Background Malignant brain edema (MBE) is a devastating complication in ischemic stroke. Data on MBE in patients who have had mechanical thrombectomy (MT) are relatively scarce.

Objective To investigate the incidence, predictors, and clinical outcomes of MBE in patients after MT.

Methods We included 130 consecutive patients after MT caused by anterior circulation large vessel occlusion stroke, treated with MT. MBE was defined as a midline shift of ≥5 mm on the follow-up imaging within 72 hours after MT. Characteristics of patients at admission and details of treatment were collected. The 90-day modified Rankin scale score was used as a measure of functional outcomes.

Results Of the 130 patients (age, 68.6±10.9 years; male, 50%), 35 (26.9%) patients developed MBE. The patients with MBE had a lower rate of functional independence (OR=7.831; 95% CI 1.731 to 35.427; p=0.008) and significantly higher mortality at 90 days (OR=7.958; 95% CI 2.274 to 27.848; p=0.001) than patients without MBE. In 104 (80%) patients with successful recanalization (modified Thrombolysis in Cerebral Infarction score of 2b–3), 24 (23.1%) patients exhibited MBE. After adjustment for confounding, ICA occlusion (OR=3.746; 95% CI 1.169 to 12.006; p=0.026) and worse collateral score (grade 1 vs grade 0: OR=0.727; 95% CI 0.192 to 2.753; p=0.638; grade 2 vs grade 0: OR=0.130; 95% CI 0.021 to 0.819; p=0.030) were significantly associated with the development of MBE, despite successful recanalization.

Conclusions MBE after MT is not uncommon and was related to poor functional outcomes. Localization of a vessel occlusion and collateral status may play a role in the development of MBE.