Parinaud's syndrome in hydrocephalus due to a basilar artery aneurysm.

A 65-year-old woman appeared with a progressive dementia, gait disturbance, and Parinaud's syndrome. A computed tomography scan, an angiogram of the vertebral artery, and metrizamide ventriculography demonstrated a marked hydrocephalus. A giant aneurysm at the termination of the basilar artery projected into the third ventricle producing partial obstruction of the aqueduct. The symptoms were resolved by a ventriculoperitoneal shunt; but after a month, the patient again showed the upward-gaze palsies concomitant with occurrence of shunt malfunction. The possible mechanisms of Parinaud's syndrome observed in the patient are discussed.