Impulse Control Disorder in Parkinson's Disease: A Meta-Analysis of Cognitive, Affective, and Motivational Correlates

Unravelling the Parkinson's puzzle, from medications and surgery to stem cells and genes: a comprehensive review of current and future management strategies

Parkinson's disease (PD) is a neurodegenerative disorder, prevalent in the elderly population. Neuropathological hallmarks of PD include loss of dopaminergic cells in the nigro-striatal pathway and deposition of alpha-synuclein protein in the neurons and synaptic terminals, which lead to a complex presentation of motor and non-motor symptoms. This review focuses on various aspects of PD, from clinical diagnosis to currently accepted treatment options, such as pharmacological management through dopamine replacement and surgical techniques such as deep brain stimulation (DBS). The review discusses in detail the potential of emerging stem cell-based therapies and gene therapies to be adopted as a cure, in contrast to the present symptomatic treatment in PD. The potential sources of stem cells for autologous and allogeneic stem cell therapy have been discussed, along with the progress evaluation of pre-clinical and clinical trials. Even though recent techniques hold great potential to improve the lives of PD patients, we present the importance of addressing the safety, efficacy, ethical, cost, and regulatory concerns before scaling them to clinical use.

Dopamine agonists in Parkinson's disease: Impact of D1-like or D2-like dopamine receptor subtype selectivity and avenues for future treatment

Dopamine agonists (DAs) have demonstrated efficacy for the treatment of Parkinson's disease (PD) but are limited by adverse effects (AEs). DAs can vary considerably in their receptor subtype selectivity and affinity, chemical composition, receptor occupancy, and intrinsic activity on the receptor. Most currently approved DAs for PD treatment primarily target D2/D3 (D2-like) dopamine receptors. However, selective activation of D1/D5 (D1-like) dopamine receptors may enable robust activation of motor function while avoiding AEs related to D2/D3 receptor agonism. Full D1/D5 receptor-selective agonists have been explored in small, early-phase clinical studies, and although their efficacy for motor symptoms was robust, challenges with pharmacokinetics, bioavailability, cardiovascular AEs, and dyskinesia rates similar to levodopa prevented clinical advancement. Generally, repeated dopaminergic stimulation with full DAs is associated with frontostriatal dysfunction and sensitization that may induce plastic changes in the motor system, and neuroadaptations that produce long-term motor and nonmotor complications, respectively. Recent preclinical and clinical studies suggest that a D1/D5 receptor-selective partial agonist may hold promise for providing sustained, predictable, and robust motor control, while reducing risk for motor complications (e.g., levodopa-induced dyskinesia) and nonmotor AEs (e.g., impulse control disorders and excessive daytime sleepiness). Clinical trials are ongoing to evaluate this hypothesis. The potential emerging availability of novel dopamine receptor agonists with selective dopamine receptor pharmacology suggests that the older terminology "dopamine agonist" may need revision to distinguish older-generation D2/D3-selective agonists from D1/D5-selective agonists with distinct efficacy and tolerability characteristics.

Premorbid performances determine the deleterious effects of nigrostriatal degeneration and pramipexole on behavioural flexibility

Subtle cognitive impairment can occur early in the course of Parkinson's disease (PD) and may manifest under different forms of executive dysfunction such as impaired cognitive flexibility. The precise contribution of nigrostriatal dopaminergic neurodegeneration to these non-motor features of the disease is poorly known. Whether such cognitive impairment associated with the disease process may also predate and contribute to the development of neuropsychiatric side-effects following dopamine replacement therapy remains largely unknown. To address these issues, we investigated the respective contributions of nigrostriatal degeneration and chronic treatment with the dopamine D3-preferring agonist pramipexole on behavioral flexibility in a rat model of PD. Flexible, intermediate and inflexible rats were identified based on baseline assessment of behavioral flexibility using an operant set-shifting task. Nigrostriatal degeneration was induced by bilateral viral-mediated expression of A53T mutated human α-synuclein in the substantia nigra pars compacta and behavioral flexibility was assessed after induction of nigrostriatal degeneration, and during chronic pramipexole treatment. Nigrostriatal degeneration impaired behavioral flexibility in flexible but not in inflexible rats. Pramipexole induced a decrease of behavioral flexibility that was exacerbated in lesioned rats and in the most flexible individuals. Furthermore, the deficits induced by pramipexole in lesioned rats affected different components of the task between flexible and inflexible individuals. This study demonstrates that nigrostriatal degeneration and pramipexole unequally impair behavioral flexibility, suggesting that the susceptibility to develop non-motor impairments upon treatment initiation could primarily depend on premorbid differences in behavioral flexibility.

Neural correlates of impulse control behaviors in Parkinson's disease: Analysis of multimodal imaging data

BACKGROUND

Impulse control behaviors (ICB) are frequently observed in patients with Parkinson's disease (PD) and are characterized by compulsive and repetitive behavior resulting from the inability to resist internal drives.

OBJECTIVES

In this study, we aimed to provide a better understanding of structural and functional brain alterations and clinical parameters related to ICB in PD patients.

METHODS

We utilized a dataset from the Parkinson's Progression Markers Initiative including 36 patients with ICB (PDICB+) compared to 76 without ICB (PDICB-) and 61 healthy controls (HC). Using multimodal MRI data we assessed gray matter brain volume, white matter integrity, and graph topological properties at rest.

RESULTS

Compared with HC, PDICB+ showed reduced gray matter volume in the bilateral superior and middle temporal gyrus and in the right middle occipital gyrus. Compared with PDICB-, PDICB+ showed volume reduction in the left anterior insula. Depression and anxiety were more prevalent in PDICB+ than in PDICB- and HC. In PDICB+, lower gray matter volume in the precentral gyrus and medial frontal cortex, and higher axial diffusivity in the superior corona radiata were related to higher depression score. Both PD groups showed disrupted functional topological network pattern within the cingulate cortex compared with HC. PDICB+ vs PDICB- displayed reduced topological network pattern in the anterior cingulate cortex, insula, and nucleus accumbens.

CONCLUSIONS

Our results suggest that structural alterations in the insula and abnormal topological connectivity pattern in the salience network and the nucleus accumbens may lead to impaired decision making and hypersensitivity towards reward in PDICB+. Moreover, PDICB+ are more prone to suffer from depression and anxiety.

Treatment for cognitive and neuropsychiatric non-motor symptoms in Parkinson's disease: current evidence and future perspectives

INTRODUCTION

Non-motor symptoms (NMS) affect patients with Parkinson's disease (PD) from the prodromal to the advanced stages. NMS phenotypes greatly vary and have a huge impact on patients' and caregivers' quality of life (QoL). The management of cognitive and neuropsychiatric NMS remains an unmet need.

AREAS COVERED

The authors, herein, review the dopaminergic and non-dopaminergic pathogenesis, clinical features, assessment, and pharmacological and non-pharmacological treatments of cognitive and neuropsychiatric NMS in PD. They discuss the current evidence and report the findings of an overview of ongoing trials on pharmacological and selected non-pharmacological strategies.

EXPERT OPINION

The treatment of cognitive and neuropsychiatric NMS in PD is poorly explored, and therapeutic options are unsatisfactory. Pharmacological treatment of cognitive NMS is based on symptomatic active principles used in Alzheimer's disease. Dopamine agonists, selective serotonin, and serotonin-norepinephrine reuptake inhibitors have some evidence on PD-related depression. Clozapine, quetiapine, and pimavanserin may be considered for psychosis in PD. Evidence on the treatment of other neuropsychiatric NMS is limited or lacking. Addressing pathophysiological and clinical issues, which hamper solid evidence on the treatment of cognitive and neuropsychiatric NMS, may reduce the impact on QoL for PD patients and their caregivers.

Impulse control disorders in hyperprolactinemic patients on dopamine agonist therapy

Dopamine agonists (DAs) represent a mainstay of therapy for hyperprolactinemia and prolactinomas. The widespread use of DAs, including bromocriptine, cabergoline and (in some countries) quinagolide, has led to the emergence and recognition of impulse control disorders (ICDs) that may occur in association with DA therapy.Such ICDs include pathological gambling, compulsive shopping, hypersexuality and punding (the performance of repetitive tasks), among others. These manifestations can lead to substantial harms to patients and their families, if left undiagnosed and untreated. Several risk factors that may increase the risk of ICDs have been proposed, including younger age, male gender, smoking and alcohol use and history of depression.The diagnosis of ICDs in hyperprolactinemic patients treated with DAs requires a high index of suspicion and a systematic approach, using available screening questionnaires. However, it should be noted that available test instruments, including questionnaires and computerized tasks, have not been validated specifically in hyperprolactinemic patients. Hyperprolactinemic patients who develop ICDs should be withdrawn from DA therapy or, at a minimum, undergo a DA dose reduction, and considered for psychiatric consultation and cognitive behavioral therapy. However, the role of psychopharmacotherapy in hyperprolactinemic patients with ICDs remains incompletely characterized.Patient counseling regarding the risk of ICDs occurring in association with DA therapy, early detection and prompt intervention may mitigate potential harms associated with ICDs. Additional studies are needed to fully characterize risk factors, underlying mechanisms and identify effective therapies for ICDs in patients with hyperprolactinemia receiving DAs.

Trait Anxiety as a Risk Factor for Impulse Control Disorders in de novo Parkinson's Disease

BACKGROUND

In addition to the well-known motor symptoms, patients with Parkinson's disease (PD) also frequently experience disabling non-motor symptoms including impulse control disorders (ICDs). ICDs are characterized by a loss of voluntary control over impulses, drives, or temptations regarding excessive hedonic behavior.

OBJECTIVE

The present study examined whether depression and anxiety in de novo PD patients predict the prospective development of ICDs.

METHODS

We selected 330 de novo PD patients from the Parkinson's Progression Markers Initiative database who were free of ICDs at the start of the study. ICD presence at baseline and follow-up assessments was evaluated via the shortened version of the Questionnaire for Impulsive-Compulsive Disorders (QUIP-S). Baseline depression and anxiety were measured via the Geriatric Depression Scale (GDS-15) and State-Trait-Anxiety Inventory (STAI-Y), respectively.

RESULTS

A total of 149 participants (45.2%) developed an ICD at follow-up and average time of ICD onset was 35 months after baseline. Results of a Cox regression analysis showed that STAI-Y scores but not GDS-15 scores significantly predicted ICD presence. Specifically, scores reflecting higher trait anxiety were associated with an increased risk of developing an ICD. This effect was not confounded by age, gender or UPDRS motor score. We also replicated the well-established result that dopamine agonist use is predictive of ICDs.

CONCLUSION

Our findings indicate that higher anxiety levels in de novo PD patients represent a risk factor for ICD development during the course of the disorder. This highlights the need for early and routine based anxiety screening in these patients.

Anxiety predicts impulsive-compulsive behaviours in Parkinson's disease: Clinical relevance and theoretical implications

Patients with Parkinson's disease (PD) often present symptoms of anxiety, depression and apathy. These negative affect manifestations have been recently associated with the presence of impulsive compulsive behaviours (ICBs). However, their relation with the use of dopamine replacement therapy (DRT), a renewed risk factor for ICBs, is still not fully understood. Elucidating the role of these different ICBs predictors in PD could inform both prevention/intervention recommendations as well as theoretical models. In the present study, we have analysed data collected in 417 PD patients, 50 patients with Parkinsonian symptoms but with scan without evidence of dopaminergic deficit (SWEDD), and 185 healthy controls (HC). We examined each patient's clinical profile over a two-year time window, investigating the role of both negative affect and DRT on ICBs. Results confirmed the presence of higher levels of anxiety in both the clinical groups, and of higher level of ICBs in SWEDD patients, respect to both PD and HC. Mixed model analyses revealed a statistically significant association between anxiety and ICBs in the SWEDD patients who did not take any DRT. Findings suggest the independence between anxiety and DRT in ICBs development, and provide new evidence for the motivational opponency theoretical framework.

Decision Making and Risk Propensity in Individuals with Tendencies towards Specific Internet-Use Disorders

The uncontrolled use of specific Internet applications is increasingly recognized as a mental health issue. Gaming disorder, which is one subtype of specific Internet-use disorders (sIUDs), has been included in the ICD-11 as disorder due to addictive behaviors. Addictive disorders are assumed to be accompanied by cognitive deficits as indicated by weaker performance in executive function and risky decision-making tasks. This study investigates risky decision-making in individuals with tendencies towards sIUDs including gaming, online buying-shopping, and social-networks-use disorders. A total of 293 individuals participated in the study. Based on specific screening instruments, the participants were assigned to a group with tendencies towards sIUD or a control group. Participants completed a risky decision-making task and questionnaires assessing risk-taking propensity, impulsivity, psychopathology, and perceived stress. The group with sIUD tendencies showed higher attentional impulsivity and higher levels of depression and anxiety compared to the control group. The groups did not differ in decision making and risk propensity. Decision making did not have significant effects on sIUD symptoms. Risk for developing sIUDs does not appear to be accompanied by altered general decision-making tendencies. Rather, psychological (pre-)load and attentional deficits appear to be relevant features in uncontrolled use of the Internet.

No Higher Risk-Seeking Tendencies or Altered Self-Estimation in a Social Decision-Making Task in Patients with Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) has been associated with a tendency towards more risky decisions. However, the commonly used paradigms typically neglect the social context.

OBJECTIVE

Here, we investigated social decision-making and self-estimation in a competitive experimental task.

METHODS

A computerized experimental setting was used in which 86 PD patients (age = 66.5 [50-79], 62.8% male, H&Y = 2 [1.5-3]) and 44 healthy controls (HC; age = 67 [54-79], 54.4% male) in groups of four performed mathematical addition tasks in which they were asked to calculate as many sums as possible in five minutes. Participants had to choose their preferred compensation scheme ("piece rate" versus "tournament") and retrospectively rank their performance in comparison to the suspected performance of the others. A comprehensive neuropsychological test battery was also conducted.

RESULTS

No significant difference was found in overall social decision-making and self-estimation between PD patients and HC. However, for those individuals who made inadequate decisions, PD patients engaged in significantly more risk-averse and HC in more risky decisions. Concerning those inadequate decisions, the PD patients made more extreme decisions (severity of social decision-making) in both directions (risk-averse, risk-seeking).

CONCLUSION

Our data indicate that social decision-making behavior and self-estimation are largely intact in PD patients with mild to moderate disease stages and intact global cognition, executive functions, and social cognition. Future studies with more heterogeneous PD samples regarding their neuropsychological profile will have to examine at which state social decision-making may be affected and by which factors this behavior might be influenced.

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.

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.

Comment on "The association between pain and impulse control behaviours in Parkinson's disease"

The recent paper by Kobylecki et al. explored the association between impulse control behaviours and pain in Parkinson's disease, under the hypothesis of shared mesolimbic dysfunction. We discuss cognitive and motivational disturbances as potential covariates and suggest the dorsolateral prefrontal cortex as a therapeutic target for this "pain-predominant" symptom subtype.

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.

Non-motor symptom burden in patients with Parkinson's disease with impulse control disorders and compulsive behaviours: results from the COPPADIS cohort

The study was aimed at analysing the frequency of impulse control disorders (ICDs) and compulsive behaviours (CBs) in patients with Parkinson's disease (PD) and in control subjects (CS) as well as the relationship between ICDs/CBs and motor, nonmotor features and dopaminergic treatment in PD patients. Data came from COPPADIS-2015, an observational, descriptive, nationwide (Spain) study. We used the validated Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) for ICD/CB screening. The association between demographic data and ICDs/CBs was analyzed in both groups. In PD, this relationship was evaluated using clinical features and treatment-related data. As result, 613 PD patients (mean age 62.47 ± 9.09 years, 59.87% men) and 179 CS (mean age 60.84 ± 8.33 years, 47.48% men) were included. ICDs and CBs were more frequent in PD (ICDs 12.7% vs. 1.6%, p < 0.001; CBs 7.18% vs. 1.67%, p = 0.01). PD patients had more frequent previous ICDs history, premorbid impulsive personality and antidepressant treatment (p < 0.05) compared with CS. In PD, patients with ICDs/CBs presented younger age at disease onset, more frequent history of previous ICDs and premorbid personality (p < 0.05), as well as higher comorbidity with nonmotor symptoms, including depression and poor quality of life. Treatment with dopamine agonists increased the risk of ICDs/CBs, being dose dependent (p < 0.05). As conclusions, ICDs and CBs were more frequent in patients with PD than in CS. More nonmotor symptoms were present in patients with PD who had ICDs/CBs compared with those without. Dopamine agonists have a prominent effect on ICDs/CBs, which could be influenced by dose.

Management of psychiatric disorders in Parkinson's disease : Neurotherapeutics - Movement Disorders Therapeutics

Affective disorders (depression and anxiety), psychosis, impulse control disorders, and apathy are common and sometimes disabling psychiatric conditions in Parkinson disease (PD). Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their high frequency, there remains incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically co- or multimorbid, and there is great intra- and interindividual variability in presentation [1]. The neuropathophysiological changes that occur in PD, as well as the association between PD treatment and particular psychiatric disorders, suggest a neurobiological contribution to many psychiatric symptoms. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated, and although psychotropic medication use is common, randomized controlled trials demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors, and most importantly, establishing efficacious and well-tolerated treatment strategies.

Non-invasive Brain Stimulation for Gambling Disorder: A Systematic Review

Background: Gambling disorder (GD) is the most common behavioral addiction and shares pathophysiological and clinical features with substance use disorders (SUDs). Effective therapeutic interventions for GD are lacking. Non-invasive brain stimulation (NIBS) may represent a promising treatment option for GD.

Objective: This systematic review aimed to provide a comprehensive and structured overview of studies applying NIBS techniques to GD and problem gambling.

Methods: A literature search using Pubmed, Web of Science, and Science Direct was conducted from databases inception to December 19, 2019, for studies assessing the effects of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (t-DCS) on subjects with GD or problem gambling. Studies using NIBS techniques on healthy subjects and those without therapeutic goals but only aiming to assess basic neurophysiology measures were excluded.

Results: A total of 269 articles were title and abstract screened, 13 full texts were assessed, and 11 were included, of which six were controlled and five were uncontrolled. Most studies showed a reduction of gambling behavior, craving for gambling, and gambling-related symptoms. NIBS effects on psychiatric symptoms were less consistent. A decrease of the behavioral activation related to gambling was also reported. Some studies reported modulation of behavioral measures (i.e., impulsivity, cognitive and attentional control, decision making, cognitive flexibility). Studies were not consistent in terms of NIBS protocol, site of stimulation, clinical and surrogate outcome measures, and duration of treatment and follow-up. Sample size was small in most studies.

Conclusions: The clinical and methodological heterogeneity of the included studies prevented us from drawing any firm conclusion on the efficacy of NIBS interventions for GD. Further methodologically sound, robust, and well-powered studies are needed.

Increased large-scale inter-network connectivity in relation to impulsivity in Parkinson's disease

Impulsivity is a neuropsychiatric feature of Parkinson’s disease (PD). We investigated the pathophysiology of impulsivity in PD using resting-state functional magnetic resonance imaging (rs-fMRI). We investigated 45 patients with idiopathic PD and 21 healthy controls. Based on Barratt Impulsiveness Scale (BIS-11) score, PD patients were classified as higher (PD-HI) or lower impulsivity (PD-LI). Functional connectivity (FC) between various large-scale brain networks were analysed using the CONN toolbox. FC between the right frontoparietal network (FPN) and medial visual network (MVN) was significantly higher in PD-HI patients than PD-LI patients (false discovery rate [FDR]-adjusted p = 0.0315). FC between the right FPN and MVN had a significant positive correlation with total BIS-11 score (FDR-adjusted p = 0.010) and the attentional impulsivity (FDR-adjusted p = 0.046) and non-planning impulsivity subscale scores (FDR-adjusted p = 0.018). On the other hand, motor impulsivity subscale score had a significant negative correlation with the FC between the default-mode and salience networks (right supramarginal gyrus, FDR-adjusted p = 0.018; anterior cingulate cortex, FDR-adjusted p = 0.027); this trend was observed in healthy controls. The attentional and non-planning impulsivity, regarded as ‘cognitive’ impulsivity, may be associated with dysfunction in integration of perceptual information and flexible cognitive control in PD.

Measuring impulsivity in Parkinson's disease: a correlational and structural neuroimaging study using different tests

BACKGROUND AND PURPOSE

Impulsivity is an aspect of personality and a major component of multiple neuropsychiatric conditions. In Parkinson's disease, it has been associated with the expression of impulse control disorders, a highly prevalent non-motor complication. Even though multiple tests of impulsivity have been used in this context, the impact of test choice has not been addressed. The aim was to evaluate whether different impulsivity measures in Parkinson's disease share substantial inter-scale and anatomical correlations or rather mirror different underlying phenomena.

METHODS

In a consecutive sample of 89 Parkinson's disease patients without impulse control disorders, four common tests were evaluated assessing different aspects of impulsivity: impulsiveness trait, decisions under implicit risk with and without losses, and delay discounting. Correlations among test scores were analysed and each score was used as a regressor in a set of grey matter volume (GMV) voxel-based morphometry analyses to explore their brain structural correlates.

RESULTS

No significant correlations were found between the different impulsivity tests. Furthermore, their structural brain correlates were divergent. Impulsiveness trait appeared to be associated with lower GMV in dorsal-lateral prefrontal cortices, implicit risk (with losses) with higher GMV in the left nucleus accumbens and lower left insular GMV, implicit risk (without losses) with higher GMV in the left lingual gyrus and lower GMV in the gyri recti and delay discounting with higher GMV in the left nucleus accumbens.

CONCLUSIONS

In Parkinson's disease, different impulsivity measures reflect very dissimilar behavioural and brain structural correlates. Our results suggest that parkinsonian impulsivity is not a unitary phenomenon but rather a heterogeneous entity.

A neurally plausible schema-theoretic approach to modelling cognitive dysfunction and neurophysiological markers in Parkinson's disease

The cognitive mechanisms underlying sequential action selection in routine or everyday activities may be understood in terms of competition within a hierarchically organised network of action schemas. We present a neurobiologically plausible elaboration of an existing schema-based cognitive model of action selection in which the basal ganglia implements an activation-based selection process that mediates between assumed cortical representations of rule-based schemas. More specifically, the model employs a network of basal ganglia units with computations performed by individual BG nuclei, embedded in a corticothalamic loop that disinhibits schemas according to the received feedback. We provide bridging assumptions for linking the operation of the model with ERP components that describe the error-related negativity (ERN) and the parietal switch positivity (PSP), and evaluate the model against behavioural and neural markers of performance of the Wisconsin Card Sorting Test by healthy control participants and Parkinson's Disease patients.

A Single-institution Study on Predictors of Short-term Progression from Mild Cognitive Impairment in Parkinson's Disease to Parkinson's Disease with Dementia

Background

Patients with non-demented Parkinson's disease (PD) sometime have mild cognitive impairment (MCI), and mild cognitive impairment in Parkinson's disease (PD-MCI) may convert to Parkinson's disease with dementia (PDD) within several years. Cognitive impairment also occurs in the early stages of the disease, gradually progressing to lower quality of life and instrumental activities of daily living. It is important to elucidate the predictors of progression from PD-MCI to PDD via longitudinal studies.

Methods

This was a single center, case-control study. We analysed data from 49 patients with PD-MCI diagnosed as level I using the Movement Disorder Society PD-MCI criteria at baseline who had completed 1.5 years of follow-up. We defined patients who progressed to PDD as patients with progressive PD-MCI and patients who did not progress to PDD as patients with non-progressive PD-MCI. Depression, apathy, sleep disorders, constipation, light-headedness, hallucinations, impulse control disorders (ICDs) and impulsive-compulsive behaviors (ICBs) at baseline were statistically analysed as predictors of progression.

Results

Of the 49 PD-MCI patients, 33 did not convert to PDD (non-progressive PD-MCI), and 16 converted to PDD (progressive PD-MCI). The Mini-Mental State Examination (MMSE) score, light-headedness and ICDs were elucidated as predictors of progressive PD-MCI via a multivariate logistic regression model. The adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for each item were MMSE score, OR 0.324, 95% CI 0.119-0.882, P = 0.027; light-headedness, OR 27.665, 95% CI 2.263-338.185, P= 0.009; and ICDs, OR 53.451, 95% CI 2.298-291.085, P = 0.010.

Conclusion

Cognitive function, ICDs and light-headedness may be risk factors for the development of PDD in PD-MCI patients.

Dopamine and Gambling Disorder: Prospects for Personalized Treatment

Purpose of Review

To address variation in the severity of gambling disorder, this review evaluates the contribution of mesocorticolimbic dopamine neurons to potential behavioral endophenotypes, the influence of individual differences in the dopamine system on gambling and related behaviors, and the possible role for dopaminergic medications in the treatment of gambling disorder.

Recent Findings

Newer work has suggested that dopaminergic dysfunction can lead to increased reward anticipation and a greater sensitivity to uncertainty, which in turn may drive addictive gambling behaviors. In addition, increased impulsivity, a well-recognized risk factor for gambling disorder, has been linked to dopaminergic dysfunction. More recently, emerging evidence has suggested that dopaminergic medications can influence the discounting of delayed rewards.

Summary

Dopaminergic drugs that increase the salience of long-term over short-term goals may ameliorate symptoms of impulsive individuals with gambling disorder. More broadly, improved understanding of intermediate behavioral and other phenotypes with a defined neurobiological substrate may allow for personalized treatment of gambling disorder and other psychiatric conditions.

Evolution of impulsive-compulsive behaviors and cognition in Parkinson's disease

The longitudinal course of ICBs in patients with Parkinson's disease (PwP) relative to controls has not been explored as of yet. The aim of this study is to determine the frequency, evolution and associated cognitive and clinical features of impulsive and compulsive behaviors (ICBs) over 4 years of prospective follow-up in a population-based cohort with early Parkinson's disease (PD). We recruited 124 cognitively intact participants with early PD and 156 matched controls from the Norwegian ParkWest study. ICBs were assessed using the self-report short form version of the Questionnaire for Impulsive-Compulsive Disorders in PD. Cognitive changes were examined in PwP with and without ICBs who completed the 4-year follow-up. Generalized linear mixed modelling and mixed linear regression were used to analyze clinical factors and cognitive changes associated with ICBs in PwP over time. ICBs were more common in PwP than controls at all visits, with an age-adjusted odds ratio (OR) varying between 2.5 (95% CI 1.1-5.6; p = 0.022) and 5.1 (95% CI 2.4-11.0; p < 0.001). The 4-year cumulative frequency of ICBs in PwP was 46.8% and 23.3% developed incident ICBs during the study period, but the presence of ICBs was non-persistent in nearly 30%. ICBs were independently associated with younger age (OR 0.95, 95% CI 0.91-0.99: p = 0.008) and use of dopamine agonist (OR 4.1, 95% CI 1.56-10.69). Cognitive changes over time did not differ between patients with and without ICBs. In conclusion, ICBs are common in PwP, but are often non-persistent and not associated with greater cognitive impairment over time.

The Neuropsychiatry of Parkinson Disease: A Perfect Storm

Affective disorders, cognitive decline, and psychosis have long been recognized as common in Parkinson disease (PD), and other psychiatric disorders include impulse control disorders, anxiety symptoms, disorders of sleep and wakefulness, and apathy. Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their frequent occurrence, there is incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically multimorbid, and there is great intra- and interindividual variability in presentation. The hallmark neuropathophysiological changes that occur in PD, plus the association between exposure to dopaminergic medications and certain psychiatric disorders, suggest a neurobiological basis for many psychiatric symptoms, although psychological factors are involved as well. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated and although psychotropic medication use is common, controlled studies demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors and establishing efficacious and well-tolerated treatment strategies.

Nigrostriatal dopamine transporter availability, and its metabolic and clinical correlates in Parkinson's disease patients with impulse control disorders

PURPOSE

Previous studies in patients with Parkinson's disease (PD) and impulse control disorders (ICDs) have produced heterogeneous results regarding striatal dopamine transporter (DaT) binding and activity in the mesocorticolimbic network. Our aim here was to study the relationship between striatal DaT availability and cortical metabolism, as well as motor, behavioural and cognitive features of PD patients with ICD.

METHODS

In a group of PD patients with ICD (PD-ICD, n = 16) and 16 matched PD patients without ICD (PD-noICD, n = 16), DaT single-photon emission computed tomography (SPECT) imaging (DaTSCAN) was used to study DaT availability in predefined striatal volumes of interest (VOIs): putamen, caudate nucleus and ventral striatum (VS). In addition, the specific association of striatal DaT binding with cortical limbic and associative metabolic activity was evaluated by ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in PD-ICD patients and investigated using statistical parametric mapping (SPM8). Finally, associations between DaT availability and motor, behavioural and cognitive features were assessed.

RESULTS

PD-ICD patients had a significantly lower DaT density in the VS than PD-noICD patients, which was inversely associated with ICD severity. Lower DaT availability in the VS was associated with lower FDG uptake in several cortical areas belonging to the limbic and associative circuits, and in other regions involved in reward and inhibition processes (p < 0.0001 uncorrected; k > 50 voxels). No significant results were observed using a higher conservative threshold (p < 0.05; FDR corrected). PD-ICD patients also displayed impairment in interference and attentional Stroop Task execution, and more anxiety, all associated with reduced DaT availability in the VS and caudate nucleus.

CONCLUSIONS

ICDs in PD patients are related to reduced DaT binding in the VS, which accounts for dysfunction in a complex cortico-subcortical network that involves areas of the mesolimbic and mesocortical systems, being associated with reward evaluation, salience attribution and inhibitory control processes.

Resting state oscillations suggest a motor component of Parkinson's Impulse Control Disorders

OBJECTIVES

Impulse control disorders (ICDs) in Parkinson's disease (PD) have been associated with cognitive impulsivity and dopaminergic dysfunction and treatment. The present study tests the neglected hypothesis that the neurofunctional networks involved in motor impulsivity might also be dysfunctional in PD-ICDs.

METHODS

We performed blind spectral analyses of resting state electroencephalographic (EEG) data in PD patients with and without ICDs to probe the functional integrity of all cortical networks. Analyses were performed directly at the source level after blind source separation. Discrete differences between groups were tested by comparing patients with and without ICDs. Gradual dysfunctions were assessed by means of correlations between power changes and clinical scores reflecting ICD severity (QUIP score).

RESULTS

Spectral signatures of ICDs were found in the medial prefrontal cortex, the dorsal anterior cingulate and the supplementary motor area, in the beta and gamma bands. Beta power changes in the supplementary motor area were found to predict ICDs severity.

CONCLUSION

ICDs are associated with abnormal activity within frequency bands and cortical circuits supporting the control of motor response inhibition.

SIGNIFICANCE

These results bring to the forefront the need to consider, in addition to the classical interpretation based on aberrant mesocorticolimbic reward processing, the issue of motor impulsivity in PD-ICDs and its potential implications for PD therapy.

Compulsive eating behaviors in Parkinson's disease

PURPOSE

Eating disorders are common in Parkinson's disease (PD) patients and often class in Impulse control disorders, however, little is known about their phenomenology. Specific symptoms and comorbidities were described in a group of PD patients in this preliminary study.

METHODS

Over a period of 6 months, 51 PD patients who experienced significant changes in eating habits following diagnosis of PD and were interviewed during regularly scheduled follow-up visits. We assessed each patient's height and weight, impulsivity, psychological distress, current eating disorder symptoms, food addiction, food habits and craving.

RESULTS

Among the PD patients who experienced modified dietary habits following diagnosis, few exhibited binge eating disorders (BED) full criteria (3.9%). However, 21.6% of patients experienced episodes of out-of-control eating with a large quantity of food in short time and 39.2% satisfied food addiction (FA) criteria without binge eating disorder. Food cravings more than once a week were experienced in approximately half of the population including all FA patients. Regarding comorbidities, FA PD patients present impulsive features and anxiety.

CONCLUSIONS

This study confirms the existence of FA profile in PD patients. Eating disorders even in PD are complex and have a cross-cutting criteria related to out-of-control eating, FA, and BED. The association of anxiety with PD-related food addiction, contrary to L-dopa equivalent daily dose mean score or the presence of dopamine agonists, underline the complex sustainability of the dopaminergic brainstem support. A study on their detailed prevalence in this population could be helpful to better understand unspecified feeding or eating disorder.

CLINICAL TRIAL NUMBER

DR-2012-007.

NAME OF THE REGISTRY

French Committee for the Protection of Persons (CPP) & French National Commission on Computing and Liberty (CNIL).

LEVEL OF EVIDENCE

Level V, descriptive study.

Impact of Cognitive Profile on Impulse Control Disorders Presence and Severity in Parkinson's Disease

Background: Impulse control disorders (ICDs) and related behaviors are frequent in Parkinson's disease (PD). Mild cognitive impairment (PD-MCI) and dementia (PDD), both characterized by heterogeneous cognitive phenotypes, are also commonly reported in PD. However, the frequency and severity of ICD within PD cognitive states is unknown.

Methods: Three hundred and twenty-six PD patients completed a comprehensive neuropsychological assessment and were classified as PD-MCI, PDD, or without cognitive alterations (PD-NC). The Minnesota impulsive disorders interview was used to ascertain the presence (ICD+) or absence (ICD–) of ICD. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale was used to assess ICD severity. A subsample of 286 patients evaluated with the same cognitive tasks was selected in order to investigate the characteristics of ICD in PD cognitive phenotypes.

Results: ICDs were present in 55% of PD-NC, in 50% of PD-MCI, and in 42% of PDD patients. Frequencies of ICD+ with attentive (ICD+: 20% vs. ICD–: 4%; p = 0.031) and executive impairments (ICD+: 44% vs. ICD–: 30%; p = 0.027) were higher in the PD-MCI and PDD subgroups, respectively. As expected, no differences were observed in the PD-NC. PD-MCI with attentive impairments presented higher percentage of ICD+ with deficits in the Trail Making Test B-A but not in the Digit Span Sequencing task. In PDD, executive failures concerned Similarities task (ICD+: 67%; ICD–: 29%; p = 0.035), with no differences between ICD+ and ICD– in the Stroop task.

Conclusions: Prevalence and severity of ICDs and related behaviors do not differ in PD with different cognitive states. However, ICD+ are more likely to show deficits, respectively in attentive and in executive domains, specifically in the Trail Making Test B-A task for the attention and working memory domain in PD-MCI and in the Similarities task for the executive function domain in PDD. Prospective studies should evaluate if these tests can be used as screening tool for ICDs in PD.

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.

Dopaminergic Neurotransmission in Patients With Parkinson's Disease and Impulse Control Disorders: A Systematic Review and Meta-Analysis of PET and SPECT Studies

Background: Around 30% Parkinson's disease (PD) patients develop impulse control disorders (ICDs) to D_2/3 dopamine agonists and, to a lesser extent, levodopa. We aim to investigate striatal dopaminergic function in PD patients with and without ICD.

Methods: PubMed, Science Direct, EBSCO, and ISI Web of Science databases were searched (from inception to March 7, 2018) to identify PET or SPECT studies reporting striatal dopaminergic function in PD patients with ICD (ICD+) compared to those without ICD (ICD–). Studies which included drug naïve patients, explored non-pharmacological procedures (e.g., deep brain stimulation), and those using brain blood perfusion or non-dopaminergic markers were excluded. Standardized mean difference (SDM) was used and random-effect models were applied. Separate meta-analyses were performed for dopamine transporter level, dopamine release, and dopamine receptors availability in the putamen, caudate, dorsal, and ventral striatum.

Results: A total of 238 studies were title and abstract screened, of which 19 full-texts were assessed. Nine studies (ICD+: N = 117; ICD–: N = 175 patients) were included in the analysis. ICD+ showed a significant reduction of dopamine transporter binding in the putamen (SDM = −0.46; 95% CI: −0.80, −0.11; Z = 2.61; p = 0.009), caudate (SDM = −0.38; 95% CI: −0.73, −0.04; Z = 2.18; p = 0.03) and dorsal striatum (SDM = −0.45; 95% CI: −0.77, −0.13; Z = 2.76; p = 0.006), and increased dopamine release to reward-related stimuli/gambling tasks in the ventral striatum (SDM = −1.04; 95% CI: −1.73, −0.35; Z = 2.95; p = 0.003). Dopamine receptors availability did not differ between groups. Heterogeneity was low for dopamine transporter in the dorsal striatum (I² = 0%), putamen (I² = 0%) and caudate (I² = 0%), and pre-synaptic dopamine release in the dorsal (I² = 0%) and ventral striatum (I² = 0%); heterogeneity was high for dopamine transporter levels in the ventral striatum (I² = 80%), and for dopamine receptors availability in the ventral (I² = 89%) and dorsal (I² = 86%) striatum, putamen (I² = 93%), and caudate (I² = 71%).

Conclusions: ICD+ patients show lower dopaminergic transporter levels in the dorsal striatum and increased dopamine release in the ventral striatum when engaged in reward-related stimuli/gambling tasks. This dopaminergic imbalance might represent a biological substrate for ICD in PD. Adequately powered longitudinal studies with drug naïve patients are needed to understand whether these changes may represent biomarkers of premorbid vulnerability to ICD.