Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS)
General description
Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a mild encephalitis/encephalopathy. Causative organisms are frequently unknown, however influenza virus or adenovirus are occasionally reported.
Clinical manifestation
Clinical manifestations include fever, vomiting, and headache, accompanied by neurological symptoms such as delirium or convulsions. Typically, these neurological symptoms manifest after a delay from the initial prodromal symptoms.
Corpus callosal lesion
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CerebrumCerebral white matter
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Middle cerebellar peduncle
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Corpus callosumSplenium
Typical imaging findings of MERS include diffusion restriction at the center of the splenium of the corpus callosum, without a contrast effect. This finding is transient and typically resolves within a few weeks without treatment.
In addition to the corpus callosum, diffusion restrictions are occasionally observed in the cerebral white matter, typically in the frontal lobe. The cerebellar peduncles may also be affected.