This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous System, Subject name: Pediatrics
Commonest cause of obstructive hydrocephalus in children: 
Select and explain. 
A. Acqueductal stenosis, B. Aqueductal gliosis, C. Subarachnoid hemorrhage, D. Tubercular meningitis
A: Acqueductal stenosis
Answer: A: Acqueductal stenosis 
Explanation: (Aqueductal stenosis) (1990-Nelson 17th) (548-Ghai7th)(A) Obstructive or Non communicating hydrocephalus - develops most common in children because of an abnormality of the aqueduct or lesion in the fourth ventricles. Aqueductal stenosis results from an abnormality narrow aqueduct of sylvius that is often associated with branching or forking.(B) Non-obstructive or communicating hydrocephalus most commonly follows as subarachnoid hemorrhage which is usually a result of intraventricular hemorrhage in a premature infants.