Age Limits for Deep Brain Stimulation of Subthalamic Nuclei in Parkinson's Disease

Background: Clinical pre-operative predictive factors of optimal STN-DBS motor outcome in Parkinson's disease (PD) have been previously reported. However, available data involving elderly patients are conflicting. Objective: To compare early post-operative outcomes in parkinsonian patients younger than 65 years old (group 1) vs patients 65 years old or older (group 2) at the time of surgery. Methods: The cognitive and motor effects of DBS were evaluated by comparison of different scores obtained before (baseline) and 6 months after surgery using a repeated measures analysis of variance. Results: Post-operative motor improvement (UPDRS part III and UPDRS part IV scores) and drug reduction were not statistically different between groups 1 and 2 (P > 0.05). Axial motor score which was significantly worse in group 2 in the on-drug condition before surgery was also significantly worse both in off-drug/on-stimulation and on-drug/on-stimulation conditions (P < 0.05). Similarly, cognitive performances (Wisconsin Card Sorting Test, Stroop interference test, Free and Cued Selective Reminding Test with Immediate Recall, Verbal Fluency) significantly worsened post-operatively in group 2. Conclusions: Although effective and safe, STN-DBS has a more negative impact on cognitive functions in elderly patient, requiring a careful preoperative selection.