[Mumps encephalitis in adulthood].

Mumps virus is one of the most common causes of viral meningitis. Although brain involvement has been observed in a low proportion of children with mumps meningitis, a pure form of mumps encephalitis is extremely uncommon in the adult. A 23 year-old man presented with a rapidly evolving syndrome of cephalalgia , vomiting, mutism, disorders of gait, somnolence and dystonic movements. The electroencephalogram showed a diffusely slowed background activity. The CSF contained no cells, but the total protein concentration was elevated. The patient recovered without sequelae, but severe intellectual and motor disturbances persisted during more than a month. Serological studies showed an increase of blood IgM mumps-specific antibodies. We conclude that mumps encephalitis, although infrequent, should be considered among viral diseases that mimic herpes simplex encephalitis in the adulthood.