Location of Neurostimulation Affects Short-Term Emotional Wellbeing Outcomes in Parkinson's Disease Patients

Emotional wellbeing is a major determinant of quality of life (QoL) in Parkinson's disease (PD) patients. Previous studies have found mixed results regarding the effect of subthalamic nucleus (STN) deep brain stimulation (DBS) on depression and anxiety, major contributors to emotional wellbeing. There is evidence that the location of neurostimulation of the STN may explain this variability. However, studies investigating this matter have also yielded inconsistent findings. Therefore, the objective of this study was to determine the effect of STN DBS on emotional wellbeing at 6 months and 1 year and to examine whether the location of neurostimulation influences outcomes.

This is a retrospective cohort study of 94 patients who received bilateral STN DBS between 2008 and 2023 in Vancouver, Canada. Emotional wellbeing was assessed using the emotional wellbeing index (EWI) of the Parkinson's disease questionnaire-39 (PDQ-39). We divided the EWI into sub-domains assessing anxiety (EWI-A) and depression (EWI-D). We analyzed clinical outcomes using linear mixed-effect models, controlling for confounding variables. We separated the group into responders and non-responders for further analysis. For subjects with appropriate imaging (n = 18), volume of tissue activated was calculated and related to clinical outcomes, to assess for a location that led to a significant improvement in EWI, EWI-A, and EWI-D.

We found no significant difference in EWI at 6 months and 1 year after STN DBS at the group level. There was a significant improvement in EWI-A at 6 months (p < 0.001) and 1 year (p = 0.045). No significant difference in EWI-D was observed at either time point. 37.1% of patients in our cohort were EWI responders, while 62.9% were non-responders. Similarly at 1 year, 35.7% of patients were responders and 64.3% were non-responders. Stimulation of the dorsal STN was associated with improved EWI outcomes at 6 months, but not at 1-year (p < 0.05 FWE corrected).

There is significant variability in EWI outcomes following STN DBS. In the imaging analysis subgroup, stimulation of the dorsal region of the STN explained some of this variability in the short-term. Improvement in motor symptoms due to DBS may be a mediating variable between location of neurostimulation in the dorsal STN and improvements in emotional wellbeing.