**4. Indications**

**3.4. Fenestration techniques**

116 Hydrocephalus: Water on the Brain

Balloon dilatation technique is the most widespread technique used for ventriculostomy [10, 20, 21]. In this technique, surgeon opens the floor using a blunt dissector or a blunt monopolar coagulator tip through the working channel of the endoscope. Then, the dissector is drawn, and a Fogarty three-French balloon catheter (might be two-French depending on the working channel diameter of the endoscope) or a specialized NeuroBalloon catheter with two balloon compartments is passed through the initial fenestration. The balloon is slowly inflated inside the fenestration to enlarge the opening (**Figure 5**). Next, the balloon is deflated and pulled back. There are many advantages with this technique: the procedure can be repeated many times safely, the floor of the ventricle and even the prepontine cistern are

**Figure 5.** Endoscopic third ventriculostomy using balloon dilatation. The floor of the third ventricle is perforated with a blunt cautery tip (A), and the NeuroBalloon is passed through the hole and inflated (B). The structures in the prepontine

cistern are visible through the fully inflated balloon (C, D).

The most common indication for ETV is obstructive hydrocephalus caused by primary aqueductal stenosis. Various authors published many series demonstrating the effectiveness of ETV in aqueductal stenosis patients. The success rate in aqueductal stenosis is reported up to 90%. Thus, ETV is established almost universally as treatment of choice for aqueductal stenosis [6, 23, 24].

Many other obstructive pathologies can be treated with ETV.Although shunting is a treatment option, hydrocephalus caused by lateral ventricle entrapment can be adequately treated with endoscopic septal fenestration combined with ETV [25]. In case of the isolated fourth ventricle, aqueductoplasty with endoscopic approach presents a safe and effective method [26]. This approach seems to be less invasive than microsurgical fenestration and more reliable than the fourth ventricle shunts. Endoscopic third ventriculostomy proved to be effective in the fourth ventricle outlet obstruction without Chiari malformation or visible obstructive mass [27]. These idiopathic stenosis cases are treated successfully with ETV even resolving accompanying pathologies like syringomyelia. Dandy-Walker malformation can also be treated with ETV and a stent between the third ventricle and posterior fossa when accompanied by aqueductal stenosis [28–30]. In complex obstructive syndromes, neuroendoscopy and ETV are frequently used by neurosurgeons.

In case of acute intraventricular hemorrhages, ETV can be used as a replacement for external ventricular drainage. In supratentorial intraventricular hemorrhages, ETV is shown to be useful for relieving acute hydrocephalus in addition to clot aspiration [31]. Although the use of the ETV for supratentorial hemorrhages is controversial, in posterior fossa hemorrhages, ETV is proven to be very effective for the treatment of acute hydrocephalus [32]. In case of obstruction caused by the fourth ventricular or cerebellar hematomas, ETV seems to be an effective and a safe alternative to external ventricular drainage.

Neuroendoscopy offers the possibility to combine ETV and tumor biopsy in selected intraventricular and paraventricular tumors [33–36]. Developing technologies like endoscopic ultrasonic aspirator makes total removal of the tumors possible. Endoscopic third ventriculostomy is even possible for tumors located in the third ventricle floor without any morbidity [37]. Although ETV is an effective treatment for relief of hydrocephalus in intraventricular tumors, neuroendoscopic approach presents a difficulty when the anatomical landmarks are distorted by the growth of the tumor.

Tectal and pineal tumors presenting with acute hydrocephalus also present an indication for tumor biopsy and ETV [38]. The management of these tumors depending on histology is combined open surgery and radiotherapy or chemotherapy. In the presence of obstructive hydrocephalus, neuroendoscopy presents an opportunity for the long term relieving the hydrocephalus and adequate tumor biopsy for determining the management. Long-term control of hydrocephalus is possible with ETV in tectal plate tumors [39].

In posterior fossa tumors, preoperative hydrocephalus can be managed with external ventricular drainage as well as ETV [40–42]. Postoperative hydrocephalus in posterior fossa tumors presents a major problem in these patients. In posterior fossa tumors, about 36% of patients need a CSF diversion surgery postoperatively [43]. The outcomes of ETV in postoperative hydrocephalus are about as good as shunting; however, failure happens earlier than VP shunts [44]. It is proven that ETV performed prior to surgery reduces significantly the incidence of postoperative hydrocephalus although it does not prevent hydrocephalus in all cases. It does however prevent acute postoperative hydrocephalus due to cerebellar swelling and presents a cleaner and more physiologic method compared to external ventricular drainage [41]. The effectiveness of ETV is also demonstrated in brain stem gliomas causing hydrocephalus [45].

The treatment of choice for suprasellar arachnoid cysts is endoscopic fenestration of the cyst into ventricular system combined with ETV (cystoventriculocisternostomy). Several series demonstrated cyst and hydrocephalus regression with this technique [46, 47]. Cystostomy and ETV might also be indicated in some pineal cysts and quadrigeminal cysts presented with hydrocephalus [48, 49].

tumors [23, 52]. However, communicating hydrocephalus cases have a rate of success about 50%. In patients who undergone shunt operations, ETV is still effective eliminating shunt dependency [59, 60]. Infants have worse outcomes in case of ETV according to literature. Failure rates vary between 20 and 50% [61]. Many authors recommend performing ETV in patients 2 years and older with their low success rates in infants [62, 63]. However, some authors indicate that ETV is still worth trying in these patients since the success rate is still

**Figure 6.** Flow void in T2-weighted sagittal MRI is clearly visible in the floor of the third ventricle after an ETV (black

Endoscopic Third Ventriculostomy

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http://dx.doi.org/10.5772/intechopen.75394

Radiographic features might be misleading as ventricular volume after EVD may not show an obvious change in the early preoperative period [66]. Early postoperative improvement and ventricular volume reduction are predictive values for the success of ETV as well as demonstrating flow void in the base of the third ventricle [67]. The patency of the ETV can be shown with flow void in T2-weighted images (**Figure 6**) and also with CSF flow cine MRI. Minor flow in the base of the third ventricle appears to be a bad prognostic factor for the patency of stoma

Failure of ETV is in general due to the closure of fenestration in the third ventricle floor. The causes of the fenestration failure include the insufficient size of initial fenestration, reduced CSF reabsorption, arachnoid membranes in the prepontine cistern, hemorrhage obstructing fenestration, and late gliosis and postoperative infection. Failure rates can be as high as 50% in

The overall complication rate of ETV series is found to be 8.5% by Bouras and Sgouros [69]. The complication rates varied between 0 and 31.2%. Overall permanent morbidity rate was

noncommunicating hydrocephalus series even with patent ventriculostomies [58].

considerable and a successful ETV provides long-term shunt independence [64, 65].

[68].

arrow).

**6. Complications**

Contrary to obstructive hydrocephalus, indications of communicating hydrocephalus are controversial [50]. There are successful series of ETV on normal pressure hydrocephalus in literature with improvement rate after ETV up to 69% [51]. However, the etiology of this success is not yet well defined. Some authors argue that the third ventriculostomy relieves periventricular tissue stress improving the perfusion [52].

In patients with Chiari malformation type I with concomitant hydrocephalus, ETV is proven to be beneficial [53]. In these patients relief of symptoms, ascent of the tonsils, regression of hydrocephalus, and syringomyelia are seen after ETV [54, 55]. The established treatment for these patients is suboccipital craniectomy and duraplasty combined with CSF diversion surgery. In these selected cases, ETV proves to be successful meaning that the cure might be achieved in a less invasive and less complicated manner. As for Chiari malformation type II, the overall success for patients with concomitant meningomyelocele and hydrocephalus is up to 72% [56]. In these patients, ETV presents a safe and an effective way to deal with hydrocephalus and long-term shunt independence [57].
