Main differentials of any lesion with radiological similarities to this include central pontine infarct or central pontine myelinolysis. However it was felt that this was central pontine myelinolysis given:

• the relatively slow onset of her drowsiness
• the subsequent symptoms (including quadriparesis)
• large, well defined, rounded, symmetrical pontine lesion with sparing at the peripheries and the corticospinal tracts
• the presence and correction of hypokalemia preceding the events