Two patients developed central pontine signal changes on magnetic resonance imaging (MRI), one after heart transplantation and one during the puerperium. In one, no lesion was found in the pons at necropsy. The other recovered clinically and the MRI lesion resolved completely. These cases raise the possibility that rapid electrolyte and biochemical perturbations can give rise to transient edema in the central pons. If more severe or chronic, the edema may cause permanent myelin damage, so‐called myelinolysis.