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

Medical comorbidity of sleep disorders

PURPOSE OF REVIEW

Recently published literature indicates that sleep disorders present with medical comorbidities quite frequently. The coexistence of a sleep disorder with a medical disorder has a substantial impact for both the patient and the health system.

RECENT FINDINGS

Insomnia and hypersomnia are highly comorbid with medical conditions, such as chronic pain and diabetes, as well as with various cardiovascular, respiratory, gastrointestinal, urinary and neurological disorders. Restless legs syndrome and periodic leg movement syndrome have been associated with iron deficiency, kidney disease, diabetes, and neurological, autoimmune, cardiovascular and respiratory disorders. Rapid eye movement behaviour disorder has been described as an early manifestation of serious central nervous system diseases; thus, close neurological monitoring of patients referring with this complaint is indicated.

SUMMARY

Identification and management of any sleep disorder in medical patients is important for optimizing the course and prognosis. Of equal importance is the search for undetected medical disorder in patients presenting with sleep disorders.

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.

Overnight distribution and motor characteristics of REM sleep behaviour disorder episodes in patients with narcolepsy-cataplexy

OBJECTIVE

The study aimed to examine the temporal distribution of episodes of REM sleep behaviour disorder (RBD) over the night and their motor and polysomnographic (PSG) characteristics in patients with narcolepsy-cataplexy (NC).

METHODS

Full-night video-PSG recordings of a continuous series of 37 drug-naïve NC patients with clinically-documented RBD were examined to detect the occurrences of RBD episodes (disclosed in 27 patients) and to classify their related PSG and motor behaviour features.

RESULTS

RBD episodes occurred with comparable frequency in REM sleep periods of the first and second halves of the night, regardless of the length of REM periods, patients' age or disease duration. Vocalisations and pantomimes occurred in comparable proportions of RBD episodes in the two halves of the night, while aggressive-violent movements were significantly more frequent in RBD episodes of the second half of the night. No sleep parameter significantly differed in patients with RBD occurring in the first/second/neither half of the night.

CONCLUSIONS

RBD episodes (a) are not an every night phenomenon in NC patients with clinically documented RBD, regardless of their age or disease duration; (b) can occur in any period of REM sleep, regardless of length; and (c) display less violent-aggressive motor features when they occur in the first half of the night. Multi-night studies with dream-report collection may disclose whether this overnight variation in the violent-aggressive features in RBD episodes of NC patients is associated with a time-of-night-related variation in dream content.

Meta-analysis of 123I-MIBG cardiac scintigraphy for the diagnosis of Lewy body-related disorders

Patients with parkinsonism pose a diagnostic challenge. Parkinson's disease may be difficult to distinguish from multiple system atrophy and progressive supranuclear palsy, whereas Parkinson's disease and dementia with Lewy bodies can be difficult to distinguish from Alzheimer's disease and other dementias. A number of studies have found diminished cardiac (123) I-metaiodobenzylguanidine uptake in Lewy body-related conditions (Parkinson's disease and Lewy body dementia). In 2005, the Dementia With Lewy Bodies Consortium considered (123) I-metaiodobenzylguanidine cardiac scintigraphy a "supportive" diagnostic feature, based on limited evidence. We report a meta-analysis of the literature and an assessment of the utility of (123) I-metaiodobenzylguanidine for the diagnosis of dementia with Lewy bodies and Parkinson's disease. A search was conducted of articles published between 1950 and June 2010. Forty-six studies involving neuropsychiatric and movement disorders, comprising 2680 subjects, were included in the analysis. A mixed-effects regression model was used to analyze the delayed mean heart-to-mediastinum ratio of (123) I-metaiodobenzylguanidine uptake. (123) I-metaiodobenzylguanidine cardiac scintigraphy sensitively detected and specifically distinguished 2 diagnostic clusters: (1) Parkinson's disease, dementia with Lewy bodies, and rapid eye movement sleep behavior disorder; and (2) normal controls and patients with Alzheimer's disease, multiple system atrophy, progressive supranuclear palsy, vascular dementia, and frontotemporal dementia. The area under the receiver operating characteristic curve was 0.987 at a cluster discriminatory heart-to-mediastinum ratio threshold of 1.77. This threshold yielded 94% sensitivity and 91% specificity for the discrimination of these diagnostic clusters. (123) I-metaiodobenzylguanidine cardiac scintigraphy can accurately distinguish between 2 movement disorders, Parkinson's disease and multiple system atrophy, and between 2 common causes of dementia, Alzheimer's disease and dementia with Lewy bodies. © 2011 Movement Disorder Society.

Comparison of the clinical features of rapid eye movement sleep behavior disorder in patients with Parkinson's disease and multiple system atrophy

AIMS

The aim of this study was to evaluate differences in the clinical presentation and polysomnographic characteristics of rapid eye movement sleep behavior disorder (RBD) between patients with Parkinson's disease (PD) and those with multiple system atrophy (MSA).

METHODS

We conducted clinical interviews examining RBD symptoms, including violent and non-violent behaviors, in 49 patients with PD and 16 patients with MSA (as well as their bed partners) and performed polysomnography on all subject patients.

RESULTS

Twenty-seven patients with PD (55.1%) and 11 patients with MSA (68.8%) had rapid eye movement sleep without atonia (RWA) on polysomnogram. The relative amounts of RWA were quite similar between the two groups. For most of the RWA-positive patients in both groups, RBD symptoms remained non-violent or silent. RBD symptoms in PD patients seemed to increase with the course of PD, while most of the RBD symptoms in the MSA patients occurred just prior to or at the onset of MSA and then disappeared within a short period.

CONCLUSION

Although PD and MSA frequently accompany RWA, RBD symptoms often remain non-violent or silent. Differences in the course of RBD symptoms in patients with PD and MSA may reflect the difference in the degeneration process of the two disorders.

Clinical characteristics, management and long-term outcome of suspected rapid eye movement sleep behaviour disorder in 14 dogs

OBJECTIVE

To describe the clinical characteristics, management and long-term outcome in dogs with suspected rapid eye movement sleep behaviour disorder.

METHOD

Medical records and video recordings of 14 dogs with suspected rapid eye movement sleep behaviour disorder were reviewed and the owners were contacted via telephone or email for further information.

RESULTS

Clinical signs included episodes of violent limb movements, howling, barking, growling, chewing, or biting during sleep. Episodes occurred at night and during daytime naps. The age at onset ranged from 8 weeks to 7·5 years with a median of 6 years but 64% of dogs were one year or less. There was no apparent sex or breed predisposition. Rapid eye movement sleep behaviour disorder events were reduced in severity and frequency in 78% of the dogs treated with 40 mg/kg/day oral potassium bromide. One dog was euthanized within 3 months of the onset of signs because of their severity. The duration of the disorder in the 13 surviving dogs ranged from 1·5 to 9 years. None of the dogs spontaneously recovered.

CLINICAL SIGNIFICANCE

Rapid eye movement sleep behaviour disorder is suspected to occur in dogs, as it does in human beings. It causes concern to the owners and disrupts the home environment. Unlike human beings, rapid eye movement sleep behaviour disorder of dogs often has a juvenile onset.

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.

Sleep-wake changes and cognition in neurodegenerative disease

With the increasing aging population, neurodegenerative disorders will become more common in clinical practice. These disorders involve multiple pathophysiological mechanisms that differentially affect cognition, mood, and physical functions. Possibly due to the involvement of common underlying neurobiological circuits, sleep and/or circadian (sleep-wake) changes are also common in this disease group. Of significance, sleep-wake changes are often a prodromal feature and are predictive of cognitive decline, psychiatric symptoms, quality of life, need for institutional care, and caregiver burden. Unfortunately, in neurodegenerative disease, few studies have included detailed polysomnography or neuropsychological assessments although some data indicate that sleep and neurocognitive features are related. Further studies are also required to address the effects of pharmacological and nonpharmacological treatments on cognitive functioning. Such research will hopefully lead to targeted early intervention approaches for cognitive decline in older people.

Phasic Electromyographic Metric detection based on wavelet analysis

The Phasic Electromyographic Metric (PEM) has been recently introduced as a sensitive indicator to differentiate Parkinson's Disease (PD) patients from controls, non-PD patients with a history of Rapid Eye Movement Disorder (RBD) from controls, and PD patients with early and late stage disease. However, PEM assessment through visual inspection is a cumbersome and time consuming process. Therefore, a reliable automated approach is required so as to increase the utilization of PEM as a reliable and efficient clinical tool to track PD progression. In this study an automated method for the detection of PEM is presented, based on the use of signal analysis and pattern recognition techniques. The results are promising indicating that an automatic PEM identification procedure is feasible.

Decreased striatal dopamine transporter uptake and substantia nigra hyperechogenicity as risk markers of synucleinopathy in patients with idiopathic rapid-eye-movement sleep behaviour disorder: a prospective study [corrected]

BACKGROUND

Patients with idiopathic rapid-eye-movement sleep behaviour disorder (IRBD) may develop neurodegenerative conditions associated with substantia nigra dysfunction such as Parkinson's disease. In patients with Parkinson's disease, ¹²³I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane (¹²³I-FP-CIT) SPECT detects striatal dopamine dysfunction resulting from nigral pathology whereas transcranial sonography (TCS) shows increased substantia nigra echogenic size, even before parkinsonism is clinically evident. We postulated that these neuroimaging changes could occur in a proportion of IRBD individuals who might then be at increased risk for development of a neurodegenerative disorder associated with substantia nigra dysfunction.

METHODS

In our prospective study, we identified patients with IRBD from individuals referred to our sleep disorders centre in Barcelona, Spain. At baseline, we assessed dopamine transporter [corrected] uptake by use of ¹²³I-FP-CIT SPECT, and estimated echogenicity of the substantia nigra by use of TCS. After a follow-up of 2·5 years, participants were clinically assessed to establish whether they had developed neurodegenerative syndromes. Data were compared with those of matched healthy controls.

FINDINGS

43 individuals with IRBD agreed to participate in the study. We found reduced ¹²³I-FP-CIT binding in the striatum (p=0·045) in 17 (40%) of 43 participants compared with 18 controls, and substantia nigra hyperechogenicity in 14 (36%) of 39 participants with IRBD, compared with 16 (11%) of 149 controls (p=0·0002). Tracer uptake reduction was more pronounced in the putamen than it was in the caudate nucleus. 27 (63%) participants had reduced ¹²³I-FP-CIT binding or substantia nigra hyperechogenicity at baseline. Eight (30%) of these participants developed a neurodegenerative disorder (five Parkinson's disease, two dementia with Lewy bodies, and one multiple system atrophy). Individuals with normal neuroimaging results remained disease-free. Sensitivity of combined ¹²³I-FP-CIT SPECT and TCS to predict conversion to synucleinopathy after 2·5 years was 100% and specificity was 55%.

INTERPRETATION

In patients with IRBD, ¹²³I-FP-CIT SPECT and TCS can detect subclinical changes much the same as those typically seen in patients with early Parkinson's disease. Decreased striatal ¹²³I-FP-CIT binding and substantia nigra hyperechogenicity might be useful markers to identify individuals at increased risk for development of synucleinopathies.

FUNDING

None.

[REM sleep behavior disorder: an overt access to motor and cognitive control during sleep]

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by violent, or potentially violent, movements during REM sleep, corresponding to enacted dreams. During sleep monitoring, there is a partial or total loss of the normal muscle atonia during REM sleep. REM sleep behavior disorder predominantly affects elderly subjects without any other disease (idiopathic RBD, a precursor of Parkinson disease and Lewy body dementia) or suffering from various neurological and neurodegenerative diseases, mainly synucleinopathies. In addition to being a treatable cause of nocturnal injury of the patients or their bed-partners, RBD is a fantastic window into motor and cognitive control during REM sleep. Notably, parkinsonism transiently disappears during RBD. The patient's voice is louder and better articulated than when awake, and movements are rapid (but jerky) suggesting that the deleterious message from the basal ganglia to the primary motor cortex is reduced or bypassed. As we observed culturally-acquired behaviors, retired patients practicing their former work with mastered gestures, as well as sentences pronounced with appropriate prosody, gesturing, fluency, and syntax during the RBD, we suggest that these behaviors are generated by the same cortical areas as during wakefulness. This model also enables the demonstration that REM during REM sleep are coded in the same direction as the arm and hand movements, as if the dreamer were scanning the dream images. This online access to the motor and verbal dream scenario (through the video and audio monitoring), and the physiological measures (via the EEG, eye movements, muscle tone, respiration, heart rate), together with the offline access to the mental content (dream report after the awakening) constitute a triangulation for validating new hypotheses about REM sleep and dreams.

REM sleep behaviour disorder in older individuals: epidemiology, pathophysiology and management

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a sleep disorder in which patients appear to be enacting their dreams while in REM sleep. The behaviours are typically violent, in association with violent dream content, so serious harm can be done to the patient or the bed partner. The disorder predominantly affects older adults, and has an estimated prevalence in adults of 0.4-0.5%. However, the frequency is much higher in certain neurodegenerative diseases, especially Parkinson's disease, dementia with Lewy bodies and multiple systems atrophy. RBD can occur in the absence of diagnosed neurological diseases (the 'idiopathic' form), although patients with this form of RBD may have subtle neurological abnormalities and often ultimately develop a neurodegenerative disorder. Data from animal models and cases of RBD developing after brainstem (pontine tegmentum, medulla) lesions have led to the understanding that RBD is caused by a lack of normal REM muscle atonia and a lack of normal suppression of locomotor generators during REM sleep. Clonazepam is used as first-line therapy for RBD and melatonin as second-line therapy, although evidence for both of these interventions comes from uncontrolled case series. Because the risk of injury to the patient or the bed partner is high, interventions to improve the safety of the sleep environment are also often necessary. This review describes the epidemiology, pathophysiology and treatment of RBD.

Electroencephalographic slowing heralds mild cognitive impairment in idiopathic REM sleep behavior disorder

OBJECTIVE

Patients with idiopathic rapid eye movement (REM) sleep behavior disorder (IRBD) may show electroencephalographic (EEG) slowing reflecting cortical dysfunction and are at risk for developing neurological conditions characterized by cognitive dysfunction including mild cognitive impairment (MCI), dementia with Lewy bodies and Parkinson's disease with associated dementia. We hypothesized that those IRBD patients who later developed MCI had pronounced cortical EEG slowing at presentation.

METHODS

Power EEG spectral analysis was blindly quantified from the polysomnographic studies of 23 IRBD patients without cognitive complaints and 10 healthy controls without RBD. After a mean clinical follow-up of 2.40+/-1.55 years, 10 patients developed MCI (RBD+MCI) and the remaining 13 remained idiopathic.

RESULTS

Patients with RBD+MCI had marked EEG slowing (increased delta and theta activity) in central and occipital regions during wakefulness and REM sleep, particularly in the right hemisphere, when compared with controls and, to a lesser extent, with IRBD subjects who remained idiopathic. The EEG spectral pattern of the RBD+MCI group was similar to that seen in patients with dementia with Lewy bodies and Parkinson's disease associated with dementia.

CONCLUSION

Our findings suggest that the presence of marked EEG slowing on spectral analysis might be indicative of the short-term development of MCI in patients initially diagnosed with IRBD.

The relationship between actigraphically defined sleep disturbance and REM sleep behaviour disorder in Parkinson's Disease

AIM

In this study, we sought to evaluate the utility of actigraphy for examining symptoms of rapid eye movement sleep behaviour disorder (RSBD).

METHODS

Twenty-two patients with idiopathic Parkinson's Disease (mean age=63.4 years, SD=7.5) underwent neurological assessment and completed sleep diaries, self-report sleep questionnaires and 2-weeks of actigraphy. They also completed the rapid eye movement sleep behavior disorder questionnaire and were classified as screening negative (RSBD-, n=9) or positive (RSBD+, n=13) for RSBD according to published criteria. Key outcome data were the number of wake bouts and duration of arousals during the sleep interval as determined by actigraphy.

RESULTS

Patients classified as RSBD+ demonstrated a higher number of wake bouts than those who were RSBD- (p=0.011).

CONCLUSIONS

These results suggest that actigraphy may be a viable tool to assist in the early identification of RSBD. In turn, this could guide early intervention approaches.

Quality of sleep in primary focal dystonia: a case-control study

BACKGROUND

Sleep disturbances are common in patients with movement disorders. Evaluating quality of sleep is of primary importance because of the effect that nocturnal and daytime sleep abnormalities exert on general health status. However, quality of sleep has never been addressed in detail in patients with dystonia. The aim of this case-control study was to analyse quality of sleep in patients with the two most common forms of primary focal dystonia, blepharospasm (BSP) and cervical dystonia (CD).

METHODS

We evaluated quality of sleep (Pittsburgh Sleep Quality Index, PSQI) and excessive daytime sleepiness (Epworth Sleepiness Scale, ESS) in 98 patients with focal adult-onset dystonia (52 with BSP; 46 with CD) and in a group of 56 age-and gender-matched healthy subjects. The Beck Depression Inventory (BDI) was used for the evaluation of depressive symptomatology.

RESULTS

Quality of sleep was impaired (significantly higher PSQI scores) in both groups of patients. However, differences in PSQI scores between patients with CD and control subjects were partly confounded by BDI scores, whereas differences in PSQI scores between patients with BSP and control subjects were not influenced by BDI. Excessive daytime sleepiness was not significantly more frequent than in control subjects in either patients with BSP or patients with CD.

CONCLUSIONS

This study suggests that the assessment and treatment of insomnia-related complaints should be considered in global management plans of patients with focal dystonia, particularly in those affected by BSP.