Enhanced associated movements in the contralateral limbs elicited by brisk voluntary contraction in choreic disorders.
To study the deficit of inhibition of excessive motor drive generated in the central nervous system in chorea. Identical associated movements in the contralateral limb elicited by rapid hand squeezing were measured in 6 patients with Huntington's disease, 7 patients with peak-dose dyskinesia, 10 patients with Parkinson's disease, 8 patients with spinocerebellar degeneration and in 8 normal subjects. The intensity of associated movements was assessed by the EMG amplitude ratio of associated contractions to active contractions. The associated movement ratios were larger in Huntington's disease and peak-dose dyskinesia as compared to other groups. The ratios in akinetic "off" phase were smaller than those in dyskinetic "on" phase in all peak-dose dyskinesia patients. Enhanced associated movements support a possible common mechanism that chorea may result from failure in inhibition of phasic neural activity pathologically generated in the brain.