Walnut kernel microbleed pattern

Last revised by Daniel J Bell on 29 Nov 2021

Citation, DOI, disclosures and article data

Citation:

Giyab O, Bell D, Bickle I, et al. Walnut kernel microbleed pattern. Reference article, Radiopaedia.org (Accessed on 18 Apr 2024) https://radiopaedia.org/articles/88315

DOI:

Permalink:

https://radiopaedia.org/articles/88315

rID:

88315

Article created:

3 Apr 2021, Omar Giyab

Disclosures:

At the time the article was created Omar Giyab had no recorded disclosures.

View Omar Giyab's current disclosures

Last revised:

29 Nov 2021, Daniel J Bell ◉

Disclosures:

At the time the article was last revised Daniel J Bell had no recorded disclosures.

View Daniel J Bell's current disclosures

Revisions:

8 times, by 6 contributors - see full revision history and disclosures

Systems:

Vascular, Central Nervous System

Sections:

Signs

Tags:

cerebral fat embolism, fat embolism syndrome

Synonyms:

Walnut kernel pattern (cerebral fat embolism)

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.