Low-frequency repetitive transcranial magnetic stimulation for dyskinesia and motor performance in Parkinson's disease

Dyskinesias are one of the most frequent and disabling complications of the long-term treatment of Parkinson's disease (PD). Although the cause is not completely understood, it appears that an imbalance between excitatory and inhibitory inputs from the basal ganglia to the motor cortex leads to overactivation of motor and premotor areas. Overactivation of the supplementary motor area (SMA) has been observed in neuroimaging studies in dyskinetic PD patients. We investigated the effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) of the SMA on levodopa-induced dyskinesias (LID) and motor performance in PD. We tested whether longer duration (10 days) and higher number of total pulses (1800 pulses) would enhance the beneficial effect. Seventeen dyskinetic PD patients were randomly assigned to real rTMS or sham (placebo) rTMS, and 1 Hz rTMS or sham rTMS was applied over the SMA for 10 consecutive days. Patients were assessed at baseline and 1 day after the last rTMS with a levodopa challenge test, and video recordings were taken. Dyskinesias and motor performance were rated off-line by two blinded raters using video recordings. After 10 days of treatment with rTMS, we observed that 1 Hz rTMS delivered over the SMA had decreased LID lasting for 24 hours without a change in motor performance, whereas sham rTMS induced no significant change in dyskinesia scores. These results support a possible therapeutic effect of low-frequency rTMS in LID. However, in order to suggest rTMS as an effective treatment, long-term observations and further investigations with a larger patient population are essential.