Impulse Control Disorders and Effort-Based Decision-Making in Parkinson's Disease Patients with Subthalamic Nucleus Deep Brain Stimulation.

BACKGROUND

Impulse control disorders (ICD) are common side effects of dopaminergic treatment in Parkinson's disease (PD). Whereas some studies show a reduction in ICD after subthalamic nucleus deep brain stimulation (STN-DBS), others report worsening of ICD or impulsivity.

OBJECTIVE

The aim was to study ICD in the context of STN-DBS using an objective measure of decision-making.

METHODS

Ten PD patients performed an effort-based decision-making task alongside neuropsychiatric and cognitive evaluation before and 4 months after STN-DBS. Further, 33 PD patients underwent the same experimental procedures just once after an average 40 months of chronic STN-DBS. Participants were examined preoperatively in the medication on state and postoperatively in the medication on/stimulation ON state. Mixed linear models were used to assess the impact of ICD and STN-DBS on acceptance rate and decision time in the task while controlling for motor symptom burden, cognitive measures, and dopaminergic medication.

RESULTS

Results revealed an increased willingness to exert high levels of effort in return for reward in patients with ICD, but acceptance rate was not modulated by chronic STN-DBS. Further, ICD, cognitive processing speed, and STN-DBS were all identified as positive predictors for faster decision speed. ICD scores showed a tendency to improve 4 months after STN-DBS, without an increase in apathy scores.

CONCLUSIONS

Chronic STN-DBS and ICD facilitate effort-based decision-making by speeding up judgment. Furthermore, ICD enhances the willingness to exert high levels of effort for reward. Both STN-DBS and dopaminergic medication impact motivated behavior and should be titrated carefully to balance neuropsychiatric symptoms.