1099 Microsurgically Occult Sequelae of Temporary Clip Application During Cerebral Aneurysm Surgery– Insights From Intraoperative Cerebral Angiography

INTRODUCTION: Temporary artery occlusion is an important technique during the microsurgical repair of cerebral aneurysms. Temporary clip application and removal maneuvers commonly appear insignificant. Intraoperative diagnostic cerebral angiography (ioDCA) facilitates understanding of temporary clipping sequelae. METHODS: Consecutive microsurgical cerebral treatments performed between 01/2020 – 06/2023 were retrospectively reviewed. We included patients >18 years undergoing cerebral aneurysm clipping and immediate ioDCA prior to closure. Independent chart-review was performed by two neurosurgeons. Videos were reviewed to determine microscopic presence of parent vessel injury. Cerebral angiographies were reviewed for presence of parent vessel injury and luminal stenosis. RESULTS: A total of 137 cerebral aneurysms were clipped in 114 patients (121 craniotomies). Ten patients (7.3%) underwent clipping for a ruptured cerebral aneurysm. Of the 127 elective clippings, 11/127 (8.7%) were previously treated endovascularly. Temporary clipping was performed in 75/137 cases (54.7%). Parent vessel vasospasm was observed in 14/75 (18.7%) with median luminal stenosis of 30% (IQR 25% - 50%) and maximum of 70% stenosis in 3/14 cases. In none (0/14) of these cases a parent vessel stenosis or other injury was microscopically evident. Among the 127 unruptured aneurysm clippings, a total of 12 patients had evidence of parent vessel vasospasm. At discharge, 3/12 vasospasm patients (25%) had an NIHSS-change with radiographic ischemic injury compared to 9/115 (7.8%) patients without vasospasm (p=0.087). One patient with unremarkable ioDCA returned on postoperative day 10 due to transient aphasia and angiography revealed a distal M1 MCA dissection at the site of previous temporary clip. After 90 days, 2.7% of elective aneurysm clippings demonstrated a persistent deficit. CONCLUSIONS: Immediate intraoperative DCA revealed parent vessel vasospasm in about 18% of cases. Angiographic parent vessel vasospasm was microsurgically occult in all cases.