[A case of familial myoclonus showing extremely benign clinical course].

We report a patient with familial myoclonus showing an extremely benign clinical course. The patient was a 70-year-old woman, who first noticed shaking of hands at age of 25. The symptom did not worsen for more than 40 years. She visited our hospital at the age of 70 because of disturbance in chores because of worsening of her hand shaking in the past one year. A family history showed that 4 members had similar symptoms and that the two were afflicted with fits of loss of consciousness. On neurologic examination, rhythmic myoclonic jerks were noted in all the extremities, more in the upper limbs, both at rest and during action. Tandem gait was mildly disturbed. The remainings of neurologic examination were normal. SEP and jerk-locked back averaging provided evidence of cortical myoclonus. EEG showed multifocal polyspike discharges. Gene analysis for DRPLA, pyruvate and lactate levels in serum and the cerebrospinal fluid, serum amino acid levels, and CSF HVA and 5-HIAA levels were all normal. No brain atrophy was noted in cranial MRI. Myoclonus was markedly reduced after administration of clonazepam. The clinical features and electrophysiological data of our patient are consistent with the clinical diagnosis of familial essential myoclonus and epilepsy/benign adult familial myoclonic epilepsy.