**6. Cochlear implantation**

Nowadays, normal or near-normal low-frequency hearing threshold is present in many patients who are candidates for cochlear implantation, and combined electric acoustic stimulation can be proposed. Consequently, preservation of residual hearing is becoming a crucial issue. Avoiding trauma to inner ear structures when placing a multi-electrode array during the cochlear implant procedure is essential to preserve residual hearing, and the first important topic is the route of insertion of the multi-electrode array.

Scala tympani is the location for multi-electrode array cochlear implants when normal anatomy is present. The reasons for this are the greater sectional dimension compared to scala vestibuli, protection of cochlear duct by osseous spiral lamina and basilar membrane that are stronger than Reissner's membrane, close proximity to the spiral ganglion cell bodies and dendrites, and direct access through the round window (RW) [33, 34].

Access to the scala tympani to introduce the multi-electrode array during the cochlear implant procedure is obtained by opening the RWM, when the RW is sufficiently visible through a posterior tympanotomy or by performing a promontorial cochleostomy in the inferior-lateral wall of the scala tympani, when the RW exposure is not adequate. The advantages of RW access are: reduced risk of intracochlear trauma, wider stimulation surface, and facilitated perimodiolar position [35, 36].

Anatomical variations in the facial nerve, chorda tympani, and the RW niche may create obstacles to approach the RWM [37], and a classification of visualization to the RWM related to surgical approachability has been proposed. Following this classification, complete RWM exposure (considering the only one that guarantees a pure RW approach) was possible in 46% of children, while in 7% the RWM was not visible. [36].

Even if the RWM is completely visible, opening of the RWM does not provide straightforward access to the scala tympani because of the presence of a sharp bony crest in the anterior-inferior border of the niche called the "crista fenestrae," the morphology of which is highly variable [38].

When the RW is not visible and a promontorial approach is needed to consent opening of the scala tympani using a cochleostomy approach without damage to the osseous spiral lamina and basilar membrane, Adunka et al. [34] demonstrated, with an anatomical study, that drilling should proceed from the inferior to the RW annulus, with gradual progression toward the undersurface of the lumen. However, the most basal part of the scala tympani forms a fish hook-like curvature in three dimensions called the "hook" region of the cochlea [39, 40]. This portion contains the cul-de-sac of the endolymphatic space where the osseous spiral lamina, spiral ligament, and basilar membrane merge [40]. The lateral wall of the "hook" region shows large size variations with the consequence of the absence of a reliable landmark for safe access to the scala tympani when promontorial access is performed.

Finally, the angle formed by a line along the plane of the basal turn and the midline (a line between the nasal septum and the internal occipital protuberance) is variable, being inversely proportional with age, thus increasing the risk of damage of the cochlear duct in children. [41].

Applying rigid endoscopy through posterior tympanotomy consents the surgeon to gain both a view of the RW, in case it is invisible, and direction of the scala tympani in children, thereby allowing soft and less traumatic insertion of the multielectrode array during cochlear implantation (**Figure 20**).

The use of an endoscope to assist cochlear implant surgery has been reported as a transcanal endoscopy by creating a tympanomeatal flap; this approach has been recently questioned because the basal turn of the cochlea align with a more posterior angle than that of the ear canal [42]. The idea to use a rigid endoscope

**125**

**Figure 21.**

*Endoscopic Ear Surgery in Children*

annulus of the RWM.

*the endoscope to visualize the RW.*

**Figure 20.**

rior tympanotomy of 2 mm (**Figure 21**).

may proceed via the microscope approach.

*RW not visible through posterior tympanotomy done by 2 mm burr.*

*DOI: http://dx.doi.org/10.5772/intechopen.84563*

to completely visualize the RW region from posterior tympanotomy has been recently reported: 0° (3 mm outer diameter, 14 cm length) and 0 and 30° (2.7 and 4 mm outer diameter, 11 and 6 cm in length) [43, 44]. Endoscopes of 2.7–4 mm diameter cannot likely enter a standard posterior tympanotomy and, that is, in case of posterior location of the RW, there is still suboptimal visualization. With a posterior tympanotomy of 2 mm and the introduction of a 1.9 mm outer diameter endoscope, the RW niche is always completely visible so that the thinning of the lips of the RW niche under endoscopic view until the projection of the lateral wall of the ST and the region of insertion of the basilar membrane are evident; this thus avoids damage to functionally relevant structures when detaching the

*(A) RW visible through posterior tympanostomy, (B) case where RW in invisible, and in (C) the advantage of* 

The technique consists of a standard mini-invasive surgical approach under general anesthesia performed with a postauricolar access and transmastoid poste-

The tip of a 0°, 1.9 mm diameter and 11 cm long endoscope is positioned in proximity of the upper part of the posterior tympanotomy to obtain a panoramic view of the inferior part of the medial wall of the tympanic cavity. The endoscope can be kept in place using a standard endoscope holder. The next steps are performed under direct endoscopic view. The bone overhanging the RW is lowered using a 1 mm microdrill under constant irrigation or irrigation/aspiration if an endoscope holder is used (**Figure 22**). At that point, exposure of the RW is now possible with a microscope through the posterior tympanotomy and the surgeon

#### **Figure 20.**

*The Human Auditory System - Basic Features and Updates on Audiological Diagnosis and Therapy*

Nowadays, normal or near-normal low-frequency hearing threshold is present in many patients who are candidates for cochlear implantation, and combined electric acoustic stimulation can be proposed. Consequently, preservation of residual hearing is becoming a crucial issue. Avoiding trauma to inner ear structures when placing a multi-electrode array during the cochlear implant procedure is essential to preserve residual hearing, and the first important topic is the route of insertion of

Scala tympani is the location for multi-electrode array cochlear implants when normal anatomy is present. The reasons for this are the greater sectional dimension compared to scala vestibuli, protection of cochlear duct by osseous spiral lamina and basilar membrane that are stronger than Reissner's membrane, close proximity to the spiral ganglion cell bodies and dendrites, and direct access through the round

Access to the scala tympani to introduce the multi-electrode array during the cochlear implant procedure is obtained by opening the RWM, when the RW is sufficiently visible through a posterior tympanotomy or by performing a promontorial cochleostomy in the inferior-lateral wall of the scala tympani, when the RW exposure is not adequate. The advantages of RW access are: reduced risk of intracochlear trauma, wider stimulation surface, and facilitated perimodiolar position [35, 36]. Anatomical variations in the facial nerve, chorda tympani, and the RW niche may create obstacles to approach the RWM [37], and a classification of visualization to the RWM related to surgical approachability has been proposed. Following this classification, complete RWM exposure (considering the only one that guarantees a pure RW approach) was possible in 46% of children, while in 7% the RWM was not visible. [36]. Even if the RWM is completely visible, opening of the RWM does not provide straightforward access to the scala tympani because of the presence of a sharp bony crest in the anterior-inferior border of the niche called the "crista fenestrae," the

When the RW is not visible and a promontorial approach is needed to consent opening of the scala tympani using a cochleostomy approach without damage to the osseous spiral lamina and basilar membrane, Adunka et al. [34] demonstrated, with an anatomical study, that drilling should proceed from the inferior to the RW annulus, with gradual progression toward the undersurface of the lumen. However, the most basal part of the scala tympani forms a fish hook-like curvature in three dimensions called the "hook" region of the cochlea [39, 40]. This portion contains the cul-de-sac of the endolymphatic space where the osseous spiral lamina, spiral ligament, and basilar membrane merge [40]. The lateral wall of the "hook" region shows large size variations with the consequence of the absence of a reliable landmark for safe access to the scala tympani when promontorial access is performed. Finally, the angle formed by a line along the plane of the basal turn and the midline (a line between the nasal septum and the internal occipital protuberance) is variable, being inversely proportional with age, thus increasing the risk of damage

Applying rigid endoscopy through posterior tympanotomy consents the surgeon to gain both a view of the RW, in case it is invisible, and direction of the scala tympani in children, thereby allowing soft and less traumatic insertion of the multi-

The use of an endoscope to assist cochlear implant surgery has been reported as a transcanal endoscopy by creating a tympanomeatal flap; this approach has been recently questioned because the basal turn of the cochlea align with a more posterior angle than that of the ear canal [42]. The idea to use a rigid endoscope

**6. Cochlear implantation**

the multi-electrode array.

window (RW) [33, 34].

morphology of which is highly variable [38].

of the cochlear duct in children. [41].

electrode array during cochlear implantation (**Figure 20**).

**124**

*(A) RW visible through posterior tympanostomy, (B) case where RW in invisible, and in (C) the advantage of the endoscope to visualize the RW.*

to completely visualize the RW region from posterior tympanotomy has been recently reported: 0° (3 mm outer diameter, 14 cm length) and 0 and 30° (2.7 and 4 mm outer diameter, 11 and 6 cm in length) [43, 44]. Endoscopes of 2.7–4 mm diameter cannot likely enter a standard posterior tympanotomy and, that is, in case of posterior location of the RW, there is still suboptimal visualization. With a posterior tympanotomy of 2 mm and the introduction of a 1.9 mm outer diameter endoscope, the RW niche is always completely visible so that the thinning of the lips of the RW niche under endoscopic view until the projection of the lateral wall of the ST and the region of insertion of the basilar membrane are evident; this thus avoids damage to functionally relevant structures when detaching the annulus of the RWM.

The technique consists of a standard mini-invasive surgical approach under general anesthesia performed with a postauricolar access and transmastoid posterior tympanotomy of 2 mm (**Figure 21**).

The tip of a 0°, 1.9 mm diameter and 11 cm long endoscope is positioned in proximity of the upper part of the posterior tympanotomy to obtain a panoramic view of the inferior part of the medial wall of the tympanic cavity. The endoscope can be kept in place using a standard endoscope holder. The next steps are performed under direct endoscopic view. The bone overhanging the RW is lowered using a 1 mm microdrill under constant irrigation or irrigation/aspiration if an endoscope holder is used (**Figure 22**). At that point, exposure of the RW is now possible with a microscope through the posterior tympanotomy and the surgeon may proceed via the microscope approach.

**Figure 21.** *RW not visible through posterior tympanotomy done by 2 mm burr.*

**Figure 22.**

*(A) Visualization of the RW by 1.9 mm endoscope through the posterior tympanostomy, (B) drilling of overhanging bone, and (C) RWM exposed.*

Otherwise, the surgeon may continue endoscopically and exploit the best use of endoscopy. The bone overhanging the RW in the anterior inferior aspect of promontory is thinned (**Figure 23A**) until a "blue line" inferiorly (corresponding to the ST) and a white line superiorly (corresponding to the insertion of the basilar membrane) are evident (**Figure 23B**). The anterior inferior part of the annulus of the RWM is detached from its bone insertion with a needle to open the ST (**Figure 23C**). The corresponding thinned bone, the crista fenestrae, is removed by a microcurette or a very low speed 0.5 mm microdrill until the direction of the canal is clearly evident. This allows gaining centered access to the ST and permits smooth linear introduction of the multi-electrode array into the basal turn (**Figure 23D**); attention must be given to avoid bone dust or fragments from entering into the ST. The diameter of the opening of the ST is not previously planned, provided that it is larger than the multielectrode array diameter to leave perilymph coming out during insertion (**Figure 23**). Dexamethasone 4 mg/ml is gently flushed into the middle ear cavity and cochleostomy site. The electrode array is slowly inserted into the ST in a standard manner.

Endoscopic assistance through posterior tympanotomy has other advantages: in cases of particularly curved external auditory canal or small facial recess overthinning of the posterior wall with potential breakdown, extensive drilling of the fallopian canal with potential facial damage is no longer necessary; finally, in case of cochlear malformation, a panoramic view of the middle ear medial wall helps to identify the site for cochleostomy with no need of transcanal opening of the middle ear.

In conclusion, endoscope-assisted round window cochleostomy is a practicable alternative to the classical microscopic approach. It allows exposure of hidden RW niche, avoids over-thinning of the posterior external auditory canal by extensive drilling, and is useful to prevent luxation or removal of the external auditory canal when cochlear drillout is indicated. Thus, it optimizes array orientation and introduction into the scala tympani and leads to better results for residual hearing.

#### **Figure 23.**

*Left ear. (A) Drilling of the RW lips, (B) exposure of the ST, (C) RW partially elevated, and (D) array insertion along the direction of the ST.*

**127**

*Endoscopic Ear Surgery in Children*

*DOI: http://dx.doi.org/10.5772/intechopen.84563*

otosurgeons than to dedicated ones.

and shorter duration of surgery.

handed procedure.

**7. The holder, a two-handed technique**

Otosurgeons are often skeptic and hesitant for endoscopic ear surgery for several reasons. First, single handedness in endoscopy is a limitation, especially in bleeding fields. When it occurs, bleeding is often a disturbing event, and frequent suction is needed so that the surgeon may be prone to interrupt the procedure and convert it to a traditional bimanual microscope technique [24, 45]. Second, otosurgeons are experienced with double-handed stereoscopic vision. Their teachings and therefore their maneuvers are based on two hands, whereas with endoscopy, otosurgeons have to manage maneuvers with one hand and lose the characteristic of the depth of vision. Differently, surgeons who practice sinus surgery are acquainted with a one hand procedure and for them approaching middle ear surgery is much preferred to operative microscope. This is why it seems to be more acceptable to nondedicated

One of the drawbacks of the technique is being single handed. In case of a bloody

Different from other endoscopic procedures where a dynamic field is required, that is, cholesteatoma removal [46], during myringoplasty, the endoscope seldom needs to be moved to adjust the field of vision, so that the application of an endoscope holder is particularly favorable. The immediate advantage noticed is the rapidity of the procedure in elevating the tympanomeatal flap and fibrous annulus without frequently stopping to aspirate blood. Washing and suctioning simultaneously always guarantees optimal vision and cleaning of the endoscope. Another advantage is evident during introduction of the flap in case of liquid in the middle ear: suction by the second hand is promptly made. Positioning the graft underneath the anterior annulus with two hands is much easier by avoiding its wrinkling, and application of gelatin sponges under the graft itself is much easier. Finally, in onehanded surgery, the scope often has blurred vision due to blood clot or liquid left by hair in the EAC during the frequent introduction and extraction of the scope. The most important advantages of the use of a holding system are control of bleeding

The endoscopic procedure consists of: (1) application of the endoscope holder on the operating table in front of the surgeon (**Figure 24**), (2) positioning of the endoscope at the mid level of the posterior part of the external auditory canal, (3) refreshing the margins of the perforation using a sickle knife and grasping forceps, (4) elevating a medial tympanomeatal flap with a semilunar incision at 12 and 6 o'clock, (5) inserting the graft under the malleus and the anterior margin of the perforation, and (6) applying gelatin sponges in the middle ear and, after repositioning the flap, in the ear canal. **Figure 25** shows the different steps of the endoscopic surgery and how it is handled bimanually, offering a clear advantage over a single-

The endoscopes used are 3 and 4 mm in diameter rigid 0° (Hopkins KARL STORZ GmbH & Co. Tuttlingen Germany), lengths 14 and 18 cm, respectively. The optic holder used is a mechanical articulating holding system (28,272 HC; 28,272 UGK; 28,172 HR: KARL STORZ GmbH & Co. Tuttlingen Germany) (**Figure 26**) or the Unitrack pneumatic holding system (Unitrac arm, RT040R, Aesculap AG, Tuttlingen Germany (**Figure 27**). All procedures are performed under general anesthesia.

The surgical maneuvers are managed better using a 3 mm vs. a 4 mm endoscope; according to our experience, we would recommend the 3 mm thanks to the greater space offered. The reason for using an 18 and 14 cm endoscope and not 6 or 11 cm

field, especially in hyperplastic mucosa of the middle ear, surgery can become demanding and time consuming. Trying to overcome this limit, since January 2016, we started using the STORZ endoscope mechanical holding system followed a few

months later by the Unitrack pneumatic holding system.

*The Human Auditory System - Basic Features and Updates on Audiological Diagnosis and Therapy*

*(A) Visualization of the RW by 1.9 mm endoscope through the posterior tympanostomy, (B) drilling of* 

Otherwise, the surgeon may continue endoscopically and exploit the best use of endoscopy. The bone overhanging the RW in the anterior inferior aspect of promontory is thinned (**Figure 23A**) until a "blue line" inferiorly (corresponding to the ST) and a white line superiorly (corresponding to the insertion of the basilar membrane) are evident (**Figure 23B**). The anterior inferior part of the annulus of the RWM is detached from its bone insertion with a needle to open the ST (**Figure 23C**). The corresponding thinned bone, the crista fenestrae, is removed by a microcurette or a very low speed 0.5 mm microdrill until the direction of the canal is clearly evident. This allows gaining centered access to the ST and permits smooth linear introduction of the multi-electrode array into the basal turn (**Figure 23D**); attention must be given to avoid bone dust or fragments from entering into the ST. The diameter of the opening of the ST is not previously planned, provided that it is larger than the multielectrode array diameter to leave perilymph coming out during insertion (**Figure 23**). Dexamethasone 4 mg/ml is gently flushed into the middle ear cavity and cochleostomy site. The electrode array is slowly inserted into the ST in a standard manner. Endoscopic assistance through posterior tympanotomy has other advantages: in cases of particularly curved external auditory canal or small facial recess overthinning of the posterior wall with potential breakdown, extensive drilling of the fallopian canal with potential facial damage is no longer necessary; finally, in case of cochlear malformation, a panoramic view of the middle ear medial wall helps to identify the site for cochleostomy with no need of transcanal opening of the middle ear. In conclusion, endoscope-assisted round window cochleostomy is a practicable alternative to the classical microscopic approach. It allows exposure of hidden RW niche, avoids over-thinning of the posterior external auditory canal by extensive drilling, and is useful to prevent luxation or removal of the external auditory canal when cochlear drillout is indicated. Thus, it optimizes array orientation and introduction into the scala tympani and leads to better results for

*Left ear. (A) Drilling of the RW lips, (B) exposure of the ST, (C) RW partially elevated, and (D) array* 

**126**

**Figure 23.**

residual hearing.

*insertion along the direction of the ST.*

**Figure 22.**

*overhanging bone, and (C) RWM exposed.*
