Abstract
We describe a case of giant middle cerebral artery aneurysm associated with cyst formation in a 51-year-old woman. She presented with a 2-month history of numbness in her right extremities. Magnetic resonance imaging revealed a large cystic lesion with the oval mixed intensity core in the left parietal lobe, which proved to be a giant aneurysm originating from the anterior parietal artery by left carotid angiogram. She underwent frontotemporal craniotomy with aneurysm resection through the cyst cavity and made a good recovery. Histologically, the aneurysm was almost totally thrombosed and the aneurysmal wall was highly vascularized with capillary channels. The cyst wall consisted of the superficial fibrous layer with hemosiderin deposits and the deep gliotic layer. Cyst fluid was yellowish and slightly turbid and seemed to be exudative. These findings suggest that initial minor bleeding and subsequent serum exudation from the capillary channels in the aneurysmal wall play important roles in pathogenetic mechanism of the cyst.
