Maintenance of wakefulness test: a polysomnographic technique for evaluation treatment efficacy in patients with excessive somnolence

Ten patients with narcolepsy were given five 20 min opportunities to remain awake throughout the day. Trials were offered at 2 h intervals beginning at 10:00. Polysomnographic variables were monitored during each trial. Sleep latency increased when patients were instructed to maintain wakefulness compared to when instructed to sleep; however, sleep latencies were still lower for narcoleptics than for control subjects. Unexpectedly, we were not always able to document patients' reports of increased ability to stay awake. The findings suggested that clinical data on symptom control in narcolepsy do not predict ability to stay awake. Objective measures of the ability are potentially more useful in evaluating treatment.

Orexin peptides prevent cataplexy and improve wakefulness in an orexin neuron-ablated model of narcolepsy in mice

Narcolepsy-cataplexy is a neurological disorder associated with the inability to maintain wakefulness and abnormal intrusions of rapid eye movement sleep-related phenomena into wakefulness such as cataplexy. The vast majority of narcoleptic-cataplectic individuals have low or undetectable levels of orexin (hypocretin) neuropeptides in the cerebrospinal fluid, likely due to specific loss of the hypothalamic orexin-producing neurons. Currently available treatments for narcolepsy are only palliative, symptom-oriented pharmacotherapies. Here, we demonstrate rescue of the narcolepsy-cataplexy phenotype of orexin neuron-ablated mice by genetic and pharmacological means. Ectopic expression of a prepro-orexin transgene in the brain completely prevented cataplectic arrests and other abnormalities of rapid eye movement sleep in the absence of endogenous orexin neurons. Central administration of orexin-A acutely suppressed cataplectic behavioral arrests and increased wakefulness for 3 h. These results indicate that orexin neuron-ablated mice retain the ability to respond to orexin neuropeptides and that a temporally regulated and spatially targeted secretion of orexins is not necessary to prevent narcoleptic symptoms. Orexin receptor agonists would be of potential value for treating human narcolepsy.

Treatment modalities for narcolepsy

Narcolepsy, a lifelong disorder, requires long-term management of symptoms. Interventions may be nonpharmacologic, such as lifestyle changes, and pharmacologic for relief of daytime sleepiness. Pharmacologic treatment of narcolepsy has depended on the use of CNS stimulants to increase wakefulness, vigilance, and performance. The medications considered effective in the treatment of narcolepsy include dextroamphetamine, pemoline, methylphenidate, methamphetamine, and modafinil; only methylphenidate hydrochloride and dextroamphetamine are approved for use in the United States. The currently available stimulants are associated with sympathomimetic side effects, limitations in efficacy, and negative effects on nighttime sleep. This has led to the development of alternative agents. Modafinil, a new wake-promoting agent, has been shown to be effective in reducing daytime sleepiness in patients with narcolepsy. The results of a United States 18-center randomized, placebo-controlled, 9-week trial of modafinil in the treatment of patients with narcolepsy has recently been reported. Patients receiving modafinil demonstrated significant improvement in all subjective and objective measures of sleepiness. Treatment with modafinil 200 mg and 400 mg daily significantly reduced mean scores on the Epworth Sleepiness Scale compared with baseline and placebo (p < 0.001) and significantly increased mean scores on the Maintenance of Wakefulness Test (p < 0.001) and the Multiple Sleep Latency Test (p < 0.001) compared with baseline and placebo. More improvement, as recorded on the Clinical Global Impression of Change scale, was seen in the modafinil group than in the placebo group at all time points (p < 0.001). Modafinil was well tolerated, with headache the only adverse event to occur significantly more often in the active treatment group (p < 0.05). These results suggest that modafinil is an important new therapeutic option for the treatment of narcolepsy.

Sleep and its disorders

Sleep disorders are very prevalent in the general population and are associated with significant medical, psychological, and social disturbances. Insomnia is the most common. When chronic, it usually reflects psychological/behavioral disturbances. Most insomniacs can be evaluated in an office setting, and a multidimensional approach is recommended, including sleep hygiene measures, psychotherapy, and medication. The parasomnias, including sleepwalking, night terrors, and nightmares, have benign implications in childhood but often reflect psychopathology or significant stress in adolescents and adults and organicity in the elderly. Excessive daytime sleepiness is typically the most frequent complaint and often reflects organic dysfunction. Narcolepsy and idiopathic hypersomnia are chronic brain disorders with an onset at a young age, whereas sleep apnea is more common in middle age and is associated with obesity and cardiovascular problems. Therapeutic naps, medications, and supportive therapy are recommended for narcolepsy and hypersomnia; continuous positive airway pressure, weight loss, surgery, and oral devices are the common treatments for sleep apnea.

Narcolepsy

Narcolepsy is among the leading causes of excessive daytime sleepiness and is the most common neurologic cause. Its classic form--narcolepsy with cataplexy--is a distinct neurologic disease with characteristic clinical and paraclinical findings. The history, epidemiology, clinical picture, pathophysiology, cause, diagnosis, and treatment, both pharmacologic and nonpharmacologic, are discussed in detail.

The delayed sleep phase syndrome: clinical and investigative findings in 14 subjects

Fourteen subjects are described in whom a clinical diagnosis of the delayed sleep phase syndrome was made. The condition is multi-factorial, dependent on lifestyle, mood and personality, as well as on familial factors but no single factor in isolation is sufficient to explain the delay in sleep timing. Refusal to attend school may be important in some instances but will not explain cases with delayed age of onset. In half the subjects the delay in sleep phase started in childhood or adolescence. The syndrome causes severe disruption to education, work and family life. Polysomnography, motor activity monitoring of rest-activity cycles, plasma melatonin profiles and urinary melatonin metabolite excretion are normal. Different patterns of sleep phase delay seen in the syndrome include stable, progressive, irregular and non-24 hour sleep-wake cycles. These patterns may result from different social and other Zeitgebers ("time-markers", for example sunrise, sunset) in the normal environment. Treatment by forced sleep-wake phase advance or with melatonin resulted in a partial sleep-phase advance but this was not maintained on stopping treatment.

Orexins: from neuropeptides to energy homeostasis and sleep/wake regulation

The neuropeptides orexin A and orexin B (also called hypocretin 1 and 2) were recently discovered by a "reverse pharmacology" approach as ligands for two previously orphan G protein coupled receptors: orexin receptors 1 and 2. Neurons producing orexins are located exclusively in the lateral hypothalamic area but project broadly to various parts of the brain, and they have been implicated in the control of energy homeostasis and arousal maintenance. The orexin receptors are also broadly expressed in the central nervous system. Murine and canine models suggest that defective signaling in the orexin system is responsible for the sleep/wake disorder narcolepsy. Although narcoleptic patients rarely have genetic defects in the orexin system, they lack these neuropeptides in the brain and cerebrospinal fluid, indicating that human narcolepsy is an orexin deficiency syndrome in the majority of cases. A connection between sleep/wake regulation and energy homeostasis is hypothesized with orexin neuropeptides as a molecular link.

Scheduled naps in the management of daytime sleepiness in narcolepsy-cataplexy

A repeated testing paradigm was used to assess the efficacy for the management of daytime sleepiness in narcolepsy-cataplexy of single long, multiple short and no-nap sleep/wake schedule conditions, with total sleep per 24 hours held constant. Eight narcoleptic subjects participated and followed each experimental schedule for two consecutive days, the second of which served as a test day during which simultaneous electroencephalogram (EEG) polygraphic recordings were made. Performance tests reported here include a grammatical transformation test and a four-choice reaction time test. A single long nap placed 180 degrees out-of-phase with the nocturnal midsleep time improved sustained performance over the no-nap condition. Reaction time performance was significantly improved in the long nap condition over the no-nap condition. Time-of-day analyses found that the greatest improvement was in the afternoon and evening. By contrast, the grammatical transformation test results suffered under the napping compared to no-nap schedules, suggesting that continuity of wakefulness and/or a long nocturnal sleep period may be important for this test. In addition, unscheduled sleep episodes tended to occur earlier in the day than the period of maximum afternoon sleep tendency seen in normal subjects. Two napping strategies are suggested for further study.

Emerging Therapies in Narcolepsy-Cataplexy

In the past, narcolepsy was primarily treated using amphetamine-like stimulants and tricyclic antidepressants. Newer and novel agents, such as the wake-promoting compound modafinil and more selective reuptake inhibitors targeting the adrenergic, dopaminergic, and/or serotoninergic reuptake sites (ie, venlafaxine, atomoxetine) are better-tolerated available alternatives. The development of these agents, together with sodium oxybate (a slow-wave sleep-enhancing agent that consolidates nocturnal sleep, reduces cataplexy, and improves sleepiness), has led to improved functioning and quality of life for many patients with the disorder. However, these treatments are all symptomatically based and do not target hypocretin, a major neurotransmitter involved in the pathophysiology of narcolepsy. In this review, we discuss emerging therapies in the area of narcolepsy. These include novel antidepressant or anticataplectic, wake-promoting, and hypnotic compounds. We also report on novel strategies designed to compensate for hypocretin deficiency and on the use of immunosupression at the time of narcolepsy onset.

Narcolepsy and the HLA region

Narcolepsy was first shown to be tightly associated with HLA-DR2 and DQ1 in 1983, suggesting a possible autoimmune mechanism. Early investigations failed to demonstrate this hypothesis, postulating that HLA-DR2 was only a linkage marker for another, unknown narcolepsy-causing gene. The autoimmune hypothesis is now being re-evaluated under the light of recent results. Like many other autoimmune disorders, narcolepsy usually starts during adolescence, is human leukocyte antigen (HLA)-associated, multigenic and environmentally influenced. Furthermore, HLA-association studies indicated a primary HLA-DQ effect with complex HLA class II allele interactions and a partial contribution of HLA to overall genetic susceptibility. Finally, recent result suggests that human narcolepsy is associated with the destruction of a small number of hypothalamic neurons containing the peptide hypocretins (orexins). This data is consistent with an immune destruction of hypocretin-containing cells as the most common etiology for human narcolepsy.

Sleep Disorders in Multiple Sclerosis

Sleep disorders are pervasive in patients with multiple sclerosis (MS) although clinically underrecognized by most physicians. The most common sleep disorders seen in patients with MS include insomnia, nocturnal movement disorders, sleep-disordered breathing, narcolepsy, and rapid eye movement sleep behavior disorder. Factors that influence the quality of sleep in this patient population include pain, nocturia, depression, medication effect, location of lesions, and disease severity. Disrupted sleep has the potential to cause daytime somnolence, increased fatigue, and nonrefreshing sleep, and it may be associated with dangerous respiratory events. Awareness and treatment of these conditions is vital to improving health and quality of life in patients with MS.

Childhood narcolepsy

Narcolepsy may present during childhood and is probably underrecognized and underdiagnosed in this population. The core symptoms of narcolepsy in children are similar to those in adults, but the expression may be different because of maturational factors. This report focuses on the presenting features that are unique to childhood narcolepsy and the appropriate diagnostic evaluation for suspected narcolepsy in children. Psychosocial and academic problems are almost universal in children with narcolepsy, and management strategies should address these areas. Although currently available stimulant medications may be helpful to some extent, the cornerstone of management is education, emotional and academic support, and careful follow-up over time. The overall goal for managing childhood narcolepsy is to assist the child and family in achieving optimal quality of life.

Health-related quality of life in narcolepsy

OBJECTIVES

To describe health-related quality of life in Norwegian patients with narcolepsy compared with data from the general population.

PATIENTS AND METHODS

Seventy-seven patients with narcolepsy with cataplexy were included in the final analysis. Health-related quality of life was assessed by SF-36 questionnaire.

RESULTS

Men and women with narcolepsy had lower scores in all SF-36 domains, except vitality. Most profoundly affected were bodily pain (men: p = 0.0001, women: p = 0.0001), social function (men: p = 0.0001, women: p = 0.0001) and general health (men p = 0.04, women: p = 0.0001).

CONCLUSIONS

Narcolepsy has a clear negative effect on quality of life which is not sufficiently counteracted by medical treatment. We suggest that earlier diagnosis and treatment after onset of symptoms may be important in reducing the negative effects on quality of life. Special attention should be paid to the patients social functioning and general well-being.

Narcolepsy and the hypocretin system--where motion meets emotion

Narcolepsy is a neurological disorder that is characterized by excessive daytime sleepiness and cataplexy--a loss of muscle tone generally triggered by certain strong emotions with sudden onset. The underlying cause of most cases of human narcolepsy is a loss of neurons that produce hypocretin (Hcrt, also known as orexin). These cells normally serve to drive and synchronize the activity of monoaminergic and cholinergic cells. Sleepiness results from the reduced activity of monoaminergic, cholinergic and other cells that are normally activated by Hcrt neurons, as well as from the loss of Hcrt itself. Cataplexy is caused by an episodic loss of activity in noradrenergic cells that support muscle tone, and a linked activation of a medial medullary cell population that suppresses muscle tone. Current treatments for narcolepsy include stimulants to combat sleepiness and antidepressants to reduce cataplexy. Sodium oxybate produces both reductions in cataplexy and improved waking alertness. Future treatments are likely to include Hcrt or Hcrt agonists to reverse the underlying neurochemical deficit.

Life effects of narcolepsy: relationships to geographic origin (North American, Asian or European) and to other patient and illness variables

A recent questionnaire survey of the life-effects of narcolepsy in 180 patients, 60 each from North American, Asian and European populations, compared to similarly distributed age and sex matched controls, documented multiple and marked effects on work, education, driving, accidents, recreation, personality, memory and other parameters. The data have now been further analysed according to the patients' geographic (culturo-genetic) origin and to a number of other patient and illness variables. The three different geographic populations showed few significant differences for the some 160 life-effects items in the questionnaire. This strongly indicates that these are an integral part of the disease or of the human reactions to it. Most of the few significant population differences appeared cultural in origin (e.g., concerning driving records, personality changes), although a few may possibly reflect genetic differences (e.g., visual problems). Analysis of the pooled data according to respondees' age, sex, age at illness onset, duration of illness and treatment led again to relatively few significant findings. It is concluded that, in general, once the disease has been diagnosed, all the major life effects are present and remain so. The results strongly support the contention that most life-effects are not related to the diagnostic 'tetrad' symptoms themselves but rather to excessive daytime sleepiness, the symptoms most resistant to ant-narcoleptic treatment.

Sleep disorders: sleep apnea and narcolepsy

Symptoms of obstructive sleep apnea, a potentially life-threatening disorder, include excessive daytime sleepiness and sleep attacks, nocturnal breath cessation, and snorting and gasping sounds. These symptoms usually become manifest before age 40 and cluster within a few years. Most patients are obese, hypertensive men who eventually develop cardiovascular abnormalities. If sleep apnea is suspected based on clinical information, a sleep laboratory evaluation is indicated. For severe obstructive sleep apnea, tracheostomy is the most effective treatment. Narcolepsy, another sleep disorder, is a life-long and usually disabling condition. In most narcoleptic patients the first symptoms develop during childhood or adolescence, yet many years pass before the proper diagnosis is made. The presence of sleep attacks together with auxiliary symptoms, particularly cataplexy, is diagnostic. Treatment of narcolepsy includes stimulants in combination with therapeutic naps for sleep attacks and tricyclic drugs for cataplexy.

The alerting effects of short and long naps in narcoleptic, sleep deprived, and alert individuals

Eleven narcoleptic patients and 22 age- and gender-matched normal controls participated in a study to determine the alerting effects of differing nap lengths. All narcoleptic patients had been previously diagnosed [mean sleep latency on the multiple sleep latency test (MSLT) < or = 5 minutes with two or more sleep-onset rapid eye movement periods (SOREMPs)]. Healthy, normal subjects with a mean sleep latency on the screening MSLT > or = 8 minutes were randomly assigned to one of two groups (i.e. sleep-deprived and alert). All subjects completed two experimental night and days with at least 5 days between sessions. On the evening prior to each experimental day, narcoleptic and alert subjects spent 8 hours in bed and sleep-deprived subjects spent 0 hours in bed. The following day, all subjects underwent one of two napping conditions, 15 or 120 minutes in bed. Both naps were terminated at noon. Every subject underwent both conditions and the order of conditions was counterbalanced. From 1215 to 1355 hours all subjects underwent a modified MSLT. At 1500 hours, the subjects had a 1-hour nap. The results showed that the 120-minute nap condition was more beneficial than the 15-minute nap. Narcoleptic and sleep deprived subjects were shown to have comparable levels of sleepiness on the modified MSLT. However, a differential response pattern on their latency to sleep was noted on the 1-hour nap. Sleep-deprived subjects were shown to be differentially more alert following a 120-minute nap opportunity. In contrast, for narcoleptic patients the beneficial effects of the nap were lost when tested 3 hours later. These results show that narcoleptic patients benefit from a longer nap but that these benefits are short-lived.

Hypocretin/orexin and narcolepsy: new basic and clinical insights

Narcolepsy is a chronic sleep disorder, characterized by excessive daytime sleepiness (EDS), cataplexy, sleep paralysis and hypnagogic hallucinations. Both sporadic (95%) and familial (5%) forms of narcolepsy exist in humans. The major pathophysiology of human narcolepsy has been recently discovered based on the discovery of narcolepsy genes in animals; the genes involved in the pathology of the hypocretin/orexin ligand and its receptor. Mutations in hypocretin-related genes are rare in humans, but hypocretin ligand deficiency is found in a large majority of narcolepsy with cataplexy. Hypocretin ligand deficiency in human narcolepsy is probably due to the post-natal cell death of hypocretin neurones. Although a close association between human leucocyte antigen (HLA) and human narcolepsy with cataplexy suggests an involvement of autoimmune mechanisms, this has not yet been proved. Hypocretin deficiency is also found in symptomatic cases of narcolepsy and EDS with various neurological conditions, including immune-mediated neurological disorders, such as Guillain-Barre syndrome, MA2-positive paraneoplastic syndrome and neuromyelitis optica (NMO)-related disorder. The findings in symptomatic narcoleptic cases may have significant clinical relevance to the understanding of the mechanisms of hypocretin cell death and choice of treatment option. The discoveries in human cases lead to the establishment of the new diagnostic test of narcolepsy (i.e. low cerebrospinal fluid hypocretin-1 levels for 'narcolepsy with cataplexy' and 'narcolepsy due to medical condition'). As a large majority of human narcolepsy patients are ligand deficient, hypocretin replacement therapy may be a promising new therapeutic option, and animal experiments using gene therapy and cell transplantations are in progress.

Orexin gene therapy restores the timing and maintenance of wakefulness in narcoleptic mice

STUDY OBJECTIVES

Narcolepsy is caused by selective loss of the orexin/hypocretin-producing neurons of the hypothalamus. For patients with narcolepsy, chronic sleepiness is often the most disabling symptom, but current therapies rarely normalize alertness and do not address the underlying orexin deficiency. We hypothesized that the sleepiness of narcolepsy would substantially improve if orexin signaling were restored in specific brain regions at appropriate times of day.

DESIGN

We used gene therapy to restore orexin signaling in a mouse model of narcolepsy. In these Atx mice, expression of a toxic protein (ataxin-3) selectively kills the orexin neurons.

INTERVENTIONS

To induce ectopic expression of the orexin neuropeptides, we microinjected an adeno-associated viral vector coding for prepro-orexin plus a red fluorescence protein (AAV-orexin) into the mediobasal hypothalamus of Atx and wild-type mice. Control mice received an AAV coding only for red fluorescence protein. Two weeks later, we recorded sleep/wake behavior, locomotor activity, and body temperature and examined the patterns of orexin expression.

MEASUREMENTS AND RESULTS

Atx mice rescued with AAV-orexin produced long bouts of wakefulness and had a normal diurnal pattern of arousal, with the longest bouts of wake and the highest amounts of locomotor activity in the first hours of the night. In addition, AAV-orexin improved the timing of rapid eye movement sleep and the consolidation of nonrapid eye movement sleep in Atx mice.

CONCLUSIONS

These substantial improvements in sleepiness and other symptoms of narcolepsy demonstrate the effectiveness of orexin gene therapy in a mouse model of narcolepsy. Additional work is needed to optimize this approach, but in time, AAV-orexin could become a useful therapeutic option for patients with narcolepsy.

Functional status in patients with narcolepsy

OBJECTIVE

To describe health and functional status in treated narcolepsy patients and to compare it with normative data and with patients with another cause of sleepiness, the obstructive sleep apnea/hypopnea syndrome (OSAHS) patients.

METHODS

A functional status survey in narcolepsy patients and in symptomatic untreated and CPAP treated OSAHS patients with an apnea-hypopnea index (AHI) >5 was assessed using the UK Short Form 36 (SF-36) questionnaire, the Functional Outcomes of Sleep Questionnaire (FOSQ) and the Epworth Sleepiness Scale (ESS). SF-36 scores in narcoleptics were compared to age and sex matched controls. Narcolepsy patients also replied to a psychosocial aspects questionnaire. Health history and demographic data were obtained via a review of medical records and postal survey.

RESULTS

Forty-nine treated narcolepsy patients, 56 untreated OSAHS and 48 CPAP treated OSAHS patients attending the sleep disorders clinic were recruited for this study. Narcoleptics presented significantly lower scores in all SF-36 domains compared to normative data. No difference in SF-36 scores was found between narcoleptics and untreated OSAHS patients but narcoleptics were sleepier and had lower FOSQ scores. These treated narcolepsy patients had lower scores in two dimensions of the SF-36 and in all FOSQ domains compared to CPAP-treated OSAHS patients.

CONCLUSIONS

Functional status in treated narcoleptics is poor.