Intracranial hemorrhage risk in patients with cerebral microbleeds after mechanical thrombectomy for acute ischemic stroke: a systematic review and meta-analysis.

Background and purpose intracranial hemorrhage risk in patients with cerebral microbleeds (CMBs) after mechanical thrombectomy for acute ischemic stroke (AIS) was investigated. We searched PubMed and Embase from inception to 29 August 2023 for relevant studies, calculated pooled odds ratio (ORs) of intracerebral hemorrhage (ICH) subtypes in AIS patients with CMB presence, 1-4 or ≥ 5 CMBs versus CMB absence, and with different CMB locations after mechanical thrombectomy. ICH subtypes included any ICH, symptomatic and asymptomatic ICH, hemorrhage outside infarct (including subarachnoid hemorrhage), hemorrhagic infarction, and parenchymal hemorrhage after mechanical thrombectomy. Five eligible studies enrolling 2051 patients were included. No significant association was shown between CMB locations (lobar, deep, infratentorial or mixed) and ICH risk. CMB presence or 1-4 CMBs did not significantly increase the risk of any ICH, symptomatic or asymptomatic ICH, ICH outside infarct, subarachnoid hemorrhage, hemorrhagic infarction, or parenchymal hemorrhage. CMBs ≥ 5 increased the risk of any ICH (OR 2.58, 95% CI 1.16-5.72), parenchymal hemorrhage (OR 3.38, 95% CI 1.43-7.97) and parenchymal hemorrhage-2 (OR 5.33, 2.05-13.86), without increasing hemorrhagic infarction or parenchymal haemorrhage-1 risk. After adjusted for possible confounding factors, increases in CMB burden were associated with hemorrhagic complications but not with symptomatic ICH. In AIS patients who received mechanical thrombectomy, no association was shown between CMB location and ICH risk. ICH risk was not significantly increased by CMB presence or 1-4 CMBs. ICH risk in patients with ≥ 5 CMBs requires further study.