Cytotoxic lesion of the corpus callosum

• Broad differential for etiology
• Can be related to seizures, ASMs, metabolic disturbances, infections, and other drugs besides ASMs
• Transient lesions of the splenium are only really appreciable on MRI where they have three distinct patterns: 
  1. well-circumscribed, small, oval lesions in the midline within the substance of the splenium (most common)
  2. more extensive less well-defined irregular lesions extending throughout the splenium and into the adjacent hemispheres (boomerang sign) 
  3. more extensive extension anteriorly into the body of the corpus callosum