Clinical Variability of Pediatric MERS: Insights from a Retrospective Observational Study

Background/Objectives: Mild encephalitis/encephalopathy with reversible splenial lesion (MERS) is a rare neurological disorder primarily affecting pediatric patients but also observed in adults. The radiological hallmark of MERS is a reversible lesion in the splenium of the corpus callosum. Although MERS generally has a favorable prognosis, its variable presentation poses diagnostic challenges. This study examines the clinical variability, diagnostic hurdles, and outcomes of pediatric MERS cases. Methods: Our retrospective study included 19 pediatric patients (11 female and 8 males with an average age of 8.41 years) diagnosed with MERS between 2016 and 2024. Clinical data, including demographic characteristics, prodromal symptoms, neurological features, MRI findings, laboratory results, treatments, and outcomes, were analyzed. Results: Among the 19 patients, 84% were previously healthy, with the remaining 16% having pre-existing medical conditions. The most common prodromal symptoms were fever (68%), vomiting (47%), and diarrhea (32%). Neurological manifestations included seizures (26%), headache (21%), and drowsiness (21%), among others. In terms of etiology, infections were identified in 52% of the patients, with viral agents, particularly rotavirus, being the most common (40%). Hyponatremia was present in 63% of the cohort. The typical MRI splenial lesion underwent complete resolution in all patients. Treatment varied, with 53% of patients receiving electrolyte rehydration, and 21% receiving intravenous immunoglobulin or corticosteroids. All patients, but one, achieved full recovery. Discussion: This study reinforces the clinical heterogeneity of MERS in pediatric patients, emphasizing its favorable prognosis independently of presentation. Viral infections and hyponatremia were the most frequent etiologies.