Walnut kernel microbleed pattern

Last revised by Daniel J Bell on 29 Nov 2021

The walnut kernel microbleed pattern along with the starfield pattern and corpus callosum diffusion restriction appears to be the most important imaging markers of cerebral fat embolism 1-3.

In this pattern, there is a diffuse presence of round microbleeds (punctate focal hypointensities) of similar size in the subcortical white matter (involving but not limited to the U-fibers), internal capsule, and the corpus callosum on T2* GRE or, more sensitively, SWI/SWAN images 1. The corona radiata and the non-subcortical centrum semiovale are relatively spared 1. The diffuse involvement of white matter, including outlining the subcortical fibers, resembles a walnut kernel.

Differential diagnosis

Diffuse cerebral microbleeds have been reported in other cases mainly involving the critically ill, such as in patients receiving extracorporeal membrane oxygenation (ECMO), or in critically ill COVID-19 patients, but in these cases, the microhemorrhages appear to be more heterogeneous in size and distribution 4,5.

See also

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