Daytime somnolence and nocturnal sleep disturbances in Huntington disease

Sleep and circadian rhythm dysfunctions in movement disorders beyond Parkinson's disease and atypical parkinsonisms

PURPOSE OF REVIEW

This review aimed to comprehensively outline sleep and circadian rhythm abnormalities in hyperkinetic movement disorders beyond Parkinson's disease and atypical parkinsonisms, including tremor, dystonia, choreiform movements, tics, and ataxia disorders.

RECENT FINDINGS

Insomnia, poor sleep quality, and excessive daytime sleepiness (EDS) are commonly reported in essential tremor, Wilson's disease, tics or Tourette's syndrome, and spinocerebellar ataxia (SCA). REM sleep behavior disorder (RBD) have been observed in Wilson's disease and SCA. A combination of REM and non-REM parasomnias, along with nocturnal stridor with the initiation of sleep and re-entering after awakening, are characterized by undifferentiated Non-REM and poorly structured N2 in anti-IgLON5 disease. Restless legs syndrome (RLS) has been reported commonly in SCAs. Sleep-related dyskinesia has been reported in ADCY5-related disease and GNAO1-related movement disorder.

SUMMARY

Sleep problems can manifest as a result of movement disorders, either through direct motor disturbances or secondary nonmotor symptoms. Medication effects must be considered, as certain medications for movement disorders can exacerbate or alleviate sleep disturbances. Distinguishing sleep problems in some diseases might involve pathognomonic symptoms and signs, aiding in the diagnosis of movement disorders.

REM Sleep Loss-Induced Elevated Noradrenaline Plays a Significant Role in Neurodegeneration: Synthesis of Findings to Propose a Possible Mechanism of Action from Molecule to Patho-Physiological Changes

Wear and tear are natural processes for all living and non-living bodies. All living cells and organisms are metabolically active to generate energy for their routine needs, including for survival. In the process, the cells are exposed to oxidative load, metabolic waste, and bye-products. In an organ, the living non-neuronal cells divide and replenish the lost or damaged cells; however, as neuronal cells normally do not divide, they need special feature(s) for their protection, survival, and sustenance for normal functioning of the brain. The neurons grow and branch as axons and dendrites, which contribute to the formation of synapses with near and far neurons, the basic scaffold for complex brain functions. It is necessary that one or more basic and instinct physiological process(es) (functions) is likely to contribute to the protection of the neurons and maintenance of the synapses. It is known that rapid eye movement sleep (REMS), an autonomic instinct behavior, maintains brain functioning including learning and memory and its loss causes dysfunctions. In this review we correlate the role of REMS and its loss in synaptogenesis, memory consolidation, and neuronal degeneration. Further, as a mechanism of action, we will show that REMS maintains noradrenaline (NA) at a low level, which protects neurons from oxidative damage and maintains neuronal growth and synaptogenesis. However, upon REMS loss, the level of NA increases, which withdraws protection and causes apoptosis and loss of synapses and neurons. We propose that the latter possibly causes REMS loss associated neurodegenerative diseases and associated symptoms.

Sleep Disorders in Patients with Choreic Syndromes

PURPOSE OF REVIEW

Patients with different types of choreic syndromes, specially those with Huntington's (HD) and Wilson's (WD) diseases, report frequent sleep complaints. This review focuses on the main findings of studies addressing the sleep features in these diseases, and other less frequent causes of chorea associated with sleep disorders, including a new syndrome described in the last decade associated with IgLON5 antibodies.

RECENT FINDINGS

Patients with HD and WD showed a bad quality of sleep and high frequency of insomnia and excessive daytime somnolence. WD patients also showed high scores on a specific scale for rapid eye movement sleep behavior disorders. HD and WD share decreased sleep efficiency and increased REM sleep latencies, percentage of sleep stage N1, and wake after sleep onset (WASO) among their polysomnographic features. Patients with HD and WD showed a high prevalence of different sleep disorders. Patients with other causes of chorea, including neuroacanthocytosis, parasomnia with sleep breathing disorder associated with antibodies to IgLON5, Sydenham's chorea, and choreic syndromes associated to certain genetic mutations show sleep disorders as well.

From parasomnia to agrypnia excitata - An illustrative case on diagnostic approach

The diagnostic approach to sleep-related movements disorders is seldom discussed. We report a case of fatal familial insomnia who initially presented with persistent limb movements in sleep, which later progressed to a state of agrypnia excitata. Here, the evaluation of abnormal movements in sleep is discussed using a step-by-step diagnostic approach. Although no cure is available for fatal familial insomnia, prompt recognition of this condition is important to facilitate proper management, including the involvement of interdisciplinary neuropalliative care.

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.

Sleep Disorders and Circadian Disruption in Huntington's Disease

Sleep and circadian alterations are common in patients with Huntington's disease (HD). Understanding the pathophysiology of these alterations and their association with disease progression and morbidity can guide HD management. We provide a narrative review of the clinical and basic-science studies centered on sleep and circadian function on HD. Sleep/wake disturbances among HD patients share many similarities with other neurodegenerative diseases. Overall, HD patients and animal models of the disease present with sleep changes early in the clinical course of the disease, including difficulties with sleep initiation and maintenance leading to decreased sleep efficiency, and progressive deterioration of normal sleep architecture. Despite this, sleep alterations remain frequently under-reported by patients and under-recognized by health professionals. The degree of sleep and circadian alterations has not consistently shown to be CAG dose-dependent. Evidence based treatment recommendations are insufficient due to lack of well-designed intervention trials. Approaches aimed at improving circadian entrainment, such as including light therapy, and time-restricted feeding have demonstrated a potential to delay symptom progression in some basic HD investigations. Larger study cohorts, comprehensive assessment of sleep and circadian function, and reproducibility of findings are needed in future in order to better understand sleep and circadian function in HD and to develop effective treatments.

Sleep Dysfunction in Huntington's Disease: Impacts of Current Medications and Prospects for Treatment

Sleep dysfunction is highly prevalent in Huntington's disease (HD). Increasing evidence suggests that such dysfunction not only impairs quality of life and exacerbates symptoms but may even accelerate the underlying disease process. Despite this, current HD treatment approaches neither consider the impact of commonly used medications on sleep, nor directly tackle sleep dysfunction. In this review, we discuss approaches to these two areas, evaluating not only literature from clinical studies in HD, but also that from parallel neurodegenerative conditions and preclinical models of HD. We conclude by summarizing a hierarchical framework of current medications with regard to their impact on sleep, and by outlining key emerging sleep therapies.

The association of saccadic abnormalities with rem sleep in patients with Huntington's disease

BACKGROUND

Huntington's disease (HD) is a progressive neurodegenerative disorder characterised by chorea, cognitive impairment, psychiatric and behavioral disturbances. Sleep disturbances including reduced REM sleep have been observed in HD.

OBJECTIVES

The aim of the study was to study the polysomnography findings in HD and to assess whether oculomotor abnormalities are associated with poor REM sleep.

METHODS

Twenty-nine genetically confirmed HD patients underwent clinical evaluation including extraocular movement and OKN examination. Twenty-six patients and 15 controls underwent overnight video polysomnography (VPSG).

RESULTS

VPSG of 23 HD patients and 13 controls were considered for analysis. Compared to controls, HD patients had higher median wake period and higher WASO percentage (p = 0.005). REM sleep percentage was reduced significantly in HD in comparison to controls (p < 0.001). Out of 23 patients, only two patients had REM sleep above 20% while 14 patients had REM sleep percentage less than 15%. Poor horizontal OKN (grades 2 and 3) was associated with the presence of low REM sleep percentage (REM sleep less than 15%) (p = 0.02). Low REM sleep was also associated with severe illness (UHDRS) (p = 0.038).

CONCLUSION

An association between decreased REM sleep and OKN abnormalities indicate that EOM abnormalities seen in HD could lead to errors in scoring REM sleep. To understand the actual degree of decreased REM sleep percentage will require additional parameters in AASM guidelines to score REM sleep in patients with EOM abnormalities like that seen in HD.

Sleep disturbances by disease type and stage in Huntington's disease

INTRODUCTION

Sleep disturbances are a common symptom in patients with Huntington's disease (HD). However, it is unclear when in the disease course of HD sleep disturbances become more frequent compared to the general population. This study investigated the frequency and odds of developing sleep disturbances between adults with HD or at-risk for HD and non-HD controls.

METHODS

Participants from the Enroll-HD study were split by both disease type and disease severity using CAG length, diagnostic confidence level, and total functional capacity score. Multivariate logistic regression was used to calculate odds ratios adjusted for age, sex, tobacco and alcohol use, depression and psychosis scores, and cognition to compare HD groups to non-HD controls. Cox proportional hazards models and Kaplan Meier curves were used to determine differences in probabilities of developing sleep disturbances and how sleep disturbances are related to age at motor onset.

RESULTS

There were significant differences between HD participants and non-HD controls in both the disease type and disease stage analyses (p < 0.001). The odds of a sleep disturbance increased with worsening disease stage and was highest in those with juvenile HD. The development of a sleep disorder in manifest HD participants was observed to be around the time of disease onset.

CONCLUSIONS

Sleep disturbances are more frequent in HD patients than those without HD. There are also differences based on disease type and stage. This is supplemented by the finding that the onset of sleep disturbances occurs near the time of motor onset of HD.

Huntington's disease: diagnosis and management

Huntington's disease (HD) is an inherited neurodegenerative disease characterised by neuropsychiatric symptoms, a movement disorder (most commonly choreiform) and progressive cognitive impairment. The diagnosis is usually confirmed through identification of an increased CAG repeat length in the huntingtin gene in a patient with clinical features of the condition. Though diagnosis is usually straightforward, unusual presentations can occur, and it can be difficult to know when someone has transitioned from being an asymptomatic carrier into the disease state. This has become increasingly important recently, with several putative disease-modifying therapies entering trials. A growing number of conditions can mimic HD, including rare genetic causes, which must be considered in the event of a negative HD genetic test. Patients are best managed in specialist multidisciplinary clinics, including when considering genetic testing. Current treatments are symptomatic, and largely directed at the chorea and neurobehavioural problems, although supporting trial evidence for these is often limited.

Circadian and Sleep Dysfunctions in Neurodegenerative Disorders-An Update

Disruptions of sleep and circadian rhythms are among the most debilitating symptoms in patients with neurodegenerative diseases. Their underlying pathophysiology is multilayered and multifactorial. Recent evidence suggests that sleep and circadian disturbances may influence the neurodegenerative processes as well as be their consequence. In this perspective, we provide an update of the current understanding of sleep and circadian dysregulation in Alzheimer's, Parkinson's, and Huntington's diseases.

Detecting and targeting neurodegenerative disorders using electrospun nanofibrous matrices: current status and applications

Neurodegeneration is defined as the progressive atrophy and loss of function of neurons; it is present in neurodegenerative disorders such as Multiple Sclerosis, Alzheimer's, Huntington's, and Parkinson's diseases. The detection of such disorders is performed by various imaging modalities while their therapeutic management is quite challenging. Besides, the pathogenesis of neurodegenerative disorders is still under ongoing research due to complex and multi-factorial mechanisms. Currently, targeting the specific proteins responsible for neurodegeneration is of great interest to many researchers. Furthermore, nanotechnology-based approaches for targeting the affected neurons became an emerging field of interest. Nanostructures of various forms have been developed aiming to act as therapeutics for neurodegeneration, in which electrospun nanofibers seem to play an important role as biomedical products for both detection and management of the diseases. Electrospinning is an intriguing method able to produce nanofibers with a wide range of sizes and morphological characteristics. Such nanofibrous matrices can be delivered through different administration routes to target various diseases. In this review, the most recent advancements in electrospun nanofibrous systems that target or detect multiple neurodegenerative diseases have been enlightened and an introduction to the general aspects of neurodegenerative diseases and the electrospinning process has been made. Finally, future perspectives of neurodegeneration targeting were also discussed.

Dream enactment behavior: review for the clinician

NONE

Dream enactment behavior commonly occurs on occasion in normal children and adults. Disruptive and frequent dream enactment behavior may come to the attention of the clinician either as the primary reason for consultation or as a prominent characteristic of a patient with other sleep disorders. Questioning patients with chronic neurologic and psychiatric disorders may also reveal previously unrecognized behavior. In the absence of sleep pathology, process of dream enactment likely begins with active, often emotionally charged dream content that may occasionally break through the normal REM sleep motor suppressive activity. Disrupted sleep resulting from many possible causes, such as circadian disruption, sleep apnea, or medications, may also disrupt at least temporarily the motor-suppressive activity in REM sleep, allowing dream enactment to occur. Finally, pathological neurological damage in the context of degenerative, autoimmune, and infectious neurological disorders may lead to chronic recurrent and severe dream enactment behavior. Evaluating the context, frequency, and severity of dream enactment behavior is guided first and foremost by a structured approach to the sleep history. Physical exam and selected testing support the clinical diagnosis. Understanding the context and the likely cause is essential to effective therapy.

Wake-Promoting and EEG Spectral Effects of Modafinil After Acute or Chronic Administration in the R6/2 Mouse Model of Huntington's Disease

Huntington's disease (HD) is characterised by progressive symptoms including cognitive deficits and sleep/wake disturbances reflected in an abnormal electroencephalography (EEG). Modafinil, a wake-promoting and cognitive-enhancing drug, has been considered as a treatment for HD. We used HD (R6/2) mice to investigate the potential for using modafinil to treat sleep-wake disturbance in HD. R6/2 mice show sleep-wake and EEG changes similar to those seen in HD patients, with increased rapid eye movement sleep (REMS), decreased wakefulness/increased non-REMS (NREMS), and pathological changes in EEG spectra, particularly an increase in gamma power. We recorded EEG from R6/2 and wild-type mice treated with modafinil acutely (with single doses between 25 and 100 mg/kg; at 12 and 16 weeks of age), or chronically (64 mg/kg modafinil/day from 6 to 15 weeks). Acutely, modafinil increased wakefulness in R6/2 mice and restored NREMS to wild-type levels at 12 weeks. It also suppressed the pathologically increased REMS. This was accompanied by decreased delta power, increased peak frequency of theta, and increased gamma power. At 16 weeks, acute modafinil also restored wakefulness and NREMS to wild-type levels. However, whilst REMS decreased, it did not return to normal levels. By contrast, in the chronic treatment group, modafinil-induced wakefulness was maintained at 15 weeks (after 9 weeks of treatment). Interestingly, chronic modafinil also caused widespread suppression of power across the EEG spectra, including a reduction in gamma that increases pathologically in R6/2 mice. The complex EEG effects of modafinil in R6/2 mice should provide a baseline for further studies to investigate the translatability of these result to clinical practice.

Photosensitive Melanopsin-Containing Retinal Ganglion Cells in Health and Disease: Implications for Circadian Rhythms

Melanopsin-containing retinal ganglion cells (mRGCs) represent a third class of retinal photoreceptors involved in regulating the pupillary light reflex and circadian photoentrainment, among other things. The functional integrity of the circadian system and melanopsin cells is an essential component of well-being and health, being both impaired in aging and disease. Here we review evidence of melanopsin-expressing cell alterations in aging and neurodegenerative diseases and their correlation with the development of circadian rhythm disorders. In healthy humans, the average density of melanopsin-positive cells falls after age 70, accompanied by age-dependent atrophy of dendritic arborization. In addition to aging, inner and outer retinal diseases also involve progressive deterioration and loss of mRGCs that positively correlates with progressive alterations in circadian rhythms. Among others, mRGC number and plexus complexity are impaired in Parkinson's disease patients; changes that may explain sleep and circadian rhythm disorders in this pathology. The key role of mRGCs in circadian photoentrainment and their loss in age and disease endorse the importance of eye care, even if vision is lost, to preserve melanopsin ganglion cells and their essential functions in the maintenance of an adequate quality of life.

Sleep Disorders in Huntington's Disease

Huntington's chorea (Huntington's disease, HD) is a genetic disorder caused by autosomal dominant mutation, leading to progressive neurodegenerative changes in the central nervous system. Involuntary movements such as chorea occur typically in HD patients, accompanied by progressive cognitive and psychiatric disturbances. Other common symptoms of HD are circadian and sleep abnormalities, which are observed from the earliest stages of the disease or even before the occurrence of clinical symptoms. The most common sleep problems reported by HD patients include insomnia, difficulties in falling asleep, frequent nocturnal awakenings, and excessive daytime sleepiness. Also, specific changes in sleep architecture have been identified in HD. In this paper, we review studies on sleep and circadian rhythm disorders in HD. We outline findings concerning sleep patterns and disturbances of circadian rhythms in HD patients, as well as the role of psychiatric disorders and motor disorders in HD patients' sleep problems. We also discuss problems related to the different methods of diagnosing sleep disorders in HD. Furthermore, the adverse effects of medication used for the treatment of core HD symptoms as one of the sources of sleep disturbances in HD are emphasized. In conclusion, the diversity and complexity of the determinants of sleep and circadian rhythm disorders in HD are highlighted. Finally, the relevance of effective treatment to improve patients' functioning and quality of life as well as the potential relief of their cognitive and emotional symptoms is addressed.

Activity Behaviour of Minipigs Transgenic for the Huntington Gene

BACKGROUND

To increase the reliability of translating preclinical findings to humans, large animal models, such as the transgenic (tg) Libechov minipig, were established. As minipigs possess high genetic homology with humans and have similarities in anatomy, physiology and metabolism to humans, they are considered for studying neurodegenerative diseases longitudinally. Recently, sleep abnormalities and changes in circadian rhythm in Huntington's disease (HD) patients were acknowledged to present one of the early symptoms in HD.

OBJECTIVE

The aim of the present study was to explore the activity behaviour of Libechov minipigs and to investigate whether tgHD and wildtype (wt) minipigs exhibit differences in activity behaviour. Furthermore, it was investigated whether activity assessments may serve as reliable endpoints for phenotyping minipigs transgenic for the Huntington gene.

METHODS

Activity behaviour of minipigs was studied by video recording the stables twice a week over a total study period of five weeks for a cohort of five tgHD minipigs and five wt minipigs. Statistical analysis was performed using the linear mixed model. Once a week, the distances covered by two minipigs in focus (tgHD, wt) were measured using the VideoMotionTracker® software.

RESULTS

Libechov minipigs showed a biphasic pattern of activity, spending most of the time inactive or grubbing in litter. Differences in activity behaviour (rooting, resting and standing) were detected between wt and tgHD minipigs. The influence of the genotype on behavioural patterns was observed during circadian monitoring. TgHD minipigs covered longer distances on average and during every 24 h observation period than wt minipigs.

CONCLUSION

Activity behaviour may be a viable marker for phenotyping minipigs transgenic for the Huntington gene. Video recordings of behavioural patterns provide a non-invasive opportunity to capture potential disease signs. Phenotypic progression including the age of disease manifestation may be explored by documentation of circadian characteristics.

Pilot Validation of Ambulatory Activity Monitors for Sleep Measurement in Huntington's Disease Gene Carriers

Sleep disturbance occurs early in Huntington's disease (HD). Consumer- and research-grade activity monitors may enable routine assessment of sleep disturbances in HD. We compared Actiwatch Spectrum Pro, Jawbone UP2 and Fitbit One to the gold standard, polysomnography, in four late presymptomatic and three early HD participants. Compared to polysomnography, all ambulatory monitors overestimated total sleep time by >60 minutes and sleep efficiency by ∼15%. Thus, for assessment of specific sleep parameters in HD, none of the activity monitors are sufficiently accurate to replace polysomnography, although they may be sufficient for estimating overall sleep-wake patterns. Larger sample replication is required.

Huntington disease

Huntington disease is a monogenic neurodegenerative disorder that displays an autosomal-dominant pattern of inheritance. It is characterized by motor, psychiatric, and cognitive symptoms that progress over 15-20 years. Since the identification of the causative genetic mutation in 1993 much has been discovered about the underlying pathogenic mechanisms, but as yet there are no disease-modifying therapies available. This chapter reviews the epidemiology, genetic basis, pathogenesis, presentation, and clinical management of Huntington disease. The principles of genetic testing are explained. We also describe recent developments in the ongoing search for therapeutics and for biomarkers to track disease progression.

Clinical Features of Huntington's Disease

Huntington's disease (HD) is the most common monogenic neurodegenerative disease and the commonest genetic dementia in the developed world. With autosomal dominant inheritance, typically mid-life onset, and unrelenting progressive motor, cognitive and psychiatric symptoms over 15-20 years, its impact on patients and their families is devastating. The causative genetic mutation is an expanded CAG trinucleotide repeat in the gene encoding the Huntingtin protein, which leads to a prolonged polyglutamine stretch at the N-terminus of the protein. Since the discovery of the gene over 20 years ago much progress has been made in HD research, and although there are currently no disease-modifying treatments available, there are a number of exciting potential therapeutic developments in the pipeline. In this chapter we discuss the epidemiology, genetics and pathogenesis of HD as well as the clinical presentation and management of HD, which is currently focused on symptomatic treatment. The principles of genetic testing for HD are also explained. Recent developments in therapeutics research, including gene silencing and targeted small molecule approaches are also discussed, as well as the search for HD biomarkers that will assist the validation of these potentially new treatments.

A Longitudinal Motor Characterisation of the HdhQ111 Mouse Model of Huntington's Disease

Background: Huntington’s disease (HD) is a rare, incurable neurodegenerative disorder caused by a CAG trinucleotide expansion with the first exon of the huntingtin gene. Numerous knock-in mouse models are currently available for modelling HD. However, before their use in scientific research, these models must be characterised to determine their face and predictive validity as models of the disease and their reliability in recapitulating HD symptoms.

Objective: Manifest HD is currently diagnosed upon the onset of motor symptoms, thus we sought to longitudinally characterise the progression and severity of motor signs in the Hdh^Q111 knock-in mouse model of HD, in heterozygous mice.

Methods: An extensive battery of motor tests including: rotarod, inverted lid test, balance beam, spontaneous locomotor activity and gait analysis were applied longitudinally to a cohort of Hdh^Q111 heterozygous mice in order to progressively assess motor function.

Results: A progressive failure to gain body weight was demonstrated from 11 months of age and motor problems in all measures of balance beam performance were shown in Hdh^Q111 heterozygous animals in comparison to wild type control animals from 9 months of age. A decreased latency to fall from the rotarod was demonstrated in Hdh^Q111 heterozygous animals in comparison to wild type animals, although this was not progressive with time. No genotype specific differences were demonstrated in any of the other motor tests included in the test battery.

Conclusions: The Hdh^Q111 heterozygous mouse demonstrates a subtle and progressive motor phenotype that begins at 9 months of age. This mouse model represents an early disease stage and would be ideal for testing therapeutic strategies that require elongated lead-in times, such as viral gene therapies or striatal transplantation.

Hypersomnia in Neurodegenerative Diseases

Hypersomnia is a common complaint in many patients with neurodegenerative diseases and a major cause of decreased quality of life. This article discusses the prevalence and factors associated with hypersomnia in patients with a variety of neurodegenerative diseases affecting the central nervous system, including tauopathies, synucleinopathies, and other conditions. Common nocturnal sleep problems that may result in daytime hypersomnia are delineated. A clinical approach to hypersomnia in patients with neurodegenerative diseases, recommended diagnostic testing, and available treatment options are also discussed.

Early-onset sleep defects in Drosophila models of Huntington's disease reflect alterations of PKA/CREB signaling

Huntington's disease (HD) is a progressive neurological disorder whose non-motor symptoms include sleep disturbances. Whether sleep and activity abnormalities are primary molecular disruptions of mutant Huntingtin (mutHtt) expression or result from neurodegeneration is unclear. Here, we report Drosophila models of HD exhibit sleep and activity disruptions very early in adulthood, as soon as sleep patterns have developed. Pan-neuronal expression of full-length or N-terminally truncated mutHtt recapitulates sleep phenotypes of HD patients: impaired sleep initiation, fragmented and diminished sleep, and nighttime hyperactivity. Sleep deprivation of HD model flies results in exacerbated sleep deficits, indicating that homeostatic regulation of sleep is impaired. Elevated PKA/CREB activity in healthy flies produces patterns of sleep and activity similar to those in our HD models. We were curious whether aberrations in PKA/CREB signaling were responsible for our early-onset sleep/activity phenotypes. Decreasing signaling through the cAMP/PKA pathway suppresses mutHtt-induced developmental lethality. Genetically reducing PKA abolishes sleep/activity deficits in HD model flies, restores the homeostatic response and extends median lifespan. In vivo reporters, however, show dCREB2 activity is unchanged, or decreased when sleep/activity patterns are abnormal, suggesting dissociation of PKA and dCREB2 occurs early in pathogenesis. Collectively, our data suggest that sleep defects may reflect a primary pathological process in HD, and that measurements of sleep and cAMP/PKA could be prodromal indicators of disease, and serve as therapeutic targets for intervention.

A 24-Hour Study of the Hypothalamo-Pituitary Axes in Huntington's Disease

Background

Huntington’s disease is an inherited neurodegenerative disorder characterised by motor, cognitive and psychiatric disturbances. Patients exhibit other symptoms including sleep and mood disturbances, muscle atrophy and weight loss which may be linked to hypothalamic pathology and dysfunction of hypothalamo-pituitary axes.

Methods

We studied neuroendocrine profiles of corticotropic, somatotropic and gonadotropic hypothalamo-pituitary axes hormones over a 24-hour period in controlled environment in 15 healthy controls, 14 premanifest and 13 stage II/III Huntington’s disease subjects. We also quantified fasting levels of vasopressin, oestradiol, testosterone, dehydroepiandrosterone sulphate, thyroid stimulating hormone, free triiodothyronine, free total thyroxine, prolactin, adrenaline and noradrenaline. Somatotropic axis hormones, growth hormone releasing hormone, insulin-like growth factor-1 and insulin-like factor binding protein-3 were quantified at 06:00 (fasting), 15:00 and 23:00. A battery of clinical tests, including neurological rating and function scales were performed.

Results

24-hour concentrations of adrenocorticotropic hormone, cortisol, luteinizing hormone and follicle-stimulating hormone did not differ significantly between the Huntington’s disease group and controls. Daytime growth hormone secretion was similar in control and Huntington’s disease subjects. Stage II/III Huntington’s disease subjects had lower concentration of post-sleep growth hormone pulse and higher insulin-like growth factor-1:growth hormone ratio which did not reach significance. In Huntington’s disease subjects, baseline levels of hypothalamo-pituitary axis hormones measured did not significantly differ from those of healthy controls.

Conclusions

The relatively small subject group means that the study may not detect subtle perturbations in hormone concentrations. A targeted study of the somatotropic axis in larger cohorts may be warranted. However, the lack of significant results despite many variables being tested does imply that the majority of them do not differ substantially between HD and controls.

Polysomnographic Findings and Clinical Correlates in Huntington Disease: A Cross-Sectional Cohort Study

STUDY OBJECTIVES

To evaluate the sleep pattern and the motor activity during sleep in a cohort of patients affected by Huntington disease (HD).

DESIGN

Cross-sectional cohort study.

SETTING

Sleep laboratory.

PATIENTS

Thirty HD patients, 16 women and 14 men (mean age 57.3 ± 12.2 y); 30 matched healthy controls (mean age 56.5 ± 11.8 y).

INTERVENTIONS

Subjective sleep evaluation: Epworth Sleepiness Scale (ESS); Berlin's Questionnaire, interview for restless legs syndrome (RLS), questionnaire for REM sleep behavior disorder (RBD). Clinical evaluation: disease duration, clinical severity (unified Huntington disease motor rating scale [UHDMRS]), genetic tests. Laboratory-based full-night attended video-polysomnography (V-PSG).

MEASUREMENTS AND RESULTS

The duration of the disease was 9.4 ± 4.4 y, UHMDRS score was 55.5 ± 23.4, CAG repeats were 44.3 ± 4.1. Body mass index was 21.9 ± 4.0 kg/m(2). No patients or caregivers reported poor sleep quality. Two patients reported symptoms of RLS. Eight patients had an ESS score ≥ 9. Eight patients had high risk of obstructive sleep apnea. At the RBD questionnaire, two patients had a pathological score. HD patients, compared to controls, showed shorter sleep, reduced sleep efficiency index, and increased arousals and awakenings. Four patients presented with sleep disordered breathing (SDB). Periodic limb movements (PLMs) during wake and sleep were observed in all patients. No episode of RBD was observed in the V-PSG recordings, and no patients showed rapid eye movement (REM) sleep without atonia. The disease duration correlated with ESS score (P < 0.02). UHMDRS correlated positively with the ESS score (P < 0.005), and negatively with the percentage of REM sleep.

CONCLUSIONS

Patients with Huntington disease showed a severe sleep disruption and a high prevalence of periodic limb movements, but no evidence of sleep disordered breathing or REM sleep behavior disorder.

Sleep Physiology Alterations Precede Plethoric Phenotypic Changes in R6/1 Huntington's Disease Mice

In hereditary neurodegenerative Huntington’s disease (HD), there exists a growing consideration that sleep and circadian dysregulations may be important symptoms. It is not known, however, whether sleep abnormalities contribute to other behavioral deficits in HD patients and mouse models. To determine the precise chronology for sleep physiology alterations and other sensory, motor, psychiatric and cognitive symptoms of HD, the same R6/1 HD transgenics and their wild-type littermates were recorded monthly for sleep electroencephalogram (EEG) together with a wide range of behavioral tests according to a longitudinal plan. We found an early and progressive deterioration of both sleep architecture and EEG brain rhythms in R6/1 mice, which are correlated timely with their spatial working memory impairments. Sleep fragmentation and memory impairments were accompanied by the loss of delta (1-4Hz) power in the transgenic mice, the magnitude of which increased with age and disease progression. These precocious sleep and cognitive impairments were followed by deficits in social behavior, sensory and motor abilities. Our data confirm the existence and importance of sleep physiology alterations in the widely used R6/1 mouse line and highlight their precedence over other plethoric phenotypic changes. The brainwave abnormalities, may represent a novel biomarker and point to innovative therapeutic interventions against HD.

Clinical Aspects of Huntington's Disease

Huntington's disease (HD) is a devastating inherited neurodegenerative condition characterized by progressive motor, cognitive, and psychiatric symptoms. Symptoms progress over 15-20 years, and there are currently no disease-modifying therapies. The causative genetic mutation is an expanded CAG repeat in the HTT gene encoding the Huntingtin protein, and is inherited in an autosomal dominant manner. In this chapter we discuss the genetics, clinical presentation, and management of this condition, as well as new data from large-scale clinical research studies on the natural history of HD.

'The clocks that time us'--circadian rhythms in neurodegenerative disorders

Circadian rhythms are physiological and behavioural cycles generated by an endogenous biological clock, the suprachiasmatic nucleus. The circadian system influences the majority of physiological processes, including sleep-wake homeostasis. Impaired sleep and alertness are common symptoms of neurodegenerative disorders, and circadian dysfunction might exacerbate the disease process. The pathophysiology of sleep-wake disturbances in these disorders remains largely unknown, and is presumably multifactorial. Circadian rhythm dysfunction is often observed in patients with Alzheimer disease, in whom it has a major impact on quality of life and represents one of the most important factors leading to institutionalization of patients. Similarly, sleep and circadian problems represent common nonmotor features of Parkinson disease and Huntington disease. Clinical studies and experiments in animal models of neurodegenerative disorders have revealed the progressive nature of circadian dysfunction throughout the course of neurodegeneration, and suggest strategies for the restoration of circadian rhythmicity involving behavioural and pharmacological interventions that target the sleep-wake cycle. In this Review, we discuss the role of the circadian system in the regulation of the sleep-wake cycle, and outline the implications of disrupted circadian timekeeping in neurodegenerative diseases.

Plasma melatonin is reduced in Huntington's disease

This study was undertaken to determine whether the production of melatonin, a hormone regulating sleep in relation to the light/dark cycle, is altered in Huntington's disease. We analyzed the circadian rhythm of melatonin in a 24-hour study of cohorts of control, premanifest, and stage II/III Huntington's disease subjects. The mean and acrophase melatonin concentrations were significantly reduced in stage II/III Huntington's disease subjects compared with controls. We also observed a nonsignificant trend toward reduced mean and acrophase melatonin in premanifest Huntington's disease subjects. Onset of melatonin rise was significantly more temporally spread in both premanifest and stage II/III Huntington's disease subjects compared with controls. A nonsignificant trend also was seen for reduced pulsatile secretion of melatonin. Melatonin concentrations are reduced in Huntington's disease. Altered melatonin patterns may provide an explanation for disrupted sleep and circadian behavior in Huntington's disease, and represent a biomarker for disease state. Melatonin therapy may help the sleep disorders seen in Huntington's disease.

Early and progressive circadian abnormalities in Huntington's disease sheep are unmasked by social environment

Insidious changes in behaviour herald the onset of progressive neurodegenerative disorders such as Huntington's disease (HD), sometimes years before overt symptoms are seen. Sleep and circadian disturbances are particularly disruptive symptoms in patients with neurological disorders, but they are difficult to measure in humans. Here we studied circadian behaviour in transgenic HD sheep expressing the full-length human huntingtin protein with an expanded CAG repeat mutation in the juvenile range. Young HD sheep with no other symptoms exhibited circadian behavioural abnormalities that worsened with age. The most obvious change was a disturbed evening behaviour reminiscent of 'sundowning' that is seen in some patients with dementia. There were no structural abnormalities seen with magnetic resonance imaging, even in 5-year-old HD sheep. Interestingly, detection of the circadian abnormalities depended upon their social grouping. Abnormalities emerged in sheep kept in an 'HD-only' flock, whereas the behaviour of HD sheep kept mixed with normal sheep was relatively normal. Sleep-wake abnormalities in HD patients are also likely to be hidden, and may precede overt symptoms by many years. Sleep disruption has deleterious effects, even in normal people. The knock-on effects of sleep-wake disturbance may exacerbate, or even cause symptoms such as irritability and depression that are common in early stage HD patients. HD sheep will be useful models for probing the mechanisms underlying circadian behavioural disorder in HD.

A review of quality of life after predictive testing for and earlier identification of neurodegenerative diseases

The past decade has witnessed an explosion of evidence suggesting that many neurodegenerative diseases can be detected years, if not decades, earlier than previously thought. To date, these scientific advances have not provoked any parallel translational or clinical improvements. There is an urgency to capitalize on this momentum so earlier detection of disease can be more readily translated into improved health-related quality of life for families at risk for, or suffering with, neurodegenerative diseases. In this review, we discuss health-related quality of life (HRQOL) measurement in neurodegenerative diseases and the importance of these "patient reported outcomes" for all clinical research. Next, we address HRQOL following early identification or predictive genetic testing in some neurodegenerative diseases: Huntington disease, Alzheimer's disease, Parkinson's disease, Dementia with Lewy bodies, frontotemporal dementia, amyotrophic lateral sclerosis, prion diseases, hereditary ataxias, Dentatorubral-pallidoluysian atrophy and Wilson's disease. After a brief report of available direct-to-consumer genetic tests, we address the juxtaposition of earlier disease identification with assumed reluctance toward predictive genetic testing. Forty-one studies examining health-related outcomes following predictive genetic testing for neurodegenerative disease suggested that (a) extreme or catastrophic outcomes are rare; (b) consequences commonly include transiently increased anxiety and/or depression; (c) most participants report no regret; (d) many persons report extensive benefits to receiving genetic information; and (e) stigmatization and discrimination for genetic diseases are poorly understood and policy and laws are needed. Caution is appropriate for earlier identification of neurodegenerative diseases but findings suggest further progress is safe, feasible and likely to advance clinical care.

Progressive sleep and electroencephalogram changes in mice carrying the Huntington's disease mutation

Sleep disturbances in Huntington's disease may be deleterious to the cognitive performance, affective behaviour, and general well-being of patients, but a comprehensive description of the progression of changes in sleep and electroencephalogram in Huntington's disease has never been conducted. Here we studied sleep and electroencephalogram disturbances in a transgenic mouse model of Huntington's disease (R6/2 mice). We implanted 10 R6/2 mice and five wild-type littermates with electromyography electrodes, frontofrontal and frontoparietal electroencephalogram electrodes and then recorded sleep/wake behaviour at presymptomatic, symptomatic and late stages of the disease. In addition to sleep-wake scoring, we performed a spectral analysis of the sleep electroencephalogram. We found that sleep and electroencephalogram were already significantly disrupted in R6/2 mice at 9 weeks of age (presymptomatic stage). By the time they were symptomatic, R6/2 mice were unable to maintain long periods of wakefulness and had an increased propensity for rapid eye movement sleep. In addition, the peak frequency of theta rhythm was shifted progressively from 7 Hz to 6 Hz during rapid eye movement sleep, whereas slow wave activity decreased gradually during non-rapid eye movement sleep. Finally, as the disease progressed, an abnormal electroencephalogram gamma activity (30-40 Hz) emerged in R6/2 mice irrespective of sleep states. This is reminiscent of the increased gamma power described in schizophrenic patients during sleep and events of psychosis. Gaining a better understanding of sleep and electroencephalogram changes in patients with Huntington's disease should be a priority, since it will enable clinicians to initiate appropriate investigations and to instigate treatments that could dramatically improve patients' quality of life.

The Q175 mouse model of Huntington's disease shows gene dosage- and age-related decline in circadian rhythms of activity and sleep

Sleep and circadian disruptions are commonly reported by patients with neurodegenerative diseases, suggesting these may be an endophenotype of the disorders. Several mouse models of Huntington’s disease (HD) that recapitulate the disease progression and motor dysfunction of HD also exhibit sleep and circadian rhythm disruption. Of these, the strongest effects are observed in the transgenic models with multiple copies of mutant huntingtin gene. For developing treatments of the human disease, knock-in (KI) models offer advantages of genetic precision of the insertion and control of mutation copy number. Therefore, we assayed locomotor activity and immobility-defined sleep in a new model of HD with an expansion of the KI repeats (Q175). We found evidence for gene dose- and age-dependent circadian disruption in the behavior of the Q175 line. We did not see evidence for loss of cells or disruption of the molecular oscillator in the master pacemaker, the suprachiasmatic nucleus (SCN). The combination of the precise genetic targeting in the Q175 model and the observed sleep and circadian disruptions make it tractable to study the interaction of the underlying pathology of HD and the mechanisms by which the disruptions occur.

Sleep disturbance in mental health problems and neurodegenerative disease

Sleep has been described as being of the brain, by the brain, and for the brain. This fundamental neurobiological behavior is controlled by homeostatic and circadian (24-hour) processes and is vital for normal brain function. This review will outline the normal sleep-wake cycle, the changes that occur during aging, and the specific patterns of sleep disturbance that occur in association with both mental health disorders and neurodegenerative disorders. The role of primary sleep disorders such as insomnia, obstructive sleep apnea, and REM sleep behavior disorder as potential causes or risk factors for particular mental health or neurodegenerative problems will also be discussed.

Circadian and sleep disorder in Huntington's disease

Huntington's disease is a progressive neurological disorder that starts insidiously with motor, cognitive or psychiatric disturbance, and progresses through a distressing range of symptoms to end with a devastating loss of function, both motor and executive. There is a growing awareness that, in addition to cognitive and psychiatric symptoms, there are other important non-motor symptoms in HD, including sleep and circadian abnormalities. It is not clear if sleep-wake changes are caused directly by HD gene-related pathology, or if they are simply a consequence of having a neurodegenerative disease. From a patient point of view, the answer is irrelevant, since sleep and circadian disturbances are deleterious to good daily living, even in neurologically normal people. The assumption should be that, at the very least, sleep and/or circadian disturbance in HD patients will contribute to their symptoms. At worst, they may contribute to the progressive decline in HD. Here I review the state of our understanding of sleep and circadian abnormalities in HD. I also outline a set of simple rules that can be followed to improve the chances of a good night's sleep, since preventing any 'preventable' symptoms is the a logical first step in treating disease. The long-term impact of sleep disruption in HD is unknown. There have been no large-scale systematic studies of in sleep in HD. Furthermore, there has never been a study of the efficacy of pharmaceuticals that are typically used to treat sleep deficits in HD patients. Thus treatment of sleep disturbance in HD is necessarily empirical. A better understanding of the relationship between sleep/circadian abnormalities and HD pathology is needed, if treatment of this aspect of HD is to be optimized.

Neurocardiac dysregulation and neurogenic arrhythmias in a transgenic mouse model of Huntington's disease

Huntington's disease (HD) is a heritable neurodegenerative disorder, with heart disease implicated as one major cause of death. While the responsible mechanism remains unknown, autonomic nervous system (ANS) dysfunction may play a role. We studied the cardiac phenotype in R6/1 transgenic mice at early (3 months old) and advanced (7 months old) stages of HD. While exhibiting a modest reduction in cardiomyocyte diameter, R6/1 mice had preserved baseline cardiac function. Conscious ECG telemetry revealed the absence of 24-h variation of heart rate (HR), and higher HR levels than wild-type littermates in young but not older R6/1 mice. Older R6/1 mice had increased plasma level of noradrenaline (NA), which was associated with reduced cardiac NA content. R6/1 mice also had unstable R-R intervals that were reversed following atropine treatment, suggesting parasympathetic nervous activation, and developed brady- and tachyarrhythmias, including paroxysmal atrial fibrillation and sudden death. c-Fos immunohistochemistry revealed greater numbers of active neurons in ANS-regulatory regions of R6/1 brains. Collectively, R6/1 mice exhibit profound ANS-cardiac dysfunction involving both sympathetic and parasympathetic limbs, that may be related to altered central autonomic pathways and lead to cardiac arrhythmias and sudden death.

Delayed onset of the diurnal melatonin rise in patients with Huntington's disease

Sleep disturbances are very prevalent in Huntington’s disease (HD) patients and can substantially impair their quality of life. Accumulating evidence suggests considerable dysfunction of the hypothalamic suprachiasmatic nucleus (SCN), the biological clock, in both HD patients and transgenic mouse models of the disease. As melatonin has a major role in the regulation of sleep and other cyclical bodily activities and its synthesis is directly regulated by the SCN, we postulated that disturbed SCN function is likely to give rise to abnormal melatonin secretion in HD. Therefore, we compared 24 h melatonin secretion profiles between early stage HD patients and age-, sex- and body mass index-matched controls. Although mean diurnal melatonin levels were not different between the two groups (p = 0.691), the timing of the evening rise in melatonin levels was significantly delayed by more than 01:30 h in HD patients (p = 0.048). Moreover, diurnal melatonin levels strongly correlated with both motor (r = −0.70, p = 0.036) and functional impairment (r = +0.78, p = 0.013). These findings suggest a delayed sleep phase syndrome-like circadian rhythm disorder in early stage HD patients and suggest that melatonin levels may progressively decline with advancing disease.

Sleep disorders in machado-joseph disease: frequency, discriminative thresholds, predictive values, and correlation with ataxia-related motor and non-motor features

Sleep disorders are common complaints in patients with neurodegenerative diseases such as spinocerebellar ataxia type 3 (SCA3) or Machado-Joseph disease (MJD)--SCA3/MJD. We evaluated the frequency of sleep disorders in SCA3/MJD patients against controls matched by age and gender, and correlated data with demographic and clinical variables. The main sleep disorders evaluated were rapid eye movement (REM) sleep behavior disorder (RBD), restless leg syndrome (RLS), and excessive daytime sleepiness (EDS). We recruited 40 patients with clinical and molecular-proven SCA3/MJD and 38 controls. We used the following clinical scales to evaluate our primary outcome measures: RBD Screening Questionnaire, International RLS Rating Scale, and Epworth Sleepiness Scale. To evaluate ataxia-related motor and non-motor features, we applied the International Cooperative Ataxia Rating Scale, the Scale for the Assessment and Rating of Ataxia, and the Unified Parkinson's Disease Rating Scale part III. Psychiatric manifestations were tested with the Hamilton Anxiety Scale, and Beck Depression Inventory. The frequency of RBD and RLS were significantly higher in the SCA3/MJD group than in the control group (p < 0.001). There was no difference between both groups with regard to EDS. The accuracy of RDBSQ to discriminate between cases and controls was considered the best area under the ROC curve (0.86). Within-SCA3/MJD group analysis showed that anxiety and depression were significantly correlated with RDB, but not with RLS. Additionally, depression was considered the best predictive clinical feature for RDB and EDS.

Disease and Degeneration of Aging Neural Systems that Integrate Sleep Drive and Circadian Oscillations

Sleep/wake and circadian rest-activity rhythms become irregular with age. Typical outcomes include fragmented sleep during the night, advanced sleep phase syndrome and increased daytime sleepiness. These changes lead to a reduction in the quality of life due to cognitive impairments and emotional stress. More importantly, severely disrupted sleep and circadian rhythms have been associated with an increase in disease susceptibility. Additionally, many of the same brain areas affected by neurodegenerative diseases include the sleep and wake promoting systems. Any advances in our knowledge of these sleep/wake and circadian networks are necessary to target neural areas or connections for therapy. This review will discuss research that uses molecular, behavioral, genetic and anatomical methods to further our understanding of the interaction of these systems.

Huntington's Disease and Striatal Signaling

Huntington’s Disease (HD) is the most frequent neurodegenerative disease caused by an expansion of polyglutamines (CAG). The main clinical manifestations of HD are chorea, cognitive impairment, and psychiatric disorders. The transmission of HD is autosomal dominant with a complete penetrance. HD has a single genetic cause, a well-defined neuropathology, and informative pre-manifest genetic testing of the disease is available. Striatal atrophy begins as early as 15 years before disease onset and continues throughout the period of manifest illness. Therefore, patients could theoretically benefit from therapy at early stages of the disease. One important characteristic of HD is the striatal vulnerability to neurodegeneration, despite similar expression of the protein in other brain areas. Aggregation of the mutated Huntingtin (HTT), impaired axonal transport, excitotoxicity, transcriptional dysregulation as well as mitochondrial dysfunction, and energy deficits, are all part of the cellular events that underlie neuronal dysfunction and striatal death. Among these non-exclusive mechanisms, an alteration of striatal signaling is thought to orchestrate the downstream events involved in the cascade of striatal dysfunction.