Clinical and MRI features of mild encephalitis/encephalopathy with a reversible splenial lesion in children

Objective: To investigate the clinical and MRI features of mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) in children. Methods: The clinical data and MRI findings of 14 children (6 boys, 8 girls; age range: 7 months-11 years and 8 months; median age: 2.5 years) with MERS type I (12) and type II (2) were retrospectively analyzed. The initial MRI was performed 1-7 days (average: 4.3 days) from the onset of illness and follow-up MRI was 7-45 days (average: 14.2 days) later. Results: MERS type I lesions involved only the splenium of corpus callosum whereas MERS type II lesions extended from the splenium to the genu of corpus callosum (1) and centrum semiovale (1). All 14 splenium lesions were round or oval with well-defined boundary, T₁ isointense or slightly hypointense, slightly T₂ hyperintense with reduced diffusion and no edema or mass effect. The lesions completely resolved in all patients on follow-up MRI. Conclusion: MRI of MERS is characterized by the reversible splenial lesion and follow-up MRI is valuable in its diagnosis. (authors)