh in a crescentic shape and resected some fibrous tissue over the dura longitudinally to relieve the tonsils (**Figure 6E, F**), and the patient improved gradually. However the improvement was

**74**

**Figure 6.**

**Figure 5.**

*Preoperative picture (A) and postoperative 3D CT scan (B) showing the placement of flat titanium mesh by cutting the lower margin to make more space around the foramen magnum. Molding of the titanium mesh in a longitudinally split half tube (C) which gives ample space around the foramen magnum as seen in postoperative CT scan (D). Postoperative 3D CT scan showing the protrusion around the external occipital protuberance (E and F).*

that produced good results. We had to rethink of the shape of the mesh while molding, when some patients complained of some uneasiness from the little swelling under the skin from the bend at the upper part. Though we tried to merge the upper part of the tube-like bending with the external occipital protuberance, in some patients it was little more protruded than the external occipital protuberance (**Figure 7E, F**). We were afraid of skin excoriation in these patients after we were noticed about this problem. However, practically it did not produce any complication in any of the patients. We then changed the molding a little to come to the present day shape to merge the upper part with the bone near the external occipital protuberance by bending it like a longitudinally half split cone instead of a half split tube, which when fixed with the bone becomes flattened to merge with the contour of the occipital bone. Actually that gave us an additional benefit of preventing cerebellar sag also; as the upper part is flatter, this has more chance of supporting the cerebellum from sagging, if there is any chance at all through the narrow craniectomy gap (**Figure 3B**). This also gives the scope to increase the diameter of the foramen magnum (**Figure 3A, C, D**).

Treatment for CM1 is surgical and success of surgery depends on appropriate patient selection. We consider it a factor of paramount importance while selecting patients for stealth cranioplasty. Our patients are all adults, having no associated complex pathologies like hydrocephalus, platybasia, or basilar invagination, which gives us satisfactory result.

#### **7. Conclusion**

The journey to develop "stealth cranioplasty" was not a smooth one. After a lot of trial and error, now it seems to be an effective, fruitful, and cost-effective technique for management of symptomatic adult Chiari malformation type 1 with syringomyelia. This technique has the advantages of preventing complications and recurrences in addition to improvement of symptoms by addressing the basic pathology.

#### **Acknowledgements**

I am deeply indebted to the members of the team and sincerely thank them all for helping me in developing this technique with their valuable technical advices.

#### **Conflict of interest**

None.

### **Abbreviations**


### **Author details**

Asifur Rahman

Department of Neurosurgery, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh

\*Address all correspondence to: bijoun14@yahoo.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**77**

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey…*

radiological, and genetic similarities between patients with Chiari type I and type 0 malformations. Journal of Neurosurgery: Pediatrics.

[10] Mavinkurve GG, Sciubba D, Amundson E, Jallo GI. Familial Chiari type I malformation with syringomyelia in two siblings: Case report and review of the literature. Child's Nervous System. 2005;**21**(11):955-959

[11] Milhorat TH, Chou MW,

radiographic findings for 364

[13] Schanker BD, Walcott BP,

[14] Speer MC, George TM,

Wolpert C, et al. Chiari I

1999;**44**(5):1005-1017

2016;**26**(2):315-320

2011;**31**(3):E1

2000;**8**(3):1-4

Trinidad EM, Kula RW, Mandell M,

malformation redefined: Clinical and

symptomatic patients. Neurosurgery.

[12] Nagy L, Mobley J, Ray C. Familial aggregation of chiari malformation: Presentation, pedigree, and review of the literature. Turkish Neurosurgery.

Nahed BV, Kahle KT, Li YM, Coumans J-VC. Familial Chiari malformation: Case series. Neurosurgical Focus.

Enterline DS, Franklin A, Wolpert CM, Milhorat TH. A genetic hypothesis for Chiari I malformation with or without syringomyelia. Neurosurgical Focus.

[15] Stovner LJ, Cappelen J, Nilsen G,

[16] Szewka AJ, Walsh LE, Boaz JC, Carvalho KS, Golomb MR. Chiari in the family: Inheritance of the Chiari I malformation. Pediatric Neurology.

malformation in two monozygotic twins and first-degree relatives. Annals of Neurology. 1992;**31**(2):220-222

Sjaastad O. The Chiari type I

2006;**34**(6):481-485

2012;**9**(4):372-378

*DOI: http://dx.doi.org/10.5772/intechopen.89472*

[1] Bejjani GK. Definition of the adult Chiari malformation: A brief historical

overview. Neurosurgical Focus.

[2] Poretti A, Ashmawy R, Garzon-Muvdi T, Jallo GI, Huisman TA, Raybaud C. Chiari type 1 deformity in children: Pathogenetic, clinical, neuroimaging, and management aspects. Neuropediatrics. 2016;**47**(05):293-307

[3] Rahman A. "Formation" of Chiari "malformation:" Nature's philosophical

[4] Bruner E. Cranial shape and size variation in human evolution: Structural and functional perspectives. Child's Nervous System. 2007;**23**(12):1357-1365

[5] Fernandes YB, Ramina R, Campos-Herrera CR, Borges G. Evolutionary

malformation. Medical Hypotheses.

[6] Rightmire GP. Brain size and encephalization in early to mid-Pleistocene homo. American Journal of Physical Anthropology.

[7] Furtado SV, Reddy K, Hegde A. Posterior fossa morphometry in

symptomatic pediatric and adult Chiari I malformation. Journal of Clinical Neuroscience. 2009;**16**(11):1449-1454

[8] Atkinson JL, Kokmen E, Miller GM. Evidence of posterior fossa hypoplasia

in the familial variant of adult Chiari I malformation: Case report. Neurosurgery. 1998;**42**(2):401-404

[9] Markunas CA, Tubbs RS, Moftakhar R, Ashley-Koch AE, Gregory SG, Oakes WJ, et al. Clinical,

hypothesis for Chiari type I

2013;**81**(4):715-719

2004;**124**(2):109-123

way of adaptation. Journal of Craniovertebral Junction and Spine.

**References**

2001;**11**(1):1-8

2017;**8**(3):291

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

#### **References**

*Neurosurgical Procedures - Innovative Approaches*

CM Chiari malformation CM1 Chiari malformation type 1

CSF Cerebrospinal fluid CVJ Craniovertebral junction ICP Intracranial pressure MMA Methyl methacrylate

PF Posterior fossa

ACM Acquired Chiari Malformation APD Arachnoid-preserving duraplasty CCOS Chicago Chiari Outcome Scale

MRI Magnetic resonance imaging

PFD Posterior fossa decompression

Department of Neurosurgery, Bangabandhu Sheikh Mujib Medical University,

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

PFV Posterior fossa volume SCP Stealth cranioplasty SM Syringomyelia

**Abbreviations**

**76**

**Author details**

Asifur Rahman

Shahbag, Dhaka, Bangladesh

\*Address all correspondence to: bijoun14@yahoo.com

provided the original work is properly cited.

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[6] Rightmire GP. Brain size and encephalization in early to mid-Pleistocene homo. American Journal of Physical Anthropology. 2004;**124**(2):109-123

[7] Furtado SV, Reddy K, Hegde A. Posterior fossa morphometry in symptomatic pediatric and adult Chiari I malformation. Journal of Clinical Neuroscience. 2009;**16**(11):1449-1454

[8] Atkinson JL, Kokmen E, Miller GM. Evidence of posterior fossa hypoplasia in the familial variant of adult Chiari I malformation: Case report. Neurosurgery. 1998;**42**(2):401-404

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[11] Milhorat TH, Chou MW, Trinidad EM, Kula RW, Mandell M, Wolpert C, et al. Chiari I malformation redefined: Clinical and radiographic findings for 364 symptomatic patients. Neurosurgery. 1999;**44**(5):1005-1017

[12] Nagy L, Mobley J, Ray C. Familial aggregation of chiari malformation: Presentation, pedigree, and review of the literature. Turkish Neurosurgery. 2016;**26**(2):315-320

[13] Schanker BD, Walcott BP, Nahed BV, Kahle KT, Li YM, Coumans J-VC. Familial Chiari malformation: Case series. Neurosurgical Focus. 2011;**31**(3):E1

[14] Speer MC, George TM, Enterline DS, Franklin A, Wolpert CM, Milhorat TH. A genetic hypothesis for Chiari I malformation with or without syringomyelia. Neurosurgical Focus. 2000;**8**(3):1-4

[15] Stovner LJ, Cappelen J, Nilsen G, Sjaastad O. The Chiari type I malformation in two monozygotic twins and first-degree relatives. Annals of Neurology. 1992;**31**(2):220-222

[16] Szewka AJ, Walsh LE, Boaz JC, Carvalho KS, Golomb MR. Chiari in the family: Inheritance of the Chiari I malformation. Pediatric Neurology. 2006;**34**(6):481-485

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**85**

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reconstruction: A surgical technique for the treatment of Chiari I malformation and Chiari I/syringomyelia complex– preliminary results and magnetic resonance imaging quantitative assessment of hindbrain migration. Neurosurgery. 1994;**35**(5):874-885

Cervera C. Posterior fossa

treatment of Chiari 1 malformation. Journal of Clinical Neuroscience.

2014;**21**(9):1641-1646

2011;**33**(3):261-271

2014;**81**(5-6):836-841

2017;**8**(3):243

*"Stealth Cranioplasty" for Adult Chiari Malformation Type 1: A Philosophical Journey… DOI: http://dx.doi.org/10.5772/intechopen.89472*

treatment of Chiari 1 malformation. Journal of Clinical Neuroscience. 2014;**21**(9):1641-1646

*Neurosurgical Procedures - Innovative Approaches*

surgical therapy by magnetic resonance imaging. Journal of Neurosurgery.

[117] Chou Y-C, Sarkar R, Osuagwu FC, Lazareff JA. Suboccipital craniotomy in the surgical treatment of Chiari I malformation. Child's Nervous System.

[118] Dewaele F, Kalmar AF, Baert E, Van Haver A, Hallaert G, De Mets F, et al. The use of the trendelenburg position in the surgical treatment of extreme cerebellar slump. British Journal of Neurosurgery. 2016;**30**(1):115-119

[119] Heller JB, Lazareff J, Gabbay JS, Lam S, Kawamoto HK, Bradley JP. Posterior cranial fossa box expansion leads to resolution of symptomatic cerebellar ptosis following Chiari I malformation repair. The Journal of Craniofacial Surgery. 2007;**18**(2):

[120] Nishikawa M, Ohata K, Baba M, Terakawa Y, Hara M. Chiari I

malformation associated with ventral compression and instability: Onestage posterior decompression and fusion with a new instrumentation

technique. Neurosurgery. 2004;**54**(6):1430-1435

[121] Sakamoto H, Nishikawa M, Hakuba A, Yasui T, Kitano S, Nakanishi N, et al. Expansive suboccipital cranioplasty for the treatment of syringomyelia associated with Chiari malformation. Acta Neurochirurgica. 1999;**141**(9):949-961

[122] Takayasu M, Takagi T, Hara M, Anzai M. A simple technique for expansive suboccipital cranioplasty following foramen magnum decompression for the treatment of syringomyelia associated with Chiari I malformation. Neurosurgical Review.

[123] Assina R, Meleis AM, Cohen MA, Iqbal MO, Liu JK. Titanium meshassisted dural tenting for an expansile suboccipital cranioplasty in the

2004;**27**(3):173-177

2009;**25**(9):1111-1114

274-280

[110] Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ. Treatment of Chiari type I malformation in patients with and without syringomyelia: A consecutive series of 66 cases. Neurosurgical Focus.

[111] Stanko KM, Lee YM, Rios J,

Wu A, Sobrinho GW, Weingart JD, et al. Improvement of syrinx resolution after tonsillar cautery in pediatric patients with Chiari type I malformation. Journal of Neurosurgery: Pediatrics.

[112] Rocque BG, Oakes WJ. Surgical treatment of Chiari I malformation.

[113] Ratre S, Yadav N, Yadav YR, Parihar VS, Bajaj J, Kher Y. Endoscopic

management of Arnold-Chiari malformation type I with or without syringomyelia. Journal of Neurological Surgery Part A: Central European Neurosurgery. 2018;**79**(01):045-051

[114] Zagzoog N, Reddy KK. Use of minimally invasive tubular retractors for foramen magnum decompression of Chiari malformation: A technical note and case series. World Neurosurgery.

[115] Di X, Luciano MG, Benzel EC. Acute respiratory arrest following partial suboccipital cranioplasty for cerebellar ptosis from Chiari malformation decompression: Report of 2 cases. Neurosurgical Focus.

[116] Holly LT, Batzdorf U. Management

of cerebellar ptosis following craniovertebral decompression for Chiari I malformation. Journal of Neurosurgery. 2001;**94**(1):21-26

1988;**68**(5):726-730

2001;**11**(1):1-9

2016;**17**(2):174-181

Neurosurgery Clinics. 2015;**26**(4):527-531

2019;**128**:248-253

2008;**25**(6):E12

**84**

[124] Oró JJ, Mueller DM. Posterior fossa decompression and reconstruction in adolescents and adults with the Chiari I malformation. Neurological Research. 2011;**33**(3):261-271

[125] Udani V, Holly LT, Chow D, Batzdorf U. Posterior fossa reconstruction using titanium plate for the treatment of cerebellar ptosis after decompression for Chiari malformation. World Neurosurgery. 2014;**81**(5-6):836-841

[126] Rahman A, Rana MS, Bhandari PB, Asif DS, Uddin ANW, Obaida ASMA, et al. "Stealth cranioplasty:" a novel endeavor for symptomatic adult Chiari I patients with syringomyelia: Technical note, appraisal, and philosophical considerations. Journal of Craniovertebral Junction and Spine. 2017;**8**(3):243

[127] Sahuquillo J, Rubio E, Poca M-A, Rovira A, Rodriguez-Baeza A, Cervera C. Posterior fossa reconstruction: A surgical technique for the treatment of Chiari I malformation and Chiari I/syringomyelia complex– preliminary results and magnetic resonance imaging quantitative assessment of hindbrain migration. Neurosurgery. 1994;**35**(5):874-885

**87**

Section 2

Imaging and Adjuvant

Therapies

### Section 2
