Bilateral impairments of skilled reach-to-eat in early Parkinson's disease patients presenting with unilateral or asymmetrical symptoms

Abstract

Previous studies have described limb and hand movement abnormalities in a reach-to-eat task in advanced Parkinson's disease (PD) and animal models of PD. The present study was directed toward examining reach-to-eat movements in early PD patients untreated with medication, along with a follow-up examination of a PD patient sub-group who were treated with a symptomatically stable dosage of dopamine replacement. Analysis of the reach-to-eat movement was made using blinded assessment under a validated scoring system, and comparisons were made on the total reach score and reach sub-component scores. In both examinations, PD patients had unilateral deficits or significant deficit asymmetry, as indicated by Unified Parkinson's Disease Rating Scale (UPDRS) scores. UPDRS motor scores were higher for the most-affected side of the body (mean scores of 10.45 and 4.25 for more- and less-affected upper limbs, respectively), whereas reach scores were equivalently impaired for the two sides (median scores of 12.35 and 12.56 for more- and less-affected limbs, respectively). These differences between clinical and experimental assessments of motor impairments persisted among early PD patients treated with medication. Thus, functional reaching shows bilateral and symmetrical abnormalities in early PD patients, even when clinical assessment shows asymmetrical or even unilateral impairment. These findings suggest that functional qualitative reaching evaluation is a sensitive test in early PD, and that significant bilateral abnormalities in reach function are present even in pre-clinical stages of the disease.