Giant posterior communicating artery aneurysm presenting as third ventricle mass with obstructive hydrocephalus. Case report.

The case of a giant posterior communicating artery (PCoA) aneurysm is reported in which the initial presentation was coma secondary to obstructive hydrocephalus. The primary radiological diagnosis was a probable craniopharyngioma. A cerebral angiogram revealed a partially thrombosed giant PCoA aneurysm on the right side. The patient underwent pterional craniotomy with aneurysm clipping and thrombectomy to relieve mass effect, and has made a good recovery. Review of the literature documents that giant PCoA aneurysms are rare. This is believed to be the first reported case of a PCoA aneurysm presenting as a third ventricle mass with obstructive hydrocephalus. The magnetic resonance imaging characteristics of those third ventricle masses that mandate vascular workup are discussed.