**7. Pathomorphological changes of the brain around long-standing ventricular shunts**

The puncture canal is a model of minor surgical brain damage and its outcome. Prolonged presence of an inert foreign body (shunt) determines the features of changes in the surrounding brain tissue [30].

As shown by a postmortem examination of brain tissue around shunts installed in occlusive hydrocephalus with various pathologies, a structured gliomesodermal capsule is formed more than 20 days ago (**Figure 6**).

As a result of completed reparative processes after puncture damage, along with a capsule mainly formed by mast astrocytes with connective tissue elements, a zone of perifocal changes in brain matter is detected, manifested by damage to myelin fibers and microcystic transformation (**Figure 7**).

Despite minimal brain damage during puncture, the outcome of reparative processes around the canal is the formation of a functionally "mute" zone, which is recorded during MRI examination in the form of a hyperintensive signal on T2 VI, IR IP, extending from the wall of the puncture canal up to 3 cm. The observed severity of perifocal changes around the shunt may cause neurological manifestations.

#### **Figure 6.**

*Puncture canal in the right frontal lobe after installing a ventriculoperitoneal shunt through the anterior horn of the right lateral ventricle. The limitation period is 30 days. A—MRI T2-VI, axial plane. The three-layer structure of the puncture canal zone is differentiated; B—MRI IP-IR, axial plane. Puncture canal in the form of an oval hypointensive focus surrounded by a zone of perifocal changes; C—anatomical preparation, a type of puncture canal from the convexital surface; D is an anatomical preparation, a horizontal section at the level of the corresponding MR image. Perifocal changes recorded on MRI are not visualized; E—along the edge of the puncture canal is a gliomesodermal capsule with the presence of coarse collagen fibers of connective tissue. X 50. Mallory coloring; F—loose granulation tissue with an abundance of thin-walled vessels and reticulin fibers. X100. Impregnation with silver; G—cell gliosis of fibrous and obese astrocytes, around fragments of myelin fibers. X400. Coloring by Shpilmeyer.*

*CSF Bypass Surgery in Children with Hydrocephalus: Modern Possibilities, Prospects… DOI: http://dx.doi.org/10.5772/intechopen.110871*

#### **Figure 7.**

*Perifocal changes of the brain around the puncture canal. A—microcystic transformation of brain matter. X 50 H&E; B—demyelination of white matter around the channel. X 50, Shpilmeyer painting; C—single thinned myelin fibers with bulbous thickenings in the demyelination zone. X 200, Shpilmeyer coloring; D—fragmentation and formation of ring-shaped structures of damaged myelin fibers. .X 200, Shpilmeyer coloring.*

### **8. Complications of LSO and their correction**

The purpose of CSF shunting operations using valve drainage systems is to remove "excess" CSF outside the CSF system, eliminate ICH, and reduce the severity of deformation and expansion of CSF cavities [31].

In some cases, the goal is not achieved, and, with a liquor-shunting system implanted certain pathological manifestations occur. They are mainly associated with the peculiarities of the CSF shunting system functioning, namely with its permanent or transient dysfunction, and are combined into a single group of complications associated with inadequate operation of the shunting system [13, 31–33].

Pathological conditions, which are based on inadequate intensity of CSF outflow, are divided into two large groups: hyperdrainage and hypodrainage complications.

#### **8.1 Hypodrainage conditions**

In cases when the CSF outflow through the shunting system is insufficient to balance the CSF circulation and eliminate craniocerebral disproportion, manifestations of decompensated hydrocephalus persist even after CSF shunting operations [33].

This complication manifests in headaches, lethargy, drowsiness, hypophasia, hypodynamia, convergence disorders, paresis of looking up, suppression of photoreactions, suppression of abdominal reflexes, less often paroxysmal manifestations, the occurrence or preservation of pathological stop signs, and oral reflexes are observed. Ophthalmological studies reveal the persistence or reappearance of stagnant phenomena on the fundus, deterioration of vision, the field of vision narrowing.

#### **Figure 8.**

*MRI scan, axial projection of the brain 2 months after CSF bypass surgery. Progressive hydrocephalus. Shunt dysfunction. Ventriculomegaly with periventricular edema, absence of subarachnoid spaces. Т2WI (A, B), Flair IP (C, D).*

More often, a hypodrainage condition is detected during implantation of a drainage system of high or very high (≥ 120 mm of water) pressure, after previously performed ventriculoperitoneostomy or lumboperitoneostomy in patients with previous operations in the abdominal cavity or in the presence of pathology of the abdominal organs. Usually (in 3/4 of patients) hypodrainage is manifestated during the first week (month) after surgery, and the progressive course is slow.

CT, MRI studies reveal ventriculomegaly, narrowing of subarachnoid slits, preservation of periventricular edema (**Figure 8**).

The pathogenesis of hypodrainage conditions is far from being understood uniformly. Incorrectly chosen valve parameters of implantable systems can result in the valve pressure being higher than required. As a result, excessive CSF pressure persists. High peripheral resistance resulting from high intra-abdominal pressure, or high central venous pressure in those areas where liquor shunting systems are implanted, is considered to be another reason. There is still another mechanism leading to a hypodrainage state, which is a change in the "pressure-velocity" parameters of implantable systems under *in vivo* conditions due to obliteration of catheters and changes in the patency of the valve system [25, 33–35].

To diagnose a hypodrainage complication, one should state clinical and introscopic manifestations: the persistence of decompensated hydrocephalus, as well as ventriculomegaly, obliteration of subarachnoid spaces, periventricular edema according to CT, and MRI [33].

#### **8.2 Hyperdrainage complications**

With inadequately selected parameters of the shunting system, patients with hydrocephalus may develop specific conditions in the postoperative period, which include, inter alia, hyperdrainage complications. These conditions are based on excessively intense CSF outflow through the CSF shunting system, leading to low CSF pressure, accompanied by deformation of the CSF cavities of the brain, skull, and various clinical manifestations [33].

*CSF Bypass Surgery in Children with Hydrocephalus: Modern Possibilities, Prospects… DOI: http://dx.doi.org/10.5772/intechopen.110871*

The frequency of this complication is noted in a wide range: from 5 to 55% [31, 35] and is more often observed in children under 6 months. Hyperdrainage leads to the development of such manifestations of craniocerebral disproportion as intracranial hypotension, slit-like lateral ventricle syndrome, subdural accumulation of CSF, isolated IV ventricle syndrome, and other cranial deformities [35].

Rapid removal of CSF by shunt leads to a rapid decrease in the volume of the ventricular system and deformation of the cerebral cloak, as a result of the resulting pressure gradient, and additional fluid accumulations (CSF or blood) form around the brain. In some cases, acute intracranial hypotension can lead to dislocation of the brain stem and the development of vital disorders [15, 34].

The most common manifestation of this pathological condition is characterized in modern literature as "slit ventricular syndrome."

#### *8.2.1 The syndrome of slit ventricles of the brain*

The term "slit ventricular syndrome" is widely used to describe the condition of chronic or transient headaches suffered by patients with hydrocephalus after CSF bypass operations accompanied by narrow (slit) ventricles (**Figure 9**).

There are several main pathophysiological mechanisms that cause slit ventricular syndrome: transient shunt dysfunction, intracranial hypotension, and against this background, a paroxysmal increase in ICP in the presence of a functioning shunt. At the same time, it is very important to distinguish situations when the ventricles are smaller than usual, or even almost invisible, but the clinical picture is asymptomatic and hence surgical correction is not required. Only when, in the presence of slit ventricles detected by CT/MRI examination, patients begin to suffer from an intense headache that interferes with normal life, and the diagnosis of "slit ventricular syndrome" is valid, requiring observation and treatment [36, 37].

Rekate H. suggests limiting the use of the term "slit ventricular syndrome" to cases characterized by a triad of signs: intermittent headache lasting 10–30 minutes, smaller than the normal size of the brain ventricles according to neuroimaging, slow filling of the pump reservoir after its mechanical pressure [37].

Headaches, hypodynamia, and general cerebral symptoms in these patients may be caused by both transient ICH and hypotension, and the relative significance of these mechanisms in each case seems difficult to determine.

#### **Figure 9.**

*CT scan, axial projection of the brain 20 years after ventriculoperitoneostomy. Congenital communicating hydrocephalus. Lateral ventricles are not traced, narrow subarachnoid slits, thickened skull bones with an enhanced pattern of finger depressions.*

To accurately verify the diagnosis of slit ventricular syndrome, a comprehensive examination is required, including monitoring of intracranial pressure, which will help to exclude other causes of cephalgia, for example, cases of "childhood migraine", that is, not requiring surgical manipulations [37].

The frequency of this condition ranges from 0.9–37%, depending on the analyzed group of patients [36].

There are several pathogenetic mechanisms described in the literature and characteristic of the formation of this syndrome, underlying clinical manifestations: a sharp fluctuation of liquor pressure, deformation of liquor-containing cavities, changes in cerebrovascular conjugation, deformation of vascular collectors and redistribution of blood flow, changes in the viscoelastic properties of CSF, changes in the parameters of the regulatory mechanism implementation.

At the initial stage of the development of the slit ventricular syndrome, there is an inadequately intense CSF outflow through the shunting system, a hypotensive state, which actually leads to an excessive reduction in the size of the ventricular system. Further on, periventricular fibrosis, transient occlusion of the ventricular catheter, a decrease in the malleability of the brain, violations of venous outflow, increased intracranial pressure, etc. become the leading factors.

Neuroimaging methods are crucial in the diagnosis of slit ventricular syndrome, establishing the fact of microventriculia [37] (**Figure 10**).

Hyperdrainage syndrome requires replacement of the CSF bypass system with higher valve opening pressure values, implantation of an anti-siphon system. With narrow but asymmetric lateral ventricles, additional drainage of the opposite lateral ventricle, endoscopic perforation of the transparent septum is also proposed.

In case of confirmed dysfunction of the CSF system, it is revised with the replacement of occluded parts of the system. It is recommended to combine the revision of the liquor bypass system with the installation of an anti-siphon system, as well as during the primary implantation of the liquor bypass system, and this component should be used, which, in their opinion, prevents the development of slit ventricular syndrome [38].

In case of already formed craniostenosis with hyperdrainage in the background, when minimally invasive interventions are ineffective, when transient cephalgia persists while the shunt is functioning, and decompressive craniotomy or correction of

#### **Figure 10.**

*MRI scan of the brain 9 months after CSF bypass surgery by a low pressure valve. Posthemorrhagic hydrocephalus. Expansion of the cavity of the IV ventricle against the background of slit-like lateral and III ventricles. A, B— T2WI, axial projection; C—Т1WI, sagittal projection.*

*CSF Bypass Surgery in Children with Hydrocephalus: Modern Possibilities, Prospects… DOI: http://dx.doi.org/10.5772/intechopen.110871*

craniosynostosis is recommended. According to the authors, an increase in the volume of the cranial box, in this category of children, in most cases leads to a persistent positive effect and significantly reduces the frequency of repeated revisions of the CSF system [39].

Treatment of slit ventricular syndrome should be aimed at correcting the main mechanisms of this condition development, namely, the cessation of excessive CSF outflow through the CSF bypass system, correction of craniosynostosis, microcrania, and deformation of venous collectors through craniofacial or cranial reconstructive operations [33].

#### *8.2.2 Isolated IV ventricle syndrome*

One of the specific complications of cerebrospinal bypass surgery, in particular, as a manifestation of hyperdrainage, is the "sequesterization" of various parts of the ventricular system as a result of occlusion of interventricular openings (Monroe), Monroe openings in combination with brain plumbing, brain plumbing in combination with IV ventricular openings—isolated IV ventricular syndrome.

As a result of the closure of the plumbing of the brain and the openings of the IV ventricle (Lyushka and Majendi), its isolation from the CSF system occurs. With CSF continually produced, there is a gradual expansion of the cavity of the IV ventricle and compression of adjacent structures (brain stem, cerebellum), accompanied by appropriate clinical manifestations.

This variant is rare and this pathological condition in most cases is considered as a consequence of a hyper-drainage condition. The manifestation of the isolated IV ventricle syndrome consists in cerebellar disorders and signs of stem dysfunction. More often, patients complain of impaired coordination, double vision, headache, vomiting. The progression of the pathological process often leads to an increase in bulbar symptoms, impaired consciousness, and up to coma as a result of stem structure compression [14].

The introscopic picture in isolated IV ventricle syndrome has a specific character: A significantly expanded spherical IV ventricle is visualized, squeezing the stem structures anteriorly, the cerebellum posteriorly, the bottom of the rhomboid fossa being flattened, and dislocated anteriorly. With a pronounced and prolonged nature of the pathological process, there is a caudal displacement of the amygdala of the cerebellum and rostral dislocation in the tentorial tenderloin. Other manifestations of the hyperdrainage state of the supratentorial ventricles of the brain are also typical: dilation of subarachnoid spaces, narrow or slit-shaped lateral ventricles, subdural hydromes, or hematomas of the cerebral hemispheres [40].

Isolation of the IV ventricular cavity from the CSF system is clarified by contrast examination methods (CT-ventriculography). The pathogenesis of the formation of an isolated IV ventricle can be presented in several variants (**Figure 11**).

Correction of functional occlusion of the brain's plumbing is achieved by restoring adequate control over hydrocephalus (correction of hyperdrainage state). On the other hand, a positive result in the treatment of functional occlusion of the aqueduct and thereby regression of the isolated IV ventricle syndrome can be achieved after its temporary drainage by regular punctures or implantation of the Omaya reservoir (an undesirable option) [40].

Elimination of the pressure gradient between the supra- and subtentorial spaces makes it possible to restore the participation of the IV ventricle in the CSF circulation in the functional form of this syndrome.

#### **Figure 11.**

*Ways of formation of an isolated IV ventricle in patients with hydrocephalus after CSF bypass surgery.*

In case of occlusion of the brain plumbing caused by morphological changes, surgical treatment is indicated. A number of authors practice open interventions with an isolated IV ventricle, performing microsurgical excision of adhesions, membranes causing the closure of the lumen of the brain plumbing, and ventricular openings, thus eliminating the "isolation" of the IV ventricular cavity and restoring liquor circulation by forming ventriculocysternostomy. At the same time, Dollo C. et al. recommend in some cases to complete the operation with "internal" shunting: implantation of a catheter from the cavity of the IV ventricle into the subarachnoid spinal space. The advantage of this method, according to the authors, is the prevention of reovergrowth of the formed holes, the absence of a valve, and the position of the catheter along the rhomboid fossa bottom, which excludes damage to the latter [41].

IV ventricular bypass surgery has long been the most common method of surgical correction of the syndrome. It is worth noting that the course of the ventricular catheter should be as parallel as possible to the bottom of the rhomboid fossa, and its fixation should be reliable in order to avoid its migration into the cavity of the IV ventricle and traumatizing its bottom. When implanting a ventricular catheter, it is necessary to avoid damage to the transverse, sigmoid, and occipital sinuses [33].

A ventricular catheter is implanted through the hemispheres or, more rarely, the cerebellar worm [35] (**Figure 12**, A, B). The disadvantage of this method, according to some authors, is the impossibility of installing a ventricular catheter strictly parallel to the rhomboid fossa bottom, which does not exclude damage to the latter during surgery or when moving the brain stem against the background of ventricular drainage. With a decrease in the drainage cavity in volume, the risk of the ventricular catheter exit openings being obturated increases, which is also characteristic of this access [14].

The technique of shunting the IV ventricle through the frontal transventricular access can be described as follows: With the help of endoscopic assistance, a proximal catheter is passed through the lateral, III ventricles and installed into the cavity of the IV ventricle through the occluded water supply of the brain [42].

With this operation, simultaneous drainage of the lateral ventricles is possible with the formation of additional holes on the corresponding segments of the proximal

*CSF Bypass Surgery in Children with Hydrocephalus: Modern Possibilities, Prospects… DOI: http://dx.doi.org/10.5772/intechopen.110871*

#### **Figure 12.**

*Isolated IV ventricle syndrome. A—Ventricular ventricular IV ventricular peritoneostomy scheme; B—CT scan, axial projection of the brain after CSF bypass surgery with IV ventricular cavity catheterization; C—IV ventricular catheterization scheme. 1—Ventricular catheter; 2—Y-shaped connector; 3—Valve.*

catheter, which will allow, if necessary, to avoid implantation of additional CSF bypass systems [14].

Unfortunately, this method is not feasible in the case of narrow or slit-shaped lateral ventricles, which is often characteristic of isolated IV ventricle syndrome.

The most adequate and pathophysiologically justified method, namely, peritoneostomy through the Y-shaped system, should still be considered, in which the IV and lateral ventricles are drained by a single valve system after being preliminarily connected (ventricular-ventricular IV ventricle). The technique of the operation has already been developed. The lateral and IV ventricles are catheterized, after which the extracerebral ends of both catheters are connected by a Y-shaped system, and the third arm of the connector is connected to the valve. Next, the distal catheter is implanted in the peritoneal cavity in the usual way. This is how uniform drainage of these isolated cerebrospinal cavities is carried out (**Figure 12**, C).

After implantation, the proximal catheter is included in the general cerebrospinal bypass system through a Y-shaped connector, or separate CSF bypass systems is implanted. At the same time, according to a number of authors, preference should be given to the first option, since this allows balancing the pressure above and below the tentorium [13, 32].

At the present stage, endoscopic methods of treatment of isolated IV ventricle syndrome are most popular: aqueductoplasty with or without stenting, perforation of the bottom of the III ventricle, and restoration of patency of the holes of Lyushka and Majendi [15]. However, due to the high risk of perioperative complications (bleeding, damage to vital structures), these manipulations are recommended to be carried out only in highly qualified medical institutions.

#### **8.3 General complications of LSO**

All CSF shunting operations create artificial homeostasis, which is characterized by depressurization of the CSS, constant removal of CSF into the extracranial cavities,

prolonged implantation into the CSF system and other body cavities of a foreign body (drainage system), and fixation of intracranial pressure at a predetermined level. Under these conditions, objective prerequisites are created for the development of complications both during surgery and in the postoperative period [43, 44].

### *8.3.1 Complication of punctures*

Puncturing of the ventricles of the brain when the proximal shunt is inserted into them can be complicated by hemorrhages into the brain tissue along the puncture channel, subdural, and intraventricular hematomas [44, 45]. In some cases, when the shunt is standing for a long time, a gliomesodermal scar forms in the surrounding brain matter. According to various authors, from 5 to 48% of liquor bypass operations are complicated by the development of epilepsy [45]. Such a large spread of data is probably explained by different ways of performing operations by different authors. For example, the risk of epilepsy development increases significantly when a shunt is performed through the frontal or temporal lobes—the zones where epileptogenic foci are most often formed. Patients who have had at least a single convulsive attack in their anamnesis or who showed high convulsive readiness during EEG examination require special attention when performing LSO.

#### *8.3.2 Inflammatory complications*

Depressurization of the cranial cavity and prolonged implantation into the ventricular shunt system creates conditions for inflammatory complications [15, 46, 47]. In 3–17% of cases, there are limited or diffuse ventriculitis, meningitis, and encephalitis of varying severity [15, 46, 47]. In these cases, it is possible to spread the infection through the shunt and the occurrence of limited or diffuse peritonitis in this regard (with ventriculoperitoneostomy). With ventriculoatriostomy, the infectious agent gets directly into the blood, which sometimes leads to the development of sepsis [15, 41]. The greatest number of inflammatory complications develops in patients operated by underqualified neurosurgeons, as well as in emaciated patients and in the absence of drug prevention [44].

#### *8.3.3 Thromboembolic complications*

The imposition of ventriculovenous anastomoses is accompanied with the introduction of a foreign body directly into the bloodstream, which can lead to thrombosis in the lumen of the sinuses, veins, or right atrium [15, 44]. Blood clots cause either vascular occlusion or serve as a source of thromboembolism of the vessels of the small circle. The death of patients in this case may occur due to reflex cardiac arrest with thromboembolism of the main vessels. Closure of the lumen of the intrapulmonary vessels can lead to the development of lung infarcts and infarct-pneumonia. Our data include a case of jugular vein thrombosis and a case a pulmonary embolism of the branches of the pulmonary artery.

## *8.3.4 Perineal cyst*

This complication occurs when the CSF is excreted into the abdominal cavity. In the abdominal cavity, a yellowish liquid rich in protein accumulates locally around the *CSF Bypass Surgery in Children with Hydrocephalus: Modern Possibilities, Prospects… DOI: http://dx.doi.org/10.5772/intechopen.110871*

peritoneal end of the catheter, around which a connective tissue capsule is formed as a result of the adhesive process, without any lining [15, 43, 48].

#### *8.3.5 Tumor metastasis by shunt*

Before cerebrospinal bypass surgery became a regular practice, extracranial metastasis of intracranial and especially glial tumors, even with a pronounced degree of anaplasia, used to be extremely rare, which, apparently, is associated with the protective function of the blood-brain barrier [49]. The artificial CSF pathway greatly facilitates the metastasis of the tumor beyond the skull, bypassing the blood-brain barrier. Depending on the type of bypass surgery, metastatic tumors may occur in the abdominal cavity (peritoneal location of the catheter) or in the lungs (with ventriculoatriostomy) [50]. We observed metastasis of a malignant glial tumor (medulloblastoma) [44]. The primary node was located in the cerebellum, and there were multiple cerebrospinal metastases to the brain and spinal cord. Tumor tissue growths similar to the primary node were also found around the distal part of the catheter located in the retroperitoneal tissue.

#### *8.3.6 Violations of water-electrolyte metabolism*

The development of water-electrolyte metabolism disorders is most likely during ventriculoatriostomy, since with this type of bypass a significant and incalculable amount of CSF is removed directly into the bloodstream for a short period of time. The protein content in the liquor is 0.3 g / l, and in the blood plasma 65–85 g/l; thus, almost protein-free liquid is poured directly into the blood, which can lead to the development of hemodilution. In case this risk is ignored, the signs of hemodilution a decrease in the number of red blood cells, hemoglobin content, protein, can be regarded as post-hemorrhagic anemia, which in turn leads to improper treatment transfusion of a large amount of fluid [32]. In one of our observations, the child is 10 months old. During the operation, 500 ml of protein-free solutions were poured during the anesthetic aid. Immediately after the operation, a picture of stagnation in the small circle of blood circulation developed (tachypnea, diffuse wet wheezing in both lungs, tachycardia, an increase in central venous pressure), anemia, microcirculation disorders (marbled color, increased turgor, and moisture of the skin), and stem symptoms. The patient's condition was regarded as dyscirculatory (hemic) hypoxia as a result of blood loss during surgery. Blood and blood-substituting fluids (250 ml of blood and 900 ml of other solutions) were transfused, but the patient's condition continued to deteriorate, and central respiratory and hemodynamic disorders joined, resulting in death of the patient 18 hours after the operation. The cause of death of the patient in such cases is pronounced hyperhydration and hemodilution [44].

#### **8.4 Causes of death after CSF bypass surgery**

The death of patients after LSO most often occurs due to the progression of the underlying disease. For example, the recurrence of the tumor can cause death of cancer patients. In some cases, the complications listed above (subdural and intraventricular hematomas of large volume, brain collapse, or pronounced disorders of waterelectrolyte metabolism) can be the cause of death [44]. In some cases, the death of patients (usually infants) with severe occlusive hydrocephalus occurs in the coming hours after surgery. At the autopsy, no serious complications of LSO are detected. It can be assumed that the death of patients who were in a subcompensated state with coordinating systems of homeostasis damaged before the operation occurs due to central respiratory disorders and the activity of the cardiovascular system [32]. These disorders are probably associated with decompensation of brain stem structures. In patients with severe hydrocephalus, there is a prolonged dislocation of the trunk, to which the patient adapts. During surgery, part of the CSF is usually released into the external environment during ventriculopuncture, especially in patients with very high CSF pressure. Then, the CSF enters the extracranial cavities through the pump, due to which the CSF and intracranial pressure decrease and the brain stem is being redislocated; the pressure of the CSF on the trunk from the IV ventricle also decreases. This can probably explain increased blood filling of the brain stem present in such patients, up to the occurrence of small perivascular diapedetic hemorrhages, detected by microscopic examination. It can be assumed that in such severe patients, even minor additional damage to the trunk is sufficient for decompensation of its function and death of the patient.
