[Motor evoked potentials of transcranial magnetic stimulation for Parkinson's disease]

We studied motor evoked potential (MEP) elicited by transcranial magnetic stimulation (TMS) in 37 patients with Parkinson's disease (PD). TMS was used at high energy capacity (800 Volts) in all patients and normal subjects under resting position. MEPs were recorded from the abductor pollicis brevis and the abductor hallucis. Magnetic stimulator equipped with an 8-shaped coil and a flat type coil was used for TMS. The data were statistically evaluated using a paired Student t test. The latency of MEPs were slightly shorter in PD patients than that in normal subjects. There were significant differences between HV. (Healthy volunteers) and group B (Hoehn & Yahr's stage III) (p = 0.012), HV, and group C (Hoehn & Yahr's stage IV.V) (p = 0.002), group A (Hoehn & Yahr's stage I.II) and C (p = 0.005) respectively. The duration of MEPs became longer depending on the severity of PD evaluated by Hoehn & Yahr's disability rating. Significant correlations were found between HV, and group C (p = 0.001), group A and C (p = 0.015). The amplitude of MEPs also increased with the severity on the rating. There were significant differences between HV, and group C (p = 0.0002), group A and B (p = 0.0004), group B and C (p = 0.0009) respectively. These changes of MEP findings indicated the dysfunction of pyramidal motor pathways in PD. Thus, the disability in patients with PD can be well evaluated by MEP measurement.