# Mild Encephalitis/Encephalopathy With a Reversible Splenial Lesion (MERS) Type II in an Adult: A Case Report and Diagnostic Insight

## TL;DR

This paper reports a rare case of MERS in an adult, emphasizing its importance in diagnosing encephalopathy due to its good recovery and similarity to more severe conditions.

## Contribution

The novelty lies in presenting an adult case of MERS, which is typically seen in children, and highlighting its diagnostic significance.

## Key findings

- MRI showed a diffusion-restricting splenial lesion, a key diagnostic feature of MERS.
- Clinical symptoms and radiological abnormalities resolved completely, confirming the diagnosis.
- MERS should be considered in adult encephalopathy due to its good prognosis and mimicry of severe conditions.

## Abstract

Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a rare clinico-radiological syndrome characterized by transient lesions in the splenium of the corpus callosum on magnetic resonance imaging (MRI). Although increasingly recognized in pediatric populations, MERS remains underdiagnosed in adults. We report a case of adult-onset MERS that presented with nonspecific neurological symptoms following a respiratory prodrome. Brain MRI demonstrated the characteristic diffusion-restricting splenial lesion, which guided the diagnostic approach. The rapid and complete resolution of both clinical symptoms and radiological abnormalities confirmed the diagnosis. This case highlights the importance of including MERS in the differential diagnosis of adult encephalopathy, particularly due to its excellent prognosis and potential to mimic more serious neurological conditions.