Mumps-induced opsoclonus-myoclonus and ataxia.

A 9-year-old boy manifested acute cerebellar ataxia associated with mumps infection. He developed opsoclonus, myoclonus, tremor, and truncal ataxia 7 days after mumps infection. Lumbar puncture revealed pleocytosis without elevation of protein; ELISA demonstrated an increased IgM titer of cerebrospinal fluid against mumps virus. From these results it was determined that acute cerebellar ataxia was induced by a direct invasion of mumps virus. Electroencephalography demonstrated normal background activity, although alpha-like activity appeared bilaterally in the frontal regions which was induced by eye closure and decreased by eye opening. Polygraphic electroencephalography revealed that the alpha-like activity corresponded to the ocular movement recorded above or lateral to the eyelids by electro-oculography; therefore, the alpha-like activity was considered to be derived from the opsoclonus which was secondary to cerebellar involvement. His neurologic symptoms improved gradually and resolved completely within 3 months after the onset of acute cerebellar ataxia.