Section Editor: Sandy Cheng-Yu Chen, M.D.
Taipei Medical University Hospital, Taipei, Taiwan
Figure Caption
Osmotic demyelination syndrome refers to acute demyelination caused by rapid shifts in the serum osmotic gradient, often caused by iatrogenic correction of hyponatremia, as in this case. Patients with alcoholism or malnourishment are particularly vulnerable. Classic extrapontine imaging features include well-demarcated, bilateral and symmetric T2 signal hyperintensity of the deep grey nuclei, most commonly the basal ganglion and, less frequently, the thalami (A, arrows). Classic pontine imaging features include symmetric T2 signal hyperintensity within the pons, which may be depicted as a trident configuration or, as in this case, a pathognomonic “pig snout” sign (B, arrows). Signal abnormality spares the corticospinal tracts (B, blue arrows) and peripheral pons. Extrapontine myelinolysis may occur with or without central pontine myelinolysis.