**2. Indications**

In general, endoscopic third ventriculostomy is the gold-standard treatment for noncommunicating hydrocephalus. The indication for ETV includes all cases with obstruction between the third ventricle and the subarachnoid space with preserved CSF absorption from subarachnoid space into the venous system [2, 14, 15]. In case of obstruction at the level of Pacchionian granulation and venous outflow, performing ETV is definitely not recommended [14].

#### **2.1. Aqueduct stenosis**

ventricle, the dye did not appear in the spinal fluid removed by lumbar puncture. In contrast, if this solution appeared, hydrocephalus was classified as "communicating" [1]. This classification was simple and useful to understand hydrocephalus, but first was found inadequate to understand the pathophysiology [2]. The proposed classification is hydrocephalus without obstruction (true communicating hydrocephalus) in case of choroid plexus papilloma and with obstruction at the level of venous outflow (skull base anomalies and congenital heart disease), arachnoid granulations (hemorrhage and infection), basal cisterns (hemorrhage and infection), outlets of fourth ventricle (infection and Chiari malformation), Sylvian aqueduct (congenital anomalies and tumor compression), and foramen of Monro (congenital anomalies, tumor, and postshunt ventricular asymmetry) [2]. Nonetheless, the classic nomenclature remained in clinical practice

The first neuroendoscopic procedure was introduced in 1910, when L'Espinasse performed a cauterization of plexus choroideus with a cystoscope. The other pioneer in neuroendoscopy was Walter Dandy. He published his results in 1913. Clarifying the physiology, Dandy performed plexectomy to cease the cerebrospinal fluid (CSF) production as a treatment for communicating hydrocephalus. In case of obstruction, he created an internal bypass for com-

The first endoscopic third ventriculostomy (ETV) was performed by William Mixter in 1923. This successful technique later served as a model for modern neuroendoscopy. He performed a perforation of the third ventricle floor by an intraventricular approach through the foramen of Monro. The invention of Hopkins optics, cold light sources, and digital cameras was a great development in the history of endoscopy. Following technical development and clinical

For obstructive hydrocephalus, endoscopic third ventriculostomy is the procedure of choice. This is an endoscopic fenestration between the floor of third ventricle and subarachnoid space. The CSF flow can be restored and balanced out [4]. This procedure is considered effective, safe, and simple. The complication rate is lower as it has a lower infection rate; there is

Nowadays, the use and role of endoscopic ventriculostomy expand continuously. It remains challenging to estimate and define the success of the procedure [5], even though many studies

In general, endoscopic third ventriculostomy is the gold-standard treatment for noncommunicating hydrocephalus. The indication for ETV includes all cases with obstruction between

munication between the third ventricle and cortical subarachnoid space [2, 3].

application, neuroendoscopy spread over the world [3].

no foreign material and no overdrainage compared with shunt [4].

**1.3. Endoscopic third ventriculostomy nowadays**

have overall focused on this topic [5–14].

**2. Indications**

due to its simplicity.

128 Hydrocephalus: Water on the Brain

**1.2. History of neuroendoscopy**

One of most common etiology of obstructive hydrocephalus is the aqueduct stenosis [16, 17] (**Figures 1** and **2**). The obstruction can be congenital or acquired. In 75% of cases, it is idiopathic. In remaining cases, it can be caused by infections, hemorrhages, or malformation of the central nervous system or can be related to genetic factors [16]. The first and best treatment option for this is ETV. Ventriculostomy has a good outcome regardless of etiology of the stenosis, whether it is congenital, acquired, or tumor-related obstruction [14]. However, the success rate is different in certain cases of the aqueduct stenosis. It depends on the etiology, age, clinical, and radiological characteristics [13]. In certain cases, as an alternative treatment or even simultaneous, aqueductoplasty may be performed [7, 18]. The result of aqueductoplasty is comparable with the success of ETV. As alternative treatment, it may be useful in case of thick and tough floor of the third ventricle preventing the hypothalamus or vessel injuries [18].

**Figure 1.** Aqueduct stenosis (MRI scan TRUFI sequence).

**Figure 2.** Aqueduct stenosis (left) MRI scan TRUFI sequence (right) endoscopic view.

#### **2.2. Far distal obstruction**

Obstruction distal to the fourth ventricle is a rare cause of hydrocephalus [19]. It can develop through intraventricular membranous obstruction [20, 21] or extraventricular compression [22] and in case of Dandy Walker syndrome [26] and Chiari malformation [23–25] (see below) [19]. Like all obstructive hydrocephalus, it may also be treated successfully with ventriculostomy, although an additional surgical technique with flexible endoscope is required (see below).

In children, the posterior fossa is a common localization for various tumors (54–60% of brain tumors during childhood), and a hydrocephalus develops with high probability in these cases [13]. Frequent localizations are at the cerebellum, midline, brainstem, or cerebellopontine angle. Histologically the following tumors may occur: medulloblastoma, ependymoma, astrocytoma, ganglioglioma, cavernoma, primitive neuroectodermal tumor (PNET), meningioma, and others [28]. Gliomas in the midbrain and in the periaqueductal area are relatively rare and low grade. They show benign growth patterns, and malignant spreading is rare, although a suggested dissemination through CSF has already been reported [29]. The compression of the

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**Figure 4.** Arachnoid cyst with compression of the CSF pathway (cisternography). Same patient as in **Figure 3**.

**Figure 5.** (a and b) Multiple cysts of the third ventricle with obstruction of the Sylvian aqueduct. ETV (see **Figure 9**) and

cyst removal (c) were performed. (d) Free aqueduct.

#### **2.3. Tumors and cystic lesions**

Endoscopic third ventriculostomy might be a surgical option in case of tumor- or cyst-related hydrocephalus, where the CSF flow disturbance is distal from the place of ventriculostomy (**Figures 3**–**5**). Therefore, in selected cases, it might be performed in case of tumor localization in the brainstem, posterior fossa, thalamus, pineal region, third and fourth ventricle, and other localization, e.g., cerebellopontine angle, frontal lobe, or diffuse growth pattern [27].

**Figure 3.** Arachnoid cyst with compression of the CSF pathway (MRI scan TRUFI sequence). In this case, a cystostomy and simultaneous ETV were performed.

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**Figure 4.** Arachnoid cyst with compression of the CSF pathway (cisternography). Same patient as in **Figure 3**.

**2.2. Far distal obstruction**

130 Hydrocephalus: Water on the Brain

**2.3. Tumors and cystic lesions**

and simultaneous ETV were performed.

below).

Obstruction distal to the fourth ventricle is a rare cause of hydrocephalus [19]. It can develop through intraventricular membranous obstruction [20, 21] or extraventricular compression [22] and in case of Dandy Walker syndrome [26] and Chiari malformation [23–25] (see below) [19]. Like all obstructive hydrocephalus, it may also be treated successfully with ventriculostomy, although an additional surgical technique with flexible endoscope is required (see

**Figure 2.** Aqueduct stenosis (left) MRI scan TRUFI sequence (right) endoscopic view.

Endoscopic third ventriculostomy might be a surgical option in case of tumor- or cyst-related hydrocephalus, where the CSF flow disturbance is distal from the place of ventriculostomy (**Figures 3**–**5**). Therefore, in selected cases, it might be performed in case of tumor localization in the brainstem, posterior fossa, thalamus, pineal region, third and fourth ventricle, and other localization, e.g., cerebellopontine angle, frontal lobe, or diffuse growth pattern [27].

**Figure 3.** Arachnoid cyst with compression of the CSF pathway (MRI scan TRUFI sequence). In this case, a cystostomy

In children, the posterior fossa is a common localization for various tumors (54–60% of brain tumors during childhood), and a hydrocephalus develops with high probability in these cases [13]. Frequent localizations are at the cerebellum, midline, brainstem, or cerebellopontine angle. Histologically the following tumors may occur: medulloblastoma, ependymoma, astrocytoma, ganglioglioma, cavernoma, primitive neuroectodermal tumor (PNET), meningioma, and others [28]. Gliomas in the midbrain and in the periaqueductal area are relatively rare and low grade. They show benign growth patterns, and malignant spreading is rare, although a suggested dissemination through CSF has already been reported [29]. The compression of the

**Figure 5.** (a and b) Multiple cysts of the third ventricle with obstruction of the Sylvian aqueduct. ETV (see **Figure 9**) and cyst removal (c) were performed. (d) Free aqueduct.

fourth ventricle or the foramina of Magendie and Luschka leads to circulation disturbances and hydrocephalus [13]. ETV is recommended primarily for the treatment of children with midline posterior fossa tumor–related obstructions [30]. ETV can be combined with tumor biopsy, thus providing useful information for the diagnosis. In certain cases, even the tumor resection (e.g., third ventricle) might be performed [13, 30]. The resection alone can set the CSF pathway free, providing a normal CSF circulation. Therefore, performing ventriculostomy routinely is not recommended. After tumor removal, not only the causal problem of hydrocephalus might be solved. With performing the ETV an intraperitoneal spreading of the chemotherapeutic drugs through the shunt can be avoided [32]. The time of ETV in relation to the tumor resection is still under discussion [13].

Beside posterior fossa tumors, the indication expands to pineal tumors and third ventricle tumors [33]. The pathology of these is various. The pathology includes, but is not limited to glial tumors, ependymoma, pinealoblastoma, pinealocytoma, meningioma, germ cell tumors, primitive neuroectodermal tumor, teratoma, epidermoid, metastasis, and cysts [34, 35]. Colloid cysts, arachnoid cysts with extension in the ventricles or midline, and quadrigeminal cysts can be treated with endoscopic cystectomy, cystocisternostomy, cystoventriculostomy, ventriculocystostomy, and ventriculocystocysternostomy [36]. Even a combination with ventriculostomy may be performed [13].

#### **2.4. Cerebellar infarction**

Cerebellar infarction with space-occupying effect might lead to obstruction of the CSF pathway (**Figure 6**). The occurrence of stroke-related occlusive hydrocephalus is 10.9–27.2% of cerebellar stroke patients [37]. Deterioration of consciousness in case of cerebellar infarction can be caused by compression of the brainstem through increasing parenchymal edema or by hydrocephalus. A neurosurgical intervention is required in case of decline of consciousness [7, 37, 38]. For treatment of hydrocephalus, the alternative options are external ventricle drainage (EVD), shunt placement, and ETV. However, not every hydrocephalus caused by cerebellar infarction is a suitable candidate for ETV. In case of patients with severe deterioration of consciousness and/or brain stem compression, an adequate decompression should be performed [37]. In case of hydrocephalus, the high risk for infection in case of long-term ventricle drainage can be avoided with third ventriculostomy. The compression of prepontine cistern usually does not cause any surgical problems; the technique can be performed in the usual way [37]. Regarding the routine intracerebral pressure (ICP) monitoring in case of ETV patients, it is not recommended, as the level of the consciousness is an indicator for the success of ETV, and postoperative CT scan is performed to also control the ventricle size. There are many positive experiences concerning ETV procedures without routine ICP monitoring [12, 37].

only a small percentage of patients with the above-mentioned pathology are optimal candidates for ETV and its indication is rare [7, 39]. The gold standard for treatment of hemorrhagerelated acute hydrocephalus remains EVD placement. Acute hydrocephalus can arise either by intraventricular hemorrhage or by intraparenchymal hematoma with space-occupying effect compressing the CSF pathway. There are advantages and disadvantages of preforming an ETV. The endoscopic procedure might reduce the risk of the drainage-related infections and reduce the numbers of surgical procedures, as the drainage has to be changed after 7–10 days. In most cases, it is required to remove the blood clot. With endoscopic procedure, the possibility is provided; however, this procedure can be time-consuming. In case of intraventricular bleeding, the endoscopic view is unclear. The visualization can be normalized through forced irrigation, but in case of a severe hemorrhage, the visual quality remains poor despite prolonged irrigation. The space-occupying intraparenchymal hemorrhage can displace the ventricles depending on the localization. Furthermore, the anatomy of the prepontine space and basilar artery might be distorted increasing the risk of basilar injury. In the acute phase, the floor of the third ventricle is thick in contrast to the subacute and chronic obstruction. This fact likewise causes a higher risk for basilar injury. These findings lead to

**Figure 6.** Obstructive hydrocephalus in case of cerebellar infarct (left above and below) preoperative CT scan—dilatation of temporal horn and frontal horn of lateral ventricle and third ventricle (right above and below) postoperative CT scan,

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technical challenges in the endoscopic procedure [39].

reduced size of ventricle system.

#### **2.5. Hemorrhage-related obstructive hydrocephalus**

An obstruction of CSF pathway can occur in case of intraventricular or intraparenchymal bleeding with or without intraventricular extension, cerebellar hematoma, or subarachnoid hemorrhage [39, 40]. In case of intraventricular or intraparenchymal bleeding related to obstructive hydrocephalus, ETV can be an alternative to EVD placement (**Figure 7**). However, Presentation of the Success Rate of ETV in Distinct Indication Cases of Hydrocephalus http://dx.doi.org/10.5772/intechopen.72889 133

fourth ventricle or the foramina of Magendie and Luschka leads to circulation disturbances and hydrocephalus [13]. ETV is recommended primarily for the treatment of children with midline posterior fossa tumor–related obstructions [30]. ETV can be combined with tumor biopsy, thus providing useful information for the diagnosis. In certain cases, even the tumor resection (e.g., third ventricle) might be performed [13, 30]. The resection alone can set the CSF pathway free, providing a normal CSF circulation. Therefore, performing ventriculostomy routinely is not recommended. After tumor removal, not only the causal problem of hydrocephalus might be solved. With performing the ETV an intraperitoneal spreading of the chemotherapeutic drugs through the shunt can be avoided [32]. The time of ETV in relation to

Beside posterior fossa tumors, the indication expands to pineal tumors and third ventricle tumors [33]. The pathology of these is various. The pathology includes, but is not limited to glial tumors, ependymoma, pinealoblastoma, pinealocytoma, meningioma, germ cell tumors, primitive neuroectodermal tumor, teratoma, epidermoid, metastasis, and cysts [34, 35]. Colloid cysts, arachnoid cysts with extension in the ventricles or midline, and quadrigeminal cysts can be treated with endoscopic cystectomy, cystocisternostomy, cystoventriculostomy, ventriculocystostomy, and ventriculocystocysternostomy [36]. Even a combination with ven-

Cerebellar infarction with space-occupying effect might lead to obstruction of the CSF pathway (**Figure 6**). The occurrence of stroke-related occlusive hydrocephalus is 10.9–27.2% of cerebellar stroke patients [37]. Deterioration of consciousness in case of cerebellar infarction can be caused by compression of the brainstem through increasing parenchymal edema or by hydrocephalus. A neurosurgical intervention is required in case of decline of consciousness [7, 37, 38]. For treatment of hydrocephalus, the alternative options are external ventricle drainage (EVD), shunt placement, and ETV. However, not every hydrocephalus caused by cerebellar infarction is a suitable candidate for ETV. In case of patients with severe deterioration of consciousness and/or brain stem compression, an adequate decompression should be performed [37]. In case of hydrocephalus, the high risk for infection in case of long-term ventricle drainage can be avoided with third ventriculostomy. The compression of prepontine cistern usually does not cause any surgical problems; the technique can be performed in the usual way [37]. Regarding the routine intracerebral pressure (ICP) monitoring in case of ETV patients, it is not recommended, as the level of the consciousness is an indicator for the success of ETV, and postoperative CT scan is performed to also control the ventricle size. There are many positive

experiences concerning ETV procedures without routine ICP monitoring [12, 37].

An obstruction of CSF pathway can occur in case of intraventricular or intraparenchymal bleeding with or without intraventricular extension, cerebellar hematoma, or subarachnoid hemorrhage [39, 40]. In case of intraventricular or intraparenchymal bleeding related to obstructive hydrocephalus, ETV can be an alternative to EVD placement (**Figure 7**). However,

**2.5. Hemorrhage-related obstructive hydrocephalus**

the tumor resection is still under discussion [13].

triculostomy may be performed [13].

**2.4. Cerebellar infarction**

132 Hydrocephalus: Water on the Brain

**Figure 6.** Obstructive hydrocephalus in case of cerebellar infarct (left above and below) preoperative CT scan—dilatation of temporal horn and frontal horn of lateral ventricle and third ventricle (right above and below) postoperative CT scan, reduced size of ventricle system.

only a small percentage of patients with the above-mentioned pathology are optimal candidates for ETV and its indication is rare [7, 39]. The gold standard for treatment of hemorrhagerelated acute hydrocephalus remains EVD placement. Acute hydrocephalus can arise either by intraventricular hemorrhage or by intraparenchymal hematoma with space-occupying effect compressing the CSF pathway. There are advantages and disadvantages of preforming an ETV. The endoscopic procedure might reduce the risk of the drainage-related infections and reduce the numbers of surgical procedures, as the drainage has to be changed after 7–10 days. In most cases, it is required to remove the blood clot. With endoscopic procedure, the possibility is provided; however, this procedure can be time-consuming. In case of intraventricular bleeding, the endoscopic view is unclear. The visualization can be normalized through forced irrigation, but in case of a severe hemorrhage, the visual quality remains poor despite prolonged irrigation. The space-occupying intraparenchymal hemorrhage can displace the ventricles depending on the localization. Furthermore, the anatomy of the prepontine space and basilar artery might be distorted increasing the risk of basilar injury. In the acute phase, the floor of the third ventricle is thick in contrast to the subacute and chronic obstruction. This fact likewise causes a higher risk for basilar injury. These findings lead to technical challenges in the endoscopic procedure [39].

are Gram-negative bacteria during the first 14 days of age and Gram-positive bacteria after the first 2 weeks of age. Further pathogens may be Candida species at this age of life. In postnatal period, hydrocephalus may be caused by bacterial (such as Haemophilus influenzae type B), viral, or fungal (such as Cryptococcus) infections [41]. In adults, the infection can be bacterial (*Streptococcus pneumoniae*, *Neisseria meningitidis*, *Haemophilus influenzae*, *Listeria monocytogenes*, and group B Streptococcus), viral (most frequently Enteroviruses), or fungal (Cryptococcus

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The tuberculous meningitis–related hydrocephalus is discussed separately, because of peculiar pathological behavior. It is still a frequent disease in the developing countries [43]. As hematogenous dissemination from primary complex, tuberculous foci might be deposited in the cortex, meninges, choroidal plexus, or ventricular wall, and through rupture into the subarachnoid space, it leads to meningitis [44]. In acute phase, there is an acute inflammation in ventricles with ependymal infection and tuberculous exudate. Although the exudate can be washed out during ETV, ventriculostomy is more difficult due to acute inflammation and anatomical changes [14, 45]. In the chronic phase, the aqueduct can be obstructed by exudates, small tuberculomas, or infection of ependyma. In this phase, the procedure has a higher success compared to the acute phase; however, the floor of the third ventricle is thickened, which

Central nervous system (CNS) anomalies might lead to congenital hydrocephalus. The most common cause is the congenital aqueduct stenosis as mentioned above. It can be caused by infection, hemorrhage before birth, or tumors [16]. In this case, endoscopic ventriculostomy is the treatment of choice. Ventriculostomy might be also a surgical alternative in case of Chiari I and II malformation with fourth ventricle outlet obstruction, myelomeningocele, syringomyelia, and Dandy-Walker malformation–associated hydrocephalus [13, 19, 26, 46, 47]. The

Hydrocephalus develops in considerable number in cases with neural tube defect [47, 48]. The incidence of hydrocephalus in patients with meningomyelocele increases after closure the defect [48]. Performing the endoscopic procedure may be technically difficult, due to the anatomical variations (enlarged interthalamic adhesion, stenosis, or atresia of foramen of Monro and so on) [47]. Chiari malformation can be concurred either with communicating or with noncommunicating hydrocephalus. Although ETV may be a good alternative for shunt placement in these cases, the success depends highly on the optimal selection of cases for endoscopic procedure [25]. In case of obstructive hydrocephalus, there is a better chance for success. The majority of Dandy-Walker syndrome (DWS) is associated with hydrocephalus [26]. In this case, the primary treatment continues to be controversial. In general, the initial treatment remains the shunt placement. Endoscopic excision of obstructing membrane as initial procedure is not recommended because of the associated risks for morbidity and mortality. ETV may be an alternative for shunt placement in patients with frequent shunt malfunction. In DWS concurred with aqueduct stenosis, the combination of ventricle-cyst stenting and ETV

species) [42].

could complicate the surgery [40].

success of ETV in these cases is diverse.

may be performed [26].

**2.7. Congenital malformation–related hydrocephalus**

**Figure 7.** Intraventricular hemorrhage of forth ventricle with occlusive hydrocephalus. Obscured view due to the bleeding (above) and preoperative CT scan (left below) landmarks of third ventricle—infundibular recess, mammillary bodies (right below), balloon dilatation.

The clinical results are primarily influenced by the parenchymal damage. It is recommended to perform an ETV if the requirement of continuous ICP monitoring and liquor drainage for ICP reduction is excluded. In certain cases, where the CSF obstruction plays the dominant role and the hemorrhage does not have significant space-occupying effect, ETV might be the optimal option [39]. In these cases, the clinical condition can be dramatically improved. In all other cases, ETV should be considered if weaning the patients off the drainage is not successful within a week. As mentioned above, the standard treatment remains EVD placement. Thus, in case of doubt, EVD placement should be performed, even leading to an interruption of ventriculostomy [39].

#### **2.6. Infection-related hydrocephalus**

Despite the indication in postinfectious hydrocephalus (meningitis, ventriculitis, and shunt infection) with impaired CSF absorption, or ductal, foraminal obstruction is controversial, ETV might be also successful in certain cases. As consequence of the infection, cisternal scarring might occur, leading to higher failure rate [40]. Regarding the etiology in children, the occurring pathogen depends on the age. Hydrocephalus following prenatal infections may be caused by Toxoplasmosis or Cytomegalovirus. In neonatal period, the most frequently occurring bacteria are Gram-negative bacteria during the first 14 days of age and Gram-positive bacteria after the first 2 weeks of age. Further pathogens may be Candida species at this age of life. In postnatal period, hydrocephalus may be caused by bacterial (such as Haemophilus influenzae type B), viral, or fungal (such as Cryptococcus) infections [41]. In adults, the infection can be bacterial (*Streptococcus pneumoniae*, *Neisseria meningitidis*, *Haemophilus influenzae*, *Listeria monocytogenes*, and group B Streptococcus), viral (most frequently Enteroviruses), or fungal (Cryptococcus species) [42].

The tuberculous meningitis–related hydrocephalus is discussed separately, because of peculiar pathological behavior. It is still a frequent disease in the developing countries [43]. As hematogenous dissemination from primary complex, tuberculous foci might be deposited in the cortex, meninges, choroidal plexus, or ventricular wall, and through rupture into the subarachnoid space, it leads to meningitis [44]. In acute phase, there is an acute inflammation in ventricles with ependymal infection and tuberculous exudate. Although the exudate can be washed out during ETV, ventriculostomy is more difficult due to acute inflammation and anatomical changes [14, 45]. In the chronic phase, the aqueduct can be obstructed by exudates, small tuberculomas, or infection of ependyma. In this phase, the procedure has a higher success compared to the acute phase; however, the floor of the third ventricle is thickened, which could complicate the surgery [40].

#### **2.7. Congenital malformation–related hydrocephalus**

The clinical results are primarily influenced by the parenchymal damage. It is recommended to perform an ETV if the requirement of continuous ICP monitoring and liquor drainage for ICP reduction is excluded. In certain cases, where the CSF obstruction plays the dominant role and the hemorrhage does not have significant space-occupying effect, ETV might be the optimal option [39]. In these cases, the clinical condition can be dramatically improved. In all other cases, ETV should be considered if weaning the patients off the drainage is not successful within a week. As mentioned above, the standard treatment remains EVD placement. Thus, in case of doubt, EVD placement should be performed, even leading to an interruption

**Figure 7.** Intraventricular hemorrhage of forth ventricle with occlusive hydrocephalus. Obscured view due to the bleeding (above) and preoperative CT scan (left below) landmarks of third ventricle—infundibular recess, mammillary

Despite the indication in postinfectious hydrocephalus (meningitis, ventriculitis, and shunt infection) with impaired CSF absorption, or ductal, foraminal obstruction is controversial, ETV might be also successful in certain cases. As consequence of the infection, cisternal scarring might occur, leading to higher failure rate [40]. Regarding the etiology in children, the occurring pathogen depends on the age. Hydrocephalus following prenatal infections may be caused by Toxoplasmosis or Cytomegalovirus. In neonatal period, the most frequently occurring bacteria

of ventriculostomy [39].

bodies (right below), balloon dilatation.

134 Hydrocephalus: Water on the Brain

**2.6. Infection-related hydrocephalus**

Central nervous system (CNS) anomalies might lead to congenital hydrocephalus. The most common cause is the congenital aqueduct stenosis as mentioned above. It can be caused by infection, hemorrhage before birth, or tumors [16]. In this case, endoscopic ventriculostomy is the treatment of choice. Ventriculostomy might be also a surgical alternative in case of Chiari I and II malformation with fourth ventricle outlet obstruction, myelomeningocele, syringomyelia, and Dandy-Walker malformation–associated hydrocephalus [13, 19, 26, 46, 47]. The success of ETV in these cases is diverse.

Hydrocephalus develops in considerable number in cases with neural tube defect [47, 48]. The incidence of hydrocephalus in patients with meningomyelocele increases after closure the defect [48]. Performing the endoscopic procedure may be technically difficult, due to the anatomical variations (enlarged interthalamic adhesion, stenosis, or atresia of foramen of Monro and so on) [47]. Chiari malformation can be concurred either with communicating or with noncommunicating hydrocephalus. Although ETV may be a good alternative for shunt placement in these cases, the success depends highly on the optimal selection of cases for endoscopic procedure [25]. In case of obstructive hydrocephalus, there is a better chance for success. The majority of Dandy-Walker syndrome (DWS) is associated with hydrocephalus [26]. In this case, the primary treatment continues to be controversial. In general, the initial treatment remains the shunt placement. Endoscopic excision of obstructing membrane as initial procedure is not recommended because of the associated risks for morbidity and mortality. ETV may be an alternative for shunt placement in patients with frequent shunt malfunction. In DWS concurred with aqueduct stenosis, the combination of ventricle-cyst stenting and ETV may be performed [26].

#### **2.8. Obstruction due to giant aneurysm**

An obstructive hydrocephalus through giant aneurysm is rare, but it has been already reported in some cases [49–52]. Commonly, these cases are treated via shunt placement, although an aneurysm growing after shunt implantation has been already reported. The theory is that the decreased intracranial pressure after shunt placement reduces the tamponade effect, leading to aneurysm expansion and an increase in the risk for rupture [51].

**3. Surgical technique**

**3.1. Neuroendoscopic equipment**

Fogarty balloon catheter) [7].

**3.2. Surgical technique**

For endoscopic ventricular surgery, either rigid or flexible endoscope can be used. Rigid endoscopes have a higher image quality and allow an easier insertion and handling of instruments. In contrast, the flexible one allows a flexible mobility of the scope, even though producing a lower image quality [53]. Endoscopic equipment for ETV includes various rigid rod lens Hopkins optics and instruments (scissors, hooks, puncture needles, forceps for tumor biopsy and grasping, bright cold Xenon light source, HD video camera system, irrigation device, and

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The operation is performed under general anesthesia. The patient is placed in supine position, the head in 3-pin fixation and tilted slightly forward. The hair is shaved and the approach is marked. The standard placement of the burr hole is anterior to the coronal suture and 2 cm lateral to the midline. After skin disinfection and sterile draping of the operating field, the scalp is incised in a straight line, about 2–3 cm long. After placement of the burr hole (about 1 cm) and opening the dura, the operating sheath is introduced into the lateral ventricle and the trocar is inserted at about 5 cm depth of dura. The endoscope is fixed and the trocar is removed. The rigid 0° diagnostic optic is inserted for inspection and identification of the main landmarks. In the lateral ventricle, the fornix, the foramen of Monro, and the choroid plexus are identified (**Figures 9** and **10**). Under direct visual control, the endoscope is advanced through the foramen of Monro into the third ventricle. In the third ventricle, the main landmarks are the mammillary bodies and the infundibular recess. The diagnostic inspection is extended with

**Figure 9.** Steps of endoscopic third ventriculostomy. (A) View of foramen of Monro, plexus choroideus, anterior septal vein in lateral ventricle, (B) view of mammillary bodies, infundibular recess in the third ventricle, (C) ventriculostomy with bipolar diathermy, (D) ventriculostoma, (E) enlarging with perforation forceps, (F) dilatation with Fogarty balloon

catheter, (G) expanded ventriculostoma, and (H) view of basilar artery.

In certain cases, an endoscopic ventriculostomy might be performed [49, 50]. Even though the anatomy is commonly changed as a consequence of the aneurysm (e.g., the third ventricle or aqueduct may be compressed and the anatomical structures as the floor of ventricle and mammillary bodies may be displaced), the landmarks can be identified and the surgery can be performed in the usual way [49].

#### **2.9. Further indications for ETV**

Every surgical revision after shunt implantation is considered as shunt failure. Many studies established that endoscopic third ventriculostomy in shunt failures might be an effective treatment option (**Figure 8**). The presence of shunt failure does not exercise influence on the failure rate of ETV. However, the success seems to be diverse in certain etiology groups [14].

It was observed that hydrocephalus patients less than 65 years of age with idiopathic normal pressure, where the dominant symptom was gait disturbances and only minimal cognitive deficits could be observed, had a good success rate [14].

**Figure 8.** Hydrocephalus with shunt malfunction (a and b) preoperative MRI scan, (c) scarred thick floor of the third ventricle, (d) perforation of adhesions in the prepontine cistern with forceps, (e) with bipolar diathermy, and (f) view on the cisterns through the ventriculostoma.
