中大脳動脈本幹（M1）動脈瘤の特徴と外科的治療の注意点

Cerebral aneurysms of the proximal middle cerebral artery (M1) are a relatively rare condition. We report 14 cases of such aneurysms that were treated by direct surgery. There were 9 men and 5 women. Ages ranged from 5 to 70 years old (average of 50). Ten aneurysms were unruptured and 4 were ruptured. The size of the aneurysms ranged from 2 mm to 13 mm (average of 6 mm). Ten aneurysms arose from the superior wall, 3 from the inferior wall and 1 from the posterior wall of the M1 segment. The aneurysms were exposed through the pterional craniotomy and transsylvian approach. Neck clipping was accomplished successfully in 13 cases using straight or bayonet-shaped clips. A dissecting aneurysm arising from the posterior wall was clipped with a right-angle ring clip. Careful dissection of the lenticulostriate arteries from the aneurysm is important to prevent ischemic complications, especially in aneurysms arising from the superior wall.