Effects of low-frequency repetitive transcranial magnetic stimulation in Parkinson's disease

Objective: The therapeutic effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) were investigated in Parkinson's disease with cognitive dysfunction known as impaired set switching. Methods: Six patients with Parkinson's disease exhibiting impaired performances on the Wisconsin card sorting test (WCST) were enrolled. Under electroencephalogram (EEG) monitoring, rTMS was performed using a concave circular coil once a week for three months. A 0.2-Hz rTMS was applied over the frontal region (Fz) at an intensity of 1.2 x the motor threshold of the abductor pollicis brevis (APB) for a total of 100 stimuli per session. The Trail Making Test part B (TMT-B), WCST, Wechsler Adult Intelligence Scale Revised (WAIS-R), Self-rating Depression Scale (SDS), Functional Independence Measure (FIM), and 20 m Walk time were evaluated before and after rTMS. Subjective symptoms and objective findings were also evaluated. Results: Significant improvements in the TMT-B and WCST scores after rTMS were observed for all six patients. In addition, the subjective symptoms and objective findings also improved. The 20 m walk time decreased significantly in all four subjects after rTMS. The SDS scores improved in four of the five subjects, although the differences between the baseline and follow-up scores were not significant. No significant improvements in the WAIS-R, FIM scores were observed. Conclusions: Low-frequency suprathreshold rTMS applied over bilateral prefrontal areas alleviated impaired set switching in Parkinson's disease. These results suggest that rTMS can affect the functional recovery of the frontostriatal circuit.