Transcranial magnetic stimulation in patients with epilepsy.

We studied the effects of transcranial magnetic stimulation (TMS) applied in trains of 8- to 25-Hz stimuli on electroencephalographic epileptiform activity on eight patients being evaluated for epilepsy surgery. We performed the stimulation with a round water-cooled stimulation coil held flat on the scalp and centered over different positions of the International 10-20 System. We were unable to trigger seizures or induce epileptiform discharges arising from the epileptic focus in any of the eight patients with any of the stimulation protocols. However, we induced a partial motor seizure from the contralateral hemisphere to the exclusive temporal focus in the only patient stimulated with 100% maximal intensity. Precautions have to be taken when applying rapid TMS to patients because of the risk of seizure induction. Our results do not support the view that TMS specifically activates the epileptic foci.