Effects of unilateral subthalamic and pallidal deep brain stimulation on fine motor functions in Parkinson's disease.

Deep brain stimulation (DBS) is an effective treatment for selected patients with disabling Parkinson's disease (PD). The two main targets are the subthalamic nucleus (STN) and the globus pallidus internus (GPi), although it has not been established whether stimulation at one target is superior to the other. This prospective randomized study assessed the effects of unilateral DBS of the STN versus GPi on fine motor skills in 33 patients with advanced PD. Stimulation of either the STN (18 subjects) or GPi (15 subjects) in the off medication state significantly improved movement time and dexterity, but had little or no effect on reaction time. Overall, the extent of improvement did not differ between the two targets. The degree of improvement in movement time, but not dexterity, was correlated with the extent of preoperative medication responsiveness. Our findings suggest that DBS of the STN or GPi results in a similar improvement in hand movements at short-term follow-up. Preoperative medication responsiveness predicts improvement in some but not other motor tasks.