Clinical significance of the Microbleed Anatomical Rating Scale score in ischemic stroke patients treated with intravenous thrombolysis

Background Conflicting results were shown on the relationship between cerebral microbleeds (CMBs) burden and functional outcomes in patients treated with intravenous tissues plasminogen activator (IV tPA). We aimed to investigate the relationship between CMBs burden and functional outcomes using the Microbleed Anatomical Rating Scale (MARS) and determine its optimal cutoff value.Methods A retrospective study was conducted to include patients treated with IV tPA in our stroke center, and the MARS was used to assess the CMBs burden. Other clinical data including demographic factors, stroke severity, vascular risk factors, and clinical outcomes were also documented. Another mediation analysis was performed to investigate whether early neurological improvement could mediate the association between MARS and functional outcomes.Results A total of 408 patients were included. A cutoff value of 1.5 could predict functional outcomes in patients treated with IV tPA. Based on that cutoff value, MARS showed an independent relationship with functional outcomes [adjusted OR (Odds Ratio) 0.841, 95% confidence interval (CI) 0.720-0.982, P = .029]. A shift analysis showed that higher MARS score (MARS >= 1.5) was related with poor functional outcome according to mRS score distribution (OR = 0.519, 95% CI 0.336-0.803, P = .003). Total effect (indirect + direct effect) was calculated and showed in figure. Early neurological improvement mediated 24% of the effect of MARS score on functional outcomes.Conclusion Our study showed that MARS could be a potential method to assess the functional outcome based on CMBs in patients treated with IV tPA, and MARS score >= 1.5 might be an optimal threshold for poor functional outcome. What is already known on this topic Conflicting results make it difficult for neurologists to assess the hemorrhage risk before IV tPA. What this study adds Our study showed that MARS could be a potential method to assess the functional outcome based on CMBs in patients treated with IV tPA, and MARS score >= 1.5 might be an optimal threshold for poor functional outcome. The association between CMBs and functional outcome was partly mediated by ENI. How this study might affect research, practice or policy In the future, a prospective, randomized double-controlled trial could be conducted based on the cutoff of MARS derived from our study