High-Flow Intracranial-Intracranial Interposition Bypass from A1 to M2 with Proximal Occlusion for a Large Unruptured Fusiform Aneurysm of the Middle Cerebral Artery M1 Segment: A Technical Note.

Abstract

Complex fusiform aneurysms of the middle cerebral artery M1 segment are uncommon and technically demanding, characterized by circumferential dilation with frequent perforator involvement and atherosclerotic changes. When direct clipping or endovascular therapy is not feasible, intracranial-intracranial (IC-IC) bypass provides a rational revascularization option. A 55-year-old man presented with a large, unruptured fusiform aneurysm of the left middle cerebral artery M1 segment. Preoperative computed tomography angiography/digital subtraction angiography and high-resolution vessel-wall magnetic resonance imaging showed focal wall enhancement without an obvious intimal flap. Intraoperatively, given the focal morphology and perforator involvement, an IC-IC A1-M2 radial artery interposition graft with proximal M1 occlusion was performed. Intraoperative angiography demonstrated graft patency and retrograde perfusion of lenticulostriate arteries. Postoperative digital subtraction angiography confirmed preserved flow in both M2 divisions with reduced aneurysmal filling. The patient was discharged neurologically intact and remained deficit-free at 3-month follow-up. High-flow IC-IC bypass from A1 to M2 with proximal occlusion is a safe and effective strategy for selected complex fusiform M1 aneurysms, preserving distal and perforator flow while reducing aneurysm inflow when conventional options are limited.