Case Analysis of Mild Encephalitis/Encephalopathy with a Reversible Splenial Lesion (MERS-II)

Abstract: This report describes a case of a seven-year-10-month-old female patient presenting with convulsions, episodic aphasia, movement disorders, and neuropsychiatric disturbances. Cranial magnetic resonance imaging (MRI) supported a diagnosis of mild encephalitis/encephalopathy with a reversible splenial lesion, Type Ⅱ (MERS). MRI demonstrated symmetrical signal intensity abnormalities with restricted diffusion involving the splenium and genu of the corpus callosum, as well as portions of the cerebral white matter, consistent with MERS Type Ⅱ. A follow-up MRI performed 10 days post-treatment revealed near-complete resolution of the lesions, highlighting their characteristic rapid reversibility. A review of the relevant literature is included, addressing the etiology, pathogenesis, and classification of MERS. This case analysis indicates that MERS Type Ⅱ is clinically uncommon and may be associated with more severe clinical manifestations, potentially related to infection, metabolic derangements, or genetic predispositions, and requires differentiation from acute cerebrovascular infarction (stroke). The prognosis is generally favorable with appropriate supportive and symptomatic management.