Unimanual and bimanual voluntary movement in Huntington's disease

Unimanual and bimanual cyclical forearm movements were studied in 15 Huntington's disease (HD) patients and 15 healthy, gender- and age-matched controls. Whereas the unimanual task was only performed at maximal speed, the bimanual movements were performed according to the in-phase and anti-phase mode at different cycling frequencies. The HD patients also performed the tasks after 12 months of follow-up. Findings revealed that maximal cycling frequency during unimanual movement was significantly lower in HD patients as compared with controls. In addition, measures of relative phasing established that bimanual cyclical movements were performed with lower accuracy and higher variability in HD patients. The differential variability between both groups was magnified by increasing the cycling frequency and coordinative complexity whereas only coordinative complexity differentially affected the accuracy of relative phasing. The obtained performance measures were found to be significantly correlated with disease duration (unimanual) and with the score on the total motor scale, the Mini-Mental State Examination and the Stroop Interference Test (uni- and bimanual). After 12 months, maximal cycling frequency of unimanual elbow flexion-extension was significantly decreased in HD patients whereas the quality of the in-phase and anti-phase movement patterns remained stable.