Deep brain stimulation or best medical treatment for Parkinson’s disease patients: 36-month longitudinal neuropsychological and motor assessment — a prospective case-control study

INTRODUCTION: Bilateral subthalamic nucleus deep brain stimulation (DBS STN) is a very effective surgical method of treating motor symptoms in Parkinson's disease (PD) patients. The long-term cognitive outcome after the surgery is still discussed. This study compared the impact of DBS STN to best medical treatment (BMT) in patients with PD on cognitive function and mood over a 36-month observation period. MATERIAL AND METHODS: The study included PD patients divided into two groups: the BMT group (n = 17), receiving pharmacotherapy alone throughout the entire 36-month observation period, and the DBS group (n = 20), which underwent DBS STN after the baseline visit, and was subsequently observed for the next 36 months. Both groups were examined at Baseline, 9 months, 18 months and 36 months using neuropsychological assessment and the Unified Parkinson's Disease Rating Scale (UPDRS) motor examination. RESULTS: At 36 months, neither group demonstrated a significant decline in visuospatial abilities, executive functions, or memory. Both groups showed longitudinal deterioration in attention/working memory measures; however, these changes were not associated with significant between-group differences. Language performance [Wechsler Adult Intelligence Scale - Revised (WAIS-R similarities)] improved over follow-up in the DBS group relative to BMT, and DBS was associated with a marked reduction in medication across all follow-up timepoints (p < 0.05). CONCLUSIONS: The study suggests that DBS STN does not have a significant additional impact on cognition performance in PD patients. Our results also suggest that while active DBS STN continues to improve motor symptoms, it did not prevent the longitudinal worsening of OFF-motor severity (UPDRS III OFF), which progressed similarly in both groups.