Incoordination of a sequential motor task in Parkinson's disease

Abstract

The quality of life in persons with Parkinson's disease (PD) has increased significantly with improved medicines. However, as the disease progresses difficulty in performing activities of daily life occur and occupational therapy intervention is sought (Deane et al., 2001). Reviews describing the efficacy of occupational therapy intervention in PD are inconclusive (Murphy and Tickle-Degnen, 2001; Gaudet, 2002). The purpose of this study is to establish an occupational therapy protocol for PD based upon research on motor control, sensory feedback and bradykinesia. As a first stage, the present study investigated the contribution of sensory feedback in generating the most prevalent symptoms of PD, that is, bradykinesia. Fast reach-to-grasp movement without kinesthetic or visual dependence in PD patients under on-drug and off-drug conditions were investigated. Seven normal participants and 11 patients with PD voluntarily participated in the study. Movements of the upper arm as a measure of reach, and movements of the index finger as a measure of grasp were recorded using magnetic trackers. Compared to the normal participants, this index to upper arm movement relationship was severely disturbed in the patients with PD and was improved following medications. Inter-onset latency (IOL), that is, the time lag between the initiation of upper arm movement and index movement, was significantly longer in PD patients compared to normal subjects. Medications reduced IOL which lead to improvement of the relationship of upper arm and index. The results suggest that bradykinesia is due to the breakdown of co-ordination between joint movements as a result of presumably slow executive processing of motor programmes. Individual joint movements are initiated out of sequence resulting in uncoordinated movements even with antiparkinsonian drugs. It is suggested that occupational therapy intervention in PD patients should be directed to occupations that require co-ordination of joint movements essential for successful completion of various activities of daily living tasks. Copyright © 2005 John Wiley and Sons, Ltd.