Cerebral microhemorrhage
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Cerebral microhaemorrhages, or microbleeds,are usually defined as <5 mm in size, and have a number of underlying causes.
Pathology
Aetiology
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chronic hypertensive encephalopathy (common)
- typically involve the basal ganglia, thalami as well as brain stem, cerebellum and corona radiata
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cerebral amyloid angiopathy (common)
- typically involves the grey-white matter junction; usually spares the basal ganglia
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cavernous malformations
- multiple (familial) cavernous malformation syndrome
- post cerebral radiotherapy
- septic and fat emboli
- cerebral vasculitis (primary or secondary): microhaemorrhages usually located at the corticomedullary junction
- haemorrhagicdiffuse axonal injury (DAI): typically involves the grey–white matter junction, splenium of the corpus callosum, and dorso-lateral brainstem
- haemorrhagic micrometastases (rare): melanoma or renal cell carcinoma
- CADASIL (rare): microhaemorrhages have been reported to occur in 25–70%of cases without a characteristic distribution
- progressive facial hemiatrophy (PFHA), also named as Parry-Romberg syndrome (very rare)
Radiographic features
They are best seen on susceptibility weighted T2* sequences such as gradient echo (GRE) and susceptibility weighted imaging (SWI), and show up as very conspicuous punctate regions of signal drop out which blooms. This grossly overestimates the size of the lesions, and they are usually inapparent on other sequences. Thus the definition of 5 mm or less in size is difficult and should be reserved for imaging which does not suffer from blooming.
Differential diagnosis
- artificial heart valve metallic emboli (very rare)
- pneumocephalus (very rare without proceeding surgery) 2
-<li>haemorrhagic <a href="/articles/diffuse-axonal-injury-dai">diffuse axonal injury (DAI)</a>: typically involves the grey–white matter junction, splenium of the corpus callosum, and dorso-lateral brainstem </li>- +<li>haemorrhagic <a href="/articles/diffuse-axonal-injury-dai">diffuse axonal injury (DAI)</a>: typically involves the grey–white matter junction, splenium of the corpus callosum, and dorso-lateral brainstem </li>
-</ul><h4>Radiographic features</h4><p>They are best seen on susceptibility weighted T2* sequences such as <a href="/articles/gradient-echo-sequences-1">gradient echo</a> (GRE) and <a title="Susceptibility weighted imaging" href="/articles/susceptibility-weighted-imaging-1">susceptibility weighted imaging</a> (SWI), and show up as very conspicuous punctate regions of signal drop out which blooms. This grossly overestimates the size of the lesions, and they are usually inapparent on other sequences. Thus the definition of 5 mm or less in size is difficult and should be reserved for imaging which does not suffer from blooming. </p><h4>Differential diagnosis</h4><ul>- +</ul><h4>Radiographic features</h4><p>They are best seen on susceptibility weighted T2* sequences such as <a href="/articles/gradient-echo-sequences-1">gradient echo</a> (GRE) and <a href="/articles/susceptibility-weighted-imaging-1">susceptibility weighted imaging</a> (SWI), and show up as very conspicuous punctate regions of signal drop out which blooms. This grossly overestimates the size of the lesions, and they are usually inapparent on other sequences. Thus the definition of 5 mm or less in size is difficult and should be reserved for imaging which does not suffer from blooming. </p><h4>Differential diagnosis</h4><ul>
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