Communicating fourth ventricular hydrocephalus: case report.

The case of an infant with hydrocephalic enlargement of the 4th ventricle and dilatation of the basal cisterns is presented. Although the lateral ventricular shunt was proved to be functioning, the patient developed supratentorial hypertension marked by a tense fontanelle. Placement of a 4th ventricle-peritoneum shunt was followed by shrinkage of the 4th ventricle and resolution of the supratentorial hypertension. Work-up, including computed tomographic ventriculography and cisternography, demonstrated occlusion of the aqueduct of Sylvius and of subarachnoid spaces. This unique pathological process, differentiated from an isolated 4th ventricle, could be referred to as communicating 4th ventricular hydrocephalus.