Transcranial Magnetic Stimulation in Parkinson's disease

Lee, Dae Hie; Park, Kun Woo; Park, Min Kyu; Choi, Jae Cheol

Abstract

BACKGROUND: Parkinson's disease (PD) is one of the most common movement disorders, yet the pathophysiology of its signs is not clear. A transcranial magnetic stimulation (TMS) was used to measure the amplitude and latency of the motor evoked potential(MEP) by stimulation of the corticomotoneuronal descending system. By means of this simple and nontraumatic technique we intended to analyze the abnormal motor signs of PD.
METHODS
We studied 20 PD patients aged 35 to 78 years and 12 normal persons aged 37 to 67 years. Hoehn-Yahr scale of PD patients were as follows: I, 4 patients ; II ,11 patients ; III, 4 patients ; IV, 1 patient. The responses were was recorded from abductor polli-cis brevis (APB) muscles and abductor hallucis (AH) muscles. The TMS was performed on the cervical spine and ver-tex for APB muscle and on the lumbar spine and C3 or C4 for bilateral AH muscles. The responses were recorded with both target muscles relaxed and slightly contracted. We measured the threshold, latency, and amplitude of each MEP. The central motor conduction time (CMCT) was calculated by the latency difference between cortical stimulation and cervical or lumbar stimulation.
RESULTS
The central motor conduction times were shorter in PD patients (P < 0.05) compared with normal subjects but there were no differences in motor evoked potentials. Also, PD patients showed a significant increase of stimulation threshold in the facilitation state.
CONCLUSIONS
These results may suggest that con-trol of excitability of the motor system is abnormal in PD patients.