Objective: Parkinson’s disease patients with apathy and patients in the medication OFF state show reduced reward sensitivity in effort-based decision-making tasks. The effect of subthalamic nucleus deep brain stimulation (STN-DBS) on motivated behaviour remains unclear, with some studies describing stimulation-induced impulsivity and others reporting an increase in apathy and a decrease in impulse-control disorders.

Background: The aim of this study was to study the effect of STN-DBS on motivated behaviour.

Method: In this prospective study, 10 patients performed an effort-based decision-making task before and 4 months after STN-DBS surgery in the medication ON state. Further assessments included the MDS-UPDRS, Levodopa Equivalent Daily Dose, Dopamin Agonist Daily Dose, Starkstein Apathy Scale, Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease Rating Scale, Hospital Anxiety and Depression Scale and Montreal Cognitive Assessment.

Results: Motor symptoms improved and dopaminergic medication was significantly reduced 4 months after STN-DBS, with most patients remaining on a combination of a low dose of levodopa and a low dose of a dopamine agonist. Neuropsychiatric symptoms improved. Reward sensitivity in the effort-based decision-making task did not decrease despite the reduction in dopaminergic medication.

Conclusion: Neuropsychiatric symptoms and reward sensitivity are influenced by STN-DBS and dopaminergic medication and should be assessed in clinical practice to avoid postoperative apathy or impulsivity.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effort-based-decision-making-and-neuropsychiatric-symptoms-before-and-after-subthalamic-nucleus-deep-brain-stimulation-in-parkinsons-disease/