Giant aneurysm of the pericallosal artery causing acute subdural hematoma--case report.

A 66-year-old female presented with a very rare giant aneurysm of the distal pericallosal artery. She lost consciousness and was admitted. Computed tomography demonstrated a subdural hematoma over the left cerebral convexity and a mass in the frontal lobe. Cerebral angiography disclosed a giant aneurysm located on the distal segment of the right pericallosal artery. The subdural hematoma was removed and the aneurysmal neck was clipped, but she died 15 days after the operation. Autopsy found the giant aneurysm (33 x 30 x 27 mm) on the distal segment of the right pericallosal artery. Highly atheromatous changes were recognized in part of the aneurysmal wall, the arteries near the circle of Willis, and the distal anterior cerebral artery (ACA) adjacent to the aneurysm. There were no anomalous vessels such as azygos ACA. Giant aneurysms situated beyond the genu of the corpus callosum are extremely rare. Atherosclerosis was probably a major etiological factor in this case.