Evoked motor response thresholds during transcranial magnetic stimulation in patients with symptomatic partial epilepsy.

Transcranial magnetic stimulation (TMS) occupies a leading position among noninvasive neurophysiological methods used for evaluating the balance of processes of cortical inhibition and excitation. The aim of the present work was to assess motor cortical excitability in symptomatic partial epilepsy using TMS in relation to the effects of antiepileptic treatment. A total of 31 patients were studied. A decrease in the motor response threshold was seen in a group consisting of untreated patients, with changes in cortical excitability during seizures. Treated patients showed no difference as compared with healthy subjects. The shorter the interval between a seizure and TMS, the smaller the evoked motor response threshold. The low threshold seen in patients with symptomatic partial epilepsy showed a significant correlation with clinical signs of neuromuscular excitability. The data obtained here provide evidence of changes in the functional state of the cortex and, thus, the motor response threshold, in patients with epilepsy.