The Evolution of REM Sleep Behavior Disorder in Early Parkinson Disease

Advances in the Research of Risk Factors and Prodromal Biomarkers of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. With the advent of an aging population and improving life expectancy worldwide, the number of PD patients is expected to increase, which may lead to an urgent need for effective preventive and diagnostic strategies for PD. Although there is increasing research regarding the pathogenesis of PD, there is limited knowledge regarding the prevention of PD. Moreover, the diagnosis of PD depends on clinical criteria, which require the occurrence of bradykinesia and at least one symptom of rest tremor or rigidity. However, converging evidence from clinical, genetic, neuropathological, and imaging studies suggests the initiation of PD-specific pathology prior to the initial presentation of these classical motor clinical features by years or decades. This latent stage of neurodegeneration in PD is a particularly important stage for effective neuroprotective therapies, which might retard the progression or prevent the onset of PD. Therefore, the exploration of risk factors and premotor biomarkers is not only crucial to the early diagnosis of PD but is also helpful in the development of effective neuroprotection and health care strategies for appropriate populations at risk for PD. In this review, we searched and summarized ∼249 researches and 31 reviews focusing on the risk factors and prodromal biomarkers of PD and published in MEDLINE.

A case-control-family study of idiopathic rapid eye movement sleep behavior disorder

OBJECTIVE

To determine the familial aggregation of idiopathic rapid eye movement sleep behavior disorder (iRBD), neurodegenerative diseases, and related biomarkers.

METHODS

A total of 404 and 387 first-degree relatives of 102 patients with iRBD and of 89 controls were recruited, respectively. Among them, 204 and 208 relatives of patients and controls underwent face-to-face clinical assessment, whereas 97 and 75 relatives underwent further video-polysomnographic assessment, respectively.

RESULTS

Compared with relatives of controls, relatives of patients demonstrated higher levels of RBD features, including chin tonic electromyography activity (mean = 1.5 ± 7.5 vs 0.3 ± 1.0, p = 0.04) and behavioral events (n [weighted %] = 12 [11.3] vs 2 [1.9], adjusted hazard ratio [aHR] = 7.69, 95% confidence interval [CI] = 1.54-33.33, p = 0.009) during rapid eye movement sleep, probable diagnosis (n [%] = 57 [14.9] vs 20 [4.9], aHR = 3.45, 95% CI = 1.96-6.25, p < 0.001), and definite diagnosis (n [weighted %] = 10 [8.4] vs 2 [1.4], aHR = 5.56, 95% CI = 1.16-25.00, p = 0.03). They also had higher risks of Parkinson disease (3.1% vs 0.5%, aHR = 5.88, 95% CI = 1.37-25.00, p = 0.02), dementia (6.9% vs 2.6%, aHR = 2.44, 95% CI = 1.15-5.26, p = 0.02), constipation (8.3% vs 2.4%, adjusted odds ratio = 4.21, 95% CI = 1.34-13.17, p = 0.01), and motor dysfunction (Movement Disorders Society Unified Parkinson's Disease Rating Scale part III motor score, mean = 1.9 ± 3.2 vs 0.9 ± 2.3, p = 0.002). The unaffected relatives of patients demonstrated a higher likelihood ratio of prodromal Parkinson disease (median [interquartile range] = 0.27 [1.19] vs 0.22 [0.51], p = 0.03).

INTERPRETATION

iRBD is familially aggregated from isolated features to full-blown sleep disorder. Relatives of patients carry a higher risk of alpha-synucleinopathy in terms of neurodegenerative diseases and prodromal markers, suggesting a familial aggregation and staging pathology of alpha-synucleinopathy. Ann Neurol 2019;85:582-592.

Clinical progression in Parkinson's disease with features of REM sleep behavior disorder: A population-based longitudinal study

INTRODUCTION

Rapid Eye Movement (REM) sleep behavior disorder (RBD) is characterized by dream enactment and is associated with incidence of neurodegenerative disorders, especially Parkinson's disease (PD). Whether PD with RBD constitutes a distinct subtype with unique progression is unknown. Here, we investigated motor and cognitive symptom progression in patients with self-reported RBD features in adult life.

METHODS

We screened for RBD in a cohort of 776 PD patients whom we ascertained using a population-based strategy. Among participants with at least one follow-up (60%), we compared those with and without probable RBD (pRBD) estimating hazard rate ratios for progression events UPDRS-III≥ 35 and MMSE≤ 24.

RESULTS

Prevalence of pRBD at baseline was 21%. In adjusted Cox regression models among patients with a Postural Instability and Gait Dysfunction (PIGD) phenotype, those with pRBD progressed faster to a UPDRS-III≥ 35 (HR = 1.92, 95% CI = 1.12; 3.27). Also, all patients with pRBD progressed twice as fast to a MMSE score≤ 24 (HR = 2.04, 95% CI = 1.13; 3.69). In sensitivity analyses, using alternative definition of pRBD and accounting for bias due to loss to follow-up results remained similar.

DISCUSSION

Employing data from one of the largest population-based studies of PD, in which movement disorder specialists assessed patients, we confirm evidence that pRBD features are a clinical marker for faster cognitive decline and possibly also motor progression in PD patients, the latter for patients with a PIGD subtype early in disease.

Diagnostic Criteria, Differential Diagnosis, and Treatment of Minor Motor Activity and Less Well-Known Movement Disorders of Sleep

Purpose of review

Sleep-related movement disorders (SRMD) include several different motor activities during sleep. Few of them are well known and well classified, whereas others are minor motor disorders of sleep which are neither thoroughly characterized and classified nor have been extensively investigated to clarify their pathogenesis and clinical relevance. This review will focus on those minor sleep-related movement disorders.

Recent findings

Before diagnosing periodic limb movement (PLM) disorder in patients with PLM during polysomnography, other disorders associated with PLM need to be excluded, namely restless legs syndrome (RLS), narcolepsy, REM sleep behavior disorder (RBD), and sleep-related breathing disorder. For the diagnosis of propriospinal myoclonus at sleep-onset, multi-channel surface electromyography recording during polysomnography is required and a possible psychogenic origin of the movement disorder has to be considered. Excessive fragmentary myoclonus (EFM) does not require symptomatic treatment, but further evaluation is suggested as electrophysiological abnormalities are present in 50% of cases. Nine percent of healthy sleepers meet the criteria for EFM, raising the question if current, arbitrarily defined, cutoffs are valid. Hypnagogic foot tremor, rhythmic feet movements, alternating leg muscle activation, and high-frequency leg movements are somewhat overlapping minor motor activities during sleep which may exist on their own or represent stereotyped movements to relieve RLS-like symptoms. Neck myoclonus is probably a physiological phenomenon related to REM twitching. RBD is formally a parasomnia but a relevant differential diagnosis when evaluating sleep-related movement disorders. In particular, prodromal RBD is characterized by electromyographic and behavioral findings on video-polysomnography which needs to be differentiated by minor sleep-related movement disorders.

Summary

Minor SRMD beyond the well-known main motor disorders of sleep should be correctly diagnosed, distinguished from differential diagnosis, and understood in their potential clinical relevance, in order also to start an appropriate treatment if needed.

Rapid Eye Movement Sleep Behavior Disorder and Other Rapid Eye Movement Sleep Parasomnias

PURPOSE OF REVIEW

The most common rapid eye movement (REM) parasomnia encountered by neurologists is REM sleep behavior disorder (RBD), and nightmares are so frequent that every neurologist should be able to differentiate them from the dream enactment of RBD. Isolated sleep paralysis is relatively common and is often mistaken for other neurologic disorders. This article summarizes the current state of the art in the diagnosis of RBD, discusses the role of specific questionnaires and polysomnography in the diagnosis of RBD, and reviews recent studies on idiopathic RBD as an early feature of a synucleinopathy, secondary RBD, and its management. Recent diagnostic criteria and implications of nightmares and isolated sleep paralysis are also reviewed.

RECENT FINDINGS

Idiopathic RBD can now be considered as part of the prodromal stage of a synucleinopathy. Therefore, an accurate diagnosis is mandatory, and this implies detection of REM sleep without atonia. The polysomnography montage, including EMG of the submentalis and flexor digitorum superficialis muscles, provides a high sensitivity and specificity for the diagnosis. The exact diagnosis is important for patient counseling and for future neuroprotective trials.

SUMMARY

REM parasomnias include RBD, sleep paralysis, and nightmares, which have distinct clinical characteristics and different implications regarding diagnostic procedures, management, and prognosis.

Screening for idiopathic REM sleep behavior disorder: usefulness of actigraphy

Study Objectives

To evaluate the utility of multimodal low-cost approaches including actigraphy, a wrist-worn device monitoring rest/activity cycles, in identifying patients with idiopathic REM sleep behavior disorder (iRBD).

Methods

Seventy patients diagnosed with sleep disorders causing different motor manifestations during sleep (iRBD, sleep apnea, restless legs syndrome) and 20 subjects without any relevant motor manifestation during sleep, underwent video-polysomnography (vPSG) and 2 week actigraphy, completed six validated RBD screening questionnaires, and sleep apps use was assessed. Actigraphy was analyzed automatically, and visually by seven blinded sleep medicine experts who rated as "no," "possible," and "probable" RBD.

Results

Quantitative actigraphy analysis distinguished patients from controls, but not between patients with different types of motor activity during sleep. Visual actigraphy rating by blinded experts in sleep medicine using pattern recognition identified vPSG confirmed iRBD with 85%-95% sensitivity, 79%-91% specificity, 81%-91% accuracy, 57.7% ± 11.3% positive predictive value, 95.1% ± 3.3% negative predictive value, 6.8 ± 2.2 positive likelihood ratio, 0.14 ± 0.05 negative likelihood ratio and 0.874-0.933 area under the ROC curve (AUC). AUC of the best performing questionnaire was 0.868. Few patients used sleep apps; therefore, their potential utility in the evaluated patients' groups is limited.

Conclusions

Visual analysis of actigraphy using pattern recognition can identify subjects with iRBD, and is able to distinguish iRBD from other motor activities during sleep, even when patients are not aware of the disease in contrast to questionnaires. Therefore, actigraphy can be a reliable screening instrument for RBD potentially useful in the general population.

Relationships between Rapid Eye Movement Sleep Behavior Disorder and Neurodegenerative Diseases: Clinical Assessments, Biomarkers, and Treatment

OBJECTIVE

Rapid eye movement sleep behavior disorder (RBD) is characterized by dream enactment and loss of muscle atonia during rapid eye movement sleep. RBD is closely related to α-synucleinopathies including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. Many studies have investigated the markers of imaging and neurophysiological, genetic, cognitive, autonomic function of RBD and their predictive value for neurodegenerative diseases. This report reviewed the progress of these studies and discussed their limitations and future research directions.

DATA SOURCES

Using the combined keywords: "RBD", "neurodegenerative disease", "Parkinson disease", and "magnetic resonance imaging", the PubMed/MEDLINE literature search was conducted up to January 1, 2018.

STUDY SELECTION

A total of 150 published articles were initially identified citations. Of the 150 articles, 92 articles were selected after further detailed review. This study referred to all the important English literature in full.

RESULTS

Single-nucleotide polymorphisms in SCARB2 (rs6812193) and MAPT (rs12185268) were significantly associated with RBD. The olfactory loss, autonomic dysfunction, marked electroencephalogram slowing during both wakefulness and rapid eye movement sleep, and cognitive impairments were potential predictive markers for RBD conversion to neurodegenerative diseases. Traditional structural imaging studies reported relatively inconsistent results, whereas reduced functional connectivity between the left putamen and substantia nigra and dopamine transporter uptake demonstrated by functional imaging techniques were relatively consistent findings.

CONCLUSIONS

More longitudinal studies should be conducted to evaluate the predictive value of biomarkers of RBD. Moreover, because the glucose and dopamine metabolisms are not specific for assessing cognitive cognition, the molecular metabolism directly related to cognition should be investigated. There is a need for more treatment trials to determine the effectiveness of interventions of RBD on preventing the conversion to neurodegenerative diseases.

The REM Sleep Behavior Disorder Screening Questionnaire is not Valid in De Novo Parkinson's Disease

Background

Rapid eye movement (REM) sleep behavior disorder (RBD) is one of the most specific prodromal indicators for Parkinson's disease (PD).

Objectives

To test the validity of the RBD‐Screening Questionnaire (RBDSQ) in assessing RBD in early PD.

Methods

The RBDSQ was completed before video‐supported polysomnography (vPSG) by 134 de novo PD patients, 109 matched controls without neurological disorder (CTR) and 30 subjects with idiopathic RBD (iRBD) without clinical signs of PD; results were compared with vPSG‐confirmed RBD diagnosis.

Results and Conclusions

Sensitivity/specificity of the RBDSQ for the PD cohort were 0.44/0.84 at the previously published cut‐off score of 6 for PD patients, and the area under the curve (AUC) 0.68 (95% CI, 0.56–0.79). By contrast, in the iRBD/CTR cohort the RBDSQ (cut‐off = 5) had a sensitivity/specificity of 0.97/0.84 and an AUC of 0.95 (95% CI, 0.90–1.00). Subanalysis of question 6 only (4 subitems asking for dream enactment) at a cut‐off score of 1 revealed a sensitivity of 0.74 and a specificity of 0.70 for the de novo PD cohort, AUC was 0.74 (95% CI, 0.63–0.84). RBDSQ is an insufficient screening tool for RBD in de novo PD. New screening tools for RBD assessment need to be developed.

Sleep and REM sleep behaviour disorder in Parkinson's disease with impulse control disorder

INTRODUCTION

Because the association between rapid eye movement sleep behaviour disorder (RBD) and impulse control disorders (ICDs) in Parkinson's disease (PD) has been debated, we assessed the sleep characteristics and the frequency of RBD using video-polysomnography (v-PSG) in patients with PD with versus without ICDs.

METHODS

Eighty non-demented patients with PD consecutively identified during routine evaluation at three movement disorders centres were enrolled in a case-control study. Forty patients (22 men; mean age: 62.6±9.7 years, Hoehn & Yahr: 2.1±0.6) with one or more current ICDs were age-matched and sex-matched with 40 patients with no history of ICDs (22 men, mean age: 64.9±7.8 years, Hoehn & Yahr: 2.2±0.6). They underwent a detailed sleep interview followed by a full-night in-lab v-PSG. Sleep was scored blindly to ICDs condition and RBD diagnosis included a clinical complaint of enacted dreams and/or documented behaviour during rapid eye movement (REM) sleep, with the presence of quantified REM sleep without atonia (RSWA).

RESULTS

Patients with ICDs had a higher arousal index and higher RSWA than those without ICDs (51.9%±28.2%vs 32.2±27.1%, p=0.004). In addition, RBD was more frequent in the ICD group (85%vs53%, p=0.0001). RBD was still associated with ICDs in a multivariate regression analysis including age of onset, PD duration and severity, treatment duration, levodopa-equivalent and dopamine agonist-equivalent daily doses and antidepressant use (OR: 4.9 (95% CI 1.3 to 18.5), p=0.02).

CONCLUSIONS

This large, controlled series of patients with PD with ICDs assessed by v-PSG confirms the association between ICDs and RBD. Increased surveillance of symptoms of ICDs should be recommended in patients with PD with RBD.

Sleep-wake disturbances in the premotor and early stage of Parkinson's disease

PURPOSE OF REVIEW

Review of recent literature pertaining to frequency, associations, mechanisms, and overall significance of sleep--wake disturbances (SWD) in the premotor and early phase of Parkinson's disease.

RECENT FINDINGS

SWD are frequent in Parkinson's disease and their prevalence increases with disease progression. Recent studies confirm previous findings that SWD can appear as initial manifestation of Parkinson's disease even decades before motor signs appear and highlight their clinical associations in these early stages. More intriguingly, new evidence underpins their role as risk factors, predictors, or even as driving force for the neurodegenerative process. As our understanding of sleep--wake neurobiology increases, new hypotheses emerge concerning the pathophysiology of SWD in early Parkinson's disease stages involving dopaminergic and nondopaminergic mechanisms.

SUMMARY

SWD are predictors for the development of parkinsonian syndromes including Parkinson's disease. This may offer the opportunity of developing new preventive strategies and interventions at an early stage of this neurodegenerative disease.

Idiopathic REM sleep behaviour disorder and neurodegeneration - an update

So-called idiopathic rapid eye movement (REM) sleep behaviour disorder (RBD), formerly seen as a rare parasomnia, is now recognized as the prodromal stage of an α-synucleinopathy. Given the very high risk that patients with idiopathic RBD have of developing α-synucleinopathies, such as Parkinson disease (PD), PD dementia, dementia with Lewy bodies or multiple system atrophy, and the outstandingly high specificity and very long interval between the onset of idiopathic RBD and the clinical manifestations of α-synucleinopathies, the prodromal phase of this disorder represents a unique opportunity for potentially disease-modifying intervention. This Review provides an update on classic and novel biomarkers of α-synuclein-related neurodegeneration in patients with idiopathic RBD, focusing on advances in imaging and neurophysiological, cognitive, autonomic, tissue-specific and other biomarkers. We discuss the strengths, potential weaknesses and suitability of these biomarkers for identifying RBD and neurodegeneration, with an emphasis on predicting progression to overt α-synucleinopathy. The role of video polysomnography in providing quantifiable and potentially treatment-responsive biomarkers of neurodegeneration is highlighted. In light of all these advances, and the now understood role of idiopathic RBD as an early manifestation of α-synuclein disease, we call for idiopathic RBD to be reconceptualized as isolated RBD.

Can Biomarkers Help the Early Diagnosis of Parkinson's Disease?

Parkinson's disease (PD) is a complex neurodegenerative disease with progressive loss of dopamine neurons. PD patients usually manifest a series of motor and non-motor symptoms. In order to provide better early diagnosis and subsequent disease-modifying therapies for PD patients, there is an urgent need to identify sensitive and specific biomarkers. Biomarkers can be divided into four categories: clinical, imaging, biochemical, and genetic. Ideal biomarkers not only improve our understanding of PD pathogenesis and progression, but also provide benefits for early risk evaluation and clinical diagnosis of PD. Although many efforts have been made and several biomarkers have been extensively investigated, few if any have been found useful for early diagnosis. Here, we summarize recent developments in the discovered biomarkers of PD and discuss their merits and limitations for the early diagnosis of PD.

Premotor Diagnosis of Parkinson's Disease

Typical Parkinsonian symptoms consist of bradykinesia plus rigidity and/or resting tremor. Some time later postural instability occurs. Pre-motor symptoms such as hyposmia, constipation, REM sleep behavior disorder and depression may antecede these motor symptoms for years. It would be ideal, if we had a biomarker which would allow to predict who with one or two of these pre-motor symptoms will develop the movement disorder Parkinson's disease (PD). Thus, it is interesting to learn that biopsies of the submandibular gland or colon biopsies may be a means to predict PD, if there is a high amout of abnormally folded alpha-synuclein and phosphorylated alpha-synuclein. This would be of relevance if we would have available means to stop the propagation of abnormal alpha-synuclein which is otherwise one of the reasons of this spreading disease PD.

Sleep Dysfunction in Parkinson's Disease

The spectrum of sleep problems in Parkinson's disease (PD) is broad. These symptoms are recognized as being clinically relevant by the PD patients and may seriously affect their quality of life. Some studies reveal the occurrence of sleep disorders in more than half of the PD patients. The etiology is multifactorial and it mainly involves the degeneration of the sleep-regulating structures. Sleep disorders in PD can be classified into: disturbances of sleep and disturbances of wakefulness. Generic and specific scales were designed to help the screening and evaluation of sleep dysfunction. Further assessment can be done using sleep recording techniques, like actigraphy or polysomnography. All types of sleep disturbances may be encountered in PD: insomnia, excessive daytime sleepiness, rapid eye movement sleep behavior disorders, and restless legs syndrome. This chapter will focus on reviewing the main characteristics, pathophysiology, assessment, and management of the most frequent sleep disturbances encountered in PD.

Neuropathology of Nonmotor Symptoms of Parkinson's Disease

Parkinson's disease (PD), a multiorgan neurodegenerative disorder associated with α-synuclein deposits throughout the nervous system and many organs, is clinically characterized by motor and nonmotor features, many of the latter antedating motor dysfunctions by 20 or more years. The causes of the nonmotor manifestations such as olfactory, autonomic, sensory, neuropsychiatric, visuospatial, sleep, and other disorders are unlikely to be related to single lesions. They are mediated by the involvement of both dopaminergic and nondopaminergic systems, and diverse structures outside the nigrostriatal system that is mainly responsible for the motor features of PD. The nonmotor alterations appear in early/prodromal stages of the disease and its further progression, suggesting a topographical and chronological spread of the lesions. This lends further support for the notion that PD is a multiorgan proteinopathy, although the exact relationship between presymptomatic and later developing nonmotor features of PD and neuropathology awaits further elucidation.

Sleep-related movement disorders and disturbances of motor control

PURPOSE OF REVIEW

Review of the literature pertaining to clinical presentation, classification, epidemiology, pathophysiology, diagnosis, and treatment of sleep-related movement disorders and disturbances of motor control.

RECENT FINDINGS

Sleep-related movement disorders and disturbances of motor control are typically characterized by positive motor symptoms and are often associated with sleep disturbances and consequent daytime symptoms (e.g. fatigue, sleepiness). They often represent the first or main manifestation of underlying disorders of the central nervous system, which require specific work-up and treatment. Diverse and often combined cause factors have been identified. Although recent data provide some evidence regarding abnormal activation and/or disinhibition of motor circuits during sleep, for the majority of these disorders the pathogenetic mechanisms remain speculative. The differential diagnosis is sometimes difficult and misdiagnoses are not infrequent. The diagnosis is based on clinical and video-polysomnographic findings. Treatment of sleep-related motor disturbances with few exceptions (e.g. restless legs/limbs syndrome) are based mainly on anecdotal reports or small series.

SUMMARY

More state-of-the-art studies on the cause, pathophysiology, and treatment of sleep-related movement disorders and disturbances of motor control are needed.

Sleep and Neurodegeneration: A Critical Appraisal

Sleep abnormalities are clearly recognized as a distinct clinical symptom of concern in neurodegenerative disorders. Appropriate management of sleep-related symptoms has a positive impact on quality of life in patients with neurodegenerative disorders. This review provides an overview of mechanisms that are currently being considered that tie sleep with neurodegeneration. It appraises the literature regarding specific sleep changes seen in common neurodegenerative diseases, with a focus on Alzheimer disease and synucleinopathies (ie, Parkinson disease, dementia with Lewy bodies, multiple system atrophy), that have been better studied. Sleep changes may also serve as markers to identify patients in the preclinical stage of some neurodegenerative disorders. A hypothetical model is postulated founded on the conjecture that specific sleep abnormalities, when noted to increase in severity beyond that expected for age, could be a surrogate marker reflecting pathophysiological processes related to neurodegenerative disorders. This provides a clinical strategy for screening patients in the preclinical stages of neurodegenerative disorders to enable therapeutic trials to establish the efficacy of neuroprotective agents to prevent or delay the development of symptoms and functional decline. It is unclear if sleep disturbance directly impacts neurodegenerative processes or is a secondary outcome of neurodegeneration; this is an active area of research. The clinical importance of recognizing and managing sleep changes in neurodegenerative disorders is beyond doubt.