Dysfunction of the basal ganglia-thalamocortical motor circuit is a fundamental model to account for motor symptoms in Parkinson's disease (PD). Using high-frequency repetitive transcranial magnetic stimulation (rTMS) over the supplementary motor area (SMA), we investigated whether modulation of SMA excitability engenders therapeutic effects on motor symptoms in PD. In this double-blind placebo-controlled study, 99 patients were enrolled and assigned randomly to SMA-stimulation and sham-stimulation groups. For SMA stimulation, 20 trains of 50 transcranial magnetic stimuli at 5 Hz were delivered at an intensity of 110% active motor threshold for leg muscles in one session. The sham stimulation was 20 trains of electric stimuli given through electrodes fixed on the head to mimic the cutaneous sensation during rTMS. Each session of intervention was carried out once a week for the first 8 weeks. The SMA stimulation, in contrast to the sham stimulation, engendered significant improvements in total scores and motor scores of the Unified Parkinson's Disease Rating Scale. Mean improvements in motor scores were 4.5 points in the SMA-stimulation group and -0.1 points in the sham-stimulation group. Results indicate that 5 Hz rTMS over SMA modestly improves motor symptoms in PD patients; SMA is a potential stimulation site for PD treatment.
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