Microbleeds, Cerebral Hemorrhage, and Functional Outcome after Endovascular Thrombectomy.

Objective —To determine whether pre-treatment cerebral microbleeds (CMBs) presence and burden are correlated with an increased risk of intracranial hemorrhage (ICH) or poor functional outcome following endovascular thrombectomy (EVT) for acute ischemic stroke (AIS). Methods —Consecutive patients treated by EVT for anterior circulation AIS were retrospectively analyzed. Experienced neuroradiologists blinded to functional outcomes rated CMBs on T2*-MRI using a validated scale. We investigated associations of CMB presence and burden with ICH and poor clinical outcome at 3 months (modified Rankin score >2). Results —Among 513 patients, 281 (54.8%) had a poor outcome and 89 (17.3%) had ≥1 CMBs. A total of 190 (37%) patients experienced ICH, in which 66 (12.9%) were symptomatic. CMB burden was associated with poor outcome in a univariable analysis (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.03–1.36 per 1-CMB increase; P=0.02), but significance was lost after adjustment for sex, age, stroke severity, hypertension, diabetes mellitus, atrial fibrillation, prior antithrombotic medication, intravenous thrombolysis, and reperfusion status (OR, 1.05; 95% CI, 0.92–1.20 per 1-CMB increase; P=0.50). Results remained nonsignificant when taking into account CMB location or presumed underlying pathogenesis. CMB presence, burden, location, nor presumed pathogenesis was independently correlated with ICH. Conclusions —Poor functional outcome or ICH were not correlated with CMB presence or burden on pre–EVT MRI after adjustment for confounding factors. Excluding such patients from reperfusion therapies is unwarranted. Classification of Evidence —This study provides Class II evidence that in patients with AIS undergoing EVT, after adjustment for confounding factors, the presence of CMBs is not significantly associated with clinical outcome or the risk of ICH.