Background Over half of patients who receive intravenous tissue plasminogen activator for middle cerebral artery division (MCA-M2) occlusion do not recanalize, leaving a large percentage of patients who may need mechanical thrombectomy (MT). However, the outcomes of MT for M2 occlusion have not been well characterized.

Objective To determine if MT of M2 occlusion is as safe and efficacious as current standard-of-care MT for M1 occlusions.

Methods With institutional review board approval, we retrospectively reviewed records of 212 patients undergoing MT for isolated MCA M1 or M2 occlusions during a 36-month period (Sept 2013 to Sept 2016) at two centres. Treatment variables, clinical outcomes, and complications in each group were recorded.

Results There were 153 M1 MCA occlusions and 59 M2 MCA occlusions. No statistically significant difference was found in the rate of mortality (20% in M1 vs 13.6% in M2, p=0.32), excellent (34.5% vs 37.3%, p=0.75) or good (51% vs 55.9%, p=0.54) clinical outcomes between the two groups. Infarct volumes (48.4 mL vs 46.2 mL, p=0.62) were comparable between the two groups, as were the rates of hemorrhagic (3.3% vs 3.4%, p=1.0) and procedural complications (3.3% vs 5.1%, p=0.69).

Conclusion Our data on MT targeting M2 occlusions demonstrates reasonable safety and functional outcomes. Further randomized clinical trials are needed to clarify which patients may benefit from MT for M2 occlusions.