Functional Outcome and Procedure-related Subarachnoid Hemorrhage in Primary M2 Occlusion: Impact of Initial Thrombectomy Strategy and Procedural Factors

OBJECTIVE: Procedure-related subarachnoid hemorrhage (SAH) is a recognized complication of mechanical thrombectomy for M2 middle cerebral artery occlusion, but whether the first-line device strategy influences its occurrence remains unclear. This study was performed to determine whether a stent retriever (SR)-first strategy, compared with a contact aspiration (CA)-first strategy, is independently associated with procedure-related SAH. METHODS: In this single-center retrospective study, 180 consecutive patients who underwent mechanical thrombectomy for isolated M2 occlusion were classified according to the first-line device strategy. Procedure-related SAH was assessed on postprocedural imaging. Associations were examined by multivariable logistic regression adjusted for age, admission National Institutes of Health Stroke Scale score, diffusion-weighted imaging Alberta Stroke Program Early CT Score, occluded vessel diameter, M1-M2 angle, and number of passes. Inverse probability of treatment weighting, doubly robust estimation, and multiple imputation by chained equations (m = 20) were performed as sensitivity analyses. RESULTS: Procedure-related SAH occurred in 52 patients (29%), and symptomatic intracranial hemorrhage occurred in 8 patients (4.4%). An SR-first strategy was independently associated with procedure-related SAH (adjusted odds ratio, 4.24; 95% confidence interval, 1.13-16.00; P = 0.003), as were a smaller occluded vessel diameter and a greater number of passes. The association was preserved across all sensitivity analyses (adjusted odds ratio, 4.74; 95% confidence interval, 2.00-11.27). Older age, higher admission National Institutes of Health Stroke Scale score, lower diffusion-weighted imaging Alberta Stroke Program Early CT Score, and longer onset-to-puncture time were independently associated with poor 90-day functional outcome. CONCLUSION: In mechanical thrombectomy for M2 occlusion, an SR-first strategy was independently associated with procedure-related SAH. A contact aspiration-first strategy may be preferable as the initial approach, particularly in small-caliber or acutely angulated M2 branches.