Lewy body variant of Alzheimer's disease (AD) identified by postmortem ubiquitin staining in a previously reported case of AD associated with REM sleep behavior disorder

Circadian disruption and sleep disorders in neurodegeneration

Disruptions of circadian rhythms and sleep cycles are common among neurodegenerative diseases and can occur at multiple levels. Accumulating evidence reveals a bidirectional relationship between disruptions of circadian rhythms and sleep cycles and neurodegenerative diseases. Circadian disruption and sleep disorders aggravate neurodegeneration and neurodegenerative diseases can in turn disrupt circadian rhythms and sleep. Importantly, circadian disruption and various sleep disorders can increase the risk of neurodegenerative diseases. Thus, harnessing the circadian biology findings from preclinical and translational research in neurodegenerative diseases is of importance for reducing risk of neurodegeneration and improving symptoms and quality of life of individuals with neurodegenerative disorders via approaches that normalize circadian in the context of precision medicine. In this review, we discuss the implications of circadian disruption and sleep disorders in neurodegenerative diseases by summarizing evidence from both human and animal studies, focusing on the bidirectional links of sleep and circadian rhythms with prevalent forms of neurodegeneration. These findings provide valuable insights into the pathogenesis of neurodegenerative diseases and suggest a promising role of circadian-based interventions.

REM Sleep Behavior Disorder and Alzheimer's Disease: Definitely No Relationship?

Rapid eye movement (REM) sleep behavior disorder (RBD) is a REM sleep parasomnia characterized by the loss of the typical muscular atonia present during healthy REM sleep. RBD can occur in the absence of other neurological conditions or in association with a neurodegenerative disorder. It is now well established that RBD is a strong predictor of neurodegeneration, in particular synucleinopathies, such as Parkinson's disease, Lewy body dementia (LBD), or multiple system atrophy. However, some longitudinal studies report that a minority of patients develop either overlapping form of dementia or Alzheimer disease's (AD). Although AD is reported as a possible development in patients with RBD, it is in a limited number of cases and there are concerns about the accuracy of the diagnostic criteria. Neuropsychological impairments identified in cross-sectional studies of RBD patients describe a profile similar to that observed in dementia related to synucleinopathies. However, only deficits in executive function predict the development of neurodegeneration. Longitudinal studies reported the development of AD in RBD patients in about 7% of cases with variability ranging from 3% and 11%. Since the majority of longitudinal investigations do not report AD as a possible development for RBD patients the proportion may be overestimated. The study of the relationship between RBD and AD may be confounded by two factors that lead to misdiagnosis: the use of clinical criteria alone and the overlap between the clinical features and neuropathology of AD and LBD. Future studies to investigate this association must use updated diagnostic criteria incorporating ancillary investigations.

Brain Circuitry Controlling Sleep and Wakefulness

PURPOSE OF REVIEW

This article outlines the fundamental brain mechanisms that control sleep-wake patterns and reviews how pathologic changes in these control mechanisms contribute to common sleep disorders.

RECENT FINDINGS

Discrete but interconnected clusters of cells located within the brainstem and hypothalamus comprise the circuits that generate wakefulness, non-rapid eye movement (non-REM) sleep, and REM sleep. These clusters of cells use specific neurotransmitters, or collections of neurotransmitters, to inhibit or excite their respective sleep- and wake-promoting target sites. These excitatory and inhibitory connections modulate not only the presence of wakefulness or sleep, but also the levels of arousal within those states, including the depth of sleep, degree of vigilance, and motor activity. Dysfunction or degeneration of wake- and sleep-promoting circuits is associated with narcolepsy, REM sleep behavior disorder, and age-related sleep disturbances.

SUMMARY

Research has made significant headway in identifying the brain circuits that control wakefulness, non-REM, and REM sleep and has led to a deeper understanding of common sleep disorders and disturbances.

REM sleep behaviour disorder: not just a bad dream

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a parasomnia characterised by the loss of the normal atonia during the REM stage of sleep, resulting in overt motor behaviours that usually represent the enactment of dreams. Patients will seek medical attention due to sleep-related injuries or unpleasant dream content. Idiopathic RBD which occurs independently of any other disease occurs in up to 2% of the older population. Meanwhile, secondary RBD is very common in association with certain neurodegenerative conditions. RBD can also occur in the context of antidepressant use, obstructive sleep apnoea and narcolepsy. RBD can be diagnosed with a simple screening question followed by confirmation with polysomnography to exclude potential mimics. Treatment for RBD is effective and involves treatment of underlying causes, modification of the sleep environment, and pharmacotherapy with either clonazepam or melatonin. An important finding in the past decade is the recognition that almost all patients with idiopathic RBD will ultimately go on to develop Parkinson disease or dementia with Lewy bodies. This suggests that idiopathic RBD represents a prodromal phase of these conditions. Physicians should be aware of the risk of phenoconversion. They should educate idiopathic RBD patients to recognise the symptoms of these conditions and refer as appropriate for further testing and enrolment into research trials focused on neuroprotective measures.

The Synergistic Relationship between Alzheimer's Disease and Sleep Disorders: An Update

Sleep disorders are frequently reported in Alzheimer's disease (AD), with a significant impact on patients and caregivers and a major risk factor for early institutionalization. Although changes in sleep organization are a hallmark of the normal aging processes, sleep macro- and micro-architectural alterations are more evident in patients affected by AD. Degeneration of neural pathways regulating sleep-wake patterns and sleep architecture may contribute to sleep alterations. In return, several recent studies suggested that common sleep disorders may precede clinical symptoms of dementia and represent risk factors for cognitive decline, through impairment of sleep-dependent memory consolidation processes. Thus, a close relationship between sleep disorders and AD has been largely hypothesized. Here, sleep alterations in AD and its pre-dementia stage, mild cognitive impairment, and their complex interactions are reviewed.

Breakdown in REM sleep circuitry underlies REM sleep behavior disorder

During rapid eye movement (REM) sleep, skeletal muscles are almost paralyzed. However, in REM sleep behavior disorder (RBD), which is a rare neurological condition, muscle atonia is lost, leaving afflicted individuals free to enact their dreams. Although this may sound innocuous, it is not, given that patients with RBD often injure themselves or their bed-partner. A major concern in RBD is that it precedes, in 80% of cases, development of synucleinopathies, such as Parkinson's disease (PD). This link suggests that neurodegenerative processes initially target the circuits controlling REM sleep. Clinical and basic neuroscience evidence indicates that RBD results from breakdown of the network underlying REM sleep atonia. This finding is important because it opens new avenues for treating RBD and understanding its link to neurodegenerative disorders.

Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder

OBJECTIVE

To determine the pathologic substrates in patients with rapid eye movement (REM) sleep behavior disorder (RBD) with or without a coexisting neurologic disorder.

METHODS

The clinical and neuropathologic findings were analyzed on all autopsied cases from one of the collaborating sites in North America and Europe, were evaluated from January 1990 to March 2012, and were diagnosed with polysomnogram (PSG)-proven or probable RBD with or without a coexisting neurologic disorder. The clinical and neuropathologic diagnoses were based on published criteria.

RESULTS

172 cases were identified, of whom 143 (83%) were men. The mean±SD age of onset in years for the core features were as follows - RBD, 62±14 (range, 20-93), cognitive impairment (n=147); 69±10 (range, 22-90), parkinsonism (n=151); 68±9 (range, 20-92), and autonomic dysfunction (n=42); 62±12 (range, 23-81). Death age was 75±9 years (range, 24-96). Eighty-two (48%) had RBD confirmed by PSG, 64 (37%) had a classic history of recurrent dream enactment behavior, and 26 (15%) screened positive for RBD by questionnaire. RBD preceded the onset of cognitive impairment, parkinsonism, or autonomic dysfunction in 87 (51%) patients by 10±12 (range, 1-61) years. The primary clinical diagnoses among those with a coexisting neurologic disorder were dementia with Lewy bodies (n=97), Parkinson's disease with or without mild cognitive impairment or dementia (n=32), multiple system atrophy (MSA) (n=19), Alzheimer's disease (AD)(n=9) and other various disorders including secondary narcolepsy (n=2) and neurodegeneration with brain iron accumulation-type 1 (NBAI-1) (n=1). The neuropathologic diagnoses were Lewy body disease (LBD)(n=77, including 1 case with a duplication in the gene encoding α-synuclein), combined LBD and AD (n=59), MSA (n=19), AD (n=6), progressive supranulear palsy (PSP) (n=2), other mixed neurodegenerative pathologies (n=6), NBIA-1/LBD/tauopathy (n=1), and hypothalamic structural lesions (n=2). Among the neurodegenerative disorders associated with RBD (n=170), 160 (94%) were synucleinopathies. The RBD-synucleinopathy association was particularly high when RBD preceded the onset of other neurodegenerative syndrome features.

CONCLUSIONS

In this large series of PSG-confirmed and probable RBD cases that underwent autopsy, the strong association of RBD with the synucleinopathies was further substantiated and a wider spectrum of disorders which can underlie RBD now are more apparent.

Delayed emergence of a parkinsonian disorder or dementia in 81% of older men initially diagnosed with idiopathic rapid eye movement sleep behavior disorder: a 16-year update on a previously reported series

OBJECTIVE

To provide a 16-year update from the authors' 1996 report documenting a 38% conversion from idiopathic rapid eye movement sleep behavior disorder (iRBD) to a parkinsonian disorder at a mean interval of nearly 13 years after the onset of iRBD in a series of 29 males > or =50 years old.

METHODS

The methods of evaluation, diagnosis and follow-up were previously described in the 1996 report. All patients had video-polysomnography (vPSG) confirmed RBD.

RESULTS

80.8% (21/26) of patients who were initially diagnosed with iRBD eventually developed parkinsonism/dementia (three of the original 29 patients were lost to follow-up). The distribution of diagnoses was as follows: n=13, Parkinson's disease (PD); n=3, dementia with Lewy bodies (DLB); n=1, dementia (unspecified; profound); n=2, multiple system atrophy (MSA); n=2, clinically diagnosed Alzheimer's Disease (AD) with autopsy-confirmed combined AD plus Lewy body disease pathology. Among the 21 iRBD "converters," the mean age (±SD) of iRBD onset was 57.7±7.7 years; mean age (±SD) of parkinsonism/dementia onset was 71.9±6.6 years; and mean interval (±SD) from iRBD onset to parkinsonism/dementia onset was 14.2±6.2 years (range: 5-29 years).

CONCLUSION

The vast majority of men > or =50 years old initially diagnosed with iRBD in this study eventually developed a parkinsonian disorder/dementia, often after a prolonged interval from onset of iRBD, with the mean interval being 14 years while the range extended to 29 years. Also, the specificity of iRBD converting to parkinsonism/dementia is striking. These findings carry important clinical and research implications in the convergent fields of sleep medicine, neurology, and neuroscience, and identify an optimal clinical group for conducting prospective research studies utilizing putative neuroprotective agents to delay the emergence of, or halt the progression to, parkinsonism and/or cognitive impairment as manifestations of either PD, DLB or MSA.

Apolipoprotein E polymorphism and behavioral and psychological symptoms of dementia in patients with Alzheimer disease

The aims of this study were to identify subsyndromes of behavioral and psychological symptoms of dementia (BPSD) in Alzheimer disease (AD), and to investigate whether the apolipoprotein E (ApoE) gene confers a risk of distinct BPSD subsyndromes. BPSD of 96 patients with AD were assessed using the Neuropsychiatric Inventory. Factor analysis with principal component analysis and varimax rotation was used to construct the BPSD subsyndromes. ApoE genotypes were determined using the TaqMan technology. The results showed that the 5 subsyndromes can be determined, including: agitation/aggression-delusion, euphoria-disinhibition, depression-apathy, hallucination-nighttime behavior, and appetite. ApoE ε4 carriers had higher factor scores in the agitation/aggression-delusion subsyndrome. We demonstrated that ApoE ε4 confers a higher risk for the subsyndrome of agitation/aggression delusion in AD.

Circadian and sleep disorders in Parkinson's disease

Impaired sleep and alertness, initially recognized by James Parkinson in his famous monograph "An Essay on the Shaking Palsy" in 1817, is one of the most common and disabling nonmotor symptoms of Parkinson's disease (PD). It is only recently, however, that sleep disturbances in PD have received the attention of medical and research community. Dopamine, the major neurotransmitter implicated in the pathogenesis of PD, plays a pivotal role in the regulation of sleep and circadian homeostasis. Sleep dysfunction affects up to 90% of patients with PD, and may precede the onset of the disease by decades. Sleep dysfunction in PD may be categorized into disturbances of overnight sleep and daytime alertness. Etiology of impaired sleep and alertness in PD is multifactorial. Co-existent primary sleep disorders, medication side effects, overnight re-emergence of motor symptoms, and primary neurodegeneration itself, are main causes of sleep disruption and excessive daytime sleepiness among patients with PD. Increasing body of evidence suggests that the circadian system becomes dysregulated in PD, which may lead to poor sleep and alertness. Treatment options are limited and frequently associated with unwanted side effects. Further studies that will examine pathophysiology of sleep dysfunction in PD, and focus on novel treatment approaches are therefore very much needed. In this article we review the role of dopamine in regulation of sleep and alertness and discuss main sleep and circadian disturbances associated with PD.

REM behaviour disorder and neurodegenerative diseases

Rapid-eye movement (REM) sleep behaviour disorder (RBD) is an REM sleep parasomnia characterized by enactment of dream content during REM sleep associated with loss of muscle atonia. RBD can be either idiopathic or secondary to drugs or other diseases. The best recognized association is with neurodegenerative diseases, namely alpha-synucleinopathies. RBD may represent the first feature of neurodegeneration and can be considered an early marker of these disorders. This review describes the main clinical, pathogenetic, and therapeutic features of RBD, pointing to its association with neurodegenerative diseases and emphasizing the clinical and prognostic implications.

Idiopathic REM sleep behavior disorder as a long-term predictor of neurodegenerative disorders

REM sleep behavior disorder (RBD) is a parasomnia characterized by dream-enacting behavior and loss of muscle atonia during REM sleep. Idiopathic RBD occurs in the absence of any neurological disease or other possible cause, is male-predominant and its clinical course is generally chronic progressive. Secondary RBD may be related to neurodegenerative disorders such as multiple system atrophy, Parkinson’s disease and Lewy body dementia. Recent long-term prospective studies have shown that 30% to 65% of patients with idiopathic RBD will eventually develop a neurodegenerative disorder with the rate of emergence depending on the length of the follow-up period. RBD may therefore be one of the earliest signs of and/or a long-term predictor for neurodegenerative disorders. Because RBD antecedes the development of these disorders by several years or decades, its recognition may enable the delay or prevention of neurodegenerative disorders through the early application of neuroprotective or disease-modifying therapies in the future.

Sleep disorders in neurodegenerative diseases

The aim of this review is to provide data on sleep disturbances in three categories of neurodegenerative disorders: synucleinopathies, tauopathies, and other diseases (this heterogeneous group includes also spinocerebellar degeneration and amyotrophic lateral sclerosis). Analysing and knowing sleep disorders in neurodegenerative diseases may offer important insights into the pathomechanism of some of these diseases and calls attention to the still insufficiently known 'sleep neurology'. The identification of sleep disorders in some neurodegenerative conditions may make their diagnosis easier and earlier; for example, rapid eye movements sleep behaviour disorder may precede any other clinical manifestation of synucleinopathies by more than 10 years.

REM sleep behavior disorder: Updated review of the core features, the REM sleep behavior disorder-neurodegenerative disease association, evolving concepts, controversies, and future directions

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia manifested by vivid, often frightening dreams associated with simple or complex motor behavior during REM sleep. The polysomnographic features of RBD include increased electromyographic tone +/- dream enactment behavior during REM sleep. Management with counseling and pharmacologic measures is usually straightforward and effective. In this review, the terminology, clinical and polysomnographic features, demographic and epidemiologic features, diagnostic criteria, differential diagnosis, and management strategies are discussed. Recent data on the suspected pathophysiologic mechanisms of RBD are also reviewed. The literature and our institutional experience on RBD are next discussed, with an emphasis on the RBD-neurodegenerative disease association and particularly the RBD-synucleinopathy association. Several issues relating to evolving concepts, controversies, and future directions are then reviewed, with an emphasis on idiopathic RBD representing an early feature of a neurodegenerative disease and particularly an evolving synucleinopathy. Planning for future therapies that impact patients with idiopathic RBD is reviewed in detail.

The clinical and pathophysiological relevance of REM sleep behavior disorder in neurodegenerative diseases

REM sleep behavior disorder (RBD) is characterized by vigorous movements associated with unpleasant dreams and increased electromyographic activity during REM sleep. Polysomnography with audiovisual recording is needed to confirm the diagnosis of RBD and to exclude other sleep disorders that can mimic its symptoms including obstructive sleep apnea, nocturnal hallucinations and confusional awakenings. RBD may be idiopathic or related to neurodegenerative diseases, particularly multiple system atrophy, Parkinson's disease and dementia with Lewy bodies. RBD may be the first manifestation of these disorders, antedating the onset of parkinsonism, cerebellar syndrome, dysautonomia, and dementia by several years. RBD should thus be considered an integral part of the disease process. When effective, neuroprotective strategies should be considered in subjects with idiopathic RBD. Patients with other neurodegenerative diseases, though, such as spinocerebellar ataxias, may also present with RBD. When clinically required, clonazepam at bedtime is effective in decreasing the intensity of dream-enacting behaviors and unpleasant dreams in both the idiopathic and secondary forms. When part of a neurodegenerative disorder the development of RBD is thought to reflect the location and extent of the underlying lesions involving the REM sleep centers of the brain (e.g., locus subceruleus, amygdala, etc.), leading to a complex multiple neurotransmitter dysfunction that involves GABAergic, glutamatergic and monoaminergic systems. RBD is mediated neither by direct abnormal alpha-synuclein inclusions nor by striatonigral dopaminergic deficiency alone.

Nonmotor manifestations of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Traditionally, attention has focused on the motor symptomatology of PD, but it is now appreciated that the nonmotor symptoms affecting neuropsychiatric, sleep, autonomic, and sensory domains occur in up to 88% of PD patients and can be an important source of disability. Nonmotor manifestations of PD play a significant role in the impairment of disease-related quality of life. The cause of nonmotor manifestations of PD is multifactorial, but to a large extent, these manifestations are related to the nature of the neurodegenerative process and the widespread nondopaminergic neuropathological changes associated with the disease. Recognition of nonmotor disability is essential not only for ascertaining the functional status of patients but also for better appreciating the nature of the neurodegenerative process in PD. In addition, a number of nonmotor manifestations can precede the onset of motor symptoms in PD and can be used as screening tools allowing for early disease identification and for trials of possible disease-modifying interventions. This article reviews depression, sleep, and autonomic dysfunction in PD.

[The neuropathology of sleep in human neurodegenerative diseases]

The neuropathology of human sleep remains an ill-defined issue. The data concerning the main structures of human brain areas involved, or supposed to be implicated, in sleep organisation are reviewed. Five levels of organisation can be schematically recognized: (i) the ascending arousal system, (ii) the non REM and REM systems (iii) regulated by hypothalamic areas, (iv) and the biological clock, (v) modulated by a number of "allostatic" influences. These are briefly described, with emphasis on the location of structures involved in humans, and on the recently revised concepts. Current knowledge on the topography of lesions associated with the main sleep disorders in degenerative diseases is recalled, including REM sleep behavior disorders, restless legs syndrome and periodic leg movements, sleep apneas, insomnia, excessive daily sleepiness, secondary narcolepsy and disturbed sleep-wake rhythms. The lesions of sleep related structures observed in early and late stages of four degenerative diseases are then reviewed. Two synucleinopathies (Lewy lesions associated disorders, including Parkinson's disease and Dementia with Lewy bodies, and Multiple System Atrophy) and two tauopathies (Progressive Supranuclear Palsy and Alzheimer's disease) are dealt with. The distribution of lesions usually found in affected patients fit with that expected from the prevalence of different sleep disorders in these diseases. This confirms the current opinion that these disorders depend on the distribution of lesions rather than on their biochemical nature. Further studies might throw insight on the mechanism of normal and pathological sleep in humans, counterpart of the increasing knowledge provided by animal models. Specially designed prospective clinicopathological studies including peculiar attention to sleep are urgently needed.

Cognitive performance in REM sleep behaviour disorder: a possible early marker of neurodegenerative disease?

BACKGROUND

Rapid eye movement [REM] sleep behaviour disorder (RBD) may herald neurodegenerative diseases. Neurobiological deficits similar to those identified in neurodegenerative diseases have been reported in idiopathic RBD. Researchers are looking for early markers supporting a possible role of RBD as a harbinger of impending neurodegenerative disease.

OBJECTIVE

To examine the neuropsychological functions in idiopathic RBD subjects. Should they be found to present a neuropsychological dysfunction that overlaps that reported in neurodegenerative diseases, it would be possible to consider cognitive deficits as possible early markers of an underlying degenerative process.

METHODS

Twenty-three subjects with idiopathic RBD (21 males, mean age 67.0+/-7.0 years) and a group of healthy controls matched for sex, age and education underwent a neuropsychological battery evaluating different cognitive domains.

FINDINGS

Considering mean values, poorer performances were observed in the Word Span (p<.001), Rey-Osterrieth's complex figure recall (p=.003), Digit Span (p=.003) and Logic Memory (p=.003) tests. On the basis of equivalent scores, the RBD subjects performed significantly more poorly on tests of visuo-constructional learning abilities (p<.001).

INTERPRETATION

Our data show the possible presence of cognitive deficits in RBD defined as idiopathic, sharing common features in particular with Lewy body disease. Neuropsychological evaluation in RBD could lead to presymptomatic identification of neurodegenerative disease, but until more prolonged long-term follow-up data are available, the true neurobiological significance of cognitive deficits in RBD will remain unknown.

Idiopathic rapid-eye-movement sleep disorder: associations with antidepressants, psychiatric diagnoses, and other factors, in relation to age of onset

BACKGROUND

A retrospective, case-control chart review was performed to examine the relationship between the age of onset of idiopathic RBD and secondary associations.

METHODS

Forty-eight idiopathic RBD patients were divided into early-onset and late-onset groups, compared to each other, and to their respective non-RBD controls.

RESULTS

There were more females in the early-onset group as compared to their older counterparts (45% vs. 11%, p=0.007). Early-onset patients also had significantly more past and present psychiatric diagnoses [85% (both categories) vs. 46% and 36%, respectively, p<0.01 for both comparisons] and antidepressant use (80% vs. 46%, p=0.02) than the late-onset group. In comparison to non-RBD controls, early-onset patients again exhibited more psychiatric diagnoses (odds ratio=17.0 [3.5-83.4], equivalent for past and present diagnoses) and antidepressant use (odds ratio=12.0 [2.7-53.3]). Late-onset patients also had a higher frequency of past (odds ratio=7.2 [1.8-29.6]) and present (odds ratio=4.6 [1.1-19.3]) psychiatric diagnoses as compared to their non-RBD controls, but did not demonstrate a statistically significant difference in antidepressant use. There were otherwise no significant intergroup or intragroup differences with respect to the other assessed variables.

CONCLUSIONS

Although causality cannot be inferred, numerous implications can be entertained, particularly in the early-onset group, including direct or indirect correlations with medication use and/or psychopathology and the development of RBD. The relatively high number of females in the early-onset group suggests a unique clinical profile for a condition typically characterized as male-predominant.

Cardiac autonomic regulation during sleep in idiopathic REM sleep behavior disorder

OBJECTIVE

To assess cardiac autonomic and respiratory changes from stage 2 non-rapid eye movement sleep (NREM) to rapid eye movement (REM) sleep in subjects with idiopathic REM sleep behavior disorder (RBD) and controls. We tested the hypothesis that REM-related cardiorespiratory activation is altered in subjects with RBD.

DESIGN

Retrospective case-control study.

SETTING

University hospital-based sleep research laboratory.

PATIENTS

Ten subjects with idiopathic RBD (2 women, mean age 63.4 +/- 6.2 years) and 10 sex- and age-matched controls (mean age 63.9 +/- 6.3 years).

INTERVENTION

One-night polysomnography was used to assess R-R variability during NREM and REM sleep.

MEASUREMENTS AND RESULTS

Spectral analysis of R-R interval and respiration were performed. Mean R-R interval, low-frequency (LF) and high-frequency (HF) components in both absolute and normalized units (LFnu and HFnu), and the LF/HF ratio were obtained from 5-minute electrocardiogram segments selected during NREM and REM sleep under stable conditions (stable breathing pattern, no microarousals or leg movements). Respiratory frequency was also assessed. Values obtained were then averaged for each stage and analyzed by 2 x 2 analysis of variance with group (RBD subjects and controls) as factor and state (NREM and REM) as repeated measures. RR interval, HF, and HFnu components decreased from NREM to REM in controls but did not change in RBD subjects (Interaction P < 0.05). LFnu (interaction P < 0. 001), LF/HF (interaction P < 0. 001), and respiratory frequency (interaction P < 0. 05) increased from NREM to REM sleep in controls but remained stable in RBD subjects.

CONCLUSION

REM-related cardiac and respiratory responses are absent in subjects with idiopathic RBD.

Rapid-eye-movement sleep behaviour disorder and neurodegenerative diseases

Rapid-eye-movement (REM) sleep behaviour disorder (RBD) is characterised by loss of muscular atonia and prominent motor behaviours during REM sleep. RBD can cause sleep disruption and severe injuries for the patient or bed partner. The disorder is strongly associated with neurodegenerative diseases, such as multiple-system atrophy, Parkinson's disease, dementia with Lewy bodies, and progressive supranuclear palsy. In many cases, the symptoms of RBD precede other symptoms of these neurodegenerative disorders by several years. Furthermore, several recent studies have shown that RBD is associated with abnormalities of electroencephalographic activity, cerebral blood flow, and cognitive, perceptual, and autonomic functions. RBD might be a stage in the development of neurodegenerative disorders and increased awareness of this could lead to substantial advances in knowledge of mechanisms, diagnosis, and treatment of neurodegenerative disorders.

REM sleep behaviour disorder: clinical profiles and pathophysiology

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a parasomnia characterized by the intermittent loss of electromyographic atonia normally present during REM sleep and the emergence of purposeful complex motor activity associated with vivid dreams. Rapid eye movement sleep behaviour disorder usually affects older males and can be either idiopathic or symptomatic of various underlying disorders, in particular neurodegenerative diseases; in the latter case, RBD may be a prodromal symptom of the neurological disease. Several brainstem regions have been implicated in RBD pathophysiology, although the exact mechanism of the disorder in humans remains to be clarified. On clinical grounds, differentiation of RBD should be made from several non-REM parasomnias and other aberrant behaviours occurring during sleep. Rapid eye movement sleep behaviour disorder can be diagnosed on the basis of a systematic medical, neurological and psychiatric evaluation of the patient, assisted by a standard polysomnographic recording that includes continuous overnight videotaping; a brain imaging study is mandatory when an underlying brain disease is being suspected. Clonazepam at bedtime is the treatment of choice for RBD; alternatively, melatonin or pramipexole can be administered when clonazepam is contraindicated.

REM sleep behavior disorder in Parkinson's disease and dementia with Lewy bodies

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia manifested by vivid, often frightening dreams associated with simple or complex motor behavior during REM sleep. Patients appear to "act out their dreams," in which the exhibited behaviors mirror the content of the dreams. Management of RBD involves counseling about safety measures in the sleep environment; in those at risk for injury, clonazepam and/or melatonin is usually effective. In this article, the authors present a detailed review of the clinical and polysomnographic features, differential diagnosis, diagnostic criteria, management strategies, and pathophysiologic mechanisms of RBD. They then review the literature and their institutional experience of RBD associated with neurodegenerative disease, particularly Parkinson's disease and dementia with Lewy bodies. The evolving data suggests that RBD may have clinical diagnostic and pathophysiologic significance in isolation and when associated with neurodegenerative disease.

Pathology and neurotransmitter abnormalities of dementia with Lewy bodies

The neuropathology of dementia with Lewy bodies (DLB) is characterized by the presence of Lewy bodies (LBs) and Lewy neurites (LNs) in specific systems throughout the brainstem, diencephalon, basal ganglia and neocortex. DLB shares many features with Parkinson's disease (PD) with respect to LB distribution in the brainstem, and there is recent evidence that Lewy pathology (LP), which consists of LBs and LNs, may progress in a systematic fashion through the brain regardless of clinical phenotype. Increasing evidence supports a central role for LNs in Lewy neurodegeneration and engenders a 'neuritic dystrophy hypothesis' described herein. LP formation also occurs in Alzheimer's disease (AD) and other dementias, and it is unclear whether there is a common underlying pathophysiology in these diseases or if the LP merely represents a common final pathway. Cholinergic deficits are evident in both DLB and AD, with reductions in acetylcholine and abnormalities in nicotinic and muscarinic receptor expression in both diseases. Cholinergic deficits are greater in DLB than in AD, although generally there is less brain atrophy in DLB. The lower neurodegeneration and preservation of cholinergic receptors in DLB has important therapeutic implications because patients with DLB (vs. AD) may receive greater benefits from cholinergic pharmacologic therapy. Patients with DLB who display parkinsonian signs have severe dopamine neurotransmitter deficiencies similar to those in patients with PD, although the manifestation of these deficiencies is different. Both groups have striatal dopamine transporter deficiencies, but the striatal dopamine D2 receptors are reduced in DLB patients compared with PD and control subjects. D2 receptor deficiencies in DLB may be the cause of the relative lack of response to levodopa treatment and the severe adverse reaction to neuroleptics in these patients.

Sleep and quantitative EEG in neurodegenerative disorders

This paper reviews current knowledge on sleep problems, sleep architecture changes and quantitative EEG alteration brought on by various neurodegenerative diseases, such as Alzheimer's disease (AD), progressive supranuclear palsy (PSP), REM sleep behavior disorder (RBD), Parkinson's disease (PD), dementia with Lewy bodies (DLB), multiple system atrophy MSA, Huntington's disease and Creutzfeldt-Jakob disease, in comparison to normal aging. The study of sleep variables and that of the spectral composition of the EEG can provide valuable information for understanding the pathophysiology and for assisting the diagnosis of neurodegenerative diseases.

Nightmares without atonia as an early symptom of diffuse Lewy bodies disease

A male 70 years old patient with diffuse or ''pure'' Lewy body disease is described. The diagnosis was made based on clinical features of nightmares with no atonia, attention deficits with fluctuation in cognitive function, incapacity to find his way around the neighbourhood and other formerly familiar environments and mild neuropsychiatric symptoms. Neuropsychological assessment showed memory deficits, visuospatial and visuo-constructive disturbances. He had neither parkinsonism nor recurrent visual hallucinations typically well formed and detailled. Neuroimaging (computed tomography and magnetic resonance spectroscopy) showed mild diffuse cortical atrophy, mostly on the left temporal lobe and a decrease of N-acetil-aspartate levels. A cholinesterase inhibitor was prescribed to this patient during 6 months with clinically relevant behavioral effect. Diagnosis confirmation was made by post-mortem neuropathological findings. Macroscopical features were mild atrophy on the frontal, parietal and temporal lobes, notedly on the frontal lobes. Microscopically, there was neuronal loss and diffuse classic Lewy bodies. Brainstem (substantia nigra, raphe nucleus, locus coeruleus, pedunculopontine nucleus), limbic cortex, and neocortex (frontal, parietal and temporal) were the areas of predilection for Lewy bodies. Hematoxylin-eosin and Bielschowsky staining did not show neuronal swelling (balooned cell), argyrophilic inclusion (Pick's bodies), neurofibrillary tangles nor senile plaques. Immunohistochemical staining for anti-tau, anti-beta-amyloid, and anti-prion protein were negative. Antiubiquitine reaction was positive for Lewy body in the cerebral cortex and brainstem.

Idiopathic rapid eye movement sleep behavior disorder is a harbinger of dementia with Lewy bodies

Idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia clinically linked with the alpha-synucleinopathies multiple systems atrophy (MSA), Parkinson's disease (PD), and dementia with Lewy bodies (DLB). Available autopsy information is limited but suggests that the pathologic basis of idiopathic RBD may be neuronal loss and Lewy bodies in pigmented monoaminergic nuclei, including the locus coeruleus and substantia nigra, which project to pontine nuclei mediating atonia during REM sleep. Thus, idiopathic RBD may be an alpha-synucleinopathy per se and a harbinger of impending PD, DLB, or MSA. Inclusion of historical or concurrent idiopathic RBD in the diagnostic criteria for DLB may improve their sensitivity, specificity, and clinical utility.

Rapid eye movement sleep behaviour disorder: demographic, clinical and laboratory findings in 93 cases

We describe demographic, clinical, laboratory and aetiological findings in 93 consecutive patients with rapid eye movement (REM) sleep behaviour disorder (RBD), which consists of excessive motor activity during dreaming in association with loss of skeletal muscle atonia of REM sleep. The patients were seen at the Mayo Sleep Disorders Center between January 1, 1991 and July 31, 1995. Eighty-one patients (87%) were male. The mean age of RBD onset was 60.9 years (range 36-84 years) and the mean age at presentation was 64.4 years (37-85 years). Thirty-two per cent of patients had injured themselves and 64% had assaulted their spouses. Subdural haematomas occurred in two patients. Dream content was altered and involved defence of the sleeper against attack in 87%. The frequency of nocturnal events decreased with time in seven untreated patients with neurodegenerative disease. MRI or CT head scans were performed in 56% of patients. Although four scans showed brainstem pathology, all of these patients had apparently unrelated neurodegenerative diseases known to be associated with RBD. Neurological disorders were present in 57% of patients; Parkinson's disease, dementia without parkinsonism and multiple system atrophy accounted for all but 14% of these. RBD developed before parkinsonism in 52% of the patients with Parkinson's disease. Five of the 14 patients with multiple system atrophy were female, and thus the strong male predominance in RBD is less evident in this condition. Psychiatric disorders, drug use or drug withdrawal were rarely causally related to RBD. Clonazepam treatment of RBD was completely or partially successful in 87% of the patients who used the drug. We conclude that RBD is a well-defined condition and that descriptions from different centres are fairly consistent. It is commonest in elderly males and may result in serious morbidity to patients and bed partners. There is a strong relationship to neurodegenerative disease, especially Parkinson's disease, multiple system atrophy and dementia, and neurologists should explore the possibility of RBD in patients with these conditions. RBD symptoms may be the first manifestations of these disorders and careful follow-up is needed. Neuroimaging is unlikely to reveal underlying disorders not suspected clinically. We confirm the effectiveness of clonazepam, but note that attention to the safety of the bed environment may be sufficient for patients with contraindications to the drug.

Acetylcholine in mind: a neurotransmitter correlate of consciousness?

The cholinergic system is one of the most important modulatory neurotransmitter systems in the brain and controls activities that depend on selective attention, which are an essential component of conscious awareness. Psychopharmacological and pathological evidence supports the concept of a 'cholinergic component' of conscious awareness. Drugs that antagonize muscarinic receptors induce hallucinations and reduce the level of consciousness, while the nicotinic receptor is implicated as being involved in the mechanism of action of general (inhalational) anaesthetics. In degenerative diseases of the brain, alterations in consciousness are associated with regional deficits in the cholinergic system. In Alzheimer's disease (AD), there is a loss of explicit (more than implicit) memory and hypoactivity of cholinergic projections to the hippocampus and cortex, while the visual hallucinations experienced by subjects with Dementia with Lewy bodies (DLB) are associated with reductions in neocortical ACh-related activity. In Parkinson's disease, the additional loss of pedunculopontine cholinergic neurones, which control REM (rapid eye movement) sleep or dreaming, is likely to contribute to REM abnormalities, which also occur in DLB. Widespread basal-forebrain and rostral brainstem cholinergic pathways, which include converging projections to the thalamus, appear to be located strategically for generating and integrating conscious awareness. Alleviation of a range of cognitive and non-cognitive symptoms by drugs that modulate the cholinergic system, which are being developed for the treatment of AD and related disorders, could be caused by changes in consciousness.

Melatonin as a therapy in REM sleep behavior disorder patients: an open-labeled pilot study on the possible influence of melatonin on REM-sleep regulation

REM sleep behavior disorder (RBD) is clinically impressive by virtue of its vigorous sleep behaviors usually accompanying vivid, striking dreams. The main feature of the disorder, REM sleep without muscle atonia, has been shown in a variety of diseases; therefore, the disorder might possibly be underestimated. In an open-labeled trial, we treated six consecutive RBD patients over a 6-week period with 3 mg melatonin given within 30 minutes before bedtime. There was a dramatic clinical improvement in five of the six patients within a week which extended beyond the end of treatment for weeks or months. A second polysomnogram performed 6 weeks after the beginning of treatment showed a significant tendency toward normalization of the percentage of REM sleep, a significant reduction of 30-second epochs, scored as REM sleep without muscle atonia, a significant reduction of stage-shifts in REM, and a significant reduction in epochs considered as movement time in REM. All other sleep parameters were not changed consistently. We hypothesize that internal desynchrony might be a part of the underlying pathophysiology in RBD. Our data might give first evidence to the hypothesis that exogenous melatonin, administered to patients with internal desynchrony at the time of the maximal rise of melatonin secretion, might increase the overall amplitude of the circadian pacemaker by reentraining the suprachiasmatic nucleus and thereby restore circadian driven rhythms, one of them being the circadian modulation of REM sleep.