Measures of impulsivity in Parkinson's disease decrease after DBS in the setting of stable dopamine therapy

Electrode Location and Domain-Specific Cognitive Change Following Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease

BACKGROUND AND OBJECTIVES

Deep brain stimulation (DBS) is an effective treatment for Parkinson's disease (PD) motor symptoms. DBS is also associated with postoperative cognitive change in some patients. Previous studies found associations between medial active electrode contacts and overall cognitive decline. Our current aim is to determine the relationship between active electrode contact location and domain-specific cognitive changes.

METHODS

A single-institution retrospective cohort study was conducted in patients with PD who underwent subthalamic nucleus (STN) DBS from August 05, 2010, to February 22, 2021, and received preoperative and postoperative neuropsychological testing. Standardized norm-referenced test z-scores were categorized into attention, executive function, language, verbal memory, and visuospatial domains. SD change scores were averaged to create domain-specific change scores. We identified anterior commissure/posterior commissure coordinates of active electrode contacts in atlas space. We evaluated differences in active electrode contact location between patients with a domain score decrease of at least 1 SD and less than 1 SD. We performed multiple variable linear regression controlling for age, sex, education, time from surgery to postoperative neuropsychological testing (follow-up duration), disease duration, preoperative unified Parkinson's disease rating scale off medication scores, and preoperative memory scores to determine the relationship between active electrode contact location and domain change.

RESULTS

A total of 83 patients (male: n = 60, 72.3%) were included with a mean age of 63.6 ± 8.3 years, median disease duration of 9.0 [6.0, 11.5] years, and median follow-up duration of 8.0 [7.0, 11.0] months. More superior active electrode contact location in the left STN (P = .002) and higher preoperative memory scores (P < .0001) were associated with worsening memory. Active electrode contact location was not associated with change in other domains.

CONCLUSION

In patients with PD who underwent STN DBS, we found an association between superior active electrode contacts in the left STN and verbal memory decline. Our study increases understanding of factors associated with cognitive change after DBS and may help inform postoperative programming.

Clinical management model for impulse control disorders in Parkinson's disease

Over the last decade, we have gained a better understanding of impulse control disorder in Parkinson's disease (PD-ICD), a medication complication in PD. Researchers were aware of its complexity and took efforts to learn more about its diagnostic and treatment possibilities. Nevertheless, clinical management for it is currently neglected. We conducted a narrative overview of literature published from 2012 to October 2023 on various aspects of clinical management for PD-ICD. A potential "susceptibility-catalytic-stress" model in the development of PD-ICD was proposed and a profile encoding predictors for PD-ICD was created. Based on these predictors, some methods for prediction were recently developed for better prediction, such as the polymorphic dopamine genetic risk score and the clinic-genetic ICD-risk score. A variety of treatment options, including dose reduction of dopamine receptor agonists (DAs), DAs removal, DAs switch, and add-on therapy, are investigated with inconsistent reports. Based on current findings, we developed a clinical management model prototype centered on prevention, consisting of prediction, prevention, follow-up and monitoring, therapy, and recurrence prevention, for clinical reference, and further proposed 4 key clinical management principles, including standardization, prediction centered, persistence, and whole course.

Impulse control disorder: Review on clinical, pharmacologic, and genetic risk factors

INTRODUCTION

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor and non-motor symptoms, among which impulse control disorders behaviors (ICD) emerge as significant non-motor manifestations. ICD in PD patients, including pathological gambling, hypersexuality, compulsive buying, among others, lead to considerable impairment and reduced quality of life. This review aims to explore the multifaceted risk factors associated with ICD in PD patients, including clinical, pharmacological, and genetic aspects, to enhance early identification, prevention, and management strategies.

METHODS

A comprehensive review of literature was conducted to identify studies investigating risk factors for ICD in PD. Data from clinical, pharmacological, and genetic studies were analyzed to elucidate the complex interplay of factors contributing to ICD development.

RESULTS

Clinical risk factors such as young age, male gender, and specific personality traits were consistently associated with a higher incidence of ICD. Environmental factors such as cultural nuances and geographic location influence ICD prevalence. Disease characteristics include early PD onset, longer disease duration, motor fluctuations, anxiety, depression, sleep disorders, and apathy. Pharmaceutical risk factors involve dopaminergic drugs, with dopamine agonists showing a dose-dependent association with ICD. Genetic risk factors highlight the involvement of dopaminergic and serotoninergic systems, with various neurotransmitter pathways implicated.

CONCLUSIONS

ICDs are common and severe in PD. Understanding the multifaceted risk factors for ICD in PD is crucial for identifying patients at high risk to develop these adverse effects and developing targeted interventions to prevent their occurrence. Given their frequency and potential consequences for the patient and their family, the current strategy is to systematically screen for ICDs throughout patient follow-up, particularly when prescribing dopamine agonists.

Impulsivity Trait Profiles in Patients With Cerebellar Ataxia and Parkinson Disease

BACKGROUND AND OBJECTIVES

Individuals with cerebellar ataxia (CA) can develop impulsive behavioral symptoms, often resulting in negative interpersonal consequences, detrimentally affecting their quality of life. Limited evidence exists concerning impulsivity in CA and its associated behavioral changes. We assessed impulsive traits in CA using the Barratt Impulsivity Scale (BIS-11) and compared them with those of Parkinson disease (PD) to investigate the differences in the impulsive trait profiles between CA and PD.

METHODS

We conducted a dual-center cross-sectional study with individuals with CA and PD enrolled through consecutive sampling from movement disorders clinics at Columbia University Medical Center and Vanderbilt University Medical Center, respectively. Age-matched controls were recruited at the respective institutions. Participants were excluded if they had prior or comorbid neurologic and psychiatric diseases known to be associated with impulsivity. All participants completed the BIS-11 questionnaire as a measure of impulsive traits. We used a general linear model and a least absolute shrinkage and selection operation regression to compare the total, subscale, and individual items of the BIS-11 scores between groups. Subgroup analyses were performed to isolate cerebellar contributions to impulsivity from potential effects of extracerebellar pathology and dopaminergic dysfunction or medications.

RESULTS

A total of 190 participants-90 age-matched controls, 50 participants with CA, and 50 with PD-completed the assessments. Persons with CA reported 9.7% higher BIS-11 scores than controls (p < 0.001), while persons with PD reported 24.9% higher scores than controls (p < 0.001). In CA, the most affected domain of impulsivity was nonplanning. In contrast, persons with PD noted greater impulsivity across the nonplanning, attentional, and motor domains.

DISCUSSION

Impulsivity in CA is uniquely driven by the nonplanning trait, unlike in PD. This suggests that the cerebellum and basal ganglia may differentially govern impulsive behaviors with the cerebellum contributing to the brain circuitry of impulsivity in a domain-specific manner.

Predictors of short-term impulsive and compulsive behaviour after subthalamic stimulation in Parkinson disease

BACKGROUND

The effects of subthalamic stimulation (subthalamic nucleus-deep brain stimulation, STN-DBS) on impulsive and compulsive behaviours (ICB) in Parkinson's disease (PD) are understudied.

OBJECTIVE

To investigate clinical predictors of STN-DBS effects on ICB.

METHODS

In this prospective, open-label, multicentre study in patients with PD undergoing bilateral STN-DBS, we assessed patients preoperatively and at 6-month follow-up postoperatively. Clinical scales included the Questionnaire for Impulsive-Compulsive Disorders in PD-Rating Scale (QUIP-RS), PD Questionnaire-8, Non-Motor Symptom Scale (NMSS), Unified PD Rating Scale in addition to levodopa-equivalent daily dose total (LEDD-total) and dopamine agonists (LEDD-DA). Changes at follow-up were analysed with Wilcoxon signed-rank test and corrected for multiple comparisons (Bonferroni method). We explored predictors of QUIP-RS changes using correlations and linear regressions. Finally, we dichotomised patients into 'QUIP-RS improvement or worsening' and analysed between-group differences.

RESULTS

We included 55 patients aged 61.7 years±8.4 with 9.8 years±4.6 PD duration. QUIP-RS cut-offs and psychiatric assessments identified patients with preoperative ICB. In patients with ICB, QUIP-RS improved significantly. However, we observed considerable interindividual variability of clinically relevant QUIP-RS outcomes as 27.3% experienced worsening and 29.1% an improvement. In post hoc analyses, higher baseline QUIP-RS and lower baseline LEDD-DA were associated with greater QUIP-RS improvements. Additionally, the 'QUIP-RS worsening' group had more severe baseline impairment in the NMSS attention/memory domain.

CONCLUSIONS

Our results show favourable ICB outcomes in patients with higher preoperative ICB severity and lower preoperative DA doses, and worse outcomes in patients with more severe baseline attention/memory deficits. These findings emphasise the need for comprehensive non-motor and motor symptoms assessments in patients undergoing STN-DBS.

TRIAL REGISTRATION NUMBER

DRKS00006735.

Subthalamic nucleus deep brain stimulation and impulsivity in Parkinson's disease: a descriptive review

Standard treatment of Parkinson’s disease involves the dopaminergic medications. Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an important neurosurgical intervention often used as alternative treatment to drug therapy; however, it can be associated with increase of impulsive behaviors. This descriptive review focused on studies investigating the correlation between Deep brain stimulation of the subthalamic nucleus and impulsivity in Parkinson’s disease patients, arguing, the action’s mechanism and the specific role of the subthalamic nucleus. We searched on PubMed and Web of Science databases and screening references of included studies and review articles for additional citations. From initial 106 studies, only 15 met the search criteria. Parkinson’s Disease patients with and without Deep Brain Stimulation were compared with healthy controls, through 16 different tasks that assessed some aspects of impulsivity. Both Deep brain stimulation of the subthalamic nucleus and medication were associated with impulsive behavior and influenced decision-making processes. Moreover, findings demonstrated that: Impulse Control Disorders (ICDs) occurred soon after surgery, while, in pharmacological treatment, they appeared mainly after the initiation of treatment or the increase in dosage, especially with dopamine agonists. The subthalamic nucleus plays a part in the fronto-striato-thalamic-cortical loops mediating motor, cognitive, and emotional functions: this could explain the role of the Deep Brain Stimulation in behavior modulation in Parkinson’s Disease patients. Indeed, increase impulsivity has been reported also after deep brain stimulation of the subthalamic nucleus independently by dopaminergic medication status.

Should we start integrating genetic data in decision-making on device-aided therapies in Parkinson disease? A point of view

Parkinson disease (PD) is a complex heterogeneous neurodegenerative disorder. Association studies have revealed numerous genetic risk loci and variants, and about 5-10% suffer from a monogenic form. Because the presentation and course of PD is unique to each patient, personalized symptomatic treatment should ideally be offered to treat the most disabling motor and non-motor symptoms. Indeed, clinical milestones and treatment complications that appear during disease progression are influenced by the genetic imprint. With recent advances in PD, more patients live longer to become eligible for device-aided therapies, such as apomorphine continuous subcutaneous infusion, levodopa duodenal gel infusion, and deep brain stimulation surgery, each with its own inclusion and exclusion criteria, advantages and disadvantages. Because genetic variants influence the expression of particular clinical profiles, factors for better or worse outcomes for device-aided therapies may then be proactively identified. For example, mutations in PRKN, LRRK2 and GBA express phenotypes that favor suitability for different device therapies, although with marked differences in the therapeutic window; whereas multiplications of SNCA express phenotypes that make them less desirable for device therapies.

New pharmacological and neuromodulation approaches for impulsive-compulsive behaviors in Parkinson's disease

INTRODUCTION

A significant proportion of patients with Parkinson's disease (PD) display a set of impulsive-compulsive behaviors at some point during the course of illness. These behaviors range from the so-called behavioral addictions to dopamine dysregulation syndrome, punding and hoarding disorders. These behaviors have been consistently linked to the use of dopaminergic medications used to treat PD motor symptoms (dopamine agonists, levodopa, and other agents) and less consistently to neuromodulation techniques such as deep brain stimulation (DBS). Since there are still no approved treatments for these conditions, their pharmacological management is still a big challenge for clinicians.

METHODS

We conducted an extensive review of current pharmacological and neuromodulation literature for the management of impulsive-compulsive disorders in PD patients.

RESULTS

Pharmacological treatment approaches for impulsive-compulsive behaviors and DDS in PD patients include reduction of levodopa (LD), reduction/cessation of dopamine agonist (DA), and initiation of infusion therapies (apomorphine infusion and duodopa). Also, atomoxetine, a noradrenergic agent approved for the treatment of attention deficit hyperactivity disorder, showed some interesting preliminary results but there is still a lack of controlled longitudinal studies. Finally, while DBS effects on impulsive-compulsive disorders are still controversial, non-invasive techniques (such as transcranial magnetic stimulation and transcranial direct current stimulation) could have a potential positive effect but, again, there is still a lack of controlled trials.

CONCLUSION

Managing impulsivity and compulsivity in PD patients is still a non-evidence-based challenge for clinicians. Controlled trials on promising approaches such as atomoxetine and non-invasive neuromodulation techniques are needed.

Impulse Control Disorders in Parkinson's Disease: From Bench to Bedside

Parkinson’s disease (PD) is a neurodegenerative disorder that is characterized by symptoms that impact both motor and non-motor domains. Outside of motor impairments, PD patients are at risk for impulse control disorders (ICDs), which include excessively disabling impulsive and compulsive behaviors. ICD symptoms in PD (PD + ICD) can be broadly conceptualized as a synergistic interaction between dopamine agonist therapy and the many molecular and circuit-level changes intrinsic to PD. Aside from discontinuing dopamine agonist treatment, there remains a lack of consensus on how to best address ICD symptoms in PD. In this review, we explore recent advances in the molecular and neuroanatomical mechanisms underlying ICD symptoms in PD by summarizing a rapidly accumulating body of clinical and preclinical studies, with a special focus on the utility of rodent models in gaining new insights into the neurochemical basis of PD + ICD. We also discuss the relevance of these findings to the broader problem of impulsive and compulsive behaviors that impact a range of neuropsychiatric syndromes.

Impulsivity Markers in Parkinsonian Subthalamic Single-Unit Activity

BACKGROUND

Impulsive-compulsive behaviors are common in Parkinson's disease (PD) patients. However, the basal ganglia dysfunctions associated with high impulsivity have not been fully characterized. The objective of this study was to identify the features associated with impulsive-compulsive behaviors in single neurons of the subthalamic nucleus (STN).

METHODS

We compared temporal and spectral features of 412 subthalamic neurons from 12 PD patients with impulsive-compulsive behaviors and 330 neurons from 12 PD patients without. Single-unit activities were extracted from exploratory microrecordings performed during deep brain stimulation (DBS) implant surgery in an OFF medication state.

RESULTS

Patients with impulsive-compulsive behaviors displayed decreased firing frequency during bursts and a larger fraction of tonic neurons combined with weaker beta coherence. Information carried by these features led to the identification of patients with impulsive-compulsive behaviors with an accuracy greater than 80%.

CONCLUSIONS

Impulsive-compulsive behaviors in PD patients are associated with decreased bursts in STN neurons in the OFF medication state. © 2021 International Parkinson and Movement Disorder Society.

Basal impulses: findings from the last twenty years on impulsivity and reward pathways using deep brain stimulation

INTRODUCTION

Deep brain stimulation (DBS) is an important treatment modality for movement disorders. Its role in tasks and processes of higher cortical function continues to increase in importance and relevance. This systematic review investigates the impact of DBS on measures of impulsivity.

EVIDENCE ACQUISITION

A total of 45 studies were collated from PubMed (30 prospective, 8 animal, 4 questionnaire-based, and 3 computational models), excluding case reports and review articles. Two areas extensively studied are the subthalamic nucleus (STN) and nucleus accumbens (NAc).

EVIDENCE SYNTHESIS

While both are part of the basal ganglia, the STN and NAc have extensive connections to the prefrontal cortex, cingulate cortex, and limbic system. Therefore, understanding cause and treatment of impulsivity requires understanding motor pathways, learning, memory, and emotional processing. DBS of the STN and NAc shell can increase objective measures of impulsivity, as measured by reaction times or reward-based learning, independent from patient insight. The ability for DBS to treat impulse control disorders, and also cause and/or worsen impulsivity in Parkinson's disease, may be explained by the affected closely-related neuroanatomical areas with discrete and sometimes opposing functions.

CONCLUSIONS

As newer, more refined DBS technology emerges, large-scale prospective studies specifically aimed at treatment of impulsivity disorders are needed.

The role of dopamine pharmacotherapy and addiction-like behaviors in Parkinson's disease

Addictions involve a spectrum of behaviors that encompass features of impulsivity and compulsivity, herein referred to as impulsive-compulsive spectrum disorders (ICSDs). The etiology of ICSDs likely involves a complex interplay among neurobiological, psychological and social risk factors. Neurobiological risk factors include the status of the neuroanatomical circuits that govern ICSDs. These circuits can be altered by disease, as well as exogenous influences such as centrally-acting pharmacologics. The 'poster child' for this scenario is Parkinson's disease (PD) medically managed by pharmacological treatments. PD is a progressive neurodegenerative disease that involves a gradual loss of dopaminergic neurons largely within nigrostriatal projections. Replacement therapy includes dopamine receptor agonists that directly activate postsynaptic dopamine receptors (bypassing the requirement for functioning presynaptic terminals). Some clinically useful dopamine agonists, e.g., pramipexole and ropinirole, exhibit high affinity for the D2/D3 receptor subtypes. These agonists provide excellent relief from PD motor symptoms, but some patients exhibit debilitating ICSD. Teasing out the neuropsychiatric contribution of PD-associated pathology from the drugs used to treat PD motor symptoms is challenging. In this review, we posit that modern clinical and preclinical research converge on the conclusion that dopamine replacement therapy can mediate addictions in PD and other neurological disorders. We provide five categories of evidences that align with this position: (i) ICSD prevalence is greater with D2/D3 receptor agonist therapy vs PD alone. (ii) Capacity of dopamine replacement therapy to produce addiction-like behaviors is independent of disease for which the therapy is being provided. (iii) ICSD-like behaviors are recapitulated in laboratory rats with and without PD-like pathology. (iv) Behavioral pathology co-varies with drug exposure. (v) ICSD Features of ICSDs are consistent with agonist pharmacology and neuroanatomical substrates of addictions. Considering the underpinnings of ICSDs in PD should not only help therapeutic decision-making in neurological disorders, but also apprise ICSDs in general.

The effect on deep brain stimulation of subthalamic nucleus and dopaminergic treatment in Parkinson disease

Impulsivity is a frequent non-motor symptom in Parkinson disease (PD). It comprises psycho-behavioral alterations that negatively impact quality of life. Dopaminergic treatments underpin many impulsive controls disorders however, side effects, such as increased impulsivity, are described also after neurosurgical procedure of deep brain stimulation (DBS). We investigated the effect of deep brain stimulation on psycho-behavioral alterations and quality of life (QoL) in PD patients, analyzing, also, the role of dopaminergic therapies.Twenty idiopathic PD patients with and 20 idiopathic PD patients without DBS were included in the study. All patient underwent to neuropsychological assessment for a screening of executive functions, impulsivity, anxiety and depressive symptoms and QoL.Differences were found between DBS and no DBS groups and in term of dopaminergic therapies. The comparison between 2 groups showed a greater motor and attentional impulsivity in DBS patients. Moreover, this impulsivity worse QoL and interpersonal relationships. The combination of Levodopa and dopamine agonists exerted a great impact on impulsivity behavior.The emergence of postoperative impulsivity seems to be a neurostimulator phenomenon related to the computational role of the subthalamic nucleus in modulation of behavior.

Spectrum of impulse control behaviours in Parkinson's disease: pathophysiology and management

Impulse control behaviours (ICBs) are a range of behaviours linked by their reward-based, repetitive natures. They can be precipitated in Parkinson's disease (PD) by dopamine replacement therapy, often with detrimental consequences for patients and caregivers. While now a well-recognised non-motor feature of treated PD, much remains unknown about the influence of risk factors, pathophysiological mechanisms, vulnerability factors for specific types of behaviour and the optimal management strategies. Imaging studies have identified structural and functional changes in striatal and prefrontal brain regions, among others. Gene association studies indicate a role for genetic predisposition to PD-ICB. Clinical observational studies have identified potential modifiable and non-modifiable risk factors. Psychological studies shed light on the neurocognitive domains implicated in PD-ICBs and identify psychosocial determinants that may perpetuate the cycle of impulsive and harm-avoidance behaviours. Based on these results, a range of pharmacological and non-pharmacological management strategies have been trialled in PD-ICBs with varying success. The purpose of this review is to update clinicians on the evidence around the pathophysiology of PD-ICB. We aim to translate our findings into an interpretable biopsychosocial model that can be applied to the clinical assessment and management of individual cases of PD-ICB.

The Impact of Impulsivity on Quality of Life in Early Drug-Naïve Parkinson's Disease Patients

Objective

Impulse control disorders (ICDs) in Parkinson’s disease (PD) are mostly related to dopamine replacement therapy (DRT); however, drug-naïve PD patients have also frequently experienced impulsivity. This phenomenon makes clinicians hesitate treating patients with DRT. In this study, we assessed the effect of impulsivity on quality of life (QOL) in drug-naïve PD patients.

Methods

Two hundred three newly diagnosed, nonmedicated PD patients were enrolled, and they received structured clinical interviews, physical examinations and validated questionnaires to evaluate motor and nonmotor symptoms and QOL. Impulsivity was evaluated using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease-Rating Scale (QUIP-RS).

Results

Thirty-eight patients (18.7%) had impulsivity with QUIP-RS scores ≥ 1 and 4 patients (2.0%) were diagnosed with combined ICDs. Motor and nonmotor symptoms were significantly correlated with the Parkinson’s Disease Questionnaire-39 summary index. Female sex and QUIP-RS scores were also correlated with QOL in drug-naïve PD patients.

Conclusion

The results of the present study showed that impulsivity negatively influences QOL in early drug-naïve PD patients. In addition, more severe motor and nonmotor symptoms were also associated with lower QOL. Such findings complicate treatment but provide valuable information for managing early PD.

Treatment of psychiatric disturbances in hypokinetic movement disorders

Introduction: We reviewed studies that assessed the treatment of psychiatric disturbances in Parkinson's disease and atypical parkinsonisms. Neuropsychiatric disturbances in these conditions are frequent and have a profound impact on quality of life of patients and of their caregivers. It is therefore important to be familiar with the appropriate pharmacological and non-pharmacological interventions for treating these disorders. Areas covered: The authors searched for papers in English in Pubmed using the following keywords: Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration, Lewy body dementia, depression, apathy, anxiety, fatigue, sleep disorders, obsessive compulsive disorders, psychosis, hallucinations, delusions, impulse control disorders. Expert opinion: In Parkinson's disease, depression may benefit from the optimization of dopaminergic therapy, from the use of antidepressants acting on both the serotoninergic and noradrenergic pathways and from cognitive behavioral therapy. Psychosis in Parkinson's disease may improve with the use of clozapine; the serotonin inverse agonist pimavanserin has been shown to be effective. Treatment of impulse control disorders is primarily based on the removal of dopamine agonists. No controlled studies have investigated the treatment of neuropsychiatric disorders in multiple system atrophy, progressive supranuclear palsy or corticobasal degeneration. Acethylcholinesterase inhibitors may be used to treat hallucinations in Lewy body dementia.

Medications, Deep Brain Stimulation, and Other Factors Influencing Impulse Control Disorders in Parkinson's Disease

Impulse control disorders (ICDs) in Parkinson's disease (PD) have a high cumulative incidence and negatively impact quality of life. ICDs are influenced by a complex interaction of multiple factors. Although it is now well-recognized that dopaminergic treatments and especially dopamine agonists underpin many ICDs, medications alone are not the sole cause. Susceptibility to ICD is increased in the setting of PD. While causality can be challenging to ascertain, a wide range of modifiable and non-modifiable risk factors have been linked to ICDs. Common characteristics of PD patients with ICDs have been consistently identified across many studies; for example, males with an early age of PD onset and dopamine agonist use have a higher risk of ICD. However, not all cases of ICDs in PD can be directly attributable to dopamine, and studies have concluded that additional factors such as genetics, smoking, and/or depression may be more predictive. Beyond dopamine, other ICD associations have been described but remain difficult to explain, including deep brain stimulation surgery, especially in the setting of a reduction in dopaminergic medication use. In this review, we will summarize the demographic, genetic, behavioral, and clinical contributions potentially influencing ICD onset in PD. These associations may inspire future preventative or therapeutic strategies.

Effects of subthalamic nucleus stimulation and levodopa on decision-making in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is frequently associated with behavioral disorders, particularly within the spectrum of motivated behaviors such as apathy or impulsivity. Both pharmacological and neurosurgical treatments have an impact on these impairments. However, there still is controversy as to whether subthalamic nucleus deep brain stimulation (STN-DBS) can cause or reduce impulsive behaviors.

OBJECTIVES

We aimed to identify the influence of functional surgery on decision-making processes in PD.

METHODS

We studied 13 PD patients and 13 healthy controls. The experimental task involved squeezing a dynamometer with variable force to obtain rewards of various values under four conditions: without treatment, with l-dopa or subthalamic stimulation alone, and with both l-dopa and subthalamic stimulation. Statistical analyses consisted of generalized linear mixed models including treatment condition, reward value, level of effort, and their interactions. We analyzed acceptance rate (the percentage of accepted trials), decision time, and force applied.

RESULTS

Comparatively to controls, patients without treatment exhibited lower acceptance rate and force applied. Patients under l-dopa alone did not exhibit increased acceptance rate. With subthalamic stimulation, either with or without added l-dopa, all measures were improved so that patients' behaviors were undistinguishable from healthy controls'.

CONCLUSIONS

Our study shows that l-dopa administration does not fully restore cost-benefit decision-making processes, whereas STN-DBS fully normalizes patients' behaviors. These findings suggest that dopamine is partly involved in cost-benefit valuation, and that STN-DBS can have a beneficial effect on motivated behaviors in PD and may improve certain forms of impulsive behaviors. © 2019 International Parkinson and Movement Disorder Society.