**5. Outcome**

However, in exclusion to adult-type obstructive hydrocephalus, there is still a lack of strong

**Figure 2.** CT of the brain of a previously shunted 12-year-old male with aqueductal stenosis that had signs of increased tension and VP shunt failure; the CT shows enlarged ventricles (A) where ETV was performed without removing the shunt. Follow-up CT of the brain 3 months afterward showed decline in the ventricular size (B) which was accompanied

Under general anesthesia, the patient is restrained, disinfected, and draped as for a frontal burr hole; after opening the dura, a small corticectomy is performed, and a blunt obturator cannula is inserted, with free hands, directed medially toward the ipsilateral medial epicanthus and posteriorly toward the tragus of the ear. After insuring being in the ventricles by the outflow of CSF, the optical visualization system is inserted; we use the Lotta endoscope (Karl

The first structure identified is the foramen of Monro, with the choroid plexus attached to the posterior margin (**Figure 1A**). The endoscope is introduced through the foramen to the third ventricle, and the floor is identified (**Figure 1B**). A small puncture is done using the decq forceps as posterior as possible to the infundibular recess and avoiding the mammillary bodies and the small arterioles running in this area. The endoscope is then advanced near to the puncture to visualize Liliequist's membrane which must be opened, after which, the CSF flow

It is important to clearly visualize the fornix before introducing the endoscope to the third ventricle. Opening the floor of the third ventricle with ballooning the fenestra aiming for its

should be clearly visualized through the opening (**Figure 1C,D**).

evidence that supports the procedure.

**4. Surgical technique**

by clinical improvement of the patient.

98 Hydrocephalus: Water on the Brain

Storz, Tuttlingen, Germany) [7].

### **5.1. Clinical evaluation and radiological evaluation**

The ETV Success Score (ETVSS) has been developed and validated to predict ETV success based on certain variables [34, 35]. It depends on predicting the success according to the age of the patient, cause of hydrocephalus, and presence of the previous shunt operation. The success rate can be predicted according to these variables. However, intraoperative factors "like the presence of excessive adhesions, mobility of the stoma, excessive bleeding, and opening of Liliequist's membrane" (**Figure 3**) should be taken into consideration in predicting the success of ETV [36]. In addition, the VP shunt independence is considered a generalized but competent method to measure the success of ETV after VP shunt failure [37, 38].

The change of the ventricular size with a deterioration of the clinical condition has been well known as one of the signs that identify hydrocephalus. In addition, the decrease of the ventricular size after management which accompanied improvement of the general condition has its additional value of success confirmation (**Figure 2**). However, the change of the ventricular size is not well supported as an accurate measurement of the effective treatment of hydrocephalus, especially when it is irrelevant to the clinical condition of the patient [39].

Specific intraoperative factors are considered significant in addition to the associated morbidity. This would include the duration of surgery, type(s) of endoscope used, and degree of intraoperative bleeding [33, 36].

**Figure 3.** Another patient during ETV where thick arachnoid membranes (arrow) surrounding the basilar artery (b) denoting possibility of ETV failure.
