Obstructive hydrocephalus secondary to an ectatic basilar artery.

A 57 year-old white hypertensive male presented with a five-month history of progressive dementia and a clinical picture suggestive of normal pressure hydrocephalus. A CT scan and vertebral angiogram demonstrated an ectatic basilar artery obstructing the posterior third ventricle; the resulting hydrocephalus was relieved by a ventriculo-peritoneal shunt and the patient's symptoms resolved completely.