Is a reversible splenial lesion a sign of encephalopathy?

A reversible splenial lesion of the corpus callosum has been recognized in patients with mild encephalitis/encephalopathy associated with various infectious diseases. All reported cases of encephalitis/encephalopathy, by definition, present with neurologic signs, many of which involve seizures or mildly altered states of consciousness, such as drowsiness. We report an 8-year-old boy with influenza A infection not associated with neurologic signs, whose brain magnetic resonance images incidentally revealed a reversible splenial lesion in the corpus callosum. This case indicates that a transient splenial lesion in the corpus callosum may occur during a febrile illness, without neurologic manifestations. Therefore, physicians should not diagnose or treat a patient as encephalopathic merely because of the presence of a splenial lesion on magnetic resonance imaging.