274 High-Flow Bypass With Clip-Trapping and Endovascular Flow Diversion for the Treatment of Blister Aneurysms of the Supraclinoid Internal Carotid Artery: Long-Term Outcomes and Complications

INTRODUCTION: Blister aneurysms (BAs) of the supraclinoid internal carotid artery (ICA) pose unique treatment challenges due to their broad neck, friable adventitial walls, complex angioarchitecture and heterogeneity. There is a paucity of data on long-term outcomes of microsurgical bypass with clipping or trapping, and endovascular flow diversion (FD). METHODS: Data on all BAs treated by either bypass with clip-trapping or FD between 2005-2024 was retrospectively reviewed. Outcomes and complications were assessed in the immediate post-operative, 3months and long-term (>12months) follow-up periods. RESULTS: 22 patients with BAs [mean age 45yrs(SD ±11), 59%(13/22) females] were treated with bypass (13) and FD (9). The mean follow-up was 14months. The choice between endovascular and microsurgical treatment was based on Hunt-Hess grade at presentation and surgeon’s preference. The average aneurysm size was 3.5mm(range 1-8.2mm). Thirty-one percent (4/13) of the bypass patients had failed prior treatment. Patients undergoing endovascular FD had higher proportion of poor-grade subarachnoid hemorrhage (Hunt-Hess 4 or more) on presentation [55% (5/9) vs. 23% (3/13)]. Intraprocedural rupture rate was 23% (3/13) for the microsurgical group, and 11% (1/9) for the FD group. The immediate and follow-up aneurysm occlusion rate was 92% (12/13) and 100% (9/9) for the microsurgery group; and 33% (3/9) and 80% (4/5) for the FD group, respectively. Bypass graft patency was 100% immediately post-operation and 92% (12/13) at last-known imaging. The microsurgery group had no rebleeding or hemorrhage, 15% (2/13) stroke, and 8% (1/13) mortality. The FD group had 22%(2/9) rebleeding, 22%(2/9) intracerebral hemorrhage, 11%(1/9) stroke, and 22%(2/9) mortality. CONCLUSIONS: Both bypass with clip/trapping and endovascular flow diversion are useful treatments for supraclinoid ICA blister aneurysms. Cerebrovascular centers must have the ability to provide both treatment options for patients.