Objective: To investigate the effects of repetitive transcranial magnetic stimulation (rTMS) on vocal function in Parkinson's disease (PD).
Material and methods: Two different sets of rTMS parameters were investigated on 30 patients with PD: active or sham 15 Hz rTMS of the left dorsolateral prefrontal cortex (LDLPFC) (110% of motor threshold (MT), 3000 pulses per session) and active 5 Hz rTMS of the primary motor cortex (M1)-mouth area (90% MT, 2250 pulses per session). A blind rater evaluated speech characteristics (acoustic and perceptual analysis of voice) and voice-related quality of life (V-RQOL).
Results: rTMS of LDLPFC resulted in mood amelioration and subjective improvement of the V-RQOL only (71.9% improvement, P < 0.001), but not in objective measures such as fundamental frequency (P = 0.86) and voice intensity (P = 0.99). On the other hand, rTMS of M1-mouth induced a significant improvement of the fundamental frequency (12.9% for men and 7.6% for women, P < 0.0001) and voice intensity (20.6%, P < 0.0001).
Conclusions: Our findings provide initial evidence that rTMS of the primary motor cortex might yield a beneficial effect on vocal function in PD.