Cerebral microhemorrhage
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Cerebral microhaemorrhages, or cerebral microbleeds,are small focal intracerebral haemorrhages, often only visible on susceptibility-sensitive MRI sequences.
Pathology
Common aetiologies
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cavernous malformations 1,8
- especially Zabramski classification type IV malformations
- causes include multiple (familial) cavernous malformation syndrome and post-cerebral radiotherapy
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cerebral amyloid angiopathy (common) 1,8
- typically involves the grey-white matter junction; usually spares the basal ganglia
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chronic hypertensive encephalopathy (common) 1,8
- typically involve the basal ganglia, thalami as well as brainstem, cerebellum and corona radiata
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diffuse axonal injury (DAI) and other trauma 1,8
- typically involves the grey-white matter junction, splenium of the corpus callosum, and dorsolateral brainstem
Less common aetiologies
- acute haemorrhagic leukoencephalitis (AHLE) 8
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CADASIL 1,8
- microhaemorrhages have been reported to occur in 25–70% of cases without a characteristic distribution
- cerebral hyperperfusion syndrome 11
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cerebral vasculitis (primary or secondary) 1,8
- microhaemorrhages usually located at the corticomedullary junction
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COL4A1 brain small-vessel disease
- microhaemorrhages have been reported in up to 53% of cases, characteristically in the centrum semiovale, deep gray matter, or brainstem 5,8
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haemorrhagic micrometastases 1,8
- especially melanoma or renal cell carcinoma
- hypoxia (e.g. acute respiratory distress syndrome, high-altitude exposure, being critically ill) 8-10
- intracranial embolism
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fat embolism
- usually from fractures 4,8,14
- gas embolism 6,7
- many causes including: intravenous catheter placement, decompression sickness, extracorporeal membrane oxygenation, hydrogen peroxide ingestion, etc.
- septic embolism
- usually from infective endocarditis 3,8
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fat embolism
- intracranial infection (e.g. cerebral malaria, mycotic aneurysm) 8
- intravascular lymphoma 8
- neurosarcoidosis 12,13
- posterior reversible encephalopathy syndrome (PRES) 8
- progressive facial hemiatrophy (PFHA) 1,8
- radiation-induced cerebral vasculopathy 1,8
- thrombotic microangiopathies (e.g. haemolytic uraemic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP)) 8
Radiographic features
Cerebral microhaemorrhages are only seen on MRI and are best seen on susceptibility weighted T2* sequences such as gradient-recalled echo (GRE) and susceptibility weighted imaging (SWI).
They appear as conspicuous 2-10 mm punctate regions of signal drop out with blooming artifact. This blooming grossly overestimates the size of the lesions, thus they are usually inapparent on other MRI sequences and CT.
Differential diagnosis
- artificial heart valve metallic emboli (very rare)
- pneumocephalus (very rare without preceding surgery) 2
- flow voids of veins 8
- intracranial calcification 8
-<a href="/articles/cerebral-fat-embolism">fat embolism</a><ul><li>usually from fractures <sup>4,</sup><sup>8</sup>- +<a href="/articles/cerebral-fat-embolism">fat embolism</a><ul><li>usually from fractures <sup>4,</sup><sup>8,14</sup>
References changed:
- 14. Giyab O, Balogh B, Bogner P, Gergely O, Tóth A. Microbleeds Show a Characteristic Distribution in Cerebral Fat Embolism. Insights Imaging. 2021;12(1):42. <a href="https://doi.org/10.1186/s13244-021-00988-6">doi:10.1186/s13244-021-00988-6</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/33788069">Pubmed</a>
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