Cerebral fat embolism
Cerebral fat embolism is one manifestation of fat embolism syndrome.
Cerebral fat embolism typically occurs in patients with bony fractures (usually long bones of the lower limb). Rarely it has been described as part of a sickle cell crisis with bone marrow fat necrosis and subsequent embolism 4.
Fat emboli usually reach the brain through either right-to-left cardiac shunt or through an intact pulmonary circulation in those without a shunt 3.
Cerebral manifestations of fat embolism syndrome can be highly variable and non-specific: the symptoms spectrum includes headache, lethargy, irritability, delirium, stupor, convulsions, or coma. Most cases can occur as subclinical events. Concurrent pulmonary or cutaneous features may aid in diagnosis.
The CT brain can be normal in most cases 8. The may be evidence of diffuse oedema with scattered low-attenuating areas and haemorrhage in some situations.
- T2: may show multiple non-confluent areas of high signal intensity
- DWI: may show bright spots on a dark background (starfield pattern) corresponding to the region of T2 signal abnormality.
- SWI: may distinctly demonstrate multiple minute hypointense foci in the brain 12-13
- T1: corresponding focal regions may show low T1 signal 9
A differential to consider for the starfield pattern on MRI includes many other causes of multiple small foci of infarction or haemorrhage, although generally, only fat emboli will result in the very large number of tiny lesions characteristic of a starfield appearance. Other diagnoses to consider 6:
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