<prompt> Commonest cause of obstructive hydrocephalus in children:Acqueductal stenosisAqueductal gliosisSubarachnoid hemorrhageTubercular meningitis  <response>: Aqueductal stenosis 1990-Nelson 17th 548-Ghai7thA 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. 