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Cerebral microbleeds: a review of clinical, genetic, and neuroimaging associations
Paul A Yates1, Victor L Villemagne2, Kathryn A Ellis3
1Department of Nuclear Medicine and Centre for PET, Austin Health , Heidelberg, VIC , Australia ; Department of Medicine, The University of Melbourne , Parkville, VIC , Australia.
Abstract:
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.
Insights
Cerebral microbleeds, identified via MRI, are linked to impaired brain small vessel integrity. Their presence may increase risks for hemorrhage and complications, especially during anticoagulation or AD immunotherapy.
Area of Science:
- Neurology
- Neuroradiology
- Neuroimaging
Background:
- Cerebral microbleeds are MRI-detected lesions indicating prior microscopic hemorrhages.
- They result from impaired small vessel integrity, often due to hypertensive vasculopathy or cerebral amyloid angiopathy.
- Microbleeds are more common in Alzheimer's disease dementia, stroke patients, and asymptomatic individuals, with prevalence increasing with age and APOE ε4 allele presence.
Purpose of the Study:
- To summarize the current understanding of cerebral microbleeds.
- To highlight associations between microbleeds and other neuroimaging findings.
- To discuss the clinical implications and risks associated with microbleeds.
Main Methods:
- Review of T2* Gradient-Recall Echo (GRE) and Susceptibility-Weighted (SWI) MRI sequences.
- Correlation with clinical conditions such as Alzheimer's disease and stroke.
- Association with other neuroimaging markers like lacunar infarcts, white matter hyperintensities, and amyloid burden.
Main Results:
- Microbleeds are linked to impaired small vessel integrity.
- Associations observed with Alzheimer's disease, stroke, aging, APOE ε4 allele, lacunar infarcts, white matter hyperintensities, and cerebral amyloid burden.
- Microbleeds may increase the risk of intracerebral hemorrhage and complications from Alzheimer's disease immunotherapy.
Conclusions:
- Cerebral microbleeds are significant imaging biomarkers associated with various neurological conditions.
- Their presence warrants consideration for risks related to hemorrhage and specific treatments.
- Further prospective research is needed to fully elucidate their natural history and clinical impact.
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