Pathobiology of Cognitive Impairment in Parkinson Disease: Challenges and Outlooks

Cognitive impairment (CI) is a characteristic non-motor feature of Parkinson disease (PD) that poses a severe burden on the patients and caregivers, yet relatively little is known about its pathobiology. Cognitive deficits are evident throughout the course of PD, with around 25% of subtle cognitive decline and mild CI (MCI) at the time of diagnosis and up to 83% of patients developing dementia after 20 years. The heterogeneity of cognitive phenotypes suggests that a common neuropathological process, characterized by progressive degeneration of the dopaminergic striatonigral system and of many other neuronal systems, results not only in structural deficits but also extensive changes of functional neuronal network activities and neurotransmitter dysfunctions. Modern neuroimaging studies revealed multilocular cortical and subcortical atrophies and alterations in intrinsic neuronal connectivities. The decreased functional connectivity (FC) of the default mode network (DMN) in the bilateral prefrontal cortex is affected already before the development of clinical CI and in the absence of structural changes. Longitudinal cognitive decline is associated with frontostriatal and limbic affections, white matter microlesions and changes between multiple functional neuronal networks, including thalamo-insular, frontoparietal and attention networks, the cholinergic forebrain and the noradrenergic system. Superimposed Alzheimer-related (and other concomitant) pathologies due to interactions between α-synuclein, tau-protein and β-amyloid contribute to dementia pathogenesis in both PD and dementia with Lewy bodies (DLB). To further elucidate the interaction of the pathomechanisms responsible for CI in PD, well-designed longitudinal clinico-pathological studies are warranted that are supported by fluid and sophisticated imaging biomarkers as a basis for better early diagnosis and future disease-modifying therapies.

Palliative Care for Parkinson Disease

Palliative care (PC) is an approach to the care of persons affected by serious illness that focuses on reducing suffering by addressing medical, psychosocial, and spiritual needs. Persons living with Parkinson disease have PC needs that begin at the time of diagnosis and continue throughout the course of the illness including nonmotor symptom burden, caregiver distress, grief, and increased mortality. Primary PC refers to essential PC skills that may be practiced by nonpalliative medicine specialists to improve outcomes for their patients.

Scales to assess impulsive and compulsive behaviors in Parkinson's disease: Critique and recommendations

Impulse control disorders (ICDs) and related impulsive and compulsive behaviors (together called ICBs) have been increasingly recognized in the context of Parkinson's disease (PD) and treatment. The International Parkinson's and Movement Disorder Society commissioned a task force to assess available clinical screening instruments and rating scales, including their clinimetric properties, make recommendations regarding their utility, and suggest future directions in scale development and validation. The literature was systematically searched for scales measuring a range of reported ICBs in PD. A scale was designated "recommended" if the scale had been employed in PD studies, been used beyond the group that developed it, and had adequate clinimetric data published for PD. Numerous diagnostic screening tools and severity rating scales were identified for a range of ICBs, including compulsive medication use, punding/hobbyism, walkabout, pathological gambling, hypersexuality, compulsive or binge eating, compulsive buying, reckless driving, compulsive exercise, pyromania, trichotillomania, hoarding, kleptomania, intermittent explosive disorder, and internet addiction. For screening across the range of ICBs (except compulsive medication use), the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease (QUIP) and QUIP-Rating Scale (QUIP-RS) are recommended, and for severity rating across the range of ICBs the QUIP-RS and the Ardouin Scale of Behavior in Parkinson's Disease are recommended. The Scale for Outcomes in Parkinson's Disease-Psychiatric Complications is recommended for rating of hypersexuality and the compulsive behaviors gambling/shopping. Further testing of established scales against gold standard diagnostic criteria is urgently required for all other individual ICBs in PD. © 2019 International Parkinson and Movement Disorder Society © 2019 International Parkinson and Movement Disorder Society.

Palliative medicine and end-of-life care

Palliative care is an approach to the care of patients, affected by serious illness, and their families that aims to reduce suffering through the management of medical symptoms, psychosocial issues, spiritual well-being, and setting goals of care. Patients and families affected by a neurodegenerative illness have significant palliative care needs beginning at the time of diagnosis and extending through end-of-life care and bereavement. We advocate an approach to addressing these needs where the patient's primary care provider or neurologist plays a central role. Key skills in providing effective palliative care to this population include providing the diagnosis with compassion, setting goals of care, anticipating safety concerns, caregiver assessment, advance care planning, addressing psychosocial concerns, and timely referral to a hospice. Managing distressing medical and psychiatric symptoms is critical to improving quality of life throughout the disease course as well as at end-of-life. Many symptoms are common across illnesses; however, there are issues that are specific to the most common classes of neurodegenerative illness, namely dementia, parkinsonism, and motor neuron disease. Incorporating a palliative approach to care, although challenging in many ways, empowers physicians to provide greater support and guidance to patients and families in making the difficult journey through a neurodegenerative illness.

Markers of impaired motor and cognitive volition in Parkinson's disease: Correlates of dopamine dysregulation syndrome, impulse control disorder, and dyskinesias

INTRODUCTION

Dopaminergic therapy in Parkinson's disease (PD) can be associated with both motoric (e.g., dyskinesias) and neuropsychiatric adverse effects. Examples of the latter include Dopamine Dysregulation Syndrome (DDS) and impulse control disorder (ICD), which are separate but related behavioral/psychiatric complications of treatment in PD. Dysregulation of volition characterizes both dyskinesias and DDS/ICD; thus, we analyzed potential disease-related correlates in a large PD cohort.

METHODS

We analyzed cross-sectional data from 654 participants collected through the NINDS Parkinson's Disease Biomarkers Program. DDS/ICD symptoms and dyskinesias were assessed using the Movement Disorders Society (revised) Unified Parkinson's Disease Rating Scale. Potential associated variables were selected from PD-validated or PD-specific scales of neuropsychiatric or motoric status. Multivariable models with DDS/ICD or dyskinesia presence outcomes were produced with backward stepwise regression to identify factors independently associated with DDS/ICD and/or dyskinesias.

RESULTS

Fifty-three (8.1%) participants endorsed DDS and/or ICD symptoms and 150 (22.9%) were dyskinetic. In multivariable analysis, psychosis was independently associated with both dyskinesias (p = 0.006) and DDS/ICD (p < 0.001). Unpredictable motor fluctuations (p = 0.026) and depression (p = 0.023) were also associated with DDS/ICD; female sex (p = 0.025), low tremor score (p = 0.001) and high akinesia-rigidity score (p < 0.001) were associated with dyskinesias.

CONCLUSIONS

Our findings suggest that psychosis may be an important marker of impaired volition across motor and cognitive domains. Unpredictable motor fluctuations, psychosis, and depression may together comprise a phenotypic profile of patients at increased risk for DDS/ICD. Similarly, dyskinetic PD patients should be closely monitored for psychotic symptoms and treated appropriately.

Parkinson's disease psychosis: presentation, diagnosis and management

Parkinson's disease is a neurodegenerative disorder characterized by motor and nonmotor symptoms. Psychosis is a common feature of Parkinson's disease. Parkinson's disease psychosis (PDP) encompasses minor phenomena (illusions, passage hallucinations and presence hallucinations), visual and nonvisual hallucinations and delusions. PDP is associated with reduced function and quality of life. The initial management approach should focus on identification and treatment of any contributory medical factors, reduction or discontinuation of medications with potential to induce or worsen psychosis, nonpharmacological strategies and consideration of acetylcholinesterase inhibitor treatment in the setting of dementia. Pimavanserin, quetiapine and clozapine may all be considered for use in PDP. In this review, we discuss the presentation, diagnosis and management of PDP.

A systematic review of the literature on disorders of sleep and wakefulness in Parkinson's disease from 2005 to 2015

Sleep disorders are among the most common non-motor manifestations in Parkinson's disease (PD) and have a significant negative impact on quality of life. While sleep disorders in PD share most characteristics with those that occur in the general population, there are several considerations specific to this patient population regarding diagnosis, management, and implications. The available research on these disorders is expanding rapidly, but many questions remain unanswered. We thus conducted a systematic review of the literature published from 2005 to 2015 on the following disorders of sleep and wakefulness in PD: REM sleep behavior disorder, insomnia, nocturia, restless legs syndrome and periodic limb movements, sleep disordered breathing, excessive daytime sleepiness, and circadian rhythm disorders. We discuss the epidemiology, etiology, clinical implications, associated features, evaluation measures, and management of these disorders. The influence on sleep of medications used in the treatment of motor and non-motor symptoms of PD is detailed. Additionally, we suggest areas in need of further research.

Cerebral correlates of psychotic syndromes in neurodegenerative diseases

Psychosis has been recognized as a common feature in neurodegenerative diseases and a core feature of dementia that worsens most clinical courses. It includes hallucinations, delusions including paranoia, aggressive behaviour, apathy and other psychotic phenomena that occur in a wide range of degenerative disorders including Alzheimer's disease, synucleinopathies (Parkinson's disease, dementia with Lewy bodies), Huntington's disease, frontotemporal degenerations, motoneuron and prion diseases. Many of these psychiatric manifestations may be early expressions of cognitive impairment, but often there is a dissociation between psychotic/behavioural symptoms and the rather linear decline in cognitive function, suggesting independent pathophysiological mechanisms. Strictly neuropathological explanations are likely to be insufficient to explain them, and a large group of heterogeneous factors (environmental, neurochemical changes, genetic factors, etc.) may influence their pathogenesis. Clinico-pathological evaluation of behavioural and psychotic symptoms (PS) in the setting of neurodegenerative and dementing disorders presents a significant challenge for modern neurosciences. Recognition and understanding of these manifestations may lead to the development of more effective preventive and therapeutic options that can serve to delay long-term progression of these devastating disorders and improve the patients' quality of life. A better understanding of the pathophysiology and distinctive pathological features underlying the development of PS in neurodegenerative diseases may provide important insights into psychotic processes in general.

Nonmotor manifestations in Parkinson disease

BACKGROUND

Although the diagnosis of Parkinson disease (PD) still relies mainly on the appearance of its classical motor features of resting tremor, rigidity, bradykinesia, and postural instability, nonmotor manifestations in PD are now recognized as an integral component of this multisystem disorder.

REVIEW SUMMARY

Nonmotor complications in PD occur commonly. The current understanding of cognitive dysfunction; neuropsychiatric manifestations including psychosis, impulsive control, and compulsive disorders, depression, anxiety and apathy; autonomic complications such as hypotension, erectile dysfunction, and urinary complications; sleep disorders and other nonmotor manifestations are summarized in this review.

CONCLUSION

Nonmotor complications often carry a greater impact than motor features in PD. Therefore, heightened awareness and proper recognition of these features are critical in improving a Parkinson patient's quality of life.

The effect of dopamine agonists on adaptive and aberrant salience in Parkinson's disease

Clinical evidence suggests that after initiation of dopaminergic medications some patients with Parkinson's disease (PD) develop psychotic symptoms, such as hallucinations and delusions. Here, we tested the hypothesis that the neurocognitive basis of this phenomenon can be defined as the formation of arbitrary and illusory associations between conditioned stimuli and reward signals, called aberrant salience. Young, never-medicated PD patients and matched controls were assessed on a speeded reaction time task in which the probe stimulus was preceded by conditioned stimuli that could signal monetary reward by color or shape. The patients and controls were re-evaluated after 12 weeks during which the patients received a dopamine agonist (pramipexole or ropinirole). Results indicated that dopamine agonists increased both adaptive and aberrant salience in PD patients, that is, formation of real and illusory associations between conditioned stimuli and reward, respectively. This effect was present when associations were assessed by means of faster responding after conditioned stimuli signaling reward (implicit salience) and overt rating of stimulus-reward links (explicit salience). However, unusual feelings and experiences, which are subclinical manifestations of psychotic-like symptoms, were specifically related to irrelevant and illusory stimulus-reward associations (aberrant salience) in PD patients receiving dopamine agonists. The learning of relevant and real stimulus-reward associations (adaptive salience) was not related to unusual experiences. These results suggest that dopamine agonists may increase psychotic-like experiences in young patients with PD, possibly by facilitating dopaminergic transmission in the ventral striatum, which results in aberrant associations between conditioned stimuli and reward.

Cognitive-behavioral therapy for pathological gambling in Parkinson's disease: a pilot controlled study

OBJECTIVES

The main objective of this study was to compare the clinical characteristics and differences in response to treatment of two groups of pathological gamblers: with comorbid Parkinson's disease (PG + PD) and without (PG - PD).

METHODS

Clinical and psychopathological profiles and response to cognitive-behavioral treatment were assessed in 15 PG + PD and 45 PG - PD individuals consulting a specialized hospital Unit.

RESULTS

Statistically significant differences were observed between the two groups on a series of clinical variables. PG + PD patients were older and presented later onset of problematic gambling behaviors, lower alcohol consumption and higher bingo playing than PG - PD patients. No significant differences were noted in psychopathology except for lower measures of hostility in the PG + PD group. No statistical differences were detected between groups in terms of response to treatment.

CONCLUSION

These results may provide guidance for obtaining accurate diagnostic information in pathological gamblers by properly identifying patients with specific needs that may be targeted with treatment.

Clinicopathological correlates of behavioral and psychological symptoms of dementia

Behavioral and psychological symptoms are commonly observed in a majority of demented patients at some time during the course of their illness. Many of these psychiatric manifestations, especially those related to mood, may be early expressions of dementia and/or mild cognitive impairment. The literature suggests that behavioral and psychological symptoms of dementia (BPSD) are an integral part of the disease process. The dissociation, in many cases, between BPSD and the rather linear decline in cognitive functions suggests that independent pathophysiological mechanisms give rise to these symptoms. A review of the neuroimaging and neuropathology literature indicates that BPSD are the expression of regional rather than diffuse brain pathology. Psychotic symptoms in demented patients usually demonstrate preferential involvement of the frontal lobe and/or limbic regions. Visual hallucinations differentiate themselves from other psychotic symptoms by their tendency to involve the occipital lobes. There is a significant association between apathy and structural changes of the anterior cingulate gyrus. White matter hyperintensities occur in a significant number of depressed patients; otherwise, there is lack of association between depression and either specific brain changes or affected regions. Strictly neuropathological explanations are likely to be insufficient to explain BPSD. Environmental changes, neurochemical abnormalities, past psychiatric history (including premorbid personality), social history (e.g., intellectual achievement and life-long learning), family history, and genetic susceptibility are factors, among others, that influence BPSD.

MDS Task Force on mild cognitive impairment in Parkinson's disease: critical review of PD-MCI

There is controversy regarding the definition and characteristics of mild cognitive impairment in Parkinson's disease. The Movement Disorder Society commissioned a Task Force to critically evaluate the literature and determine the frequency and characteristics of Parkinson's disease-mild cognitive impairment and its association with dementia. A comprehensive PubMed literature review was conducted using systematic inclusion and exclusion criteria. A mean of 26.7% (range, 18.9%-38.2%) of nondemented patients with Parkinson's disease have mild cognitive impairment. The frequency of Parkinson's disease-mild cognitive impairment increases with age, disease duration, and disease severity. Impairments occur in a range of cognitive domains, but single domain impairment is more common than multiple domain impairment, and within single domain impairment, nonamnestic is more common than amnestic impairment. A high proportion of patients with Parkinson's disease-mild cognitive impairment progress to dementia in a relatively short period of time. The primary conclusions of the Task Force are that: (1) Parkinson's disease-mild cognitive impairment is common, (2) there is significant heterogeneity within Parkinson's disease-mild cognitive impairment in the number and types of cognitive domain impairments, (3) Parkinson's disease-mild cognitive impairment appears to place patients at risk of progressing to dementia, and (4) formal diagnostic criteria for Parkinson's disease-mild cognitive impairment are needed.

Clinical review of treatment options for select nonmotor symptoms of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is associated with a host of nonmotor symptoms, including psychosis, cognitive impairment, depression, sleep disturbance, swallowing disorders, gastrointestinal symptoms, and autonomic dysfunction. The nonmotor symptoms of PD have the potential to be more debilitating than the motor features of the disorder.

OBJECTIVE

The aim of this article was to review treatment options for the nonmotor manifestations of PD, including pharmacologic and nonpharmacologic interventions.

METHODS

The PubMed and MEDLINE databases were searched for articles published in English between January 1966 and April 2010, using the terms Parkinson's disease, nonmotor, psychosis, hallucination, antipsychotic, cognitive impairment, dementia, depression, sleep disturbance, sleepiness, REM (rapid eye movement) sleep behavior disorder, dysphagia, swallowing disorder, sialorrhea, gastrointestinal, constipation, autonomic dysfunction, orthostatic hypotension, gastroparesis, erectile dysfunction, sexual dysfunction, and urinary dysfunction. Articles were selected for review if they were randomized controlled trials (RCTs), meta-analyses, or evidence-based reviews of treatment of patients with PD, and/or expert opinion regarding the treatment of nonmotor symptoms of PD.

RESULTS

A total of 148 articles, including RCTs, meta-analyses, and evidence-based reviews, were included in this review. The treatment of hallucinations or psychosis in PD should include a stepwise reduction in medications for motor symptoms, followed by the use of quetiapine or clozapine. Dementia may be treated with acetylcholinesterase inhibitors. Evidence is lacking concerning the optimal pharmacologic treatment for depression in PD, with expert opinions indicating selective serotonin reuptake inhibitors as the antidepressants of choice. However, the largest study to date found nortriptyline therapy to be efficacious compared with placebo, whereas paroxetine controlled release was not. A variety of sleep disturbances may plague a person with PD, and treatment must be individualized to the patient's specific sleep disturbance pattern and contributing factors. Swallowing disorders may lead to aspiration and pneumonia, and patients with dysphagia should be referred to a speech therapist for further evaluation and treatment. Orthostasis may be treated with nonpharmacologic interventions as well as pharmacologic treatments (eg, fludrocortisone, midodrine, indomethacin). Other autonomic symptoms are managed in a manner similar to that in patients without PD, although careful attention must be aimed at avoiding dopamine-blocking therapies in the treatment of gastrointestinal dysfunction and gastroparesis.

CONCLUSIONS

Various pharmacologic and nonpharmacologic strategies are available for the management of the nonmotor symptoms of PD. The challenges associated with nonmotor symptoms must not be forgotten in light of the motor symptoms of PD, and treatment of nonmotor symptoms should be encouraged.

From the cell to the clinic: a comparative review of the partial D₂/D₃receptor agonist and α2-adrenoceptor antagonist, piribedil, in the treatment of Parkinson's disease

Though L-3,4-dihydroxyphenylalanine (L-DOPA) is universally employed for alleviation of motor dysfunction in Parkinson's disease (PD), it is poorly-effective against co-morbid symptoms like cognitive impairment and depression. Further, it elicits dyskinesia, its pharmacokinetics are highly variable, and efficacy wanes upon long-term administration. Accordingly, "dopaminergic agonists" are increasingly employed both as adjuncts to L-DOPA and as monotherapy. While all recognize dopamine D(2) receptors, they display contrasting patterns of interaction with other classes of monoaminergic receptor. For example, pramipexole and ropinirole are high efficacy agonists at D(2) and D(3) receptors, while pergolide recognizes D(1), D(2) and D(3) receptors and a broad suite of serotonergic receptors. Interestingly, several antiparkinson drugs display modest efficacy at D(2) receptors. Of these, piribedil displays the unique cellular signature of: 1), signal-specific partial agonist actions at dopamine D(2)and D(3) receptors; 2), antagonist properties at α(2)-adrenoceptors and 3), minimal interaction with serotonergic receptors. Dopamine-deprived striatal D(2) receptors are supersensitive in PD, so partial agonism is sufficient for relief of motor dysfunction while limiting undesirable effects due to "over-dosage" of "normosensitive" D(2) receptors elsewhere. Further, α(2)-adrenoceptor antagonism reinforces adrenergic, dopaminergic and cholinergic transmission to favourably influence motor function, cognition, mood and the integrity of dopaminergic neurones. In reviewing the above issues, the present paper focuses on the distinctive cellular, preclinical and therapeutic profile of piribedil, comparisons to pramipexole, ropinirole and pergolide, and the core triad of symptoms that characterises PD-motor dysfunction, depressed mood and cognitive impairment. The article concludes by highlighting perspectives for clarifying the mechanisms of action of piribedil and other antiparkinson agents, and for optimizing their clinical exploitation.