Enhanced associated movements in the contralateral limbs elicited by brisk voluntary contraction in choreic disorders

Objectives: To study the deficit of inhibition of excessive motor drive generated in the central nervous system in chorea. Methods: Identical associated movements in the contralateral limb elicited by rapid hand squeezing were measured in 6 patients with Huntingtonʹs disease, 7 patients with peak-dose dyskinesia, 10 patients with Parkinsonʹs 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. Results: The associated movement ratios were larger in Huntingtonʹs 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. Conclusions: 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.