Mild Encephalopathy With a Reversible Splenial Lesion Type II in a Probable Post-infectious SARS-CoV-2 Context: A Case Report

Mild encephalopathy with a reversible splenial lesion (MERS) is a clinico-radiological syndrome characterized by acute encephalopathy and a transient lesion in the splenium of the corpus callosum on magnetic resonance imaging (MRI). We report a case of a six-year-old girl who presented with behavioral disturbance and altered mental status after one week of a viral prodrome in the setting of household SARS-CoV-2 exposure. Cerebrospinal fluid analysis was unremarkable, and SARS-CoV-2 serology showed positive immunoglobulin G (IgG) and negative immunoglobulin M (IgM). Brain MRI demonstrated a focal splenial lesion with bilateral cerebellar involvement of the dentate nuclei, consistent with MERS type II. The patient initially received ceftriaxone and acyclovir for suspected encephalitis. Neurological deterioration with dysphagia led to treatment with intravenous methylprednisolone followed by intravenous immunoglobulin. Follow-up MRI at one month showed complete lesion resolution, and complete neurological recovery was achieved by three months. This case highlights the importance of recognizing this reversible clinico-radiological pattern in children with acute encephalopathy to facilitate diagnosis, guide management, and avoid unnecessary investigations.