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

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.

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.

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.

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.