This patient had had hyponatremia and dehydration corrected recently. 

Osmotic demyelination syndrome was formerly known as central pontine myelinolysis.  It classically occurs when there is an increase in the serum sodium levels caused by rapid correction of hyponatremia as presented in this case.

The typical image characteristic of this lesion on MRI can be round, triangular, "bat wing"-shaped, or "trident"-shaped, which is hyperintense on T2WI/FLAIR and hypointense on T1WI, and demonstrates restricted diffusion.