Peduncular hallucinosis associated with ruptured basilar-superior cerebellar artery aneurysm--case report.

A 65-year-old female developed peduncular hallucinosis 3 days after rupture of a basilar-superior cerebellar artery aneurysm. There were no neurological deficits except slight anisocoria when she first complained of hallucinations. Vasospasm of the perforating arteries to the upper brainstem, rather than direct brainstem damage caused by the bleeding, was probably the cause. Peduncular hallucinosis is possibly the only localizing sign of ruptured upper posterior circulation aneurysm.