Flow- and caliber-matched dual bypass for fusiform MCA bifurcation aneurysm.

Complex fusiform aneurysms of the middle cerebral artery (MCA) bifurcation remain challenging when the diseased segment incorporates both M2 trunks, precluding reconstructive clipping or endovascular options. We present a video article demonstrating a tailored dual revascularization strategy for a fusiform MCA bifurcation aneurysm involving both M2 divisions. Through a frontotemporal approach with wide sylvian fissure dissection, the aneurysm and the origins of the superior and inferior M2 trunks were exposed. Donor selection and bypass configuration were guided by the anticipated flow requirements of each M2 division, estimated from recipient territory, relative vessel caliber, and intraoperative Doppler assessment: an internal maxillary artery-radial artery (IMax-RA) graft was used to revascularize the larger-caliber M2 trunk supplying the larger territory and judged to require higher flow, while a superficial temporal artery (STA)-M2 bypass was performed for the second M2 division with lower anticipated flow demand. Only one suitable STA branch was available, precluding a double-barrel STA strategy. The video details graft tailoring, temporary clipping, end-to-side anastomoses, and bypass sequencing. Intraoperative indocyanine green angiography and Doppler ultrasonography were used to confirm bypass patency and robust distal flow through both reconstructions. To preserve proximal perforators, distal trapping only was performed, allowing progressive aneurysm thrombosis while maintaining distal perfusion. Postoperative imaging demonstrated near-complete aneurysm thrombosis with preserved distal MCA flow. A flow-guided dual revascularization strategy can provide a reliable microsurgical solution for complex fusiform MCA bifurcation aneurysms involving both M2 trunks, emphasizing physiologic donor selection and perforator-preserving aneurysm exclusion.