Cortical reflex myoclonus responds to intravenous lisuride

Six patients with myoclonus were given 0.1-0.15 mg lisuride i.v. All patients had stimulus-sensitive myoclonus and an increased size of somatosensory evoked potentials, and in three there was electrophysiological evidence of a cortical event time-locked to the jerks. All subjects showed a considerable diminution of spontaneous, action- and stimulus-evoked jerking. Lisuride has potent central dopaminergic and serotonergic actions. Administration of the dopamine agonists levodopa or apomorphine had no effect on myoclonic jerking in any of the six patients. Detailed pharmacological analysis of the myoclonus in one patient showed that levodopa, apomorphine, and haloperidol had no effect, and that haloperidol did not prevent the therapeutic action of lisuride. 5-Hydroxytryptophan abolished the myoclonus, and methysergide prevented the beneficial effect of lisuride, although it did not alter spontaneous myoclonus. These observations suggest that lisuride improves some types of reflex, stimulus-sensitive cortical myoclonus by a serotonin agonist action.