Mild Encephalopathy With Reversible Splenium Lesion in Pediatric Patients: A Case Series

11/09/2026

AI Summary

Mild encephalopathy with reversible splenium lesion on MRI predominantly affects children, presenting as MERS type 1 (splenium only) or type 2 (white matter involvement).
Viral aetiologies predominate in paediatric MERS; identified pathogens in this series included rotavirus, influenza A and human herpesvirus 6.
Early MRI is essential for unexplained acute encephalopathy; MYRF genetic testing should be reserved for selected patients with extensive white matter involvement.

Pediatr Infect Dis J. 2026 Sep 11. doi: 10.1097/INF.0000000000005398. Online ahead of print.

ABSTRACT

BACKGROUND: Mild encephalopathy with reversible splenium lesion (MERS) is a clinical-radiologic entity characterized by a reversible lesion in the splenium of the corpus callosum, visible on magnetic resonance imaging (MRI) imaging, predominantly affecting children. Despite the unclear pathogenesis, some etiologies have been identified, with viral infections being the most common cause in children. Moreover, a minority of patients carry a genetic variant in the MYRF gene, which has been associated with reversible myelin vacuolization.

METHODS: Here we present 4 cases of pediatric MERS (age 2-10 years) admitted to Niguarda Hospital, Milan, Italy, in a time span of 13 months between December 2023 and January 2025.

RESULTS: Three patients exhibited MRI findings consistent with MERS type 1, involving only the splenial corpus callosum. The other one had a more severe clinical presentation, with stroke-like symptoms and a MERS type 2 MRI presentation, involving the white matter as well. In all of them, a viral etiology was identified (rotavirus, influenza A virus, human herpetic virus [HHV6]).

CONCLUSIONS: We support the importance of early MRI in acute unexplained encephalopathy and suggest that genetic testing for MYRF variants should be reserved for selected cases with extensive white matter involvement.

PMID:42723070 | DOI:10.1097/INF.0000000000005398

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