Endoscopic Third Ventriculostomy Success Score – a calculated score based on the patient’s age, etiology of the hydrocephalus and whether or not the patient’s hydrocephalus has been previously treated with a shunt. Age of less than 1 month, hydrocephalus due to an infection and a history of previous shunting predict the least likelihood of success (0%) while an age of greater than 10 years, hydrocephalus sue to an obstruction at the level of the aqueduct of Sylvius and no previous shunting predicts the highest likelihood of success (90%).