In Situ M2 Bypass for Treatment of Fusiform Middle Cerebral Artery Bifurcation Aneurysm: Technical Case Instruction and Operative Video.

Background And Importance: Fusiform middle cerebral artery (MCA) bifurcation aneurysms can be challenging to treat with standard endovascular or microsurgical techniques. The in situ side-to-side bypass technique represents an elegant revascularization option for these aneurysms when trapping becomes necessary.

Clinical Presentation: A man in his 50s presented for evaluation of an incidentally found fusiform, 10 mm, right MCA bifurcation aneurysm with involvement of both the inferior and superior M2 trunks. Plan was initially made for a right pterional craniotomy for trapping of the aneurysm with exclusion of the inferior M2 trunk, preservation of the superior M2 trunk, with superficial temporal artery bypass to the inferior M2 trunk. Intraoperatively, after arachnoid dissection, it became clear that the distal superior and inferior M2 branches would lie in close approximation without tension, thus superficial temporal artery-M2 bypass was deferred, and instead in situ side-to-side M2 bypass was performed. Here in our operative video, we highlight the critical steps of in situ side-to-side M2 bypass technique.

Conclusion: We present a technical case instruction and operative video highlighting the in situ side-to-side bypass technique for treatment of a large fusiform MCA bifurcation aneurysm.