THE EFFECT OF UNILATERAL POSTEROVENTRAL PALLIDOTOMY ON THE KINEMATICSOF THE REACH TO GRASP MOVEMENT

Objective-to assess postoperative effects of unilateral posteroventral pallidotomy on the organisation of upper limb movement. Methods-A thr ee dimensional kinematic system (ELITE, B\T\S\ Italy) was used to reco rd reach to grasp movements to objects of either small (0.7 cm) or lar ge (8 cm) diameter placed at a reaching distance of either 20 or 30 cm . Four patients with Parkinson's disease were assessed in ''off'' (12 hours without medication) and ''on'' (1 hour after administration of m edication) preoperatively and postoperatively. Results-Duration of the movement and the time spent in arm deceleration were significantly re duced after surgery. However, movement patterning according to object size was adversely affected. Postoperatively, all four patients showed an abnormal pattern of a longer movement duration, and three showed a longer time of reaching arm deceleration, for reach to grasp movement s to the large object than for those to the small object. Conclusion-P osteroventral pallidotomy seems to be beneficial in reducing bradykine sia of upper limb movements but may have ''costs'' to movement pattern ing, particularly for reach to grasp movements to objects of differing sizes. This study raises interesting questions about the role of the globus pallidus interna in coordinating stimulus bound visual informat ion with appropriate motor patterning.