The Vanishing Act: Reversible Splenial Lesion Syndrome (RESLES) in a Case of Mild Encephalitis with Isolated Splenium of Corpus Callosum Involvement; A Case Report

Abstract

Reversible isolated lesions characterized by transient restricted diffusion in the splenium of the corpus callosum (SCC) have been linked to a variety of diseases and clinical situations, with a notable occurrence among patients presenting with encephalitis, encephalopathy, and those undergoing treatment with antiepileptic drugs (AED). This fascinating radiological phenomenon has been recognized as a unique clinical and radiological condition known as "Reversible Splenial Lesion Syndrome (RESLES)." In this report, we describe a case involving a 24-year-old male who came with a one-week history of high fever and headache. The initial MRI with contrast showed an area of restricted diffusion in the splenium of the corpus callosum, lacking post-contrast enhancement, which was interpreted as an infarct. A follow-up CT carotid angiography conducted two days later identified subtle hypodensity within the SCC, corresponding to the previously noted restricted diffusion on MRI. A subsequent MRI done one month later revealed changes of encephalitis in the bifrontal parasagittal cortices. Notably, no abnormal signals were detected within the splenium of the corpus callosum, indicating a transient nature of this particular lesion. This case highlights the variability of reversible splenial lesions with restricted diffusion that can present across a spectrum of diseases and conditions.