Cerebral microbleeds (CMBs) can occur in stroke, brain aging, dementia, Alzheimer disease, cerebral amyloid angiopathy, and hypertension. They have been found to predict the risk of overall mortality in elderly patients and in those with cognitive impairment.
The clinical significance of CMBs has remained unclear over the last two decades but they are not uncommonly encountered and are often discovered incidentally on brain imaging.
Anticoagulation is the standard of care for patients with atrial fibrillation (AF) and other risk factors for stroke but may increase the incidence of CMBs. The clinical significance of incidentally discovered CMBs in patients with AF who require chronic anticoagulation, however, remains uncertain. A recent analysis published online before print in September 2014 in Neurology suggested that CMBs in patients with AF who are on anticoagulation may actually be a marker for worse prognosis with respect to death from ischemic or hemorrhagic stroke compared to those who are not on anticoagulation.
In this retrospective hospital-based observational analysis of 504 consecutive patients with AF and ischemic stroke, CMBs were characterized on brain MRI and correlated with data for causes of death using data from the Korean National Statistical Office. The mean age of the patients was 70 years; 57.1% were male; and nearly a third of the patients had CMBs. The overall death rate was 34.9% at 2.5 years of follow-up. After adjustment for age, sex, and other variables, patients who had CMBs on brain MRI had an approximately 2-times higher hazard for all-cause mortality, a 3.4-times higher hazard for ischemic stroke mortality, and a 5.9-times increase in hemorrhagic stroke mortality (in lobar CMBs only). In addition, the presence of 5 or more CMBs was an independent predictor of all-cause or ischemic stroke death.
This observational study of AF patients who present with stroke is hypothesis-generating and suggests that using the presence or absence of CMBs may be a useful factor in refining risk prognostication in patients with AF. One can imagine that CMBs could someday become incorporated into one of the clinical risk scores. Note however that, in this study, an oral anticoagulant was prescribed in 96.6% of patients at hospital discharge. Therefore, the prognostic implications of CMBs in those with AF who are not on anticoagulation remain uncertain. Furthermore, whether the presence of CMBs should affect the decision to use an antithrombotic or anticoagulant also warrants further study.
Song TJ, Kim J, Song D, et al. Association of cerebral microbleeds with mortality in stroke patients having atrial fibrillation. Neurology. 2014; DOI: 10.1212/WNL.0000000000000862.