The impact of cerebral microbleeds on intracerebral hemorrhage and poor functional outcome of acute ischemic stroke patients treated with intravenous thrombolysis: a systematic review and meta-analysis

It is still controversial whether pre-existing cerebral microbleeds (CMBs) increase the risks of intracranial hemorrhage (ICH) and poor functional outcome (PFO) in acute ischemic stroke (AIS) patients treated with intravenous thrombolysis (IVT). Therefore, we performed a systematic review and meta-analysis to determine the impact of CMBs on ICH and PFO of AIS patients with IVT. We searched PubMed, EMBASE and Web of Science from inception to August 3, 2016, with language restriction in English. We included studies that reported the relationship between CMBs and ICH or PFO after thrombolysis. Two retrospective and nine prospective studies met inclusion criteria (total 2702 patients). The overall prevalence of CMBs on pre-IVT MRI scans was 24.0%. Pre-existing CMBs on MRI scans were not significantly associated with a higher risk of early sICH (OR 1.74; 95% CI 0.91–3.33; I2 = 44.5%). Subgroup analyses did not substantially influence these associations. The presence of CMBs was associated with the increased risk of 3-month PFO (OR 1.58; 95% CI 1.08–2.31; I2 = 54.2%), PH (OR 2.14; 95% CI 1.34–3.42; I2 = 11.0%) and any ICH (OR 1.42; 95% CI 1.04–1.95; I2 = 0.0%), respectively. This meta-analysis showed that CMBs presence was not significantly associated with the increased risk of early sICH after IVT. However, the results also demonstrated that CMBs presence increased the risks of 3-month PFO, PH and any ICH after IVT. Due to a small number of included studies and methodological limitations, the results of this meta-analysis should be interpreted cautiously. CMBs presence should not be a contraindication to IVT for AIS patients based on the existing evidence.