Reverse hot cross bun sign

Case contributed by Sze Yuen Lee

Presentation

Underlying diabetes and hypertension. Worsening left-sided hearing loss for 6 months, associated with tinnitus.

Patient Data

Age: 70 years
Gender: Female
mri

T2W/FLAIR hyperintensities in the mid pons (mildly hypointense on T1W) with cruciform hypointensities giving rise to reverse ‘hot cross bun’ sign. No restricted diffusion on DWI/ADC.

Fazekas grade 2 white matter hyperintensities in both cerebral hemispheres.

No mass seen in bilateral cerebellopontine angles.

Annotated image

Axial T2W image showing the reverse hot cross bun sign (arrow) in the pons

Case Discussion

The hot cross bun sign in the pons is usually associated with multiple system atrophy (MSA), however may also be seen in various neurodegenerative diseases. The appearance is attributed to the cruciform-shaped T2 hyperintensity due to degeneration of the transverse pontocerebellar tracts and median pontine raphe nuclei, forming the shape of a hot cross bun.

The reverse hot cross bun sign on the other hand is due to hyperintensities within the pons with cruciform hypointensity, also forming the shape of a hot cross bun and is best seen on T2/FLAIR images. It is a rare finding and has so far been described in a case of pontine infarcts 1, Wilson disease 2 and primary progressive aphasia 3

In this patient, the reverse hot cross bun sign in the pons was an incidental findings on MRI scan done to rule out a cerebellopontine tumor due to unilateral hearing loss, and is likely due to bilateral pontine infarcts.

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