<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