The effect of frontoparietal lesions on stability and tremor in the finger.

Assessment of stability and tremor in the fingers in patients with unilateral frontoparietal lesions involved the task of attempting to keep the finger still on a typewriter key connected to a strain gauge. In patients with no or minimal pyramidal motor signs and/or cortical sensory signs, the amplitudes of tremor compared with normal controls showed that the contralateral side was not significantly different from normal but that the ipsilateral side was significantly less stable than normal. In normal subjects the tremor seen during the task, and determined from the fast Fourier transform, (FFT), showed a peak at 1-3Hz and a gradual falling off to background levels by 6Hz or so. In patients with spasticity, weakness and sensory impairment there was an additional peak of tremor seen at 6-7Hz ipsilateral to the cerebral lesion.