Quantitative assessment of daytime motor activity provides a responsive measure of functional decline in patients with Huntington's disease

Voluntary motor impairment is a functionally important aspect of Huntington 's disease (HD). Therefore, quantitative assessment uf disturbed voluntary movement might be important in follow-up. We investigated the relation betw een quantitatively assessed daytime motor activity and symptom severity in HD and evaluated whether assessment of daytime motor activity is a responsi ve measure in the follow-up of patients. Sixty-four consecutive HD patients and 67 age- and sex-matched healthy cont rols were studied. Daytime motor activity was recorded using a wrist-worn a ctivity monitor that counts all movements during a period of five consecuti ve days. Patients were rated clinically for voluntary motor impairment, dys kinesias, posture & gait, depression, cognitive impairment and functional c apacity. Follow-up was available from 40 patients (mean follow-up 2.0 years ) and 29 controls (mean follow-up 5.9 years). Despite chorea, patients had less daytime motor activity than controls (P < 0.005). This hypokinesia correlated with impaired voluntary movements (r = 0.37; P < 0.01), disturbed posture & gait (r = 0.38; P < 0.005) and especi ally with reduced functional capacity (r = 0.51; P < 0.0005). During follow -up, hypokinesia remained unchanged in clinically stable patients, but beca me worse in those whose functional disability progressed (P < 0.005). Hypokinesia seems a core symptom of HD which is related to functional capac ity. Actimetric assessment of hypokinesia is responsive to disease progress ion and can be used as an objective tool for follow-up. (C) 2001 Movement D isorder Society.