Objective: The results presented herein are part of a larger study looking at the impact of medication and deep brain stimulation (DBS) on voluntary and involuntary movements in patients with Parkinson’s disease (PD). Here, we explore the impact of those treatments on visuo-motor coordination during the performance of a manual tracking task.

Background: Dopamine replacement therapy is the gold standard for the treatment of PD. In addition to reducing the severity of motor symptoms, medication can improve functional tasks. However, as the disease progresses, medications are no longer as effective and can lead to debilitating side-effects. Thus, some patients undergo DBS to better manage their symptoms.

Method: We recruited a prospective cohort of patients with PD scheduled for bilateral subthalamic (STN) DBS. Here we present the results of 17 patients that completed all the pre- and post-surgery data collection where they were asked to perform a manual tracking task lasting 55s. Patients were seated with their right arm bent by their side. They were holding a ball which was connected to an angular displacement sensor that controlled a line on a computer screen. Patients were told to match the position of a line that was moving pseudo-randomly from left to right by doing pronation/supination movements. They performed the baseline tests off and on meds prior to surgery. The post-surgery tests were performed at least 6 months postoperatively. Those tests were performed on meds/on stim, on meds/off stim, off meds/on stim, off meds/off stim, off meds/on stim of right side only, and off meds/on stim of left side only.

Results: The error observed in the off meds/off stim condition was statistically greater than in several conditions: pre-surgery on meds, off meds/on stim, on meds/on stim, and off meds/on stim of left side only (p<0.05). These statistically significant differences were observed for the magnitude of the total error, magnitude of the error in the slow segments, and magnitude of the error in the fast segments.

Conclusion: Both medication and STN DBS improve visuo-motor coordination in patients with PD. However, there does not seem to be additive effects of medication and DBS postoperatively such that performance is not better than pre-surgery on meds. Unilateral stimulation also appears to be most effective contralateral to the movement.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-impact-of-medication-and-deep-brain-stimulation-on-visuo-motor-coordination-in-parkinsons-disease/