Cerebral microbleeds (microbleeds) are small, punctuate hypointense lesions seen in T2* Gradient-Recall Echo (GRE) and Susceptibility-Weighted (SWI) Magnetic Resonance Imaging (MRI) sequences, corresponding to areas of
hemosiderin breakdown products from prior microscopic
hemorrhages. They occur in the setting of impaired small vessel integrity, commonly due to either hypertensive vasculopathy or
cerebral amyloid angiopathy. Microbleeds are more prevalent in individuals with
Alzheimer's disease (AD)
dementia and in those with both ischemic and
hemorrhagic stroke. However they are also found in asymptomatic individuals, with increasing prevalence with age, particularly in carriers of the
Apolipoprotein (
APOE) ε4 allele. Other neuroimaging findings that have been linked with microbleeds include
lacunar infarcts and white matter hyperintensities on MRI, and increased cerebral β-
amyloid burden using (11)C-PiB Positron Emission Tomography. The presence of microbleeds has been suggested to confer increased risk of incident
intracerebral hemorrhage - particularly in the setting of anticoagulation - and of complications of
immunotherapy for AD. Prospective data regarding the natural history and sequelae of microbleeds are currently limited, however there is a growing evidence base that will serve to inform clinical decision-making in the future.