A 45-year-old chronic alcoholic is treated aggressively for severe symptomatic hyponatremia with normal saline. Two days later he develops flaccid quadriparesis, dysarthria and altered sensorium. MRI shows symmetric central T2 hyperintensity within the basis pontis with sparing of the peripheral pontine fibers and corticospinal tracts. This appearance is called:

• A Hot cross bun sign
• B Face of the giant panda sign
• C Trident (piglet) sign ✓
• D Light bulb sign

Explanation

Osmotic demyelination (central pontine myelinolysis) follows overly rapid correction of hyponatremia. On axial T2 images the central pontine lesion spares the peripheral transverse pontine fibers and corticospinal tracts, producing a trident or piglet-shaped signal abnormality. The hot cross bun sign is seen in multiple system atrophy due to degeneration of transverse pontocerebellar fibers, a completely different entity.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.