Deep brain stimulation outcomes in Parkinson's disease: a clinical and instrumental longitudinal study

Introduction: Subthalamic nucleus deep brain stimulation(STN-DBS) is a widely regarded surgical treatment for Parkinson’s disease(PD). However, concerns remain regarding its effects on axial signs, cognition, and behavior, emphasizing the importance of tailoring surgical indications to optimize outcomes. Objective: To describe STN-DBS effects trough a comprehensive evaluation of motor and non-motor outcomes, while exploring the interconnections among these aspects. Additionally, to examine controversial issue surrounding STN-DBS through instrumental assessments, including kinematic analysis and cardiovascular reflex tests(CRTs). Methods: This longitudinal cohort study included 98 PD patients, evaluated before and 6 months post-surgery. Clinical assessments covered motor, cognitive, neuropsychiatric, sleep, autonomic, and quality of life aspects. Pre and post-DBS scores were compared using the Wilcoxon signed-rank test, and reliable change indexes(RCI) were calculated. Logistic regression identified predictors of stimulation outcomes, followed by cluster analysis based on RCI to capture inter-variability in clinical outcomes. Results: Motor symptoms and quality of life improved by 48% and 29%, respectively. Cognitive functions declined in some patients, with an incidental risk of mild cognitive impairment at 11%. Neuropsychiatric evaluations showed a significant reduction in behavioral fluctuations after surgery. Cluster analysis revealed three distinct groups: one with mild PD and limited motor benefits post-DBS, one with severe cognitive deficits showing further cognitive and functional declines; and a third group with severe motor symptoms but better cognition that achieved the highest improvements. Kinematic analysis documented significant enhancements in gait parameters following surgery, with stimulation outperforming levodopa in gait speed, stride length, and turning. CRTs showed no significant differences; however, the proportion of LD-induced orthostatic hypotension decreased from 25% to 5%. Conclusion: This study introduces a multidimensional approach for assessing STN-DBS outcomes, highlighting the varied motor and non-motor benefits across patient profiles, and underscoring the importance of personalized approaches. Instrumental analysis also suggest that STN-DBS improves gait without affecting cardiovascular responses.