Deviations in upper-limb function of the less-affected side in congenital hemiparesis

In the present study we examined upper-limb function of the less-affected side in young adolescents with congenital hemiparesis (cerebral palsy: CP). Five participants with hemiparetic CP and five control participants performed a cyclical reach-and-grasp task with the less-affected hand towards targets placed at 60%, 100%, and 140% of the participant's arm-length. Trunk involvement, end-effector kinematics and activation of the biceps and triceps were examined together with several clinical measures. Movements at the less-affected side were slower and peak velocity was reached later in the experimental group. Even though total trunk involvement was identical in both groups, it was selectively limited to forward bending in participants with CP. Elbow amplitudes of these participants were smaller for the 60% and 100% arm-length target distances. Additionally, participants with CP showed weak positive correlations between agonist (triceps) activity and elbow amplitude, suggesting that deficient agonist rather than antagonist innervation was responsible for the decreased elbow involvement. Especially the more severely affected participants with CP proved to compensate their relatively small elbow amplitudes by increased forward bending. Collectively, the findings demonstrate deviations in upper-limb control of the less-affected body side in congenital hemiparesis.