Abstract
De novo aneurysms following superficial temporal artery–middle cerebral artery (STA–MCA) bypass are rare but potentially serious postoperative complications. We report three cases of ruptured or unruptured aneurysms near the anastomotic site that were successfully treated with direct surgery. Case 1 involved a 40-year-old man with Moyamoya disease who developed a subarachnoid hemorrhage 4 years after STA-MCA bypass. Cerebral angiography revealed a 3-mm aneurysm on the contralateral wall of the MCA relative to the anastomosis. The aneurysm was successfully clipped using a bayonet-type fenestrated clip to avoid interference with dural closure. Case 2 involved a 68-year-old woman with MCA occlusion who developed a 4-mm fusiform aneurysm at the recipient MCA near the anastomosis site 1 year after surgery. The aneurysm was treated using the clip-on-wrap technique with circumferential polyglycolic acid felt reinforcement. Case 3 involved a 48-year-old woman with a history of a ruptured blister-like internal carotid artery aneurysm treated with STA-MCA bypass and parent artery occlusion. A progressively enlarging aneurysm in the STA proximal to the anastomosis was treated 4 years postoperatively. Intraoperative indocyanine green (ICG) angiography was used to confirm the STA course before dural opening, minimizing the dissection of dural adhesions. The aneurysm, which was histologically confirmed as a true aneurysm, was clipped with a short-head clip and reinforced using the wrap-on-clip technique. All patients showed no recurrence at 7, 4, and 2 years of follow-up. These cases highlight the need for specific microsurgical strategies distinct from standard aneurysm surgery, including flexible surgical strategies tailored to the aneurysm morphology, safe exposure minimizing STA dissection from dural adhesions, and clip placement to avoid interference with dural closure. Based on our experience and a literature review, we propose a 4-type classification of aneurysm location: Type 1—true anastomotic aneurysm; Type 2—contralateral aneurysm; Type 3—recipient artery aneurysm; and Type 4—donor artery aneurysm. This classification may aid in understanding the mechanisms underlying their development.
