Myoclonus in a case of suspected progressive rubella panencephalitis.

Predominantly unilateral myoclonus induced by movement of the affected parts in a 21-year-old Japanese man with suspected progressive rubella panencephalitis appeared in the course of treatment for epilepsy with anticonvulsant drugs after five years. Antirubella antibody levels in the serum and CSF were elevated and IgM antibody against rubella was found in the serum. An EEG recorded while the patient was awake showed diffuse 3- to 4-Hz theta activity with high voltage. The neurological symptoms are progressing slowly.