**4. Indications**

Obstructive hydrocephalus.


#### **4.1 Communicating hydrocephalus**

Even though this indication may be controversial, various studies have published its usefulness in normal pressure hydrocephalus. Sufficient evidence is lacking to establish a grade of recommendation [12, 17–19].

### **5. ETVSS**

Kulkarni et al. created a scale considering the etiology of the hydrocephalus, the patient's age, and the presence of a previous shunt to calculate the success of the ETV with which the ETVSS was created [20].

This scale predicts the 6-month success rate of ETV for children with hydrocephalus, based on some characteristics Scores range from 0 (extremely poor chance of ETV success) to 90 (extremely high chance of ETV success), and it is calculated as the sum of the age score (max 50), etiology score (max 30), and previous shunt score (max 10).

The high-ETVSS group [21] is associated with a lower risk of failure right from the early postoperative phase. The moderate-ETVSS group [22–42] has a higher initial failure rate, but, after about 3 months, the risk of ETV failure becomes slightly lower than shunt failure. Finally, in the low-ETVSS group [43], the early risk of ETV failure is much higher than the risk of shunt failure, but the risk becomes lower than the risk of shunt failure at about 6 months following the procedure [20, 44, 45].

### **6. Preoperative imaging**


7.Cine phase-contrast magnetic resonance imaging (CISS o FIESTA) can be utilized as a method of distinguishing between communicating and noncommunicating hydrocephalus and any abnormality in basal cisterns [46, 47].
