CASE REPORT Widening Spectrum of a Reversible Splenial Lesion with Transiently Reduced Diffusion

SUMMARY: Four patients with encephalitis/encephalopathy and parenchymal lesions accompanying reversible splenial lesions were retrospectively evaluated. In 3 patients, reversible lesions with tran-siently reduced diffusion were seen in the splenium and symmetrically in the peripheral frontoparietal white matter, clinical signs and symptoms were mild, and recovery was complete. These and previous observations suggest a less severe course and outcome for patients with reversible lesions isolated to the splenium or to the splenium and peripheral frontoparietal white matter. An MR imaging finding of a reversible lesion in the centralportion of the splenium of the corpus callosum (SCC) without any accompanying lesions has been reported in pa-tients with epilepsy receiving antiepileptic drugs.1,2 Fifteen pa-tients with clinically mild encephalitis/encephalopathy with a reversible isolated SCC lesion (MERS) were recently reported, 7 of whom had no history of seizures or administration of antiepileptic drugs.3 All the patients withMERS hadmild clin-ical courses and recovered completely without any sequelae. Because the SCC lesion in the 2 conditions revealed transientl