Clinical Benefit of Thrombectomy in Large‐Core Infarction Patients Is Mediated by Malignant Cerebral Edema Reduction

Background The impact of endovascular thrombectomy‐mediated reperfusion on malignant cerebral edema (MCE) in large‐core infarction remains unclear. We assessed the reperfusion–MCE relationship and MCE’s mediating role in poor outcomes. Methods This retrospective analysis used data from the national MAGIC (Prospective Multicenter Registry on Early Management of Acute Ischemic Stroke) registry (750 patients with large‐core infarction, 38 Chinese centers, 2021–2023). MCE was defined as a midline shift of ≥5 mm on follow‐up imaging within 72 hours after stroke onset. Recanalization was confirmed by computed tomography angiogram or magnetic resonance angiogram during hospitalization in the overall cohorts. Successful reperfusion was defined using the modified Treatment in Cerebral Ischemia classification 2b‐3 in the endovascular thrombectomy arm. Functional outcome was 90‐day modified Rankin scale score. Mediation analysis used reperfusion status as the independent variable and MCE as the mediator. Results Among 698 patients, (306 women [43.8%]; median age, 70 [interquartile range, 61–78] years; median, Alberta Stroke Program Early Computed Tomography] Scores, 4 [interquartile range, 2–5]), successful recanalization (adjusted odds ratio [aOR], 0.68 [95% CI, 0.47–0.99]; P =0.042) and reperfusion (aOR, 0.34 [95% CI, 0.18–0.67]; P =0.002) reduced MCE likelihood. MCE was partially responsible for worse modified Rankin Scale scores in patients without recanalization or reperfusion (MCE changed the logistic regression coefficients by 15.0% and 32.5%, respectively). Recanalization improved functional outcomes partly by mitigating MCE formation (indirect effect β=−0.10, 11.5% mediation proportion, P =0.028) in those with Alberta Stroke Program Early Computed Tomography Scores 3 to 5 but not in those with 0 to 2 (β=−0.26, P =0.140). Conclusions Successful reperfusion attenuates MCE formation and improves clinical outcomes in patients with large‐core infarction.