Objective: To determine whether there is a relationship between dopaminergic medication reduction and cognitive, mood, or quality of life outcomes after STN DBS for PD.

Background: Reducing patients’ medication burden is often a goal of STN DBS. However, lower dopaminergic doses may have negative effects on non-motor symptoms that are also dopamine sensitive and do not benefit from stimulation. DBS outcome studies have found non-significant correlations between absolute medication change and non-motor outcomes. To our knowledge, none have examined the effect of eliminating DA agonists, specifically.

Methods: This retrospective study included 96 patients with idiopathic PD who underwent full neuropsychological evaluations before and approximately 6 months after unilateral (N=63) or bilateral (N=33) STN DBS. Patients were categorized into Decreased, Stable, or Increased groups based on a 20% post-operative change in levodopa equivalent daily dosage (LEDD). A subset of 52 patients who were taking a DA agonist prior to surgery were grouped based on whether agonists were Retained or Discontinued after STN DBS. Multiple linear regression analysis (or Poisson regression analysis, where appropriate) was used to compare LEDD change groups and agonist change groups on postoperative cognitive, mood, and QoL outcomes, while controlling for associated preoperative score.

Results: Following surgery, 53 patients had greater than 20% reductions in their total LEDD (Decreased group), 10 patients had greater than 20% increases in their LEDD (Increased group), and 33 patients remained within 20% of their pre-operative LEDD (Stable group). Compared to those who remained on a stable LEDD dose, those with LEDD increase had significantly poorer quality of life outcome when controlling for preoperative PDQ summary index. There were no other cognitive, mood, or QoL differences among the LEDD change groups. When controlling for appropriate preoperative score, the 15 patients who lost an agonist displayed higher postoperative depression scores, more Stroop inhibition errors, lower categorical fluency scores, and poorer quality of life scores compared to patients who retained an agonist.

Conclusions: Our data suggest that overall dopaminergic load change has little influence on non-motor outcomes after STN DBS. However, discontinuing DA agonists are associated with poorer mood, executive function, and quality of life metrics. The potential mechanism for these effects, the relationship to other disease variables, and implications for clinical care are considered.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dopaminergic-medication-changes-affect-cognitive-mood-and-quality-of-life-outcomes-after-stn-dbs/