Repetitive transcranial magnetic stimulation causes a short-term increase in the duration of the cortical silent period in patients with Parkinson's disease

In ten patients with Parkinson's disease (PD) and ten age-matched healthy c ontrols, we applied 15 30-s trains of subthreshold 5-Hz repetitive transcra nial magnetic stimulation (rTMS) over the primary motor hand area. Ten minu tes after rTMS, PD patients showed a significant prolongation of the transc ranially evoked silent period (SP) in the contralateral first dorsal intero sseus muscle, whereas the SP remained unchanged in healthy subjects. Since the duration of the transcranially evoked SP is a well-established measure of intracortical inhibition, this finding demonstrates that rTMS is capable of inducing a short-term increase in intracortical inhibition in PD. The l ack of a prolongation of the SP in healthy controls suggests that PD patien ts may be particularly susceptible to modulatory effects of rTMS on motorco rtical inhibition. (C) 2000 Elsevier Science Ireland Ltd. All rights reserv ed.