Sleep latency on the maintenance of wakefulness test (MWT) for 530 patients with narcolepsy while free of psychoactive drugs

Oral Orexin Receptor 2 Agonist in Narcolepsy Type 1

BACKGROUND

Narcolepsy type 1 is caused by severe loss or lack of brain orexin neuropeptides.

METHODS

We conducted a phase 2, randomized, placebo-controlled trial of TAK-994, an oral orexin receptor 2-selective agonist, in patients with narcolepsy type 1. Patients with confirmed narcolepsy type 1 according to clinical criteria were randomly assigned to receive twice-daily oral TAK-994 (30 mg, 90 mg, or 180 mg) or placebo. The primary end point was the mean change from baseline to week 8 in average sleep latency (the time it takes to fall asleep) on the Maintenance of Wakefulness Test (range, 0 to 40 minutes; normal ability to stay awake, ≥20 minutes). Secondary end points included the change in the Epworth Sleepiness Scale (ESS) score (range, 0 to 24, with higher scores indicating greater daytime sleepiness; normal, <10) and the weekly cataplexy rate.

RESULTS

Of the 73 patients, 17 received TAK-994 at a dose of 30 mg twice daily, 20 received 90 mg twice daily, 19 received 180 mg twice daily, and 17 received placebo. The phase 2 trial and an extension trial were terminated early owing to hepatic adverse events. Primary end-point data were available for 41 patients (56%); the main reason for missing data was early trial termination. Least-squares mean changes to week 8 in average sleep latency on the MWT were 23.9 minutes in the 30-mg group, 27.4 minutes in the 90-mg group, 32.6 minutes in the 180-mg group, and -2.5 minutes in the placebo group (difference vs. placebo, 26.4 minutes in the 30-mg group, 29.9 minutes in the 90-mg group, and 35.0 minutes the 180-mg group; P<0.001 for all comparisons). Least-squares mean changes to week 8 in the ESS score were -12.2 in the 30-mg group, -13.5 in the 90-mg group, -15.1 in the 180-mg group, and -2.1 in the placebo group (difference vs. placebo, -10.1 in the 30-mg group, -11.4 in the 90-mg group, and -13.0 in the 180-mg group). Weekly incidences of cataplexy at week 8 were 0.27 in the 30-mg group, 1.14 in the 90-mg group, 0.88 in the 180-mg group, and 5.83 in the placebo group (rate ratio vs. placebo, 0.05 in the 30-mg group, 0.20 in the 90-mg group, and 0.15 in the 180-mg group). A total of 44 of 56 patients (79%) receiving TAK-994 had adverse events, most commonly urinary urgency or frequency. Clinically important elevations in liver-enzyme levels occurred in 5 patients, and drug-induced liver injury meeting Hy's law criteria occurred in 3 patients.

CONCLUSIONS

In a phase 2 trial involving patients with narcolepsy type 1, an orexin receptor 2 agonist resulted in greater improvements on measures of sleepiness and cataplexy than placebo over a period of 8 weeks but was associated with hepatotoxic effects. (Funded by Takeda Development Center Americas; TAK-994-1501 and TAK-994-1504 ClinicalTrials.gov numbers, NCT04096560 and NCT04820842.).

Effects of Chronic Administration of Green Tea Ethanol Extract on Sleep Architecture in Mice: A Comparative Study with a Representative Stimulant Caffeine

Wakefulness is defined as a state in which individuals can react to a change in situations. The number of people staying awake and compensating for lack of sleep has increased in recent years. Caffeine, a representative stimulant, is the most extensively consumed compound globally and is mainly consumed through coffee. Although green tea (Camellia sinensis L.) contains high caffeine content like coffee, its arousal-inducing effects have not yet been studied. In the present study, we aimed to identify the arousal-inducing effect of GT during a chronic administration period (three weeks) using analysis of sleep architecture. Treatment with GT (1500 mg/kg) significantly elevated the sleep latency and wakefulness throughout the treatment period, and chronic administration of GT consistently maintained an increase in wakefulness for up to 3 h. During the treatment period, the arousal-inducing effect of GT (1500 mg/kg) occurred without any change in the tolerance phenomenon or withdrawal symptoms, similar to that observed with caffeine (25 mg/kg). GT (1500 mg/kg) containing 95.6 mg/kg of caffeine did not produce a better arousal-inducing effect than caffeine at 25 mg/kg. These results indicate that the arousal-inducing effect of GT persisted for three weeks without adverse effects and that GT can control the arousal-inducing effects of caffeine due to the hypnotic effects of its other constituents.

High prevalence of pathological alertness and wakefulness on maintenance of wakefulness test in adults with focal-onset epilepsy

BACKGROUND

Excessive daytime sleepiness (EDS) is a common complaint in adults with epilepsy (AWE), but objective evaluation is lacking. We used the maintenance of wakefulness test (MWT) to objectively measure the ability of adults with focal-onset epilepsy to maintain wakefulness in soporific conditions.

METHODS

Adults with epilepsy participating in a study investigating the effects of lacosamide on sleep and wakefulness underwent baseline ambulatory polysomnography (PSG)/EEG followed by MWT. Mean sleep latency (MSL) and mean percent sleep time (MST, mean percentage of non-wake EEG scored in 3-sec bins from lights out to sleep onset averaged over the 4 MWT trials) were quantified. Subjective sleepiness was assessed by the Epworth Sleepiness Scale (ESS). Spearman correlation and linear regression assessed relationships between MWT parameters, ESS and relevant sleep and epilepsy-related variables.

RESULTS

Maintenance of wakefulness test MSL in 51 AWE (mean age 43.5 ± 13 years, 69% female, mean BMI 24.6 ± 11.2 kg/m²) was 21.7 ± 11.9 min; 45.1% had an abnormally short MSL <19.4 min and 15.7% <8 min. MST was 9.3% [3.3, 19.1]. Mean ESS score was 8.8 ± 5.7; 39% had elevated ESS (>10). No correlation between subjective ESS and objective MSL (p = 0.67) or MST (p = 0.61) was found. MSL was significantly shorter in subjects with focal to bilateral tonic-clonic seizures (FBTCS; 7.9 min [13.6, 22.3]) compared to those without (27.4 min [21.2, 33.6], p = 0.013). Younger subjects had shorter MSL; MSL increased 3.2 min for every 10-year increase in age.

CONCLUSION

We found a high prevalence of objective sleepiness/difficulty maintaining wakefulness on the MWT and subjective sleepiness using the ESS in AWE without a correlation between the two. More severe objective sleepiness was found in subjects with a history of FBTCS and younger age. Further research is needed to determine mechanistic underpinnings and optimal measurements of pathological sleepiness in people with epilepsy given the burden of it on quality of life.

Sleep Measurements in Women

Sleep in women and men have been studied in several studies with higher prevalence of sleep complaints in women compared with men. Several factors can affect sleep and could be argued to contribute to sex and gender differences in general sleep. There are no differences in guidelines when measuring sleep in women but several sleep assessment tools have been validated or compared between sexes. Because there is still a lack of knowledge on sleep measurements in women, the present review aimed to produce an overview of the current knowledge of objective and subjective sleep measurements in women.

Efficacy of pitolisant in patients with high burden of narcolepsy symptoms: pooled analysis of short-term, placebo-controlled studies

STUDY OBJECTIVE

To evaluate the efficacy of pitolisant, a histamine 3 (H₃)-receptor antagonist/inverse agonist, in adult patients with high burden of narcolepsy symptoms.

METHODS

Data were pooled from two randomized, placebo-controlled, 7- or 8-week studies of pitolisant (titrated to a potential maximum dose of 35.6 mg/day) in adults with narcolepsy. Analyses included three independent patient subgroups: Epworth Sleepiness Scale (ESS) baseline score ≥16, Maintenance of Wakefulness Test (MWT) sleep latency ≤8 min, and ≥15 cataplexy attacks per week.

RESULTS

The analysis populations included 118 patients for ESS (pitolisant, n = 60; placebo, n = 58), 105 for MWT (pitolisant, n = 59; placebo, n = 46), and 31 for cataplexy (pitolisant, n = 20; placebo, n = 11). On the ESS, least-squares mean change from baseline was significantly greater for pitolisant (-6.1) compared with placebo (-2.3; P < 0.001). Significantly more pitolisant-treated patients were classified as treatment responders: ESS score reduction ≥3, 69.0% in the pitolisant group versus 35.1% in the placebo group (P = 0.001); final ESS score ≤10, 36.2% versus 10.5%, respectively (P = 0.005). On the MWT, mean sleep latency increased from 3.5 min to 10.4 min with pitolisant and from 3.4 min to 6.8 min with placebo (P = 0.017). Least-squares mean change in the weekly rate of cataplexy was significantly greater for pitolisant (-14.5; baseline, 23.9; final, 9.4) compared with placebo (-0.1; baseline, 23.1; final, 23.0; P = 0.004). Headache was the most common adverse event with pitolisant.

CONCLUSIONS

Pitolisant, at once-daily doses up to 35.6 mg, was efficacious for reducing excessive daytime sleepiness and cataplexy in patients with severe narcolepsy symptom burden.

The effects of caffeine on drowsiness in patients with narcolepsy: a double-blind randomized controlled pilot study

PURPOSE

The effects of caffeine on drowsiness and reaction time in patients with narcolepsy are unclear. We aimed to assess the effects of caffeine as add-on therapy in narcolepsy patients.

METHODS

A randomized, double-blind, placebo-control clinical pilot trial was conducted with a parallel, two-arm trial allocation ratio of 1:1. Participants attended two study visits 7 days apart. The drug was administered orally in a single opaque capsule containing 200 mg caffeine/placebo daily in the morning for 1 week. Sleepiness was assessed objectively using infrared reflectance oculography to measure the percentage of long eye closure (LEC%) and subjectively using two sleepiness scales, the Stanford Sleepiness Scale (SSS) and Karolinska Sleepiness Scale (KSS). Parameters were measured at baseline (BL) prior to taking the drug, after taking the first dose (FD), and after 1 week (WD) of daily caffeine.

RESULTS

Sixteen participants with narcolepsy were included. No significant differences between groups in baseline measurements were observed. LEC% was significantly decreased after the FD and WD compared with baseline levels (BL 1.4 ± 2.1 vs. FD 0.06 ± 0.0.6 and WD 0.03 ± 0.04). Significant improvements in alertness were observed using the KSS when comparing BL with FD and WD (6.3 ± 1.6, 4.9 ± 1.7, and 4.7 ± 1.7, respectively; p = 0.01). No changes in reaction time or SSS scores were noted.

CONCLUSION

Our findings suggest that a small dose of caffeine has positive effects on alertness in patients with narcolepsy. However, larger trials are required to confirm these findings.

TRIAL REGISTRATION NO

ClinicalTrial.gov NCT02832336.

Clinical and Experimental Human Sleep-Wake Pharmacogenetics

Sleep and wakefulness are highly complex processes that are elegantly orchestrated by fine-tuned neurochemical changes among neuronal and non-neuronal ensembles, nuclei, and networks of the brain. Important neurotransmitters and neuromodulators regulating the circadian and homeostatic facets of sleep-wake physiology include melatonin, γ-aminobutyric acid, hypocretin, histamine, norepinephrine, serotonin, dopamine, and adenosine. Dysregulation of these neurochemical systems may cause sleep-wake disorders, which are commonly classified into insomnia disorder, parasomnias, circadian rhythm sleep-wake disorders, central disorders of hypersomnolence, sleep-related movement disorders, and sleep-related breathing disorders. Sleep-wake disorders can have far-reaching consequences on physical, mental, and social well-being and health and, thus, need be treated with effective and rational therapies. Apart from behavioral (e.g., cognitive behavioral therapy for insomnia), physiological (e.g., chronotherapy with bright light), and mechanical (e.g., continuous positive airway pressure treatment of obstructive sleep apnea) interventions, pharmacological treatments often are the first-line clinical option to improve disturbed sleep and wake states. Nevertheless, not all patients respond to pharmacotherapy in uniform and beneficial fashion, partly due to genetic differences. The improved understanding of the neurochemical mechanisms regulating sleep and wakefulness and the mode of action of sleep-wake therapeutics has provided a conceptual framework, to search for functional genetic variants modifying individual drug response phenotypes. This article will summarize the currently known genetic polymorphisms that modulate drug sensitivity and exposure, to partly determine individual responses to sleep-wake pharmacotherapy. In addition, a pharmacogenetic strategy will be outlined how based upon classical and opto-/chemogenetic strategies in animals, as well as human genetic associations, circuit mechanisms regulating sleep-wake functions in humans can be identified. As such, experimental human sleep-wake pharmacogenetics forms a bridge spanning basic research and clinical medicine and constitutes an essential step for the search and development of novel sleep-wake targets and therapeutics.

Manipulation of core body and skin temperature improves vigilance and maintenance of wakefulness in narcolepsy

CONTEXT

Impaired vigilance and sleepiness are two majordaily complaints of patients with narcolepsy. We previously showed their sleepiness to be correlated to an abnormally regulated skin temperature, i.e., increased distal skin temperature compared with proximal skin temperature.

OBJECTIVE

Our goal was to investigate a possible causal contribution of skin temperature disturbances to impairments in the ability to maintain vigilance and wakefulness in narcolepsy.

DESIGN

In a modified constant routine protocol, the Psychomotor Vigilance Task (PVT) and the Maintenance of Wakefulness Test (MWT) were repeatedly assessed. Meanwhile, skin and core body temperatures were mildly manipulated within the thermoneutral range of the normal diurnal rhythm using a thermosuit and hot or cold food and drinks.

SETTING

Tertiary narcolepsy referral center in a university hospital

PATIENTS OR OTHER PARTICIPANTS

Eight patients (5 males) diagnosed with narcolepsy with cataplexy according to the ICSD-2 criteria (mean age +/- SD: 28.6 +/- 6.4, range 18-35 years).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

MWT sleep latency and PVT response speed.

RESULTS

Compared to core cooling, core warming attenuated the typical decline in PVT response speed with increasing time-on-task by 25% (P = 0.02). Compared to distal skin warming, distal skin cooling increased the time that the patients were able to maintain wakefulness by 24% (distal warming: 1.88 min. vs. distal warming: 2.34 min.; P < 0.01).

CONCLUSIONS

Core body and skin temperatures causally affect vigilance and sleepiness in narcolepsy. This could lead to future practical applications.

Clinical and neurobiological aspects of narcolepsy

Narcolepsy is characterized by excessive daytime sleepiness (EDS), cataplexy and/or other dissociated manifestations of rapid eye movement (REM) sleep (hypnagogic hallucinations and sleep paralysis). Narcolepsy is currently treated with amphetamine-like central nervous system (CNS) stimulants (for EDS) and antidepressants (for cataplexy). Some other classes of compounds such as modafinil (a non-amphetamine wake-promoting compound for EDS) and gamma-hydroxybutyrate (GHB, a short-acting sedative for EDS/fragmented nighttime sleep and cataplexy) given at night are also employed. The major pathophysiology of human narcolepsy has been recently elucidated based on the discovery of narcolepsy genes in animals. Using forward (i.e., positional cloning in canine narcolepsy) and reverse (i.e., mouse gene knockout) genetics, the genes involved in the pathogenesis of narcolepsy (hypocretin/orexin ligand and its receptor) in animals have been identified. Hypocretins/orexins are novel hypothalamic neuropeptides also involved in various hypothalamic functions such as energy homeostasis and neuroendocrine functions. Mutations in hypocretin-related genes are rare in humans, but hypocretin-ligand deficiency is found in many narcolepsy-cataplexy cases. In this review, the clinical, pathophysiological and pharmacological aspects of narcolepsy are discussed.

ACNS Clinical Controversy: MSLT and MWT Have Limited Clinical Utility

The Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT) are two commonly used laboratory-based objective tests to measure sleepiness and alertness, respectively. Data suggest both are extremely sensitive tests when measuring the effects of sleep deprivation within subjects, but are less sensitive for confirming sleepiness and response to treatment in groups of patients with different sleep disorders. Inconsistent and even sometimes paradoxical test results may be partly explained by data that show the MSLT and MWT are not selectively sensitive to either sleepiness or alertness, but sensitive to both the sleep and the arousal systems. Sleep latencies seen on both the MSLT and MWT are affected to varying degrees by a myriad of internal and external influences that can alter what we would prefer each test to show. If we continue to use these tests to measure sleepiness or alertness in patients with different sleep disorders, we need to understand more about the nature and impact of different sources of internal and external arousal so that we can better control the test environment. Improved understanding of the determinants of sleep onset is essential because excessive sleepiness has important consequences for both individuals and society.

EEG-mapping differences between narcolepsy patients and controls and subsequent double-blind, placebo-controlled studies with modafinil

The aim of the present study was to investigate the role of EEG mapping as an objective and quantitative measure of vigilance in untreated and modafinil-treated narcoleptics, and compare it with the conventional neurophysiological method of the Multiple Sleep Latency Test (MSLT) and the subjective Epworth Sleepiness Scale (ESS). In 16 drug-free narcoleptics and 16 normal controls a baseline 3-min vigilance-controlled EEG (V-EEG) and a 4-min resting EEG (R-EEG) were recorded during midmorning hours. Thereafter, in a double-blind, placebo-controlled crossover design, patients were treated with a 3-week fixed titration of modafinil (200, 300, 400 mg) and placebo. EEG-mapping, MSLT and ESS measures were obtained before and at the end of the third week of therapy. Statistical overall analysis by means of the omnibus significance test demonstrated significant EEG differences between untreated patients and controls in the resting condition only (R-EEG). Subsequent univariate analysis revealed an increase in absolute and relative theta power, a decrease in alpha-2 and beta power as well as a slowing of the dominant frequency and the centroids of the alpha, beta and total power spectrum and thus objectified a vigilance decrement in narcolepsy. Modafinil 400 mg/d significantly improved vigilance as compared with placebo (p < or = 0.01), inducing changes opposite to the aforementioned baseline differences (key-lock principle). The MSLT and the ESS also improved under modafinil as compared with placebo, but changes were less consistent. Spearman rank correlations revealed the highest correlations between EEG mapping and the ESS, followed by those between EEG mapping and the MSLT, while the lowest correlation was found between the MSLT and the ESS. In conclusion, EEG mapping is a valuable instrument for measuring vigilance decrements in narcolepsy and their improvement under psychostimulant treatment.

Pharmacotherapy for excessive daytime sleepiness

Excessive daytime sleepiness (EDS) has recognized detrimental consequences such as road traffic accidents, impaired psychological functioning and reduced work performance. EDS can result from multiple causes such as sleep deprivation, sleep fragmentation, neurological, psychiatric and circadian rhythm disorders. Treating the underlying cause of EDS remains the mainstay of therapy but in those who continue to be excessively sleepy, further treatment may be warranted. Traditionally, the amphetamine derivatives, methylphenidate and pemoline (collectively sympathomimetic) psychostimulants were the commonest form of therapy for EDS, particularly in conditions such as narcolepsy. More recently, the advent of modafinil has broadened the range of therapeutic options. Modafinil has a safer side-effect profile and as a result, interest in this drug for the management of EDS in other disorders, as well as narcolepsy, has increased considerably. There is a growing school of thought that modafinil may have a role to play in other indications such as obstructive sleep apnea/hypopnea syndrome already treated by nasal continuous positive airway pressure but persisting EDS, shift work sleep disorders, neurological causes of sleepiness, and healthy adults performing sustained operations, particularly those in the military. However, until adequately powered randomised-controlled trials confirm long-term efficacy and safety, the recommendation of wakefulness promoters in healthy adults cannot be justified.

Pupil staging and EEG measurement of sleepiness

The goal of this multi-method study was to examine the validity (accuracy) of the pupillometric Alertness Level Test (ALT) as a physiologic measure of sleepiness. The study used a pooled-time series-correlation design with 16 untreated narcolepsy (8 F, 8 M), 16 untreated obstructive sleep apnea (OSA) (7 F, 9 M) and 16 healthy control (8 F, 8 M) subjects. Participants underwent EEG/polysomnography testing using standard Multiple Sleep Latency Test electrode placement concurrent with the 15 min pupillometric ALT. EEG data were examined to determine if theta power (4-7 Hz) increased during 2-s periods of proportional pupil size decreases (pupil Stage 1, 95% or more of maximal pupil size to Stage 4, 65-74% of maximal size). Printed EEG records also were visually scored. Self-report sleepiness measures included the Pittsburgh Sleep Quality Index, the Profile of Mood States and the Epworth Sleepiness Scale. Within subject groups, theta power ratios significantly increased across pupil stages for the sleep disorder groups but not for controls (theta activity increased 42% for narcoleptic and 36% for OSA subjects). Between subject groups, the amount of theta activity was significantly greater for narcoleptic and OSA subjects than that for controls. Visual EEG scoring and self-report measures were usually consistent with objective findings. The ALT is convenient, easily repeatable and less technically demanding than EEG sleepiness measures, and it deserves more comprehensive testing as a valid measure of sleepiness.

Factors associated with maintenance of wakefulness test mean sleep latency in patients with mild to moderate obstructive sleep apnoea and normal subjects

This study investigated the possible factors related to the Maintenance of Wakefulness Test (MWT) mean sleep latency. A second analysis explored the characteristics of subjects who had discrepant Epworth Sleepiness Scale (ESS) and MWT scores. A total of 151 subjects (110 mild to moderate obstructive sleep apnoea (OSA) patients and 41 control subjects) were recruited for the study. The subjects completed an overnight Polysomnography (PSG), MWT, cognitive, performance and vigilance tasks and answered self-report questionnaires on mood and sleepiness. A forward stepwise multiple regression was performed on MWT mean sleep latency. The predictor variables age (r = 0.28), subjective sleep history for 1 week prior to MWT (sleep diary; r = 0.19) and number of >4% SaO2 Dips during the PSG (r = -0.21) best explained the MWT results, but only accounted for 12.8% of the variance in the test. It was found that 33% of subjects had discrepant ESS and MWT scores. A new variable was created to analyse these subjects (MWT/ESS discrepancy score; MED). A forward stepwise multiple regression analysis found that depression, performance errors and sleep disordered breathing explained 13.4% of the variance in MED scores. The MWT is a complex behavioural test whose scores do not seem to have a very robust relationship with potential predictors and co-correlates. Further comprehensive study is needed if the test is to be used in a diagnostically meaningful way.

Narcolepsy in the older adult: epidemiology, diagnosis and management

Narcolepsy is a disorder of impaired expression of wakefulness and rapid-eye-movement (REM) sleep. This manifests as excessive daytime sleepiness and expression of individual physiological correlates of REM sleep that include cataplexy and sleep paralysis (REM sleep atonia intruding into wakefulness), impaired maintenance of REM sleep atonia (e.g. REM sleep behaviour disorder [RBD]), and dream imagery intruding into wakefulness (e.g. hypnagogic and hypnopompic hallucinations). Excessive sleepiness typically begins in the second or third decade followed by expression of auxiliary symptoms. Only cataplexy exhibits a high specificity for diagnosis of narcolepsy. While the natural history is poorly defined, narcolepsy appears to be lifelong but not progressive. Mild disease severity, misdiagnoses or long delays in cataplexy expression often cause long intervals between symptom onset, presentation and diagnosis. Only 15-30% of narcoleptic individuals are ever diagnosed or treated, and nearly half first present for diagnosis after the age of 40 years. Attention to periodic leg movements (PLM), sleep apnoea and RBD is particularly important in the management of the older narcoleptic patient, in whom these conditions are more likely to occur. Diagnosis requires nocturnal polysomnography (NPSG) followed by multiple sleep latency testing (MSLT). The NPSG of a narcoleptic patient may be totally normal, or demonstrate the patient has a short nocturnal REM sleep latency, exhibits unexplained arousals or PLM. The MSLT diagnostic criteria for narcolepsy include short sleep latencies (<8 minutes) and at least two naps with sleep-onset REM sleep. Treatment includes counselling as to the chronic nature of narcolepsy, the potential for developing further symptoms reflective of REM sleep dyscontrol, and the hazards associated with driving and operating machinery. Elderly narcoleptic patients, despite age-related decrements in sleep quality, are generally less sleepy and less likely to evidence REM sleep dyscontrol. Nonpharmacological management also includes maintenance of a strict wake-sleep schedule, good sleep hygiene, the benefits of afternoon naps and a programme of regular exercise. Thereafter, treatment is highly individualised, depending on the severity of daytime sleepiness, cataplexy and sleep disruption. Wake-promoting agents include the traditional psychostimulants. More recently, treatment with the 'activating' antidepressants and the novel wake-promoting agent modafinil has been advocated. Cataplexy is especially responsive to antidepressants which enhance synaptic levels of noradrenaline (norepinephrine) and/or serotonin. Obstructive sleep apnoea and PLMs are more common in narcolepsy and should be suspected when previously well controlled older narcolepsy patients exhibit a worsening of symptoms. The discovery that narcolepsy/cataplexy results from the absence of neuroexcitatory properties of the hypothalamic hypocretin-peptidergic system will significantly advance understanding and treatment of the symptom complex in the future.

Clinical aspects and pathophysiology of narcolepsy

Narcolepsy is a chronic debilitating sleep disorder first described in the late 19th century. It is characterized by two major symptoms, excessive daytime sleepiness and cataplexy, and two so-called auxiliary symptoms, hypnagogic hallucinations and sleep paralysis. The final diagnosis relies on polysomnography showing the presence of sleep onset rapid eye movement periods (SOREMPs) during the multiple sleep latency test. The presence of HLA DQA1*0102-DQB1*0602 is supportive of the diagnosis. The pathophysiology of the disorder is still unknown but an imbalance between monoamines and acetylcholine is generally accepted. Recent findings in narcoleptic dogs, a natural model of narcolepsy, and in knockout mice revealed that a mutation of type 2 hypocretin receptor plays a major role in the etiology of narcolepsy. Up to now, no mutation has been found in humans except a case of early onset and atypical narcolepsy. However, a marked reduction of hypocretin type 1 has been found in the cerebrospinal fluid (CSF) of a majority of patients and a global loss of hypocretins was noted in post-mortem brain tissue of narcoleptic subjects. Conversely, no hypocretin neuron degeneration has been observed in the genetic form of narcolepsy in dogs but no trace of hypocretin was seen in the brain or the CSF in cases of sporadic canine narcolepsy. This suggests that different hypocretinergic mechanisms are involved in sporadic and genetic forms of canine narcolepsy. Treatment has not evolved significantly over the last few years. However, new drugs, such as hypocretin agonists, are currently being developed.

SIGNIFICANCE

After the discovery of the type 2 hypocretin receptor mutation in canine narcolepsy and the finding of a CSF hypocretin-1 deficiency in human narcolepsy, the major stream of research has involved the hypocretinergic system. However, other lines of research deserve to be pursued simultaneously, in view of comprehensive advancements in the understanding of narcolepsy.

Narcolepsy: clinical features, new pathophysiologic insights, and future perspectives

Narcolepsy is characterized by excessive daytime sleepiness and abnormal manifestations of rapid eye movement sleep such as cataplexy. The authors review the clinical features of narcolepsy, including epidemiology, symptoms, diagnosis, and treatment, in detail. Recent findings show that a loss of hypocretin-producing neurons lies at the root of the signs and symptoms of narcolepsy. The authors review the current state of knowledge on hypocretin anatomy, physiology, and function with special emphasis on the research regarding the hypocretin deficiency in narcolepsy, which may also explain associated features of the disorder, such as obesity. Lastly, they discuss some future perspectives for research into the pathophysiology of sleep/wake disorders, and the potential impact of the established hypocretin deficiency on the diagnosis and treatment of narcolepsy.

Current concepts in the etiology, diagnosis and treatment of narcolepsy

Background and purpose: Narcolepsy is the most common neurologic cause of excessive daytime sleepiness. Rapid eye movement (REM) sleep phenomena such as cataplexy, sleep paralysis and hypnagogic hallucinations can also occur. Cataplexy, a sudden bilateral loss of muscle tone usually brought on by emotional reactions such as excitement, is essentially unique to narcolepsy. Narcolepsy, which has a prevalence of 0.02-0.05% in the US, has a profound influence on the quality of life and safety of affected individuals.Patients and methods: The most characteristic and striking physiological abnormality observed in narcolepsy is the sleep-onset REM, or the occurrence of REM sleep at, or within 20 min of, the onset of sleep. The diagnosis is established by nocturnal polysomnography, and the Multiple Sleep Latency Test (MSLT).Results: Familial cases of narcolepsy have been reported, with the risk to first-degree relatives estimated at 1-2%; however, most cases are sporadic and the syndrome is generally believed to involve environmental factors acting on a specific genetic background. The observation of an HLA association in narcolepsy suggests that autoimmunity may play a role in the disorder. However, extensive studies have failed to find convincing evidence of an autoimmune process. Patients with narcolepsy have recently been shown to be deficient in hypocretin, also called orexin, in the cerebrospinal fluid and have a reduction in hypocretin cells in the lateral hypothalamus. This suggests that hypocretins could potentially provide a novel therapeutic approach to the treatment of narcolepsy.Conclusions: Although non-pharmacologic measures can be helpful in treating narcolepsy, most patients require pharmacotherapy that includes psychostimulants or modafinil. Cataplexy is controlled by tricyclic antidepressants or selective serotonin reuptake inhibitors.

Efficacy and safety of herbal stimulants and sedatives in sleep disorders

World-wide use of herbal medicines is increasing, following regulatory and manufacturing developments. Herbs are attractive alternative medications to many patients with sleep disorders, who may be averse to using conventional drugs. We review here the most common herbal stimulants and sedatives. Caffeine, in herbal teas, black tea, coffee, soft drinks and pharmaceuticals, is used widely to control sleepiness, but more research is needed on its use in sleep disorders. Ephedra, and its constituent ephedrine, are used in both stimulant and weight loss preparations, sometimes with caffeine; safety concerns have arisen with this practice. Yohimbe is another herb used in stimulant and body-building preparations which has safety concerns. Asian and Siberian ginseng have been traditionally used for fatigue, and have some supportive experimental evidence for this use. Herbal sedatives also have some evidence for efficacy; the observations that certain plant flavonoid compounds bind to benzodiazepine receptors adds interest to their use. Valerian and kava have received the most research attention; both have decreased sleep onset time and promoted deeper sleep in small studies, and kava also shows anxiolytic effects. German chamomile, lavender, hops, lemon balm and passionflower are reputed to be mild sedatives but need much more experimental examination.

What is causing excessive daytime sleepiness? Evaluation to distinguish sleep deprivation from sleep disorders

Many people have a temporary spell, often in early afternoon, when they feel drowsy. This passing desire for a quick nap is completely different from excessive daytime sleepiness, which is a much more significant problem. Considering the potentially dire personal and economic consequences of falling asleep unintentionally or at inappropriate times, excessive daytime sleepiness must be taken very seriously. A thorough evaluation, as described by Dr. Mahowald, virtually always leads to a specific underlying cause, allowing effective treatment recommendations.