Motor responses to afferent stimulation in juvenile myoclonic epilepsy.

PURPOSE: To document whether the mechanisms responsible for myoclonic jerks in juvenile myoclonic epilepsy (JME) are similar to those causing other forms of myoclonus. METHODS: We studied somatosensory evoked potentials, the conditioning effect of cutaneous afferents on motor potentials evoked by transcranial magnetic stimulation (TMS), and intracortical inhibition and facilitation in response to paired TMS in a group of nine patients with JME and 20 normal controls. RESULTS: Intracortical inhibition was abnormal, whereas cortical somatosensory evoked potentials and TMS conditioned by cutaneous afferents were unaltered in JME patients. CONCLUSIONS: Abnormal processing of cutaneous afferents would not appear to contribute to myoclonus in JME.