<prompt> Answer this question truthfullyWhat is a congenital stenosis that can occur in the channel responsible for draining CSF from the 3rd ventricle to the 4th ventricle?  <response>: <reason> Cerebral aqueduct stenosis is a congenital stenosis that can occur in the channel responsible for draining CSF from the 3rd ventricle to the 4th ventricle. 