Supplementary Material for: Mechanical Thrombectomy for Middle Cerebral Artery Division Occlusions: A Systematic Review and Meta-Analysis

<p><b><i>Background:</i></b> Middle cerebral artery division (M2) occlusion was significantly underrepresented in recent mechanical thrombectomy (MT) randomized controlled trials, and the approach to this disease remains heterogeneous. <b><i>Objective:</i></b> To conduct a systematic review and meta-analysis of outcomes at 90 days among patients undergoing MT for M2 middle cerebral artery (MCA) occlusions. <b><i>Methods:</i></b> Five clinical databases were searched from inception through September 2016. Observational studies reporting 90-day modified Rankin Scale scores for patients undergoing MT for M2 MCA occlusions with an M1 MCA control group were selected. The primary outcome of interest was good clinical outcome 90 days after MT of an M1 or M2 MCA occlusion. Secondary outcomes of interest included mortality and excellent clinical outcome, recanalization rates, significant intracerebral hemorrhage, and procedural complications. <b><i>Results:</i></b> A total of 323 publications were identified, and 237 potentially relevant articles were screened. Six studies were included in the analysis (M1 = 1,203, M2 = 258; total <i>n</i> = 1,461). We found no significant differences in good clinical outcomes (1.10 [95% CI, 0.83-1.44]), excellent clinical outcomes (1.07 [0.65-1.79]), mortality at 3 months (0.85 [0.58-1.24]), recanalization rates (1.06 [0.32-3.48]), and significant intracranial hemorrhage (1.19 [0.61-2.30]). <b><i>Conclusions:</i></b> MT of M2 MCA occlusions is as safe as that of main trunk MCA occlusions, and comparable in terms of clinical outcomes and hemorrhagic complications. Randomized clinical trials are needed to assess the impact of MT in patients with M2 occlusions, given that M1 MCA occlusions have different natural histories than M2 occlusions.</p