Cerebral microbleeds (CMBs) are tiny, chronic deposits of hemosiderin within brain tissue, caused by leakage from fragile small vessels. They act as markers of small vessel disease and are linked to stroke, dementia, and aging. 🧲 Their iron content makes them visible on MRI sequences sensitive to magnetic susceptibility (GRE, SWI).

ℹ️ About

Found in ~10–20% of older adults, higher in stroke and dementia patients.
Seen as biomarkers of cerebral small vessel disease.
Detection has improved with susceptibility-weighted MRI.

⚙️ Etiology

Small foci of chronic blood leakage → hemosiderin deposition.
Size usually 2–10 mm.
Associated with microangiopathy from hypertension, amyloid angiopathy, trauma, or anticoagulation.

📌 Common Causes

👴 Aging – prevalence rises with age.
💉 Hypertensive vasculopathy – deep microbleeds (basal ganglia, thalamus, brainstem, cerebellum).
🧩 Cerebral amyloid angiopathy (CAA) – lobar microbleeds, esp. occipital cortex.
🧠 Alzheimer’s disease – often coexists with CAA.
🤕 Trauma – diffuse axonal injury.
🫀 Haemorrhagic transformation of ischemic stroke.
📌 Other: melanoma mets, cavernomas, anticoagulation, radiotherapy.

🖥️ Imaging

T2*-GRE MRI: CMBs appear as dark, round lesions (blooming effect).
SWI MRI: More sensitive; detects smaller and more numerous lesions.
No surrounding edema or mass effect (distinguishes from acute haemorrhage).

🩺 Clinical Significance

⚠️ ↑ risk of intracerebral haemorrhage, esp. with anticoagulation.
🧑‍🧠 Associated with cognitive decline and vascular dementia.
📉 Predicts recurrence of stroke (ischemic & haemorrhagic).
📊 Guides decisions about antithrombotics and thrombolysis safety.

📍 Distribution Patterns

🟤 Lobar: CAA, Alzheimer’s.
⚫ Deep: Hypertension-related.
🟠 Infratentorial: Hypertension or mixed pathology.

💊 Management Implications

✔️ Optimise vascular risk factors (HTN, diabetes, lipids).
✔️ Anticoagulation decisions must balance stroke vs bleed risk.
✔️ Lifestyle advice: smoking cessation, diet, exercise.
✔️ Serial MRI can monitor progression.

🧾 Comparing T2* GRE vs SWI

SWI is more sensitive than T2*-GRE for detecting CMBs and amyloid angiopathy. The image below shows SWI detecting far more lesions in CAA than GRE.

Comparison of SWI and GRE Imaging in CAA

Comparison of GRE (left) and SWI (right) in CAA (Wikimedia Commons).

⚠️ Limitations

False positives: calcifications, vessel flow voids, iron deposits.
Protocol variability between MRI scanners.
Not all CMBs are symptomatic – interpret in clinical context.

📌 Conclusion

Cerebral microbleeds are silent but significant markers of small vessel disease. They predict risk of future stroke, dementia, and treatment complications. Advanced MRI (SWI) enhances detection, allowing better risk stratification and patient counselling.

📚 References

Greenberg SM et al. Cerebral microbleeds: detection & interpretation. Lancet Neurol. 2009.
Wardlaw JM et al. Neuroimaging standards in small vessel disease. Lancet Neurol. 2013.
Yakushiji Y et al. Distribution of CMBs in Alzheimer’s disease. J Alzheimers Dis. 2012.
Shams S et al. SWI vs T2* for CMB detection. PLoS One. 2015.

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Cerebral microbleeds

🧠 Introduction