Giant true posterior communicating artery aneurysm.

The case of a giant posterior communicating artery (PCoA) aneurysm is reported in which the clinical presentation was Korsakoff's syndrome. Left carotid angiography revealed a partially thrombosed giant PCoA aneurysm. Three-dimensional computed tomography angiography showed the precise neck of aneurysm and surrounding structures from a multidirectional view. Hypoperfusion of the bilateral frontal, temporal, and medial inferior thalamus was seen on single-photon emission computed tomography. According to previous reports, giant true PCoA aneurysms are rare; in fact, there has been only one report of a giant true PCoA aneurysm. We discuss the radiological characteristics and the clinical presentation of giant true PCoA aneurysms.