Three Dissecting Aneurysms of the Middle Cerebral Artery with Subarachnoid Hemorrhage

We describe 3 cases with dissecting aneurysm of middle cerebral artery suffered from subarachnoid hemorrhage. Two cases were male and the other was female. All patients presented with headache and/or deterioration of consciousness without any symptom of cerebral ischemia. Angiography disclosed aneurysmal dilatation of M2 or M3 segment of middle cerebral artery with no branching, and in 1 case, the middle cerebral artery was occluded just distal to the aneurysmal dilatation. All were treated within Day 1, trapping was performed in 2 cases, while proximal clipping was performed in 1. Proximal clipping was followed by STA-MCA anastomosis, because reduction of regional cerebral blood flow was indicated by preoperative 133Xe single photon emisson CT. The postoperative course was excellent in all cases without any ischemic symptom. Including our 3 patients, 10 cases of dissecting middle cerebral artery aneurysm presenting with subarachnoid hemorrhage were reported previously. Although dissection of middle cerebral artery was thought to occur frequently in the proximal segment of the middle cerebral artery, 7 aneurysms of 10 cases with subarachnoid hemorrhage were located M2 to M3 segment. Rupture of dissecting middle cerebral artery seemed to occur more frequently in the distal segment. Although treatment for dissecting aneurysm of the middle cerebral artery with subarachnoid hemorrhage is controversial, early surgery with trapping or proximal clipping obtained satisfactory results in prevention of rebleeding. The necessity of additional revascularization for distal artery should be decided with findings of angiographical collateral flow, preoperative regional cerebral blood flow and intraoperative flowmetry.