TRANSCRANIAL MAGNETIC STIMULATION IN PARTIAL EPILEPSY - DRUG-INDUCED CHANGES OF MOTOR EXCITABILITY

Single-pulse transcranial magnetic stimulation (s-TMS) with recording of motor evoked potentials (MEPs) from thenar muscles of both hands wa s performed on 84 patients with cryptogenic partial epilepsy and 50 he althy controls. We analyzed the cortical latency (CL), central conduct ion time (CCT), and threshold intensity (TI) required to elicit limina l. MEPs at rest. In the patients,CL and CCT were normal, but TI was si gnificantly higher than in the controls. Of the 84 patients, 65 were t aking one or more antiepileptic drugs and 19 were untreated. The untre ated patients had a significantly lower TI than the treated patients. In the treated patients, the TI increase paralleled the number of drug s taken. Additionally, in 2 subgroups of patients undergoing major mod ifications of antiepileptic treatment, TI dropped after partial withdr awl of medication and increased following the commencement of therapy. The results suggest that anticonvulsants depress the excitability of human motor pathways in epileptic subjects.