Clinical relevance of microbleeds in acute stroke thrombolysis

OBJECTIVE: We performed a systematic review and meta-analysis to assess whether the presence of cerebral microbleeds (CMBs) on pretreatment MRI of patients with acute ischemic stroke treated with IV thrombolysis is associated with increased risk of symptomatic intracerebral hemorrhage (ICH) and poor functional outcome. METHODS: We searched PubMed for relevant studies and calculated pooled odds ratios (OR) for symptomatic ICH and poor (i.e., modified Rankin Scale score >2) 3- to 6-month functional outcome using random effects models with DerSimonian-Laird weights among individuals with vs without CMBs. RESULTS: Eight eligible studies including 2,601 stroke patients treated with IV thrombolysis were pooled in a meta-analysis. The cumulative CMBs prevalence was 24% (95% confidence interval [CI] 18%-30%). The pooled symptomatic ICH incidence was 5% (95% CI 4%-7%) among patients with CMBs and 3% (95% CI 2%-5%) in patients without CMBs. CMB presence was associated with higher risk of symptomatic ICH compared to patients without CMBs (OR 2.18; 95% CI 1.12-4.22; p = 0.021). Four studies (n = 1,665) reported data on 3- to 6-month poststroke functional outcome. The pooled incidence of poor functional outcome was 52% (95% CI 45%-59%) in patients with CMBs vs 41% (95% CI 35%-46%) in those without CMBs. Meta-analysis of these studies demonstrated OR for CMBs presence and adverse outcome to be 1.58 (95% CI 1.18-2.14; p = 0.002). CONCLUSIONS: CMBs are associated with greater symptomatic ICH risk and poor functional outcome in ischemic stroke patients undergoing thrombolytic therapy. In the absence of adjusted analyses and randomized evidence, this risk seems acceptable and should probably not discourage recanalization therapies in this patient population (Level B recommendation: nonrandomized Class IIa evidence).