Impulse control disorders in Parkinson disease and RBD: A longitudinal study of severity

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.

Psychiatric and cognitive symptoms of Parkinson's disease: A life's tale

INTRODUCTION

Neuropsychiatric symptoms are highly prevalent in Parkinson's disease (PD) and significantly affect the quality of life of patients and their significant others. The aim of this work is to describe typical neuropsychiatric symptoms and their treatment.

METHODS

This is a narrative opinion paper, illustrated by a fictional case report. The most common neuropsychiatric symptoms such as depressive symptoms, anxiety, apathy, psychotic symptoms, impulse control disorders, as well as cognitive impairment are discussed in the context of prodromal stage, early stage, fluctuations stage, post-surgical intervention, and late stage of PD.

RESULTS

Multiple factors such as pathophysiology, dopaminergic medication, deep brain stimulation, personality traits and individual life circumstances influence neuropsychiatric symptoms. Since the complexity and causes of neuropsychiatric symptoms can change, management strategies have to be adapted and individualised throughout the disease trajectory.

DISCUSSION

Recognising neuropsychiatric symptoms within the framework of the disease stage and identifying their potential causes is pivotal to provide adequate interventions.

Excessive Daytime Sleepiness as a Risk Factor for Impulse Control Disorders in Parkinson's Disease

Purpose

Impulse control disorders (ICDs) and excessive daytime sleepiness (EDS) are common symptoms in Parkinson's disease (PD). Few longitudinal studies have focused on the association between EDS and ICDs. This longitudinal study aimed at assessing association between EDS and ICDs in PD.

Patients and Methods

Patients without ICDs were incorporated from the Parkinson's Progression Markers Initiative. All patients were followed until the onset of ICDs or the end of 4 years. A total of 260 PD patients were included. Univariable and multivariable logistic regression were used to explore association between EDS and ICDs.

Results

The overall frequency of ICDs at the end of follow-up was 23.8% (62 patients). The mean duration from dopamine replacement therapy to develop ICDs was 3.30 ± 2.42 years. Patients with ICDs had significantly higher Epworth Sleepiness Scale (ESS) score (P = 0.002) and higher proportion of EDS (P = 0.030) when compared to patients without ICDs. The multivariable logistic regression analysis indicated that high ESS (OR = 2.01, 95% CI 1.01-4.04, p = 0.049) score, high dopamine agonist equivalent daily dose (OR = 2.54, 95% CI 1.37-4.71, p = 0.003), high Geriatric Depression Scale (OR = 2.33, 95% CI 1.27-4.28, p = 0.006) score and postural instability (OR = 3.03, 95% CI 1.26-7.29, p = 0.013) were associated with ICDs occurrence.

Conclusion

Our results indicated that EDS acts as a risk for ICDs occurrence in PD. Clinicians should pay attention to EDS in clinical practice. This may be a promising new approach to better understand and therapy ICDs.

Diagnostics and treatment of impulse control disorders, psychosis and delirium: systemic review-based recommendations - guideline "Parkinson's disease" of the German Society of Neurology

BACKGROUND AND OBJECTIVE

Impulse control disorders (ICD), psychosis and delirium are part of the spectrum of behavioural changes associated with Parkinson's disease (PD). The diagnostic and therapeutic management of these rather complex neuropsychiatric conditions has been updated in the clinical guideline by the German Society of Neurology (DGN).

METHODS

Recommendations are based on a systematic literature reviews, other relevant guidelines and expert opinion.

RESULTS

Patients receiving dopamine agonists (DA) therapy should be informed about the symptoms and risks of an ICD and should be routinely screened for ICD symptoms. In the presence of an ICD, DA should be reduced or discontinued and psychotherapeutic treatment may be considered. Non-oral therapies (levodopa/carbidopa intestinal gel infusion or deep brain stimulation) may also be an option for appropriate candidates. Psychosis in PD often has a gradual onset. Cognitive and affective disorders, psychiatric and medical comorbidities as well as polypharmacy are risk factors for a psychosis. Non-pharmacological treatments should be implemented as soon as possible and anti-parkinsonian medications should be adjusted/reduced if feasible. For psychosis associated with PD, quetiapine or clozapine should be used on an as-needed basis and for as short a time as is necessary, with safety monitoring. Delirium in PD may be underdiagnosed due to an overlap with chronic neuropsychiatric features of PD. Although transient by definition, delirium in PD can lead to permanent cognitive decline, motor impairment and increased mortality. Management of delirium includes pharmacological and non-pharmacological interventions.

CONCLUSION

The updated guideline encompasses the evidence-based diagnostic, non-pharmacological and pharmacological management of ICD, psychosis and delirium in PD.

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.

Subthalamic control of impulsive actions: insights from deep brain stimulation in Parkinson's disease

Control of actions allows adaptive, goal-directed behaviour. The basal ganglia, including the subthalamic nucleus, are thought to play a central role in dynamically controlling actions through recurrent negative feedback loops with the cerebral cortex. Here, we summarize recent translational studies that used deep brain stimulation to record neural activity from and apply electrical stimulation to the subthalamic nucleus in people with Parkinson's disease. These studies have elucidated spatial, spectral and temporal features of the neural mechanisms underlying the controlled delay of actions in cortico-subthalamic networks and demonstrated their causal effects on behaviour in distinct processing windows. While these mechanisms have been conceptualized as control signals for suppressing impulsive response tendencies in conflict tasks and as decision threshold adjustments in value-based and perceptual decisions, we propose a common framework linking decision-making, cognition and movement. Within this framework, subthalamic deep brain stimulation can lead to suboptimal choices by reducing the time that patients take for deliberation before committing to an action. However, clinical studies have consistently shown that the occurrence of impulse control disorders is reduced, not increased, after subthalamic deep brain stimulation surgery. This apparent contradiction can be reconciled when recognizing the multifaceted nature of impulsivity, its underlying mechanisms and modulation by treatment. While subthalamic deep brain stimulation renders patients susceptible to making decisions without proper forethought, this can be disentangled from effects related to dopamine comprising sensitivity to benefits versus costs, reward delay aversion and learning from outcomes. Alterations in these dopamine-mediated mechanisms are thought to underlie the development of impulse control disorders and can be relatively spared with reduced dopaminergic medication after subthalamic deep brain stimulation. Together, results from studies using deep brain stimulation as an experimental tool have improved our understanding of action control in the human brain and have important implications for treatment of patients with neurological disorders.

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.

Behavioral disorders in Parkinson disease: current view

Patients with Parkinson disease (PD) frequently experience several behavioral symptoms, such as anxiety, apathy, irritability, agitation, impulsive control and obsessive-compulsive or REM sleep behavior disorders, which can cause severe psychosocial problems and impair quality of life. Occurring in 30-70% of PD patients, these symptoms can manifest at early stages of the disease, sometimes even before the appearance of classic motor symptoms, while others can develop later. Behavioral changes in PD show distinct patterns of brain atrophy, dopaminergic and serotonergic deterioration, altered neuronal connectivity in frontostriatal, corticolimbic, default mode and other networks due to a cascade linking molecular pathologies and deficits in multiple behavior domains. The changes suggest a multi-system neurodegenerative process in the context of a specific α-synucleinopathy inducing a variety of biochemical and functional changes, the neurobiological basis and clinical relevance of which await further elucidation. This paper is intended to review the recent literature with focus on the main behavioral disturbances in PD patients, their epidemiology, clinical features, risk factors, animal models, neuroimaging findings, pathophysiological backgrounds, and treatment options of these deleterious lesions.

Neural Reinforcement Learning Signals Predict Recovery From Impulse Control Disorder Symptoms in Parkinson's Disease

BACKGROUND

Impulse control disorders (ICDs) in Parkinson's disease are associated with a heavy burden on patients and caretakers. While recovery can occur, ICDs persist in many patients despite optimal management. The basis for this interindividual variability in recovery is unclear and poses a major challenge to personalized health care.

METHODS

We adopted a computational psychiatry approach and leveraged the longitudinal, prospective Personalized Parkinson Project (136 people with Parkinson's disease, within 5 years of diagnosis) to combine dopaminergic learning theory-informed functional magnetic resonance imaging with machine learning (at baseline) to predict ICD symptom recovery after 2 years of follow-up. We focused on change in Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease Rating Scale scores in the entire sample regardless of an ICD diagnosis.

RESULTS

Greater reinforcement learning signals during gain trials but not loss trials at baseline, including those in the ventral striatum and medial prefrontal cortex, and the behavioral accuracy score measured while on medication were associated with greater recovery from impulse control symptoms 2 years later. These signals accounted for a unique proportion of the relevant variability over and above that explained by other known factors, such as decreases in dopamine agonist use.

CONCLUSIONS

Our results provide a proof of principle for combining generative model-based inference of latent learning processes with machine learning-based predictive modeling of variability in clinical symptom recovery trajectories. We showed that reinforcement learning modeling parameters predicted recovery from ICD symptoms in Parkinson's disease.

Impulse Control Disorders in Parkinson's Disease: An Overview of Risk Factors, Pathogenesis and Pharmacological Management

Impulse control disorders in Parkinson's disease are relatively common drug-induced addictive behaviours that are usually triggered by the dopamine agonists pramipexole, ropinirole and rotigotine. This narrative review aimed to provide a comprehensive overview of the current knowledge of impulse control disorders in Parkinson's disease. We summarised the prevalence, clinical features, risk factors and potential underlying mechanisms of impulse control disorders in Parkinson's disease. Moreover, recent advances in behavioural and imaging characteristics and management strategies are discussed. Early detection as well as a tailored multidisciplinary approach, which typically includes careful adjustment of the dopaminergic therapy and the treatment of associated neuropsychiatric symptoms, are necessary. In some cases, a continuous delivery of levodopa via a pump or the dopamine D1 receptor agonist, apomorphine, can be considered. In selected patients without cognitive or speech impairment, deep brain stimulation of the subthalamic nucleus can also improve addictions. Finding the right balance of tapering dopaminergic dose (usually dopamine agonists) without worsening motor symptoms is essential for a beneficial long-term outcome.

Aberrant brain topological organization and granger causality connectivity in Parkinson's disease with impulse control disorders

Introduction

Impulse control disorders (ICDs) refer to the common neuropsychiatric complication of Parkinson's disease (PD). The white matter (WM) topological organization and its impact on brain networks remain to be established.

Methods

A total of 17 PD patients with ICD (PD-ICD), 17 without ICD (PD-NICD), and 18 healthy controls (HCs) were recruited. Graph theoretic analyses and Granger causality analyses were combined to investigate WM topological organization and the directional connection patterns of key regions.

Results

Compared to PD-NICD, ICD patients showed abnormal global properties, including decreased shortest path length (Lp) and increased global efficiency (Eg). Locally, the ICD group manifested abnormal nodal topological parameters predominantly in the left middle cingulate gyrus (MCG) and left superior cerebellum. Decreased directional connectivity from the left MCG to the right medial superior frontal gyrus was observed in the PD-ICD group. ICD severity was significantly correlated with Lp and Eg.

Discussion

Our findings reflected that ICD patients had excessively optimized WM topological organization, abnormally strengthened nodal structure connections within the reward network, and aberrant causal connectivity in specific cortical- limbic circuits. We hypothesized that the aberrant reward and motor inhibition circuit could play a crucial role in the emergence of ICDs.

Altered Impulsivity Across Drug-Naïve Parkinsonism, Isolated Rapid Eye Movement Sleep Behavior Disorder, and Their High-Risk Relatives

OBJECTIVE

To determine multidimensional impulsivity levels across different early stages of α-synucleinopathy.

METHODS

This cross-sectional study investigated motor and decisional impulsivity levels using a panel of computerized tasks among drug-naïve parkinsonism patients, isolated/idiopathic rapid eye movement sleep behavior disorder (iRBD) patients and their first-degree relatives (iRBD-FDRs), and control participants. Trait impulsivity and impulse control behaviors were assessed by self-reported questionnaires.

RESULTS

A total of 27 drug-naïve parkinsonism patients, 157 iRBD patients, 66 iRBD-FDRs, and 82 control participants were recruited. Parkinsonism and iRBD patients had fewer numbers of extracted beads in beads task 1 and 2 (both p < 0.001), and a higher rate of irrational choice in task 1 (p = 0.046) before making decisions, and fewer numbers of pumps of unexploded blue balloons in the balloon analog risk task (p = 0.004) than control participants, indicating a higher level of reflection impulsivity and a lower level of risk taking, respectively. iRBD patients had more no-go errors in the go/no-go task than control participants (padjusted  = 0.036), suggesting a higher level of motor impulsivity. iRBD-FDRs with dream-enactment behaviors had fewer numbers of extracted beads (p = 0.047) in beads task 2 than FDRs without dream-enactment behaviors, suggesting a possible higher level of reflection impulsivity.

INTERPRETATION

A complex construct of altered impulsivity with decreased risk taking, but increased reflection and motor impulsivity, has already occurred at the prodromal and early stages of α-synucleinopathy, which have implications for underlying pathophysiology and clinical management of α-synucleinopathy, especially for impulse control behaviors upon dopaminergic drug treatment. ANN NEUROL 2024;95:544-557.

Associations between Sleep Disorders and Impulsive-Compulsive Behaviors in Parkinson's Disease: A Prospective Cohort Study

OBJECTIVE

To examine the associations of excessive daytime sleepiness (EDS) and probable rapid eye movement sleep behavior disorder (pRBD), respectively, with impulsive-compulsive behaviors (ICBs) over a 5-year follow-up in patients with early Parkinson's disease (PD).

METHODS

The Parkinson's Progression Markers Initiative is a multicenter cohort study based on an ongoing and open-ended registry. Longitudinal associations of sleep disorders with ICB over 5-year follow-up visits were estimated using generalized linear mixed-effects models among PD participants.

RESULTS

A total of 825 PD participants were enrolled at baseline. The study sample had a median baseline age of 63.1 (interquartile range: 55.6-69.3) years and comprised 496 (61.5%) men. Among them, 201 (24.9%) had ICB at baseline. In the generalized mixed-effects models, EDS (odds ratio [OR] = 1.09, 95% confidence interval [CI] 1.05, 1.12) and RBD (OR = 1.07, 95% CI 1.03, 1.12) were substantially associated with higher odds of developing ICB over time in PD patients, after multivariate adjustment including age, gender, family history, GDS score, STAI-Y score, MDS-UPDRS part III score, LEDD, and disease duration. Consistent results were observed when stratifying by age at baseline, gender, and PD family history.

CONCLUSIONS

The study findings suggest a longitudinal association between EDS and pRBD with an increased risk of developing ICB in patients with PD. The findings emphasize the significance of evaluating and addressing sleep disorders in PD patients as a potential approach to managing ICB.

Management of Impulse Control and Related Disorders in Parkinson's Disease: An Expert Consensus

BACKGROUND

Impulse-control and related behavioral disorders (ICBDs) significantly impact the lives of Parkinson's disease (PD) patients and caregivers, with lasting consequences if undiagnosed and untreated. While ICBD pathophysiology and risk factors are well-studied, a standardized severity definition and treatment evidence remain elusive.

OBJECTIVE

This work aimed to establish international expert consensus on ICBD treatment strategies. To comprehensively address diverse treatment availabilities, experts from various continents were included.

METHODS

From 2021 to 2023, global movement disorders specialists engaged in a Delphi process. A core expert group initiated surveys, involving a larger panel in three iterations, leading to refined severity definitions and treatment pathways.

RESULTS

Experts achieved consensus on defining ICBD severity, emphasizing regular PD patient screenings for early detection. General treatment recommendations focused on continuous monitoring, collaboration with significant others, and seeking specialist advice for legal or financial challenges. For mild to severe ICBDs, gradual reduction in dopamine agonists was endorsed, followed by reductions in other PD medications. Second-line treatment strategies included diverse approaches like reversing the last medication change, cognitive behavior therapy, subthalamic nucleus deep brain stimulation, and specific medications like quetiapine, clozapine, and antidepressants. The panel reached consensus on distinct treatment pathways for punding and dopamine dysregulation syndrome, formulating therapy recommendations. Comprehensive discussions addressed management strategies for the exacerbation of either motor or non-motor symptoms following the proposed treatments.

CONCLUSION

The consensus offers in-depth insights into ICBD management, presenting clear severity criteria and expert consensus treatment recommendations. The study highlights the critical need for further research to enhance ICBD management. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Impulse control disorders in Parkinson's disease: a retrospective analysis of 1824 patients in a 12-year period

OBJECTIVE

This study aims to clinically evaluate the impulse control disorders (ICDs) encountered in treating Parkinson's disease.

METHOD

This is a retrospective analysis between 2010 and 2022. We retrieved the medical records of all patients diagnosed with idiopathic Parkinson's disease. The demographic and clinical findings were recorded. ICDs constituted a specific item in the examination, and each one (compulsive shopping, compulsive eating, pathological gambling, hypersexuality, punding, dopamine dysregulation syndrome, and hobbyism) was noted separately.

RESULTS

In the study period, we identified 1824 patients (56.2% men, n = 1025). The mean age was 70.5 ± 11.9 years. In the cohort, 128 (7%) patients with Parkinson's disease had one or more ICDs. The ICDs were compulsive shopping, punding/hobbyism, compulsive eating, hypersexuality, pathological gambling, and dopamine dysregulation syndrome. When we compared patients with and without ICDs, patients with ICDs were younger (p ≤ 0.001), and the men/women ratio was higher in this group with ICDs. Although the mean daily pramipexole dose was higher in patients with ICDs, mean daily long-acting pramipexole dose was only 1.4 ± 0.92 mg/day.

CONCLUSION

The significant findings in this study were (i) the lower frequency of ICDs (7%); (ii) the common occurrence of compulsive shopping, punding/hobbyism, and compulsive eating; and (iii) the development of ICDs under relatively lower doses of pramipexole. We suggest that ICDs in Parkinson's disease should be associated with a personal trait with dopamine agonists, and potential electrophysiological or genetic markers of this trait warrant further analysis to avoid treatment in these patients.

Evaluation of risk factors for impulse control disorder in Parkinson's disease in northern China

INTRODUCTION

Impulse control disorder (ICD) is a common non-motor symptom of Parkinson's disease (PD), but its risk factors are still controversial. This study aimed to determine the prevalence of ICD in northern China and analyze the risk factors associated with ICD, multiple ICDs, and four subtypes.

METHODS

A total of 285 PD patients were enrolled in this study. Each patient was screened using the Questionnaire for Impulse and Compulsive Control Disorders (QUIP). Stepwise regression analysis was performed to identify independent risk factors, and a prediction model was developed.

RESULTS

The prevalence of ICD in the study population was 11.6%. Stepwise regression analysis showed that ICD was associated with disease duration, motor symptoms, dyskinesia, depression, REM sleep behavior disorder (RBD) and cognitive decline; multiple ICDs were related to coffee history, motor symptoms, dyskinesia, depression, apathy and RBD. The prediction model demonstrated good performance with AUC values of 0.93, 0.88, and 0.66 on the balanced train set, balanced test set, and the original imbalanced data set, respectively.

CONCLUSION

The risk factors for PD-ICD are complex and influenced by regional economic and cultural backgrounds. Clarifying these factors and developing predictive models can help to delay or even prevent the development of ICD through early screening and intervention.

Decision-making under ambiguity and risk and executive functions in Parkinson's disease patients: A scoping review of the studies investigating the Iowa Gambling Task and the Game of Dice

Evidence shows that patients affected by Parkinson's disease (PD) display the tendency toward making risky choices. This is due, at least in part, to the pathophysiological characteristics of the disease that affects neural areas underlying decision making (DM), in which a pivotal role is played by nonmotor corticostriatal circuits and dopamine. Executive functions (EFs), which can be impaired by PD as well, may sustain optimal choices in DM processes. However, few studies have investigated whether EFs can support PD patients to make good decisions. Adopting the scoping review approach, the present article is designed to deepen the cognitive mechanisms of DM under conditions of ambiguity and risk (that are conditions common to everyday life decisions) in PD patients without impulse control disorders. We focused our attention on the Iowa Gambling Task and the Game of Dice Task, because they are the most commonly used and reliable tasks to assess DM under ambiguity and under risk, respectively, and analyzed the performances in such tasks and their relationships with EFs tests in PD patients. The analysis supported the relationships between EFs and DM performance, especially when a higher cognitive load is required to make optimal decisions, as it happens under conditions of risk. Possible knowledge gaps and further research directions are suggested to better understand DM mechanisms in PD sustaining patients' cognitive functioning and preventing negative consequences in everyday life derived from suboptimal decisions.

Rapid Eye Movement Sleep Behavior Disorder in Parkinson's Disease: A Survey-Based Study

OBJECTIVE

To characterize Parkinson's disease (PD) symptoms based on the presence, onset time, and severity of rapid eye movement sleep behavior disorder (RBD) and their association with impulse control disorders (ICD).

BACKGROUND

RBD is a frequent non-motor symptom in PD, usually described as prodromal. The severity of RBD according to the start time and its relationship with ICD in PD needs further clarification.

METHODS

A survey-based study was performed to determine the presence of RBD symptoms, their severity, and the temporal relationship with the PD onset. The survey included RBD1Q, the Mayo Sleep, and the RBDQ-HK questionnaires and questions about clinical characteristics, including ICD. Only PD patients with care partners spending night hours in the same room were included.

RESULTS

410 PD patients were included: 206 with RBD (50.2%) and 204 non-RBD (49.8%). The PD-RBD patients were younger and their daily levodopa dose was higher than the non-RBD group. Most of these patients developed RBD symptoms after the onset of clinical PD were younger at motor symptom onset and had higher scores in the hallucinations and psychosis subsection of MDS-UPDRS-I. RBD group had a more severe non-motor phenotype, including more ICD than those without RBD, mainly due to higher compulsive eating.

CONCLUSIONS

In our study, most patients recognized RBD symptoms after the onset of the PD motor symptoms and the clinical features of PD with and without RBD were distinctive, supporting the hypothesis that PD-RBD might represent a variant pattern of neurodegeneration.

Neurologic and psychiatric features of impending neurodegeneration in iRBD

Introduction

Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is linked to Parkinson's disease and other alpha-synucleinopathies, but various subsets of iRBD may not carry equal risk (i.e., those with depression are at higher risk than those without). Here, we prospectively focus on neurologic and psychiatric aspects of subjects with iRBD, in an attempt to determine what factors are prominent in those who undergo phenoconversion as opposed to those who do not.

Methods

We analyzed data from the "REM Sleep Behavior Disorder Associations with Parkinson's Disease Study (RAPiDS)" cohort both at baseline and then at follow-up evaluations (1 to 3 years later) utilizing several neurologic batteries, including the Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS), the Montreal Cognitive Assessment (MoCA), the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP), the 10-M Walk Test (10MWT), and the Epworth Sleepiness Scale. Determination of phenoconversion was ascertained from physical examination and medical chart review from the initial evaluation onward.

Results

Of those who completed both evaluations, there were 33 subjects with iRBD, with an average age of 63.1 ± 12.8 years, with 9 women and 24 men. Of these, 8 (24%) iRBD subjects developed neurodegenerative illness, and demonstrated multiple areas of neurologic and psychiatric signs and symptoms, such as speech and movement problems as well as anxiety and depression.

Conclusions

Our data adds to the literature regarding risk of phenoconversion in those with iRBD. Further study will be needed, but it is clear that not all subjects with iRBD present the same risk for neurodegeneration.

An Update on Nondopaminergic Treatments for Motor and Non-motor Symptoms of Parkinson's Disease

Nondopaminergic neurotransmitters such as adenosine, norepinephrine, serotonin, glutamate, and acetylcholine are all involved in Parkinson's disease (PD) and promote its symptoms. Therefore, nondopaminergic receptors are key targets for developing novel preparations for the management of motor and non-motor symptoms in PD, without the potential adverse events of dopamine replacement therapy. We reviewed English-written articles and ongoing clinical trials of nondopaminergic treatments for PD patients till 2014 to summarize the recent findings on nondopaminergic preparations for the treatment of PD patients. The most promising research area of nondopaminergic targets is to reduce motor complications caused by traditional dopamine replacement therapy, including motor fluctuations and levodopa-induced dyskinesia. Istradefylline, Safinamide, and Zonisamide were licensed for the management of motor fluctuations in PD patients, while novel serotonergic and glutamatergic agents to improve motor fluctuations are still under research. Sustained- release agents of Amantadine were approved for treating levodopa induced dyskinesia (LID), and serotonin 5HT1B receptor agonist also showed clinical benefits to LID. Nondopaminergic targets were also being explored for the treatment of non-motor symptoms of PD. Pimavanserin was approved globally for the management of hallucinations and delusions related to PD psychosis. Istradefylline revealed beneficial effect on daytime sleepiness, apathy, depression, and lower urinary tract symptoms in PD subjects. Droxidopa may benefit orthostatic hypotension in PD patients. Safinamide and Zonisamide also showed clinical efficacy on certain non-motor symptoms of PD patients. Nondopaminergic drugs are not expected to replace dopaminergic strategies, but further development of these drugs may lead to new approaches with positive clinical implications.

Characteristics of behavioural addiction in Parkinson's disease patients with self-reported impulse control disorder and controls matched for levodopa equivalent dose: a matched case-control study

Impulse control disorders (ICD) in Parkinson's disease (PD) frequently occur, not always as a direct consequence of dopaminergic medication. This study investigated premorbid personality traits and behavioural characteristics in non-demented PD patients with self-reported symptoms of ICD (PD-srICD). From a total of 200 non-demented PD patients who filled out questionnaires assessing symptoms and severity of ICD, those were classified as PD-srICD (n = 32) who reported current occurrence of at least one compulsive behaviour (gambling, sexual behaviour, buying behaviour, or eating). As a control group, 32 patients with no self-reported ICD symptoms were matched for levodopa equivalent daily dose. The demographic, clinical, and premorbid personality profiles were compared between both groups. Frequency of psychological characteristics indicating substance use disorder was evaluated in patients with PD-srICD. Patients with PD-srICD were more frequently male, younger at examination, had earlier PD onset, more depression, higher non-motor burden, less quality of life (p < 0.05, respectively), and more frequently reported premorbid sensation seeking/novelty orientation (p = 0.03) and joyful experience of stress (p = 0.04) than patients in the control group. Of patients with PD-srICD, 90.6% reported at least one behavioural characteristic of substance use disorder, most frequently positive expectations following ICD behaviour and illusional beliefs about its behavioural control. Signs of addiction were common among patients with PD-srICD. Therefore, the profile of psychological characteristics in patients with PD-srICD resembled that of patients with substance use disorder. It can be concluded that dopamine replacement therapy (DRT) alone does not account for PD-srICD and that thorough psychological diagnostics are recommended.

Dissociable behavioural signatures of co-existing impulsivity and apathy in decision-making

Apathy and impulsivity are expressed in a wide range of neuropsychiatric disorders, and, to a less severe extent, in healthy people too. Although traditionally considered to be opposite extremes of a single motivational spectrum, recent epidemiological questionnaire-based data suggest that both traits can in fact co-exist within the same individual. Here, we sought to investigate the relationship between these constructs in healthy people within a controlled task environment that examines the ability to make a decision under temporal uncertainty and measures the vigour of the response. Sixty participants performed a new version of the Traffic Light Task and completed self-report questionnaire measures of apathy and impulsivity. The task required individuals to make rapid decision-making for time-sensitive reward by squeezing a hand-held dynamometer as quickly as possible after a predictable event occurred (a traffic light turning green). Although apathy and impulsivity were positively correlated in questionnaire assessments, the two traits were associated with distinct behavioural signatures on the task. Impulsivity was expressed as an inflexible tendency to generate rapid anticipatory responses, regardless of cost-benefit information. Apathy, on the other hand, was associated with a blunted effect of reward on response vigour. These findings reveal how apathy and impulsivity are related to distinct dimensions of goal-directed behaviour, explaining how these traits might co-exist in the same individuals.

Longitudinal Studies of Sleep Disturbances in Parkinson's Disease

PURPOSE OF REVIEW

Sleep disorders are among the most common non-motor symptoms in Parkinson's disease (PD). Recent longitudinal studies of sleep in PD have utilized validated sleep questionnaires and video-polysomnography performed over multiple time points. This review summarizes existing longitudinal studies focusing on the prevalence, associations, and changes of sleep disorders in PD over time, as well as the methodologies used in these studies.

RECENT FINDINGS

Fifty-three longitudinal studies of sleep in PD were identified: excessive daytime sleepiness, insomnia, obstructive sleep apnea, rapid eye movement sleep behavior disorder (RBD), restless legs syndrome, and shift work disorder were studied in addition to other studies that had focused on either multiple sleep disorders or broadly on sleep disorders as a whole. The prevalence of sleep disorders increases over time and are associated particularly with non-motor features of disease. RBD is now considered an established prodromal feature of PD, but other sleep disorders do not clearly increase risk of subsequent PD. Further work is necessary to determine if treatment of sleep disorders in PD alters disease symptom and their progression or reduces PD risk. Longitudinal studies of sleep in PD have demonstrated a high prevalence of sleep disorders that are associated with non-motor features of PD which can increase over time. More work is necessary to determine if treatment of sleep disorders can alter the course of PD.

Bidirectional Correlations Between Dopaminergic Function and Motivation in Parkinson's Disease

OBJECTIVE

To test the hypothesis that striatal dopamine function influences motivational alterations in Parkinson disease (PD), we compared vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DaT) imaging data in PD patients with impulse control disorders (ICDs), apathy, or neither.

METHODS

We extracted striatal binding ratios (SBR) from VMAT2 PET imaging (18F-AV133) and DaTscans from the Parkinson's Progression Markers Initiative (PPMI) multicenter observational study. Apathy and ICDs were assessed using the Movement Disorders Society-revised Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP), respectively. We used analysis of variance (ANOVA) and log-linear mixed-effects (LME) regression to model SBRs with neurobehavioral metrics.

RESULTS

Among 23 participants (mean age 62.7 years, mean disease duration 1.8 years) with VMAT2 imaging data, 5 had apathy, 5 had an ICD, and 13 had neither. ANOVA indicated strong groupwise differences in VMAT2 binding in right anterior putamen [F(2,20) = 16.2, p < 0.0001), right posterior putamen [F(2,20) = 16.9, p < 0.0001), and right caudate [F(2,20) = 6.8, p = 0.006)]. Post-hoc tests and repeated-measures analysis with LME regression also supported right striatal VMAT2 elevation in the ICD group and reduction in the apathy group relative to the group with neither ICD nor apathy. DaT did not exhibit similar correlations, but normalizing VMAT2 with DaT SBR strengthened bidirectional correlations with ICD (high VMAT2/DaT) and apathy (low VMAT2/DaT) in all striatal regions bilaterally.

CONCLUSIONS

Our findings constitute preliminary evidence that striatal presynaptic dopaminergic function helps describe the neurobiological basis of motivational dysregulation in PD, from high in ICDs to low in apathy.

Impulsivity is associated with firing regularity in parkinsonian ventral subthalamic nucleus

Impulsive–compulsive behaviors (ICB) are over‐represented in Parkinson's disease (PD) patients. Neurons in the ventral subthalamic nucleus (STN) might play a predominant role in the modulation of impulsivity. We characterized the firing regularity of 742 subthalamic neurons from 24 PD patients (12 ICB+ and 12 ICB‐) in an OFF medication state. We computed the firing regularity in the dorsal and ventral STN regions, and we compared their performance in discriminating ICB patients. Regularity of ventral neurons in ICB+ patients is higher and supports a significant discrimination between the two cohorts. These results substantiate a ventral location of neurons involved in impulsivity.

Relationship between sleep disorders and neuropsychiatric symptoms in Parkinson's disease: A narrative review

Aim: The objective of this narrative review was to describe the versatile links between mental status and sleep in patients with Parkinson's disease. Methods: We searched randomized controlled studies, observational studies, meta-analyses, systematic reviews, and case reports written in English in PubMed during 2015 - 2021. Additionally, to ensure the completeness of the review, a second, more in-depth literature search was performed using the same electronic database with the search inquiries of increased specificity. Results: The information on pathophysiology, epidemiology, clinical features and risk factors was extracted and formed the basis for this review. Despite how widespread sleep disorders in Parkinson's disease are, there is no systematic information about their association with neuropsychiatric symptoms, such as depression, anxiety, impulse control disorders, apathy, cognitive impairment and psychosis. In this review, we described relationships between these non-motor symptoms of Parkinson's disease, their timeline occurrence, gap in knowledge and perspectives for further research. We suppose that early treatment of sleep disorders in patients with Parkinson's disease can reduce the incidence and extent of neuropsychiatric symptoms. Conclusion: We have demonstrated multiple, multidirectional relationships between sleep disorders and neuropsychiatric symptoms. However, some of them remain unexplored. The described knowledge can be applied to further study the possibility of influencing neuropsychiatric symptoms through the correction of sleep disorders in patients with different stages of Parkinson's disease.

White matter changes in drug-naïve Parkinson's disease patients with impulse control & probable REM sleep behavior disorders

BACKGROUND

According to epidemiological studies, Parkinson's disease (PD) patients with probable REM sleep behavior disorder (pRBD) are more prone to develop impulse control disorders (ICDs), which is shown to be present in drug-naïve PD patients, and vice versa.

OBJECTIVES

To investigate white-matter integrity differences, with and without comorbid pRBD and ICDs.

METHODS

149 de-novo PD patients and 30 age- and gender-matched controls from the Parkinson's Progression Markers Initiative were studied. PD subjects were categorized into four groups with and without these comorbidities. We investigated the white matter integrity differences between these groups.

RESULTS

PDs with only ICDs manifested greater fractional anisotropy (FA) and lower mean diffusivity (MD) in ipsilateral cerebellar connections when compared to controls and to Parkinson's with both comorbid disorders. In contrast, significantly lower FA and higher MD in the ipsilateral fornix-stria-terminalis was observed in PDs with only pRBD compared to controls and to PDs without either comorbid disorder. Also, PDs with only pRBD manifested greater FA in contralateral putamen when compared to controls.

CONCLUSIONS

Our results suggest the presence of an underlying neural network in PDs with ICDs, particularly involving cerebellar connections, which makes the subjects susceptible to pRBD. Lower white-matter integrity in the fornix of PDs with only pRBD suggests a neuropathological pathway specific to sleep behavior disorder, independent of impulse control disorders. Greater white-matter integrity observed in PDs without comorbid ICDs, regardless of their comorbid pRBD status, might reflect compensatory mechanisms. Targeted therapies for this particular neuropathology may help prevent these comorbidities.

Preexisting Bipolar Disorder Influences the Subsequent Phenotype of Parkinson's Disease

Background

Patients with bipolar spectrum disorders (BSDs) exhibit an increased risk of Parkinson's disease (PD).

Objective

The aim is to investigate whether a previous diagnosis of BSDs influences the phenotype of PD.

Methods

Of 2660 PD patients followed for at least 6 years (6–27), 250 (BSD‐PD) had BSDs, 6–20 years before PD diagnosis; 48%–43% had a PD or BSD family history, and 34 carried glucocerebrosidase (GBA) and Parkin (PRKN) mutations. The cohort was split into a subset of 213 BSD‐PD patients, compared with 426 matched PD patients without BSDs, and a subset of 34 BSD‐PD and 79 PD patients carrying GBA or PRKN mutations. Carriers of mutations absent in BSD‐PD patients and of synuclein triplication were excluded. Structured clinical interviews and mood disorder questionnaires assessed BSDs. Linear mixed models evaluated the assessment scales over time. Thirteen BSD‐PD patients underwent subthalamic nucleus deep brain stimulation (STN‐DBS) and were compared with 27 matched STN‐DBS‐treated PD patients.

Results

Compared to PD patients, BSD‐PD showed (1) higher frequency of family history of PD (odds ratio [OR] 3.31; 2.32–4.71) and BSDs (OR 6.20; 4.11–9.35) 5); (2) higher incidence of impulse control disorders (hazard ratio [HR] 5.95, 3.89–9.09); (3) higher frequency of functional disorders occurring before PD therapy (HR, 5.67, 3.95–8.15); (4) earlier occurrence of delusions or mild dementia (HR, 7.70, 5.55–10.69; HR, 1.43, 1.16–1.75); and (5) earlier mortality (1.48; 1.11–1.97). Genetic BSD‐PD subjects exhibited clinical features indistinguishable from nongenetic BSD‐PD subjects. STN‐DBS‐treated BSD‐PD patients showed no improvements in quality of life compared to the control group.

Conclusions

BSDs as a prodrome to PD unfavorably shape their course and are associated with detrimental neuropsychiatric features and treatment outcomes. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Risk factors of impulsive-compulsive behaviors in PD patients: a meta-analysis

OBJECTIVE

To summarize the reliable risk factors of impulsive-compulsive behaviors (ICBs) in Parkinson's disease (PD) patients through a meta-analysis on studies in which PD-ICBs were diagnosed by clinical interview.

METHODS

PubMed, Embase, Web of Science, CNKI and Wanfang databases were searched. We selected studies ensuring that diagnosis of ICBs in PD patients depends on semi-structured interviews according to the clinical diagnostic criteria of ICBs. The Newcastle-Ottawa Scale was used to evaluate quality of the included studies. The analyzed factors included demographic information, clinical characteristics of PD and medications.

RESULTS

A total of 856 records were screened and 66 full texts were evaluated, and 13 studies (684 PD patients with ICBs [PD-ICBs] and 3,382 PD patients without ICBs [PD-non-ICBs]) were included. Compared with PD-non-ICBs, PD-ICBs were younger in age (- 3.7 [- 5.53, - 1.87], P < 0.0001), with a greater proportion of males (1.64 [1.21, 2.22], P = 0.001), with a younger age of PD onset (- 5.42 [- 7.87, - 2.97], P < 0.0001) and a longer course of PD (1.30 [0.38, 2.22], P = 0.005). PD-ICBs were also associated with higher HAM-D (1.74 [0.47, 3.01], P = 0.007), more levodopa dosage (1.74 [1.09, 2.77], P = 0.02) and dopamine receptor agonists (DA) use (3.96 [2.74, 5.71), P < 0.00001), and higher average dose (levodopa 117.53 [53.59, 181.46], P = 0.0003; DA 80.03 [46.16, 113.90], P < 0.00001), as well as more amantadine use (2.20 [1.42, 3.40], P = 0.0004). The meta-analysis of most factors showed less heterogeneity, except age, age of onset, PD duration, Hoehn and Yahr stage, MMSE and drug dosage. However, whether rapid eye movement sleep behavior disorder, dyskinesia, genetic polymorphism and other factors are risk factors for PD-ICBs remains unclear.

CONCLUSION

This meta-analysis suggests that males, young, early disease onset, long disease duration, depression, dose of levodopa, dopamine receptor agonists and amantadine are risk factors of ICBs in PD patients.

An Update on Medical and Surgical Treatments of Parkinson's Disease

Parkinson’s disease (PD) is characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta and other neuronal populations. The worldwide prevalence of PD is over 7 million and has been increasing more rapidly than many other neurodegenerative disorders. PD symptoms can be broadly divided into motor (slowness, stiffness, tremor) and non-motor symptoms (such as depression, dementia, psychosis, orthostatic hypotension). Patients can also have prodromal symptoms of rapid eye movement sleep behavior disorder, hyposmia, and constipation. The diagnosis of PD is mainly clinical, but dopamine transporter single-photon emission computed tomography can improve the accuracy of the diagnosis. Dopamine based therapies are used for the treatment of motor symptoms. Non-motor symptoms are treated with other medications such as selective serotonin reuptake inhibitors (depression/anxiety), acetylcholinesterase inhibitors (dementia), and atypical antipsychotics (psychosis). Patients with motor fluctuations or uncontrolled tremor, benefit from deep brain stimulation. Levodopa-carbidopa intestinal gel is an alternative to deep brain stimulation for uncontrolled motor fluctuations. Rehabilitative therapies such as physical, occupational, and speech therapy are important during all stages of the disease. Management of PD is complex but there have been significant advancements in the treatment of motor and non-motor symptoms over the past few years. This review discusses the updates in the medical and surgical management of PD.

Effectiveness of Electroconvulsive Therapy in Patients With Advanced Parkinson Disease

OBJECTIVES

In addition to motor symptoms, patients with Parkinson disease (PD) experience various psychiatric comorbidities, including impulse control disorders (ICDs). Moreover, antiparkinsonian drugs sometimes cause psychiatric symptoms. Antiparkinsonian and antipsychotic drugs are competitive in pharmacodynamics, and psychotropic drugs, including antidepressants, may worsen motor symptoms or induce adverse reactions. Considering this conflicting situation, we examined the effectiveness of electroconvulsive therapy (ECT) on both motor and psychiatric symptoms in PD.

METHODS

We retrospectively examined 12 PD patients with advanced motor symptoms and drug-resistant psychiatric symptoms, including ICDs, who had undergone ECT. Both before and after ECT, the severity of PD motor symptoms were evaluated using Hoehn and Yahr staging, while psychiatric symptoms were evaluated using the Neuropsychiatric Inventory. The patients' doses of antiparkinsonian and antipsychotic drugs were also assessed before and after ECT.

RESULTS

Both the mean Hoehn and Yahr and Neuropsychiatric Inventory scores were significantly decreased after ECT. The symptoms of ICDs, which were observed in 5 patients, disappeared following ECT. Improvements in motor symptoms and psychiatric symptoms lasted for more than 1 year in 5 cases and 9 cases, respectively. Furthermore, the daily dose of antiparkinsonian drugs was significantly decreased in 6 cases.

CONCLUSIONS

Our results demonstrated that ECT was effective for both severe motor symptoms and psychiatric symptoms in advanced PD patients. ECT might be a solution for the conflicting problem of treating both motor and psychiatric symptoms in PD.

Impulse control disorders and related behaviors in Parkinson's disease: risk factors, clinical and genetic aspects, and management

PURPOSE OF REVIEW

To review recent findings and research directions on impulse control disorders and related behaviors (ICDRBs) in Parkinson's disease (PD).

RECENT FINDINGS

Longitudinal studies found that prevalence increases during PD progression, incident ICDRBs being around 10% per year in patients treated with dopaminergic therapies. Screening tools and severity scales already developed have been validated and are available in several countries and languages. The main clinical risk factors include young age, male gender, type, doses and duration of dopaminergic therapy, PD motor severity and dyskinesia, depression, anxiety, apathy, sleep disorders, and impulsivity traits. Genetic factors are suspected by a high estimated heritability, but individual genes and variants remain to be replicated. Management of ICDRBs is centered on dopamine agonist decrease, with the risk to develop withdrawal symptoms. Cognitive behavioral therapy and subthalamic nucleus deep brain stimulation also improve ICDRBs. In the perspective of precision medicine, new individual prediction models of these disorders have been proposed, but they need further independent replication.

SUMMARY

Regular monitoring of ICDRB during the course of PD is needed, particularly in the subject at high risk of developing these complications. Precision medicine will require the appropriate use of machine learning to be reached in the clinical setting.

Impact of rapid eye movement sleep behavior disorder and autonomic disorders on Parkinson's disease: a review

Parkinson's disease (PD) has heterogeneous clinical manifestations and prognoses. It is accompanied by a group of motor and non-motor symptoms ranging from independence to total disability, limiting work and personal care activities. Currently, disease subtype markers for informing prognosis remain elusive. However, some studies have reported an association between rapid eye movement (REM) sleep behavior disorder (RBD) and faster motor and non-motor symptom progression, including autonomic dysfunction and cognitive decline. Moreover, since autonomic dysfunction has been described in idiopathic forms of RBD, and they share some central regulatory pathways, it remains unclear whether they have a primary association or if they are more severe in patients with PD and RBD, and thus are a disease subtype marker. This article aimed at critically reviewing the literature on the controversies about the prevalence of RBD in PD, the higher incidence of PD non-motor symptoms associated with RBD, the evidence of faster motor worsening in parkinsonian patients with this parasomnia, and the main pathophysiological hypotheses that support these findings.

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.

Limbic hypoconnectivity in idiopathic REM sleep behaviour disorder with impulse control disorders

INTRODUCTION

Current neuroimaging research has revealed several brain alterations in idiopathic REM sleep behaviour disorder (iRBD) that mirror and precede those reported in PD. However, none have specifically addressed the presence of changes across the reward system, and their role in the emergence of impulse control disorders (ICDs). We aimed to compare the volumetric and functional connectivity characteristics of the reward system in relation to the psychobehavioral profile of patients with iRBD versus healthy controls and PD patients.

METHODS

Twenty patients with polysomnography confirmed iRBD along with 17 PD patients and 14 healthy controls (HC) underwent structural and functional resting-state brain MRI analysis. Participants completed the questionnaire for impulsive-compulsive disorders in PD (QUIP), the short UPPS-P impulsive behaviour scale, as well as neuropsychological testing of cognitive function.

RESULTS

A higher percentage of iRBD patients reported hypersexuality, compared to HC and PD (p = 0.008). Whole-brain and striatal voxel-based morphometry analyses showed no significant clusters of reduced grey matter volume between groups. However, iRBD compared to HC demonstrated functional hypoconnectivity between the limbic striatum and temporo-occipital regions. Furthermore, the presence of ICDs correlated with hypoconnectivity between the limbic striatum and clusters located in cuneus, lingual and fusiform gyrus.

CONCLUSION

Altered functional connectivity between the limbic striatum and posterior cortical regions was associated with increased hypersexuality in iRBD. It is possible that this change may ultimately predispose individuals to the emergence of ICDs when they receive dopaminergic medications, after transitioning to PD.

The relationship between apathy and impulsivity in large population samples

Apathy and impulsivity are debilitating conditions associated with many neuropsychiatric conditions, and expressed to variable degrees in healthy people. While some theories suggest that they lie at different ends of a continuum, others suggest their possible co-existence. Surprisingly little is known, however, about their empirical association in the general population. Here, gathering data from six large studies (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$n = 3755$$\end{document}n=3755), we investigated the relationship between measures of apathy and impulsivity in young adults. The questionnaires included commonly used self-assessment tools—Apathy Evaluation Scale, Barratt Impulsiveness Scale (BIS-11) and UPPS-P Scale—as well as a more recent addition, the Apathy Motivation Index (AMI). Remarkably, across datasets and assessment tools, global measures of apathy and impulsivity correlated positively. However, analysis of sub-scale scores revealed a more complex relationship. Although most dimensions correlated positively with one another, there were two important exceptions revealed using the AMI scale. Social apathy was mostly negatively correlated with impulsive behaviour, and emotional apathy was orthogonal to all other sub-domains. These results suggest that at a global level, apathy and impulsivity do not exist at distinct ends of a continuum. Instead, paradoxically, they most often co-exist in young adults. Processes underlying social and emotional apathy, however, appear to be different and dissociable from behavioural apathy and impulsivity.

Olfactory Testing in Parkinson Disease and REM Behavior Disorder: A Machine Learning Approach

OBJECTIVE

We sought to identify an abbreviated test of impaired olfaction amenable for use in busy clinical environments in prodromal (isolated REM sleep behavior disorder [iRBD]) and manifest Parkinson disease (PD).

METHODS

Eight hundred ninety individuals with PD and 313 controls in the Discovery cohort study underwent Sniffin' Stick odor identification assessment. Random forests were initially trained to distinguish individuals with poor (functional anosmia/hyposmia) and good (normosmia/super-smeller) smell ability using all 16 Sniffin' Sticks. Models were retrained using the top 3 sticks ranked by order of predictor importance. One randomly selected 3-stick model was tested in a second independent PD dataset (n = 452) and in 2 iRBD datasets (Discovery n = 241, Marburg n = 37) before being compared to previously described abbreviated Sniffin' Stick combinations.

RESULTS

In differentiating poor from good smell ability, the overall area under the curve (AUC) value associated with the top 3 sticks (anise/licorice/banana) was 0.95 in the Development dataset (sensitivity 90%, specificity 92%, positive predictive value 92%, negative predictive value 90%). Internal and external validation confirmed AUCs ≥0.90. The combination of the 3-stick model determined poor smell, and an RBD screening questionnaire score of ≥5 separated those with iRBD from controls with a sensitivity, specificity, positive predictive value, and negative predictive value of 65%, 100%, 100%, and 30%.

CONCLUSIONS

Our 3-Sniffin'-Stick model holds potential utility as a brief screening test in the stratification of individuals with PD and iRBD according to olfactory dysfunction.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that a 3-Sniffin'-Stick model distinguishes individuals with poor and good smell ability and can be used to screen for individuals with iRBD.

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.

Impulse Control Disorders in Parkinson's Disease: Epidemiology, Pathogenesis and Therapeutic Strategies

Impulse control disorders (ICDs) in Parkinson's disease (PD) are aberrant behavior such as pathological gambling, hypersexuality, binge eating, and compulsive buying, which typically occur as a result of dopaminergic therapy. Numerous studies have focused on the broad spectrum of ICDs-related behaviors and their tremendous impact on patients and their family members. Recent advances have improved our understanding of ICDs. In this review, we discuss the epidemiology, pathogenesis and treatment of ICDs in the setting of PD.

Contributing Factors and Evolution of Impulse Control Disorder in the Luxembourg Parkinson Cohort

Background: To establish the frequency of impulse control disorder (ICD) in Parkinson's disease (PD).

Methods: Within the Luxembourg Parkinson's Study, PD patients were evaluated for ICD presence (score ≥ 1 on MDS-UPDRS I item 1.6), use of dopamine agonists (DA) and other medications.

Results: 470 patients were enrolled. Among 217 patients without DA use, 6.9% scored positive for ICD, vs. 15.4% among 253 patients with DA use (p = 0.005). The regression analysis showed that age at PD diagnosis had only a minor impact on ICD occurrence, while there was no influence by gender or co-medications. The longitudinal study over 2 years in 156 patients demonstrated increasing ICD frequency in DA users (p = 0.005).

Conclusion: This large and non-interventional study confirms that PD patients with DA treatment show higher frequency of ICD than patients without DA use. It newly demonstrates that ICD can develop independently from age, gender, or co-medications.

Neuropsychiatric sequelae of Parkinson's disease: what every clinician needs to know

Jones et al's review of the assessment and management of the neuropsychiatric manifestations of Parkinson's disease serves as a practical guide to clinicians. This commentary outlines some of the underlying neuroscience and psychological sequelae of this range of conditions, offering a takeaway message to the clinician with an interest in Parkinson's neuropsychiatry.

An update on the use of non-ergot dopamine agonists for the treatment of Parkinson's disease

INTRODUCTION

Long-term treatment of Parkinson's disease (PD) with levodopa is hampered by motor complications related to the inability of residual nigrostriatal neurons to convert levodopa to dopamine (DA) and use it appropriately. This generated a tendency to postpone levodopa, favoring the initial use of DA agonists, which directly stimulate striatal dopaminergic receptors. Use of DA agonists, however, is associated with multiple side effects and their efficacy is limited by suboptimal bioavailability.

AREAS COVERED

This paper reviewed the latest preclinical and clinical findings on the efficacy and adverse effects of non-ergot DA agonists, discussing the present and future of this class of compounds in PD therapy.

EXPERT OPINION

The latest findings confirm the effectiveness of DA agonists as initial treatment or adjunctive therapy to levodopa in advanced PD, but a more conservative approach to their use is emerging, due to the complexity and repercussions of their side effects. As various factors may increase the individual risk to side effects, assessing such risk and calibrating the use of DA agonists accordingly may become extremely important in the clinical management of PD, as well as the availability of new DA agonists with better profiles of safety and efficacy.

Dopamine and reward hypersensitivity in Parkinson's disease with impulse control disorder

Impulse control disorders in Parkinson's disease are common neuropsychiatric complications associated with dopamine replacement therapy. Some patients treated with dopamine agonists develop pathological behaviours, such as gambling, compulsive eating, shopping, or disinhibited sexual behaviours, which can have a severe impact on their lives and that of their families. In this study we investigated whether hypersensitivity to reward might contribute to these pathological behaviours and how this is influenced by dopaminergic medication. We asked participants to shift their gaze to a visual target as quickly as possible, in order to obtain reward. Critically, the reward incentive on offer varied over trials. Motivational effects were indexed by pupillometry and saccadic velocity, and patients were tested ON and OFF dopaminergic medication, allowing us to measure the effect of dopaminergic medication changes on reward sensitivity. Twenty-three Parkinson's disease patients with a history of impulse control disorders were compared to 26 patients without such behaviours, and 31 elderly healthy controls. Intriguingly, behavioural apathy was reported alongside impulsivity in the majority of patients with impulse control disorders. Individuals with impulse control disorders also exhibited heightened sensitivity to exogenous monetary rewards cues both ON and OFF (overnight withdrawal) dopamine medication, as indexed by pupillary dilation in anticipation of reward. Being OFF dopaminergic medication overnight did not modulate pupillary reward sensitivity in impulse control disorder patients, whereas in control patients reward sensitivity was significantly reduced when OFF dopamine. These effects were independent of cognitive impairment or total levodopa equivalent dose. Although dopamine agonist dose did modulate pupillary responses to reward, the pattern of results was replicated even when patients with impulse control disorders on dopamine agonists were excluded from the analysis. The findings suggest that hypersensitivity to rewards might be a contributing factor to the development of impulse control disorders in Parkinson's disease. However, there was no difference in reward sensitivity between patient groups when ON dopamine medication, suggesting that impulse control disorders may not emerge simply because of a direct effect of dopaminergic drug level on reward sensitivity. The pupillary reward sensitivity measure described here provides a means to differentiate, using a physiological measure, Parkinson's disease patients with impulse control disorder from those who do not experience such symptoms. Moreover, follow-up of control patients indicated that increased pupillary modulation by reward can be predictive of the risk of future emergence of impulse control disorders and may thereby provide the potential for early identification of patients who are more likely to develop these symptoms.

Parkinson's disease: etiopathogenesis and treatment

The concept of 'idiopathic' Parkinson's disease (PD) as a single entity has been challenged with the identification of several clinical subtypes, pathogenic genes and putative causative environmental agents. In addition to classic motor symptoms, non-motor manifestations (such as rapid eye movement sleep disorder, anosmia, constipation and depression) appear at prodromic/premotor stage and evolve, along with cognitive impairment and dysautonomia, as the disease progresses, often dominating the advanced stages of the disease. The key molecular pathogenic mechanisms include α-synuclein misfolding and aggregation, mitochondrial dysfunction, impairment of protein clearance (associated with deficient ubiquitin-proteasome and autophagy-lysosomal systems), neuroinflammation and oxidative stress. The involvement of dopaminergic as well as noradrenergic, glutamatergic, serotonergic and adenosine pathways provide insights into the rich and variable clinical phenomenology associated with PD and the possibility of alternative therapeutic approaches beyond traditional dopamine replacement therapies.One of the biggest challenges in the development of potential neuroprotective therapies has been the lack of reliable and sensitive biomarkers of progression. Immunotherapies such as the use of vaccination or monoclonal antibodies directed against aggregated, toxic α-synuclein.as well as anti-aggregation or protein clearance strategies are currently investigated in clinical trials. The application of glucagon-like peptide one receptor agonists, specific PD gene target agents (such as GBA or LRRK2 modifiers) and other potential disease modifying drugs provide cautious optimism that more effective therapies are on the horizon. Emerging therapies, such as new symptomatic drugs, innovative drug delivery systems and novel surgical interventions give hope to patients with PD about their future outcomes and prognosis.

Using Deep Brain Stimulation to Unravel the Mysteries of Cardiorespiratory Control

This article charts the history of deep brain stimulation (DBS) as applied to alleviate a number of neurological disorders, while in parallel mapping the electrophysiological circuits involved in generating and integrating neural signals driving the cardiorespiratory system during exercise. With the advent of improved neuroimaging techniques, neurosurgeons can place small electrodes into deep brain structures with a high degree accuracy to treat a number of neurological disorders, such as movement impairment associated with Parkinson's disease and neuropathic pain. As well as stimulating discrete nuclei and monitoring autonomic outflow, local field potentials can also assess how the neurocircuitry responds to exercise. This technique has provided an opportunity to validate in humans putative circuits previously identified in animal models. The central autonomic network consists of multiple sites from the spinal cord to the cortex involved in autonomic control. Important areas exist at multiple evolutionary levels, which include the anterior cingulate cortex (telencephalon), hypothalamus (diencephalon), periaqueductal grey (midbrain), parabrachial nucleus and nucleus of the tractus solitaries (brainstem), and the intermediolateral column of the spinal cord. These areas receive afferent input from all over the body and provide a site for integration, resulting in a coordinated efferent autonomic (sympathetic and parasympathetic) response. In particular, emerging evidence from DBS studies have identified the basal ganglia as a major sub-cortical cognitive integrator of both higher center and peripheral afferent feedback. These circuits in the basal ganglia appear to be central in coupling movement to the cardiorespiratory motor program. © 2020 American Physiological Society. Compr Physiol 10:1085-1104, 2020.

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.

Association between REM sleep behavior disorder and impulsive-compulsive behaviors in Parkinson's disease: a systematic review and meta-analysis of observational studies

BACKGROUND

Both REM sleep behavior disorder (RBD) and impulsive-compulsive behaviors (ICBs) are well-recognized non-motor features in patients with Parkinson's disease (PD). Studies have given contradictory results about the potential association between RBD and ICBs.

METHODS

PubMed, Embase (via Ovid), and the Cochrane Central Registry of Controlled Trials (CENTRAL) databases were systematically searched till August 20, 2019 to identify studies that explored the possible correlation between RBD and ICBs in patients with PD. Two authors independently screened records, extracted data and evaluated quality of included studies. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated by employing a random or fixed-effects model. We performed subgroup and sensitivity analyses, and we assessed potential publication bias.

RESULTS

A total of 134 references were screened and 10 studies involving 2781 PD patients were included. Overall, RBD was associated with a more than twofold higher risk of developing ICBs (OR 2.12, 95% CI 1.43-3.14, I² = 56.7%, P < 0.01). Similar results were obtained in sensitivity analyses and in meta-analyses of subgroups stratified based on multivariable adjustment and methods for diagnosing RBD and ICBs. No significant risk of publication bias was found.

CONCLUSION

RBD in PD is confirmed to be a risk factor for ICBs. Clinicians should be aware of this association to help them improve patient management.