A splenial lesion with transiently reduced diffusion in clinically mild encephalitis is not always reversible: A case report.

The MR imaging finding of a reversible splenial lesion with transiently reduced diffusion has been reported in patients with clinically mild encephalitis/encephalopathy, leading to a new clinical-radiological syndrome, clinically mild encephalitis/encephalopathy with a reversible splenial lesion. We recently experienced a 3-year-old boy with clinically mild encephalitis with a splenial lesion exhibiting transient reduced diffusion on admission. He recovered completely with no particular treatment within 2 weeks. Though the splenial lesion decreased in size, it was detected for over 5 months in T2-weighted imaging. It is suggested that a splenial lesion with transiently reduced diffusion in clinically mild encephalitis/encephalopathy is not always reversible, and could result in gliosis.