Cerebral microbleeds on MRI: prevalence, associations, and potential clinical implications.

OBJECTIVE: To assess the potential role of cerebral microbleeds (CMB) in intracerebral hemorrhage (ICH), as indicators of cerebral small-vessel disease, and their possible implications for antithrombotic treatment.
METHODS: The author reviewed literature published through July 2005 from electronic MEDLINE, PubMed, and hand searches. CMB prevalence analyses were performed for subjects without cerebrovascular disease, with ICH, and with ischemic cerebrovascular disease.
RESULTS: Prevalence data from more than 5,200 subjects were analyzed. In elderly subjects without cerebrovascular disease, CMB prevalence is between 5% and 6%, associated with advanced age, while data are inconsistent with regard to CMB and chronic hypertension. CMB are prevalent in 68% of patients with spontaneous ICH and 40% of those with ischemic cerebrovascular disease. Cerebral microangiopathy (lacunes, leukoaraiosis) is associated with the highest prevalence (57%) of CMB among patients with ischemic stroke. In patients with suspected cerebral amyloid angiopathy (CAA) or Alzheimer disease, CMB are predominantly located in the cortical-subcortical area. Current data provide no evidence that CMB increase the risk of ICH among patients on antithrombotic treatment or those treated with thrombolysis for acute stroke.
CONCLUSIONS: Cerebral microbleeds might indicate a higher risk of future intracerebral hemorrhage and may be a marker of cerebral small-vessel disease and cerebral amyloid angiopathy. However, more prospective data are required in order to confirm these assumptions. Recommendations to guide antithrombotic treatment based on the detection of cerebral microbleeds are presently not justified.