Arterial Bypass in the Treatment of Complex Middle Cerebral Artery Aneurysms: Lessons Learned from 40 Patients

Complex MCA aneurysms incorporating parent or branching vessels are often not amenable to standard microsurgical clipping or endovascular embolization treatments. We aim to discuss the treatment of such aneurysms via a combination of surgical revascularization and aneurysm exclusion based on our institutional experience.Thirty-four patients with complex MCA aneurysms were treated with bypass and aneurysm occlusion, five with surgical clipping or wrapping only, and one with aneurysm excision and primary re-anastomosis. Bypasses included STA-MCA, double-barrel STA-MCA, OA-MCA, and ECA-MCA. Following bypass, aneurysms were treated by surgical clipping, Hunterian ligation, trapping, or coil embolization.The average age at diagnosis was 46 years. 67% of the aneurysms were large and most involved the MCA bifurcation. Most bypasses performed were STA-MCA bypasses, 12 of which were double-barrel. There were two wound healing complications. All but two of the aneurysms treated demonstrated complete occlusion at the last follow up. There were three hemorrhagic complications, three graft thromboses, and four ischemic insults. Mean follow up is 73 months. 83% of patients reported stable or improved symptoms from presentation and 73% reported a functional status (GOS 4 or 5) at the latest available follow up.Cerebral revascularization by bypass followed by aneurysm or parent artery occlusion is an effective treatment option for complex MCA aneurysms that cannot be safely treated by standard microsurgical or endovascular techniques. Double-barrel bypass consisting of two STA branches to two MCA branches yields adequate flow replacement in the majority of cases.