Control of multijoint arm movements in Huntington's Disease

Multijoint arm movements of individuals with Huntington's disease (HD) were exam ined using three-dimensional kinematic analysis. Six HD patients with chorea and four healthy subjects performed pointing movements to a 2.5 cm target positioned at three distances in the sagittal plane, two of which required trunk motion. Healthy subjects moved in relatively straight hand paths to the targets. All HD patients produced curved hand paths, in which they brought their hand first upward and then outward to the target. Healthy subjects made single smooth movements, while HD patients made large initial movements followed by multiple submovements as the hand honed in on the target. Lower functioning HD patients had particular difficulty moving to the farthest target, which required the greatest amount of trunk motion. Although the HD patients had longer movement times across all conditions, their initial velocity was often sim ilar to that of the healthy subjects. This suggests that bradykinesia is related to the pro duction of submovements, rather than a deficit in initial force production. The pres ence of submovements in Huntington's disease might reflect a deficit in controlling deceleration of the limb or an adaptive strategy to maximize accuracy