Depression and impulse control disorders in Parkinson's disease: two sides of the same coin?

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.

Unveiling the Burden of Drug-Induced Impulsivity: A Network Analysis of the FDA Adverse Event Reporting System

INTRODUCTION

Impulsivity induced by dopaminergic agents, like pramipexole and aripiprazole, can lead to behavioral addictions that impact on social functioning and quality of life of patients and families (e.g., resulting in unemployment, marital problems, anxiety). These secondary effects, interconnected in networks of signs and symptoms, are usually overlooked by clinical trials, not reported in package inserts, and neglected in clinical practice.

OBJECTIVE

This study explores the syndromic burden of impulsivity induced by pramipexole and aripiprazole, pinpointing key symptoms for targeted mitigation.

METHODS

An event-event Information Component (IC) on the FDA Adverse Event Reporting System (FAERS) (January 2004 to March 2022) identified the syndrome of events disproportionally co-reported with impulsivity, separately for pramipexole and aripiprazole. A greedy-modularity clustering on composite network analyses (positive pointwise mutual information [PPMI], Ising, Φ) identified sub-syndromes. Bayesian network modeling highlighted possible precipitating events.

RESULTS

Suspected drug-induced impulsivity was documented in 7.49% pramipexole and 4.50% aripiprazole recipients. The highest IC concerned obsessive-compulsive disorder (reporting rate = 26.77%; IC median = 3.47, 95% confidence interval [CI] = 3.33-3.57) and emotional distress (21.35%; 3.42, 3.26-3.54) for pramipexole, bankruptcy (10.58%; 4.43, 4.26-4.55) and divorce (7.59%; 4.38, 4.19-4.53) for aripiprazole. The network analysis identified delusional jealousy and dopamine dysregulation sub-syndromes for pramipexole, obesity-hypoventilation and social issues for aripiprazole. The Bayesian network highlighted anxiety and economic problems as potentially precipitating events.

CONCLUSION

The under-explored consequences of drug-induced impulsivity significantly burden patients and families. Network analyses, exploring syndromic reactions and potential precipitating events, complement traditional techniques and clinical judgment. Characterizing the secondary impact of reactions will support informed patient-centered decision making.

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.

Hydrogen sulfide attenuates depression-like behaviours in Parkinson's disease model rats by improving synaptic plasticity in a hippocampal Warburg effect-dependent manner

BACKGROUND

Depression is a highly prevalent comorbidity arising in patients with Parkinson's disease (PD). However, depression in patients with PD is poorly treated. Hydrogen sulfide (H2S), a neuromodulator, has the potential to relieve depression.

OBJECTIVE

To investigate whether H2S attenuates depression-like behaviours in a rat model of PD and examine the underlying mechanisms.

METHODS

We utilised rotenone to develop a PD model with subcutaneous injections in the dorsal cervical region of Sprague-Dawley rats. The depression-like behaviours in the rotenone-induced PD model rats were assessed through forced swimming, tail suspension, open field, novelty-suppressed feeding, and elevated plus-maze tests. The expression of postsynaptic density protein-95 and synapsin-1, related to synaptic plasticity, was detected using Western blot in the hippocampus. The hippocampal ultrastructure, including the synaptic density, length of the synaptic active zone, postsynaptic density thickness, and synaptic gap width, was detected using transmission electron microscopy.

RESULTS

We proved that sodium hydrosulfide (NaHS; a donor of H2S) significantly attenuated the depression-like behaviours and disorders of hippocampal synaptic plasticity in rotenone-induced PD rats. Furthermore, inhibition of the hippocampal Warburg effect by 2-deoxyglucose abolished NaHS-enhanced hippocampal synaptic plasticity and reversed NaHS-attenuated depression-like behaviours in the rotenone-induced PD rats.

CONCLUSION

H2S attenuates PD-associated depression by improving the hippocampal synaptic plasticity in a hippocampal Warburg effect-dependent manner.

Non-Pharmacological Interventions for Depression and Anxiety in Parkinson's Disease

Non-pharmacological interventions, including cognitive-behavioral therapy (CBT), non-invasive brain stimulation (NIBS), electroconvulsive therapy (ECT), light therapy (LT), and physical rehabilitation/exercise, have shown promise as effective approaches to treat symptoms of depression and anxiety in individuals with Parkinson's disease (PD). In this narrative literature overview, we discuss the state-of-the-art regarding these treatment options and address future perspectives for clinical practice and research. Non-pharmacological interventions hold promise to treat depression and anxiety in PD. There is meta-analytic evidence for the efficacy of CBT, NIBS, ECT, LT, and exercise on improving depressive symptoms. For the treatment of anxiety symptoms, CBT shows large effects but scientific evidence of other non-pharmacological interventions is limited. Importantly, these treatments are safe interventions with no or mild side-effects. More research is needed to tailor treatment to the individuals' needs and combined interventions may provide synergistic effects.We conclude that non-pharmacological interventions should be considered as alternative or augmentative treatments to pharmacological and neurosurgical approaches for the treatment of depression and anxiety in individuals with PD.

Uncovering the neurophysiology of mood, motivation and behavioral symptoms in Parkinson's disease through intracranial recordings

Neuropsychiatric mood and motivation symptoms (depression, anxiety, apathy, impulse control disorders) in Parkinson's disease (PD) are highly disabling, difficult to treat and exacerbated by current medications and deep brain stimulation therapies. High-resolution intracranial recording techniques have the potential to undercover the network dysfunction and cognitive processes that drive these symptoms, towards a principled re-tuning of circuits. We highlight intracranial recording as a valuable tool for mapping and desegregating neural networks and their contribution to mood, motivation and behavioral symptoms, via the ability to dissect multiplexed overlapping spatial and temporal neural components. This technique can be powerfully combined with behavioral paradigms and emerging computational techniques to model underlying latent behavioral states. We review the literature of intracranial recording studies investigating mood, motivation and behavioral symptomatology with reference to 1) emotional processing, 2) executive control 3) subjective valuation (reward & cost evaluation) 4) motor control and 5) learning and updating. This reveals associations between different frequency specific network activities and underlying cognitive processes of reward decision making and action control. If validated, these signals represent potential computational biomarkers of motivational and behavioural states and could lead to principled therapy development for mood, motivation and behavioral symptoms in PD.

Impulse control disorder in Parkinson's disease is associated with abnormal frontal value signalling

Dopaminergic medication is well established to boost reward- versus punishment-based learning in Parkinson's disease. However, there is tremendous variability in dopaminergic medication effects across different individuals, with some patients exhibiting much greater cognitive sensitivity to medication than others. We aimed to unravel the mechanisms underlying this individual variability in a large heterogeneous sample of early-stage patients with Parkinson's disease as a function of comorbid neuropsychiatric symptomatology, in particular impulse control disorders and depression. One hundred and ninety-nine patients with Parkinson's disease (138 ON medication and 61 OFF medication) and 59 healthy controls were scanned with functional MRI while they performed an established probabilistic instrumental learning task. Reinforcement learning model-based analyses revealed medication group differences in learning from gains versus losses, but only in patients with impulse control disorders. Furthermore, expected-value related brain signalling in the ventromedial prefrontal cortex was increased in patients with impulse control disorders ON medication compared with those OFF medication, while striatal reward prediction error signalling remained unaltered. These data substantiate the hypothesis that dopamine's effects on reinforcement learning in Parkinson's disease vary with individual differences in comorbid impulse control disorder and suggest they reflect deficient computation of value in medial frontal cortex, rather than deficient reward prediction error signalling in striatum. See Michael Browning (https://doi.org/10.1093/brain/awad248) for a scientific commentary on this article.

Decreased serum BDNF contributes to the onset of REM sleep behavior disorder in Parkinson's disease patients

BACKGROUND

Brain-derived neurotrophic factor (BDNF) promotes neuroprotection and neuroregeneration. BDNF enhances the survival of dopaminergic neurons and improves dopaminergic neurotransmission and motor performance in patients with Parkinson's disease (PD). However, the association between BDNF levels and rapid eye movement (REM) sleep behavior disorder (RBD) in PD patients has received limited attention.

METHODS

We employed the Rapid Eye Movement Sleep Behavior Disorder Questionnaire-Hong Kong version (RBDQ-HK) and the Rapid Eye Movement Sleep Behavior Disorder Screening Questionnaire (RBDSQ) for RBD diagnosis. Patients were categorized into three groups: healthy controls (n = 53), PD patients without RBD (PD-nRBD; n = 56), and PD patients with RBD (PD-RBD; n = 45). Serum BDNF concentrations, demographic information, medical history, and motor/non-motor manifestations were compared between the three groups. Logistic regression analysis was performed to identify independent factors associated with PD and RBD. P-trend analysis was used to assess the relationship between BDNF levels and the risk of PD and RBD onset. Interaction effects were analyzed between BDNF, patients' age, and gender on the risk of RBD onset in PD patients.

RESULTS

Our findings indicate that serum BDNF levels were significantly lower in PD patients compared to healthy controls (p < 0.001). PD-RBD patients exhibited higher motor symptom scores (UPDRS III) than PD-nRBD patients (p = 0.021). Additionally, the PD-RBD group demonstrated lower cognitive function scores as measured by the Montreal Cognitive Assessment (MoCA) (p < 0.001) and Mini-Mental State Examination (MMSE) (p = 0.015). PD-RBD patients displayed significantly lower BDNF levels compared to both PD-nRBD and healthy control groups (p < 0.001). Univariate and multivariate logistic regression analyses showed that reduced BDNF levels were associated with an increased risk of RBD in PD patients (p = 0.005). P-trend analysis further confirmed the progressive relationship between decreased BDNF levels and the risk of PD and RBD onset. Furthermore, our interaction analysis highlighted the importance of monitoring younger PD patients with low serum BDNF levels for potential RBD onset.

CONCLUSIONS

This study illustrates that decreased serum BDNF levels may be linked to the development of RBD in PD patients, highlighting the potential utility of BDNF as a biomarker in clinical practice.

Insulin and Disorders of Behavioural Flexibility

Behavioural inflexibility is a symptom of neuropsychiatric and neurodegenerative disorders such as Obsessive-Compulsive Disorder, Autism Spectrum Disorder and Alzheimer's Disease, encompassing the maintenance of a behaviour even when no longer appropriate. Recent evidence suggests that insulin signalling has roles apart from its regulation of peripheral metabolism and mediates behaviourally-relevant central nervous system (CNS) functions including behavioural flexibility. Indeed, insulin resistance is reported to generate anxious, perseverative phenotypes in animal models, with the Type 2 diabetes medication metformin proving to be beneficial for disorders including Alzheimer's Disease. Structural and functional neuroimaging studies of Type 2 diabetes patients have highlighted aberrant connectivity in regions governing salience detection, attention, inhibition and memory. As currently available therapeutic strategies feature high rates of resistance, there is an urgent need to better understand the complex aetiology of behaviour and develop improved therapeutics. In this review, we explore the circuitry underlying behavioural flexibility, changes in Type 2 diabetes, the role of insulin in CNS outcomes and mechanisms of insulin involvement across disorders of behavioural inflexibility.

Neurobiology of depression in Parkinson's disease: Insights into epidemiology, molecular mechanisms and treatment strategies

Parkinson's disease (PD) is characterized mainly by motor dysfunctions due to the progressive loss of dopaminergic neurons. However, PD patients experience a multitude of debilitating non-motor symptoms, including depression, which may have deleteriously detrimental effects on life. Depression is multifactorial and exhibits a bimodal progression in PD, but its underlying molecular mechanisms are poorly understood. Studies demonstrating the pathophysiology of depression in PD and the specific treatment strategies for depression-like symptoms in PD patients are largely lacking, often underrated, under-recognized and, consequently, inadequately/under-treated. Nevertheless, reports suggest that the incidence of depression is approximately 20-30% of PD patients and may precede the onset of motor symptoms. Diagnosing depression in PD becomes difficult due to the clinical overlap in symptomatology between the two diseases, and the nigrostriatal dysfunction alone is insufficient to explain depressive symptoms in PD. Therefore, the current study provides an overview of the molecular mechanisms underlying the development of depression in PD and new insights into developing current antidepressant strategies to treat depression in PD. This review will identify and understand the molecular pathological mechanisms of depression in PD that will fundamentally help tailoring therapeutic interventions for depressive symptoms in PD.

Depression differentially affects patient and caregiver perceptions of neuropsychiatric symptoms in Parkinson's disease

OBJECTIVE

The aims of this study were twofold. First, we examined the relationship between patient and caregiver ratings of neuropsychiatric symptoms in Parkinson's disease (PD). Second, we examined if the severity of depressive symptoms affects patient and caregiver perceptions of other neuropsychiatric symptoms and contributes to discrepancies between their perceptions.

METHOD

We examined data from a retrospective clinical cohort of 209 patients with PD and their caregivers. We used intra-class correlation coefficients and the Bland Altman method to assess intra-respondent (retrospective versus current) and inter-respondent (patient versus caregiver) agreement between Frontal Systems Behavior Scales (FrSBe) subscale scores. We then used generalized estimating equation models to examine FrSBe subscale scores and the magnitude of the intra- and inter-respondent discrepancies in FrSBe subscale scores, as a function of Beck Depression Inventory-2^nd Edition scores, with patient demographic variable adjustments.

RESULTS

There was low agreement between patient and caregiver ratings on all three subscales, at both time points, and high response variability within and between raters. Patients generally reported more severe neuropsychiatric symptoms than caregivers. Depression severity predicted patients' perceptions at both time points, but was more strongly associated with current perceptions. Depression severity predicted caregivers' current perceptions only. The inter-respondent discrepancy in perceived apathy and disinhibition, but not executive dysfunction, increased as a function of depression severity.

CONCLUSIONS

There are differences in how patients with PD and caregivers perceive neuropsychiatric behaviors and the extent to which depressive symptoms influence their perceptions. Shared neuropathology and negative response biases likely contribute to these relationships.

Imaging Dopaminergic Neurotransmission in Neurodegenerative Disorders

Imaging of dopaminergic transmission in neurodegenerative disorders such as Parkinson disease (PD) or dementia with Lewy bodies plays a major role in clinical practice and in clinical research. We here review the role of imaging of the nigrostriatal pathway, as well as of striatal receptors and dopamine release, in common neurodegenerative disorders in clinical practice and research. Imaging of the nigrostriatal pathway has a high diagnostic accuracy to detect nigrostriatal degeneration in disorders characterized by nigrostriatal degeneration, such as PD and dementia with Lewy bodies, and disorders of more clinical importance, namely in patients with clinically uncertain parkinsonism. Imaging of striatal dopamine D2/3 receptors is not recommended for the differential diagnosis of parkinsonian disorders in clinical practice anymore. Regarding research, recently the European Medicines Agency has qualified dopamine transporter imaging as an enrichment biomarker for clinical trials in early PD, which underlines the high diagnostic accuracy of this imaging tool and will be implemented in future trials. Also, imaging of the presynaptic dopaminergic system plays a major role in, for example, examining the extent of nigrostriatal degeneration in preclinical and premotor phases of neurodegenerative disorders and to examine subtypes of PD. Also, imaging of postsynaptic dopamine D2/3 receptors plays a role in studying, for example, the neuronal substrate of impulse control disorders in PD, as well as in measuring endogenous dopamine release to examine, for example, motor complications in the treatment of PD. Finally, novel MRI sequences as neuromelanin-sensitive MRI are promising new tools to study nigrostriatal degeneration in vivo.

The Effects of Safinamide Adjunct Therapy on Depression and Apathy in Patients With Parkinson's Disease: Post-hoc Analysis of a Japanese Phase 2/3 Study

Background and Purpose

Neuropsychiatric symptoms in Parkinson's disease (PD) have been shown to significantly affect quality of life (QOL). We investigated the impact of safinamide on depression and apathy when administered as an adjunct to levodopa in Japanese patients with PD.

Methods

This was a post-hoc analysis of data from a phase 2/3 clinical study of safinamide in Japanese patients with PD experiencing wearing-off (JapicCTI-153056; https://www.clinicaltrials.jp/cti-user/trial/ShowDirect.jsp?japicId=JapicCTI-153056). Patients received placebo, safinamide 50 mg, or safinamide 100 mg as an adjunct therapy. The endpoints for this analysis were changes from baseline to Week 24 in the Unified Parkinson's Disease Rating Scale (UPDRS) Part I item 3 (depression) and item 4 (apathy) scores and the Parkinson's Disease Questionnaire (PDQ-39) “emotional well-being” domain score. Subgroup analyses investigated the relationship between neuropsychologic symptoms and improvements in motor fluctuation and assessed which patient populations might be expected to obtain neuropsychologic benefit from safinamide.

Results

Compared with placebo, safinamide (both doses) significantly improved UPDRS Part I item 3 scores in the overall analysis population, and the 100-mg dose improved UPDRS Part I item 4 scores in the population with apathy at baseline. Changes in the PDQ-39 “emotional well-being” score showed numerical, but not significant, dose-related improvements. Notable reductions in depression were associated with a change in daily ON-time ≥1 h, pain during OFF-time at baseline, and female sex.

Conclusions

The results from this post-hoc analysis of the Japanese phase 2/3 study suggest that safinamide could bring benefits to patients with PD who have mild depression, pain during the OFF phase. In addition, safinamide might provide particular benefits for patients with PD who have mild apathy and female.

Changes in Self- and Informant-Reported Frontal Behaviors in Parkinson's Disease: A Longitudinal Study

OBJECTIVE

Frontal behaviors (i.e., executive dysfunction, disinhibition, apathy) are common in Parkinson's disease (PD). However, it is unclear if patient and informant reports of patient frontal behaviors are in agreement over time.

METHOD

Sixty-two PD patients without dementia and their informants (87% spouses/partners) completed the self- and informant-versions of the Frontal Systems Behavior Scale at baseline and 2-year follow-up. Dyad ratings were compared and predictors of behavior ratings were examined.

RESULTS

Patient and informant reports at baseline and follow-up were in agreement, with significant increases in overall frontal behaviors, executive dysfunction, and apathy. Higher levels of baseline patient depression and caregiver burden predicted decrements in patient-reported executive function; worse patient cognition at baseline predicted worsening apathy as rated by informants.

CONCLUSIONS

PD patients and their informants are concordant in their ratings of worsening frontal behaviors over time. Targeting patient depression, cognition, and caregiver burden may improve decrements in frontal behaviors (executive dysfunction and apathy) in PD.

Synaptic Density and Neuronal Metabolic Function Measured by Positron Emission Tomography in the Unilateral 6-OHDA Rat Model of Parkinson's Disease

Parkinson’s disease (PD) is caused by progressive neurodegeneration and characterised by motor dysfunction. Neurodegeneration of dopaminergic neurons also causes aberrations within the cortico-striato-thalamo-cortical (CSTC) circuit, which has been hypothesised to lead to non-motor symptoms such as depression. Individuals with PD have both lower synaptic density and changes in neuronal metabolic function in the basal ganglia, as measured using [¹¹C]UCB-J and [¹⁸F]FDG positron emission tomography (PET), respectively. However, the two radioligands have not been directly compared in the same PD subject or in neurodegeneration animal models. Here, we investigate [¹¹C]UCB-J binding and [¹⁸F]FDG uptake in the CSTC circuit following a unilateral dopaminergic lesion in rats and compare it to sham lesioned rats. Rats received either a unilateral injection of 6-hydroxydopamine (6-OHDA) or saline in the medial forebrain bundle and rostral substantia nigra (n = 4/group). After 3 weeks, all rats underwent two PET scans using [¹⁸F]FDG, followed by [¹¹C]UCB-J on a separate day. [¹⁸F]FDG uptake and [¹¹C]UCB-J binding were both lower in the ipsilateral striatal regions compared to the contralateral regions. Using [¹¹C]UCB-J, we could detect an 8.7% decrease in the ipsilateral ventral midbrain, compared to a 2.9% decrease in ventral midbrain using [¹⁸F]FDG. Differential changes between hemispheres for [¹¹C]UCB-J and [¹⁸F]FDG outcomes were also evident in the CSTC circuit’s cortical regions, especially in the orbitofrontal cortex and medial prefrontal cortex where higher synaptic density yet lower neuronal metabolic function was observed, following lesioning. In conclusion, [¹¹C]UCB-J and [¹⁸F]FDG PET can detect divergent changes following a dopaminergic lesion in rats, especially in cortical regions that are not directly affected by the neurotoxin. These results suggest that combined [¹¹C]UCB-J and [¹⁸F]FDG scans could yield a better picture of the heterogeneous cerebral changes in neurodegenerative disorders.

Role of toll-like receptor 4 and sex in 6-hydroxydopamine-induced behavioral impairments and neurodegeneration in mice

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive loss of the nigrostriatal dopaminergic neurons that are associated with motor alterations and non-motor manifestations (such as depression). Neuroinflammation is a process with a critical role in the pathogenesis of PD. In this regard, toll-like receptor 4 (TLR4) is a central mediator of immune response in PD. Moreover, there are gender-related differences in the incidence, prevalence, and clinical features of PD. Therefore, we aimed to elucidate the role of TLR4 in the sex-dependent response to dopaminergic denervation induced by 6-hydroxydopamine (6-OHDA) in mice. Female and male adult wildtype (WT) and TLR4 knockout (TLR4-/-) mice were administered with unilateral injection of 6-OHDA in the dorsal striatum, and non-motor and motor impairments were evaluated for 30 days, followed by biochemistry analysis in the substantia nigra pars compacta (SNc), dorsal striatum, and dorsoventral cortex. Early non-motor impairments (i.e., depressive-like behavior and spatial learning deficits) induced by 6-OHDA were observed in the male WT mice but not in male TLR4-/- or female mice. Motor alterations were observed after administration of 6-OHDA in both strains, and the lack of TLR4 was also related to motor commitment. Moreover, ablation of TLR4 prevented 6-OHDA-induced dopaminergic denervation and microgliosis in the SNc, selectively in female mice. These results reinforced the existence of sex-biased alterations in PD and indicated TLR4 as a promising therapeutic target for the motor and non-motor symptoms of PD, which will help counteract the neuroinflammatory and neurodegenerative processes.

A Review on SARS-CoV-2-Induced Neuroinflammation, Neurodevelopmental Complications, and Recent Updates on the Vaccine Development

Coronavirus disease 2019 (COVID-19) is a devastating viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The incidence and mortality of COVID-19 patients have been increasing at an alarming rate. The mortality is much higher in older individuals, especially the ones suffering from respiratory distress, cardiac abnormalities, renal diseases, diabetes, and hypertension. Existing evidence demonstrated that SARS-CoV-2 makes its entry into human cells through angiotensin-converting enzyme 2 (ACE-2) followed by the uptake of virions through cathepsin L or transmembrane protease serine 2 (TMPRSS2). SARS-CoV-2-mediated abnormalities in particular cardiovascular and neurological ones and the damaged coagulation systems require extensive research to develop better therapeutic modalities. As SARS-CoV-2 uses its S-protein to enter into the host cells of several organs, the S-protein of the virus is considered as the ideal target to develop a potential vaccine. In this review, we have attempted to highlight the landmark discoveries that lead to the development of various vaccines that are currently under different stages of clinical progression. Besides, a brief account of various drug candidates that are being tested to mitigate the burden of COVID-19 was also covered. Further, in a dedicated section, the impact of SARS-CoV-2 infection on neuronal inflammation and neuronal disorders was discussed. In summary, it is expected that the content covered in this article help to understand the pathophysiology of COVID-19 and the impact on neuronal complications induced by SARS-CoV-2 infection while providing an update on the vaccine development.

Electroconvulsive Therapy for Parkinson's Disease with Depression and Neuroleptic Malignant Syndrome: A Case Report

Parkinson's disease is often complicated by psychiatric symptoms. Psychiatrists are caught in a dilemma between such symptoms and physical treatment since Parkinson's disease sometimes shows treatment resistance based on pharmacological treatment-induced dopamine dysfunction. Here, we report on a 64-year-old woman with a 15-year history of Parkinson's disease with stage IV severity based on the Hoehn and Yahr scale. She was admitted to our hospital with a diagnosis of major depressive disorder with psychotic features. Unfortunately, her treatment course for depression was complicated by neuroleptic malignant syndrome. Because we were concerned about the persistence of her depressive symptoms, the risk of psychotropic drugs causing adverse effects, and progressive disuse syndrome, we administered modified electroconvulsive therapy. Her symptoms of neuroleptic malignant syndrome and depression sufficiently improved after five sessions of modified electroconvulsive therapy. Additionally, the primary motor symptoms of her Parkinson's disease also markedly improved. The improvement of neuroleptic malignant syndrome and her motor symptoms based on dopamine dysfunction can be explained by electroconvulsive therapy's effectiveness in activating dopamine neurotransmission. Besides, the marked improvement of her depressive episode with psychotic features was presumed to involve dopamine receptor activation and regulation. Because advanced Parkinson's disease can sometimes be refractory to treatment based on pharmacological treatment-induced dopamine dysfunction, psychiatrists often have difficulty treating psychiatric symptoms; electroconvulsive therapy may stabilize the dopaminergic system in such cases, presenting a possible non-pharmacologic treatment option for Parkinson's disease.

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.

Neuroimaging of Anxiety in Parkinson's Disease: A Systematic Review

BACKGROUND

The aim of this systematic review was (1) to identify the brain regions involved in anxiety in Parkinson's disease (PD) based on neuroimaging studies and (2) to interpret the findings against the background of dysfunction of the fear circuit and limbic cortico-striato-thalamocortical circuit.

METHODS

Studies assessing anxiety symptoms in PD patients and studies using magnetic resonance imaging, positron emission tomography, or single-photon emission computed tomography were included.

RESULTS

The severity of anxiety was associated with changes in the fear circuit and the cortico-striato-thalamocortical limbic circuit. In the fear circuit, a reduced gray-matter volume of the amygdala and the anterior cingulate cortex (ACC); an increased functional connectivity (FC) between the amygdala and orbitofrontal cortex (OFC) and hippocampus and between the striatum and the medial prefrontal cortex (PFC), temporal cortex, and insula; and a reduced FC between the lateral PFC and the OFC, hippocampus, and amygdala were reported. In the cortico-striato-thalamocortical limbic circuit, a reduced FC between the striatum and ACC; a reduced dopaminergic and noradrenergic activity in striatum, thalamus, and locus coeruleus; and a reduced serotoninergic activity in the thalamus were reported.

CONCLUSION

To conclude, anxiety is associated with structural and functional changes in both the hypothesized fear and the limbic cortico-striato-thalamocortical circuits. These circuits overlap and may well constitute parts of a more extensive pathway, of which different parts play different roles in anxiety. The neuropathology of PD may affect these circuits in different ways, explaining the high prevalence of anxiety in PD and also the associated cognitive, motor, and psychiatric symptoms. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Depression is Associated with Impulse-compulsive Behaviors in Parkinson's disease

BACKGROUND

Depression and impulse control disorders (ICDs) are both common in Parkinson's disease (PD) patients and their coexistence is frequent. Our aim was to determine the relationship between depression and impulsive-compulsive behaviors (ICBs) in a large cohort of PD patients.

METHODS

PD patients recruited from 35 centers of Spain from the COPPADIS cohort from January 2016 to November 2017 were included in the study. The QUIP-RS (Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale) was used for screening ICDs (cutoff points: gambling ≥6, buying ≥8, sex≥8, eating≥7) and compulsive behaviors (CBs) (cutoff points: hobbyism-punding ≥7). Mood was assessed with the BDI-II (Beck Depression Inventory - II) and major, minor, and subthreshold depression were defined.

RESULTS

Depression was more frequent in PD patients with ICBs than in those without: 66.3% (69/104) vs 47.5% (242/509); p<0.0001. Major depression was more frequent in this group as well: 22.1% [23/104] vs 14.5% [74/509]; p=0.041. Considering types of ICBs individually, depression was more frequent in patients with pathological gambling (88.9% [8/9] vs 50.2% [303/603]; p=0.021), compulsive eating behavior (65.9% [27/41] vs 49.7% [284/572]; p=0.032), and hobbyism-punding (69% [29/42] vs 49.4% [282/571]; p=0.010) than in those without, respectively. The presence of ICBs was also associated with depression (OR=1.831; 95%CI 1.048-3.201; p=0.034) after adjusting for age, sex, civil status, disease duration, equivalent daily levodopa dose, antidepressant treatment, Hoehn&Yahr stage, non-motor symptoms burden, autonomy for activities of daily living, and global perception of QoL.

LIMITATIONS

Cross-sectional design.

CONCLUSIONS

Depression is associated with ICBs in PD. Specifically, with pathological gambling, compulsive eating behavior, and hobbyism-punding.

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.

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.

Impulsive and compulsive behaviors in Parkinson's disease: Impact on quality of and satisfaction with life, and caregiver burden

INTRODUCTION

To disentangle the association between impulsive and compulsive behaviors (ICBs), health-related quality of life (HRQOL), satisfaction with life (SwL), and caregiver distress in dyads of people with Parkinson's disease (PwP) and caregivers.

METHODS

Data used in this study were obtained from the ongoing Norwegian ParkWest study, a population-based longitudinal cohort study of the incidence, neurobiology and prognosis of PD in Western Norway. One hundred and one dyads of PwP free of dementia and their caregivers were included 5 years after PD diagnosis and inclusion in the ParkWest study. Standardized clinical rating scales were used to evaluate ICBs, HRQOL, SwL and caregiver distress.

RESULTS

Of 101 PwP-caregiver dyads, self-reported ICBs were seen in 33% of PwP and only caregiver-reported ICBs in 12% of PwP. PwP-reported ICBs were associated with poorer HRQOL and SwL, whereas ICBs reported by caregivers only were associated with increased caregiver distress, but not poorer HRQOL or SwL in PwP.

CONCLUSIONS

ICBs have adverse effects on HRQOL, SwL and caregiver distress. These findings underpin the need for proper identification and management of ICBs in PwP.

Lower nucleus accumbens α-synuclein load and D3 receptor levels in Parkinson's disease with impulsive compulsive behaviours

Impulsive compulsive behaviours in Parkinson's disease have been linked to increased dopaminergic release in the ventral striatum and excessive stimulation of dopamine D3 receptors. Thirty-one patients with impulsive compulsive behaviours and Parkinson's disease who donated their brains to the Queen Square Brain Bank for Neurological Disorders were assessed for α-synuclein neuropathological load and tyrosine hydroxylase levels in the nucleus accumbens, dorsal putamen and caudate using immunohistochemistry. Dopamine D2 and dopamine D3 receptors protein levels in the nucleus accumbens, frontal cortex and putamen were determined using western blotting. Results were compared to 29 Parkinson's disease cases without impulsive compulsive behaviours matched by age, sex, disease duration, age at Parkinson's disease onset and disease duration. The majority of patients with impulsive compulsive behaviours had dopamine dysregulation syndrome. Patients with Parkinson's disease and impulsive compulsive behaviours had lower α-synuclein load and dopamine D3 receptor levels in the nucleus accumbens. No differences were seen between groups in the other brain areas and in the analysis of tyrosine hydroxylase and dopamine D2 receptor levels. Lower α-synuclein load in the nucleus accumbens of individuals with Parkinson's disease and impulsive compulsive behaviours was confirmed on western blotting. Downregulation of the dopamine D3 receptor levels may have occurred either as a consequence of the degenerative process or of a pre-morbid trait. The lower levels of α-synuclein may have contributed to an excessive stimulation of the ventral striatum resulting in impulsive compulsive behaviours.

Processing speed is related to striatal dopamine transporter availability in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) affects the integrity of the dopamine and serotonin system, and is characterized by a plethora of different symptoms, including cognitive impairments of which the pathophysiology is not yet fully elucidated.

OBJECTIVES

Investigate the role of the integrity of the dopaminergic and serotonergic system in cognitive functioning in early-stage PD using Single Photon Emission Computed Tomography (SPECT) combined with the radiotracer 123I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (123I-FP-CIT).

METHODS

We studied the association between cognitive functions and dopamine transporter (DAT) availability in the caudate nucleus and putamen - as a proxy for striatal dopaminergic integrity - and serotonin transporter (SERT) availability as a proxy for serotonergic integrity in the thalamus and hippocampus using bootstrapped multiple regression. One-hundred-and-twenty-nine (129) PD patients underwent a 123I-FP-CIT SPECT scan and a neuropsychological assessment.

RESULTS

We showed a positive association between DAT availability in the head of the caudate nucleus and the Stroop Color Word Task - card I (reading words; β = 0.32, P = 0.001) and a positive association between DAT availability in the anterior putamen and the Trail Making Test part A (connecting consecutively numbered circles; β = 0.25, P = 0.02). These associations remained after adjusting for motor symptom severity or volume of the region-of-interest and were most pronounced in medication-naïve PD patients. There were no associations between cognitive performance and SERT availability in the thalamus or hippocampus.

CONCLUSIONS

We interpret these results as a role for striatal dopamine - and its PD-related decline - in aspects of processing speed.

Neuropsychiatric aspects of Parkinson disease psychopharmacology: Insights from circuit dynamics

Parkinson disease (PD) is a neurodegenerative disorder with a complex pathophysiology characterized by the progressive loss of dopaminergic neurons within the substantia nigra. Persons with PD experience several motoric and neuropsychiatric symptoms. Neuropsychiatric features of PD include depression, anxiety, psychosis, impulse control disorders, and apathy. In this chapter, we will utilize the National Institutes of Mental Health Research Domain Criteria (RDoC) to frame and integrate observations from two prevailing disease constructions: neurotransmitter anomalies and circuit physiology. When there is available evidence, we posit how unified translational observations may have clinical relevance and postulate importance outside of PD. Finally, we review the limited evidence available for pharmacologic management of these symptoms.

Dynamical Role of Pivotal Brain Regions in Parkinson Symptomatology Uncovered with Deep Learning

BACKGROUND

The release of a broad, longitudinal anatomical dataset by the Parkinson's Progression Markers Initiative promoted a surge of machine-learning studies aimed at predicting disease onset and progression. However, the excessive number of features used in these models often conceals their relationship to the Parkinsonian symptomatology.

OBJECTIVES

The aim of this study is two-fold: (i) to predict future motor and cognitive impairments up to four years from brain features acquired at baseline; and (ii) to interpret the role of pivotal brain regions responsible for different symptoms from a neurological viewpoint.

METHODS

We test several deep-learning neural network configurations, and report our best results obtained with an autoencoder deep-learning model, run on a 5-fold cross-validation set. Comparison with Existing Methods: Our approach improves upon results from standard regression and others. It also includes neuroimaging biomarkers as features.

RESULTS

The relative contributions of pivotal brain regions to each impairment change over time, suggesting a dynamical reordering of culprits as the disease progresses. Specifically, the Putamen is initially the most critical region accounting for the overall cognitive state, only being surpassed by the Substantia Nigra in later years. The Pallidum is the first region to influence motor scores, followed by the parahippocampal and ambient gyri, and the anterior orbital gyrus.

CONCLUSIONS

While the causal link between regional brain atrophy and Parkinson symptomatology is poorly understood, our methods demonstrate that the contributions of pivotal regions to cognitive and motor impairments are more dynamical than generally appreciated.

Neuropsychiatric Disorders in Parkinson's Disease: What Do We Know About the Role of Dopaminergic and Non-dopaminergic Systems?

Besides the hallmark motor symptoms (rest tremor, hypokinesia, rigidity, and postural instability), patients with Parkinson’s disease (PD) have non-motor symptoms, namely neuropsychiatric disorders. They are frequent and may influence the other symptoms of the disease. They have also a negative impact on the quality of life of patients and their caregivers. In this article, we will describe the clinical manifestations of the main PD-related behavioral disorders (depression, anxiety disorders, apathy, psychosis, and impulse control disorders). We will also provide an overview of the clinical and preclinical literature regarding the underlying mechanisms with a focus on the role of the dopaminergic and non-dopaminergic systems.

Impulse Control Disorders in Parkinson's Disease. A Brief and Comprehensive Review

Impulse control and related disorders (ICDs-RD) encompasses a heterogeneous group of disorders that involve pleasurable behaviors performed repetitively, excessively, and compulsively. The key common symptom in all these disorders is the failure to resist an impulse or temptation to control an act or specific behavior, which is ultimately harmful to oneself or others and interferes in major areas of life. The major symptoms of ICDs include pathological gambling (PG), hypersexualtiy (HS), compulsive buying/shopping (CB) and binge eating (BE) functioning. ICDs and ICDs-RD have been included in the behavioral spectrum of non-motor symptoms in Parkinson's disease (PD) leading, in some cases, to serious financial, legal and psychosocial devastating consequences. Herein we present the prevalence of ICDs, the risk factors, its pathophysiological mechanisms, the link with agonist dopaminergic therapies and therapeutic managements.

Mesencephalic and extramesencephalic dopaminergic systems in Parkinson's disease

Neurodegeneration of the nigrostriatal dopaminergic system and concurrent dopamine (DA) deficiency in the basal ganglia represent core features of Parkinson's disease (PD). Despite the central role of DA in the pathogenesis of PD, dopaminergic systems outside of the midbrain have not been systematically investigated for Lewy body pathology or neurodegeneration. Dopaminergic neurons show a surprisingly rich neurobiological diversity, suggesting that there is not one general type of dopaminergic neuron, but rather a spectrum of different dopaminergic phenotypes. This heterogeneity on the cellular level could account for the observed differences in susceptibility of the dopaminergic systems to the PD disease process. In this review, we will summarize the long history from the first description of PD to the rationally derived DA replacement therapy, describe the basal neuroanatomical and neuropathological features of the different dopaminergic systems in health and PD, explore how neuroimaging techniques broadened our view of the dysfunctional dopaminergic systems in PD and discuss how dopaminergic replacement therapy ameliorates the classical motor symptoms but simultaneously induces a new set of hyperdopaminergic symptoms.

Functional imaging studies of Impulse Control Disorders in Parkinson's disease need a stronger neurocognitive footing

Impulse control disorders (ICDs) in Parkinson's disease (PD) are associated with dopaminergic dysfunction and treatment, but have no satisfactory therapeutic solution. While studies assessing the neurofunctional bases of ICDs are important for advancing our understanding and management of ICDs, they remain sparse and inconsistent. Based on a systematic analysis of the neuroimaging literature, the present review pinpoints various abnormalities beyond the mesocorticolimbic circuit that supports reward processing, suggesting possible dysfunction at the sensorimotor, executive and affective levels. We advocate that: 1) Future studies should use more sophisticated psychological models and behavioral designs that take into account the potentially multifaceted aspect of ICDs; this would allow a more accurate assessment of the underlying neurocognitive processes, which are not all dependent on the dopaminergic system. 2) Future neuroimaging studies should rely more strongly on task-based, event-related analyses to disentangle the various mechanisms that can be dysfunctional in ICDs. We believe these guidelines constitute a prerequisite towards distinguishing causes, correlates and individual susceptibility factors of PD patients with ICDs.

Anxiety in Parkinson's disease is associated with reduced structural covariance of the striatum

BACKGROUND

Anxiety is highly prevalent in Parkinson's disease (PD) and has great negative impact on quality of life. Functional and structural neuroimaging studies have contributed to our understanding of the symptomatology of PD but still little is known about the pathophysiology of PD-related anxiety.

METHODS

We used seed-based structural covariance analysis to study the anatomical network correlates of anxiety in PD. Structural covariance analysis is based on the statistical correlation between regional brain volumes measured on T1-weighted magnetic resonance images. We investigated the association between anxiety symptoms, as measured by the Beck Anxiety Inventory (BAI), and seed-to-whole-brain structural covariance networks in 115 patients with idiopathic PD using five bilateral seeds: basolateral amygdala, centromedial-superficial amygdala, dorsal caudate nucleus, dorsal-caudal putamen, and nucleus accumbens.

RESULTS

Severity of anxiety correlated negatively with structural covariance between the left striatal sub-regions and the contralateral caudate nucleus. Moreover, severity of anxiety was associated with reduced structural covariance between the right dorsal caudate nucleus and ipsilateral ventrolateral prefrontal cortex and between the left nucleus accumbens and ipsilateral dorsolateral prefrontal cortex. Structural covariance of the amygdalar seeds did not correlate with anxiety.

CONCLUSIONS

We interpret these findings as a reduced interhemispheric cooperation between the left and right striatum and reduced prefrontal-striatal connectivity, possibly related to impaired 'top-down' regulation of emotions. These findings shed more light on the pathophysiology of PD-related anxiety LIMITATIONS: This study did not include PD patients with an anxiety disorder.

Understanding the Latent Structure of Hypersexuality: A Taxometric Investigation

We examined the latent structure and taxonicity of hypersexuality in large university and community samples of male and female respondents. Participants completed the Hypersexual Behavior Inventory (HBI) and Sexual Compulsivity Scale (SCS), each as part of larger anonymous online surveys of sexual behavior. Exploratory factor analyses (EFA) were performed in part to prepare the data for taxometric analysis and also to identify the putative dimensions underpinning each measure. Three latent dimensions were identified from each of the Sexual Compulsivity Scale (dyscontrol, consequences, and preoccupation) and Hypersexual Behavior Inventory (coping, dyscontrol, and consequences). Taxometric analyses of the generated factors using mean above minus below a cut (MAMBAC), maximum covariance (MAXCOV), and latent mode factor analysis (L-Mode) broadly supported a dimensional latent structure for hypersexuality, particularly in female participants. Implications pertaining to the assessment of hypersexuality are discussed.

Dopamine Agonists and Impulse Control Disorders: A Complex Association

Impulse control disorders (ICDs) are a well-known adverse effect of dopamine agonists (DAAs). This critical review aims to summarize data on the prevalence and factors associated with the development of an ICD simultaneous to DAA use. A search of two electronic databases was completed from inception to July 2017. The search terms were medical subject headings (MeSH) terms including “dopamine agonists” AND “disruptive disorders”, “impulse control disorders”, or “conduct disorders”. Articles had to fulfill the following criteria to be included: (i) the target problem was an ICD; (ii) the medication was a dopaminergic drug; and (iii) the article was an original article. Of the potential 584 articles, 90 met the criteria for inclusion. DAAs were used in Parkinson’s disease (PD), restless legs syndrome (RLS) or prolactinoma. The prevalence of ICDs ranged from 2.6 to 34.8% in PD patients, reaching higher rates in specific PD populations; a lower prevalence was found in RLS patients. We found only two studies about prolactinoma. The most robust findings relative to the factors associated with the development of an ICD included the type of DAA, the dosage, male gender, a younger age, a history of psychiatric symptoms, an earlier onset of disease, a longer disease duration, and motor complications in PD. This review suggests that DAA use is associated with an increased risk in the occurrence of an ICD, under the combined influence of various factors. Guidelines to help prevent and to treat ICDs when required do exist, although further studies are required to better identify patients with a predisposition.

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

Background: In Parkinson's disease (PD), impulse control disorders (ICDs) develop as side-effect of dopaminergic replacement therapy (DRT). Cognitive, affective, and motivational correlates of ICD in medicated PD patients are debated. Here, we systematically reviewed and meta-analyzed the evidence for an association between ICD in PD and cognitive, affective, and motivational abnormalities. Methods: A systematic review and meta-analysis was performed on PubMed, Science Direct, ISI Web of Science, Cochrane, EBSCO for studies published between 1-1-2000 and 8-3-2017 comparing cognitive, affective, and motivational measures in PD patients with ICD (ICD+) vs. those without ICD (ICD-). Exclusion criteria were conditions other than PD, substance and/or alcohol abuse, dementia, drug naïve patients, cognition assessed by self-report tools. Standardized mean difference (SMD) was used, and random-effect model applied. Results: 10,200 studies were screened (title, abstract), 79 full-texts were assessed, and 25 were included (ICD+: 625 patients; ICD-: 938). Compared to ICD-, ICD+ showed worse performance reward-related decision-making (0.42 [0.02, 0.82], p = 0.04) and set-shifting tasks (SMD = -0.49 [95% CI -0.78, -0.21], p = 0.0008). ICD in PD was also related to higher self-reported rate of depression (0.35 [0.16, 0.54], p = 0.0004), anxiety (0.43 [0.18, 0.68], p = 0.0007), anhedonia (0.26 [0.01, 0.50], p = 0.04), and impulsivity (0.79 [0.50, 1.09], p < 0.00001). Heterogeneity was low to moderate, except for depression (I² = 61%) and anxiety (I² = 58%). Conclusions: ICD in PD is associated with worse set-shifting and reward-related decision-making, and increased depression, anxiety, anhedonia, and impulsivity. This is an important area for further studies as ICDs have negative impact on the quality of life of patients and their caregivers.

Repetitive transcranial magnetic stimulation of the dorsolateral prefrontal cortex to alleviate depression and cognitive impairment associated with Parkinson's disease: A review and clinical implications

The rapid methodological development and growing availability of neuromodulation techniques have spurred myriad studies investigating their clinical effectiveness. Repetitive transcranial magnetic stimulation (rTMS) of the dorsolateral prefrontal cortex (DLPFC) has in many instances been proven to exert antidepressant-like effects superior to placebo and equivalent to standard psychopharmacological treatment. Due to the similar neuroanatomy and neurophysiology of executive and affective control processes, rTMS to the DLPFC may be able to address multiple issues simultaneously. This review pools available literature on the therapeutic usage of rTMS on non-motor symptoms of Parkinson's disease associated with the DLPFC (i.e. mood disturbance and cognitive impairment). To the best of the author's knowledge, it is one of the few available of its' kind, up to this date. Most studies included in the review found beneficial effects of high frequency prefrontal rTMS on PD-related depression. In regard to the usability of rTMS to alleviate cognitive impairment associated with PD, definitive claims are yet to be established.

Standardised Neuropsychological Assessment for the Selection of Patients Undergoing DBS for Parkinson's Disease

DBS is an increasingly offered advanced treatment for Parkinson's disease (PD). Neuropsychological assessment is considered to be an important part of the screening for selection of candidates for this treatment. However, no standardised screening procedure currently exists. In this study, we examined the use of our standardised neuropsychological assessment for the evaluation of surgical candidates and to identify risk factors for subsequent decline in cognition and mood. A total of 40 patients were assessed before and after DBS. Evaluation of mood and case notes review was also undertaken. Before DBS, patients with PD demonstrated frequent impairments in intellectual functioning, memory, attention, and executive function, as well as high rates of mood disorder. Post-DBS, there was a general decline in verbal fluency only, and in one patient, we documented an immediate and irreversible global cognitive decline, which was associated with older age and more encompassing cognitive deficits at baseline. Case note review revealed that a high proportion of patients developed mood disorder, which was associated with higher levels of depression at baseline and greater reduction in levodopa medication. We conclude that our neuropsychological assessment is suitable for the screening of candidates and can identify baseline risk factors, which requires careful consideration before and after surgery.

Impulse-Control Disorders in Parkinson's Disease: A Meta-Analysis and Review of Case-Control Studies

BACKGROUND

Although several case-control studies on the prevalence of Impulse-Control Disorders (ICDs) in Parkinson's Disease (PD) have been conducted, no meta-analytic study on this topic has previously been published. Thus, knowledge about the overall prevalence rate of ICD in PD and factors that might moderate this relationship is lacking.

METHOD

Prevalence studies of ICDs in PD were identified by computer searches in the MEDLINE, PsycINFO, and Web of Science databases, covering the period from January 2000 to February 2017. Data for N = 4,539, consisting of 2,371 PD patients and 2,168 healthy controls, representing 14 case-control studies were included. Estimation of the odds ratio (OR) of ICDs in PD compared to healthy controls was conducted using random-effects models. Mixed-effects models were applied in the moderator analysis of heterogeneity. Publication bias was estimated using a contour-enhanced funnel plot, the Rüker's test, and fail-safe N test for estimating the number of potential missing studies.

RESULTS

Overall, the results showed significantly higher ratios for several ICDs in PD compared to healthy controls with the estimated overall ORs ranging between 2.07, 95% CI [1.26, 3.48], for having any ICDs, and 4.26, 95% CI [2.17, 8.36], for hypersexuality. However, the random-effects results for shopping were non-significant, though the fixed-effects model was significant (OR = 1.66, 95%CI [1.21, 2.27]). The testing of potential moderator variables of heterogeneity identified the following two variables that were both associated with increased risk: being medically treated for PD and disease duration. The results must be interpreted with some caution due to possible small-studies effect or publication bias.

CONCLUSION

Individuals with PD seem to have a significantly greater risk of suffering from ICDs compared to healthy controls. Gambling, hypersexuality, eating, punding, and hobbying are all ICDs significantly associated with PDs being medically treated for PD.

The neurobiology of impulse control disorders in Parkinson's disease: from neurotransmitters to neural networks

Impulse control disorders (ICD) are common neuropsychiatric disorders that can arise in Parkinson’s disease (PD) patients after commencing dopamine replacement therapy. Approximately 15% of all patients develop these disorders and many more exhibit subclinical symptoms of impulsivity. ICD is thought to develop due to an interaction between the use of dopaminergic medication and an as yet unknown neurobiological vulnerability that either pre-existed before PD onset (possibly genetic) or is associated with neural alterations due to the PD pathology. This review discusses genes, neurotransmitters and neural networks that have been implicated in the pathophysiology of ICD in PD. Although dopamine and the related reward system have been the main focus of research, recently, studies have started to look beyond those systems to find new clues to the neurobiological underpinnings of ICD and come up with possible new targets for treatment. Studies on the whole-brain connectome to investigate the global alterations due to ICD development are currently lacking. In addition, there is a dire need for longitudinal studies that are able to disentangle the contributions of individual (genetic) traits and secondary effects of the PD pathology and chronic dopamine replacement therapy to the development of ICD in PD.

Impulsive and Compulsive Behaviors in Parkinson's Disease: The Norwegian ParkWest Study

BACKGROUND

Impulsive and compulsive behaviors (ICBs) are frequent in Parkinson's disease (PD), but data from population-based cohorts is lacking.

OBJECTIVES

To determine the frequency and associated demographic, clinical, neuropsychiatric and cognitive features of ICBs in a population-based PD cohort.

METHODS

This cross-sectional study included 125 patients with PD and 159 age- and gender-matched normal controls recruited from the Norwegian ParkWest study. Participants underwent comprehensive neurological, neuropsychiatric and neuropsychological assessments. ICBs were assessed using the Questionnaire for Impulsive-Compulsive Disorders in PD short form. Multiple logistic regression analyses were performed to compare the odds of ICBs between groups and to identify independent correlates of ICBs in PD.

RESULTS

30.4% of patients reported at least one ICB, with an odds ratio (OR) of 3.2 (95% confidence interval [CI] 1.8-5.9) compared with controls. Multiple ICBs were experienced by 8.8% of patients vs 1.3% of controls (OR 7.6, 95% CI 1.7-34.8). Compared to controls, the ORs of having an ICB were 7.4 (95% CI 2.6-20.9) in patients taking DA without levodopa, 4.6 (95% CI 2.3-9.3) in those treated with both DA and levodopa, and 1.2 (95% CI 0.5-3.2) in patients using levodopa but not DA. In multivariate models, ICB status in patients was independently associated with DA treatment and depressive symptoms, but not with other dopaminergic medications, motor function, or cognitive performance.

CONCLUSIONS

Patients with PD treated with DA, but not other dopaminergic medications, have increased odds of having ICBs compared with age- and gender-matched controls. This has implications for individualized patient management and follow-up.

Risky decision-making and affective features of impulse control disorders in Parkinson's disease

Impulse control disorders (ICDs) in Parkinson’s disease (PD) are considered dopaminergic treatment side effects. Cognitive and affective factors may increase the risk of ICD in PD. The aim is to investigate risky decision-making and associated cognitive processes in PD patients with ICDs within a four-stage conceptual framework. Relationship between ICDs and affective factors was explored. Thirteen PD patients with ICD (ICD+), 12 PD patients without ICD (ICD−), and 17 healthy controls were recruited. Overall risky decision-making and negative feedback effect were examined with the Balloon Analogue Risk Task (BART). A cognitive battery dissected decision-making processes according to the four-stage conceptual framework. Affective and motivational factors were measured. ANOVA showed no effect of group on overall risky decision-making. However, there was a group × feedback interaction [F (2, 39) = 3.31, p = 0.047]. ICD+, unlike ICD− and healthy controls, failed to reduce risky behaviour following negative feedback. A main effect of group was found for anxiety and depression [F(2, 38) = 8.31, p = 0.001], with higher symptoms in ICD+ vs. healthy controls. Groups did not differ in cognitive outcomes or affective and motivational metrics. ICD+ may show relatively preserved cognitive function, but reduced sensitivity to negative feedback during risky decision-making and higher symptoms of depression and anxiety.

Impulse control disorders in advanced Parkinson's disease with dyskinesia: The ALTHEA study

BACKGROUND

Impulse control disorders and dyskinesia are common and disabling complications of dopaminergic treatment in Parkinson's disease. They may coexist and are possibly related. The objectives of this study were to assess the frequency and severity of impulse control disorders in Parkinson's disease patients with dyskinesia.

METHODS

The ALTHEA study enrolled 251 Parkinson's disease patients with various degrees of dyskinesia severity from 11 movement disorders centers in Italy. Each patient underwent a comprehensive assessment including Unified Dyskinesia Rating Scale and the Questionnaire for Impulsive Compulsive Disorders in Parkinson Disease-Rating Scale.

RESULTS

There was an overall 55% frequency of impulse control disorder and related behaviors (36% were clinically significant). The positive patients were younger at disease diagnosis and onset and had higher Unified Dyskinesia Rating Scale historical and total score (P = 0.001 and P = 0.02, respectively, vs negative). There was an increased frequency of clinically significant impulse control disorders in patients with severe dyskinesia (P = 0.013), a positive correlation between the questionnaire total score and dopamine agonist dose (P = 0.018), and a trend with levodopa dose.

CONCLUSIONS

More than half of Parkinson's disease patients with dyskinesia have impulse control disorders and related behaviors, which are frequently clinically significant. Dopaminergic therapy total dose is associated with their severity. Clinicians should carefully assess patients with maladaptive behaviors and dyskinesia because they do not properly evaluate their motor and nonmotor status. © 2017 International Parkinson and Movement Disorder Society.

What a neurologist should know about depression in Parkinson's disease

Depression is a frequent non-motor symptom of Parkinson's disease. Its prevalence varies widely across studies (between 2.7% and 90%); around 35% have clinically significant depressive symptoms. Although depression can have an immense impact on the quality of life of affected patients and their caregivers, depressive symptoms in Parkinson's disease frequently remain unrecognised and, as a result, remain untreated. Here we overview the diagnostic challenges and pitfalls, including the factors contributing to the underdiagnosis of depression. We also discuss current ideas on the underlying pathophysiology. Finally, we offer a treatment approach based on currently available evidence.

Unilateral ultra-brief pulse electroconvulsive therapy for depression in Parkinson's disease

OBJECTIVES

Electroconvulsive therapy (ECT) has demonstrated efficacy in treating core symptoms of Parkinson's disease (PD); however, widespread use of ECT in PD has been limited due to concern over cognitive burden. We investigated the use of a newer ECT technology known to have fewer cognitive side effects (right unilateral [RUL] ultra-brief pulse [UBP]) for the treatment of medically refractory psychiatric dysfunction in PD.

MATERIALS AND METHODS

This open-label pilot study included 6 patients who were assessed in the motoric, cognitive, and neuropsychiatric domains prior to and after RUL UBP ECT. Primary endpoints were changes in total score on the HAM-D-17 and GDS-30 rating scales.

RESULTS

Patients were found to improve in motoric and psychiatric domains following RUL UBP ECT without cognitive side effects, both immediately following ECT and at 1-month follow-up.

CONCLUSIONS

This study demonstrates that RUL UBP ECT is safe, feasible, and potentially efficacious in treating multiple domains of PD, including motor and mood, without clear cognitive side effects.

Apathy and Impulse Control Disorders: Yin & Yang of Dopamine Dependent Behaviors

Neuropsychiatric symptoms are common non-motor symptoms in Parkinson's disease (PD). Apathy and impulse control disorders (ICD) are two opposite motivational expressions of a continuous behavioural spectrum involving hypo- and hyperdopaminergia. Both syndromes share pathological (decreased vs increased) dopamine receptor stimulation states. Apathy belongs to the spectrum of hypodopaminergic symptoms together with anhedonia, anxiety and depression. Apathy is a key symptom of PD which worsens with disease progression. Animal models, imaging and pharmacological studies concur in pointing out dopaminergic denervation in the aetiology of parkinsonian apathy with a cardinal role of decreased tonic D2/D3 receptor stimulation. ICDs are part of the hyperdopaminergic behavioural spectrum, which also includes punding, and dopamine dysregulation syndrome (DDS), which are all related to non-physiological dopaminergic stimulation induced by antiparkinsonian drugs. According to clinical data tonic D2/D3 receptor stimulation can be sufficient to induce ICDs. Clinical observations in drug addiction and PD as well as data from studies in dopamine depleted rodents provide hints allowing to argue that both pulsatile D1 and D2 receptor stimulation and the severity of dopaminergic denervation are risk factors to develop punding behavior and DDS. Imaging studies have shown that the brain structures involved in drug addiction are also involved in hyperdopaminergic behaviours with increase of bottom-up appetitive drive and decrease in prefrontal top down behavioural control.