Impact of Microbleeds on Outcome Following Recanalization in Patients With Acute Ischemic Stroke

Background and Purpose- We analyzed the association between cerebral microbleeds (CMBs) and clinical outcome in acute ischemic stroke patients and especially in a subgroup of patients with successful recanalization. Methods- A total of 1532 acute ischemic stroke patients treated with intravenous thrombolysis or mechanical thrombectomy were enrolled in this prospective cohort study. The primary outcome was measured using the modified Rankin Scale at 3 months, according to the CMB status based on magnetic resonance imaging at admission. Favorable outcome was defined as functional independence with modified Rankin Scale scores of 0 to 2. Secondary outcomes included the occurrence of symptomatic intracranial hemorrhage. Results- There was no statistically significant association between the presence of CMB and favorable outcome at 3 months when considering all patients (44.3% versus 37.6%; P=0.121). In patients with recanalization, the number of patients with favorable outcomes was significantly higher in the CMB-negative than in the CMB-positive group (57.0% versus 36.0%; P<0.001). In the final multivariate analysis, the presence of CMB, and in particular high CMB burden (≥5), and lobar location, were significantly associated with less favorable 3-month outcomes (odds ratio=0.57; 95% CI, 0.33-0.97; P=0.038) and symptomatic intracranial hemorrhage (odds ratio=3.21; 95% CI, 1.37-7.49; P=0.007) in patients with recanalization. In the analysis of subgroups, a statistically significant interaction was found between CMB presence and recanalization in predicting functional outcomes at 3 months. Conclusions- These results indicate that the presence of CMBs, and especially high burden and lobar location, are independent predictors of poor 3-month clinical outcomes and may increase symptomatic intracranial hemorrhage risk in acute ischemic stroke patients with recanalization. Our findings suggest that CMBs lead to more unfavorable effects in patients with recanalization after large vessel occlusion than in those without recanalization.