Contra-Lateral Unintended Upper Arm Movement during Unimanual Tasks in Children with Cerebral Palsy

PURPOSE: To characterize associated reactions (ARs) in the contralateral arm across multiple muscles during unimanual tasks and to identify factors related to ARs in children with cerebral palsy (CP). MATERIALS AND METHODS: This was a prospective, cross-sectional study of 35 children with CP. The extent of ARs of the contra-lateral, non-task hand was assessed while performing three unimanual tasks (opening and clenching the fist, a finger opposition task, and tapping fingers). The occurrence of ARs in each trial was evaluated separately for each task using a four-point scale (total scores ranged from 0 to 12). Surface electromyography (SEMG) was used to measure the firing activity of the muscles of the opposite arm during the task. The Manual Ability Classification System and Melbourne Assessment 2 (MA-2) were used to evaluate upper limb function. RESULTS: AR scores were higher in the more-affected limb than in the less-affected limb. SEMG data on the non-task hand showed motor overflow up to the elbow muscles in the more-affected limb. Root mean square ratios of EMG signals were significantly higher in children with ARs than in children without ARs. Multiple regression analysis showed both age and MA-2 to be significant factors related to ARs in the more-affected limb. CONCLUSION: Children with visible ARs showed motor overflow in the non-task limb during unimanual hand tasks. Age and upper limb function were significantly related to the extent of ARs in the more-affected limb of children with CP.