A detailed analysis of the planning and execution of prehension movements by three adolescents with spastic hemiparesis due to cerebral palsy.

Assuming that primary symptoms of motor disorders can best be distinguished from signs of adaptation through behavioral analyses on an individual basis, the present study provides a detailed analysis of the prehension movements of three adolescents with mild spastic hemiparesis of different etiology. We investigated the extent to which the hemiparetic participants took their movement limitations into account when planning and performing sequences of prehension movements. We examined three indices of flexibility in grip planning in conjunction with an analysis of arm-joint coordination patterns as the movements unfolded. Participants were asked to repeatedly grasp a square object of which the position was gradually changed leftwards or rightwards. In half the trials the goal of the task was to lift the object, in the other half it had to be rotated back-and-forth. Trunk, arm, and hand movements were recorded with two synchronized 3-D motion-tracking systems. The movements of the hemiparetic participants were compared with the average performance of 11 control participants of which the collective data were taken to represent a typical control participant. Whereas one hemiparetic participant (GV) maintained a single grasping pattern throughout the experiment, the other two (CV and LC) only partially persevered in previously adopted grasping patterns. The shoulder contributed more and the wrist contributed less to this perseverance. No effects of task goal were found on grip selection. However, two hemiparetic participants (CV and LC) did tune their hand displacement to the task that followed the grasps. Taken collectively, the results show that the hemiparetic participants took their limitations into account when performing movements, but not when planning movements.