Essential familial myoclonus.

From a family with essential familial myoclonus, 150 members in eight generations were studied. Twenty-five of them suffered from myoclonus of varying severity. The findings in routine examinations of blood, urine and cerebrospinal fluid, EEG and skull radiographs were normal. Therapeutic trials did not produce lasting satisfactory results. The most promising results were obtained with 5-hydroxytryptophan therapy. Haloperidol worsened the symptoms, while alcohol produced a striking improvement. It is suggested that serotoninergic neurons in the brain could be involved in the triggering of essential myoclonus.