Obstructive hydrocephalus secondary to a perianeurysmal cyst: a case report.

Perianeurysmal cysts are an extremely rare association with cerebral aneurysms. We report the case of a 64 year old male who presented with obstructive hydrocephalus due to a perianeurysmal cyst. The cyst originated in association with a thrombosed, right-sided, terminal internal carotid artery aneurysm. Definitive management was offered with craniotomy and surgical clipping of the aneurysm together with endoscopic cyst fenestration. The patient made a full recovery and was asymptomatic at 3-month follow-up. We review the literature and discuss the potential mechanisms of cyst formation.