Pulsed magnetic stimulation and F waves in Parkinson's disease

Twenty-two patients with Parkinson's disease with predominantly unilateral signs in the upper extremities were studied by means of transcranial magnetic stimulation. The mean central motor conduction time (CMCT) on the clinically affected side determined by F wave technique was significantly shorter (p < .01) than that of the other side at rest. However, the mean CMCT during slight voluntary contraction was not significantly different in the two sides. Amplitudes of motor evoked potentials and F waves tended to be higher on the clinically affected side than on the other side. We conclude that reduced CMCT and high F wave amplitudes reflect hyperexcitability of the anterior horn cells in patients with Parkinson's disease.