← Radiology signsAsk Alera

Hot cross bun sign

NeuroMRI

A cruciform T2 hyperintensity in the pons, resembling the cross on a hot cross bun.

What it means

Selective degeneration of pontine transverse fibres, classically in multiple system atrophy.

Mechanism

Degeneration of the transverse pontocerebellar fibres and pontine raphe, with sparing of the corticospinal tracts, forms the cross of high signal.

Associated conditions

  • Multiple system atrophy (MSA-C)
  • Spinocerebellar ataxias
  • Other pontocerebellar degeneration
  • Rare paraneoplastic or acquired causes

Pearls

  • It is most characteristic of the cerebellar variant of multiple system atrophy.
  • Correlate with parkinsonism, autonomic failure and cerebellar signs.

References

  • Radiopaedia: Hot cross bun sign

For educational use only. This dictionary is a study aid and reference, not a diagnostic tool, and must not be used to guide clinical decisions or patient care. Imaging appearances vary; always correlate with the full clinical picture and confirm with a qualified radiologist.