Idiopathic hypersomnia

Sleep medicine, sleep research, and sleep education: a whole life devoted to sleep

This article describes my participation in sleep medicine, sleep research, and sleep education, mainly in Europe, between the years 1970 and 2000.

Idiopathic hypersomnia years after the diagnosis

Little attention has been paid to the long-term development of idiopathic hypersomnia symptoms and idiopathic hypersomnia comorbidities. The aim of this study was to describe the general health of patients with idiopathic hypersomnia years after the initial diagnosis, focusing on current subjective hypersomnolence and the presence of its other possible causes. Adult patients diagnosed with idiopathic hypersomnia ≥ 3 years ago at sleep centres in Prague and Kosice were invited to participate in this study. A total of 60 patients were examined (age 47.3 ± SD = 13.2 years, 66.7% women). In all participants, their hypersomnolence could not be explained by any other cause but idiopathic hypersomnia at the time of diagnosis. The mean duration of follow-up was 9.8 + 8.0 years. Fifty patients (83%) reported persisting hypersomnolence, but only 33 (55%) had no other disease that could also explain the patient's excessive daytime sleepiness and/or prolonged sleep. In two patients (3%), the diagnosis in the meantime had changed to narcolepsy type 2, and 15 patients (25%) had developed a disease or diseases potentially causing hypersomnolence since the initial diagnosis. Complete hypersomnolence resolution without stimulant treatment lasting longer than 6 months was reported by 10 patients (17%). To conclude, in a longer interval from the diagnosis of idiopathic hypersomnia, hypersomnolence may disappear or may theoretically be explained by another newly developed disease, or the diagnosis may be changed to narcolepsy type 2. Thus, after 9.8 years, only 55% of the examined patients with idiopathic hypersomnia had a typical clinical picture of idiopathic hypersomnia without doubts about the cause of the current hypersomnolence.

Single sessions of transcranial direct current stimulation and transcranial random noise stimulation exert no effect on sleepiness in patients with narcolepsy and idiopathic hypersomnia

Background

Hypersomnia poses major challenges to treatment providers given the limitations of available treatment options. In this context, the application of non-invasive brain stimulation techniques such as transcranial electrical stimulation (tES) may open up new avenues to effective treatment. Preliminary evidence suggests both acute and longer-lasting positive effects of transcranial direct current stimulation (tDCS) on vigilance and sleepiness in hypersomniac patients. Based on these findings, the present study sought to investigate short-term effects of single sessions of tDCS and transcranial random noise stimulation (tRNS) on sleepiness in persons suffering from hypersomnia.

Methods

A sample of 29 patients suffering from narcolepsy or idiopathic hypersomnia (IH) was recruited from the Regensburg Sleep Disorder Center and underwent single sessions of tES (anodal tDCS, tRNS, sham) over the left and right dorsolateral prefrontal cortex on three consecutive days in a double-blind, sham-controlled, pseudorandomized crossover trial. The primary study endpoint was the mean reaction time measured by the Psychomotor Vigilance Task (PVT) before and directly after the daily tES sessions. Secondary endpoints were additional PVT outcome metrics as well as subjective outcome parameters (e.g., Karolinska Sleepiness Scale; KSS).

Results

There were no significant treatment effects neither on objective (i.e., PVT) nor on subjective indicators of sleepiness.

Conclusion

We could not demonstrate any clinically relevant effects of single sessions of tDCS or tRNS on objective or subjective measures of sleepiness in patients with hypersomnia. However, we cannot exclude that repeated sessions of tES may affect vigilance or sleepiness in hypersomniac patients.

Evaluation of hypersomnolence: From symptoms to diagnosis, a multidimensional approach

Hypersomnolence is a major public health issue given its high frequency, its impact on academic/occupational functioning and on accidentology, as well as its heavy socio-economic burden. The positive and aetiological diagnosis is crucial, as it determines the therapeutic strategy. It must consider the following aspects: i) hypersomnolence is a complex concept referring to symptoms as varied as excessive daytime sleepiness, excessive need for sleep, sleep inertia, or drowsiness, all of which warrant specific dedicated investigations; ii) the boundary between physiological and abnormal hypersomnolence is blurred, since most symptoms can be encountered in the general population to varying degrees without being considered as pathological, meaning that their severity, frequency, context of occurrence and related impairment need to be carefully assessed; iii) investigation of hypersomnolence relies on scales/questionnaires as well as behavioural and neurophysiological tests, which measure one or more dimensions, keeping in mind the possible discrepancy between objective and subjective assessment; iv) aetiological reasoning is driven by knowledge of the main sleep regulation mechanisms, epidemiology, and associated symptoms. The need to assess hypersomnolence is growing, both for its management, and for assessing the efficacy of treatments. The landscape of tools available for investigating hypersomnolence is constantly evolving, in parallel with research into sleep physiology and technical advances. These investigations face the challenges of reconciling subjective perception and objective data, making tools accessible to as many people as possible and predicting the risk of accidents.

Precision Medicine for Idiopathic Hypersomnia

Idiopathic hypersomnia (IH) includes a clinical phenotype resembling narcolepsy (with repeated, short restorative naps), and a phenotype with an excess of sleep, sleep drunkenness, drowsiness, and infrequent long, nonrestorative naps. Sleep tests reflect this heterogeneity. MSLTs are greater than 8 min in 2/3 of the cases and poorly repeatable. Sleep excess is better captured by extended monitoring identifying 11 to 16h of sleep/24 h. Patients with IH are young and more often female. Possible mechanisms of IH include deficiencies in arousal systems, inappropriate stimulation of sleep-inducing systems, and long biological night. Treatments now include robust studies of modafinil, clarithromycin, and sodium oxybate.

Idiopathic Hypersomnia: Historical Account, Critical Review of Current Tests and Criteria, Diagnostic Evaluation in the Absence of Biological Markers and Robust Electrophysiological Diagnostic Criteria

Idiopathic hypersomnia was first described in 1976 under two forms: polysymptomatic, characterized by excessive daytime sleepiness, long and unrefreshing naps, nocturnal sleep of abnormally long duration and signs of sleep drunkenness upon awakening; monosymptomatic, manifested by excessive daytime sleepiness only. Yet, after 45 years, this sleep disorder is still poorly delineated and diagnostic criteria produced by successive International Classifications of Sleep Disorders are far from satisfactory. The first part of this review is a historical account of the successive names and descriptions of idiopathic hypersomnia: monosymptomatic and polysymptomatic idiopathic hypersomnia in 1976; central nervous system idiopathic hypersomnia in 1979; idiopathic hypersomnia in 1990; idiopathic hypersomnia with and without long sleep time in 2005; idiopathic hypersomnia again in 2014; and, within the last few years, the proposal of separating idiopathic hypersomnia into a well-defined subtype, idiopathic hypersomnia with long sleep duration, and a more heterogeneous subtype combining idiopathic hypersomnia without long sleep duration and narcolepsy type 2. The second part is a critical review of both current ICSD-3 diagnostic criteria and clinical features, scales and questionnaires, electrophysiological and circadian control tests, research techniques, currently used to diagnose idiopathic hypersomnia. The third part proposes a diagnostic evaluation of idiopathic hypersomnia, in the absence of biologic markers and of robust electrophysiological diagnostic criteria.

Idiopathic hypersomnia: a homogeneous or heterogeneous disease?

INTRODUCTION

Idiopathic hypersomnia (IH) is a rare orphan disease characterized by excessive daytime sleepiness, frequently accompanied by prolonged nocturnal sleep and difficulties awakening, termed sleep inertia or sleep drunkenness. Severe sleepiness usually causes a greater handicap than manifestations of narcolepsy.

METHODS

Forty-three IH patients (17 male, mean age 42.8 ± SD 12.2 years, range 20-67), diagnosed in the past 20 years according to ICSD-2 or ICSD-3 criteria were invited for clinical examination to evaluate the course, manifestations and severity of the disease, as well as clinical comorbidities. The patients completed a set of questionnaires scoring sleepiness, sleep inertia, fatigue, depression, anxiety, circadian preference, and quality of life.

RESULTS

IH patients were divided according to the duration of nocturnal sleep at the time of their diagnosis into two cohorts: (1) with normal sleep duration (n = 25, 58.1%) and (2) with long sleep duration (n = 18, 41.9%). The mean duration of ad libitum sleep per 22 h in the second cohort was 732.0 ± 115.4 min (range 603-1100), and women markedly prevailed (n = 14, 77.8%). Age at disease onset was younger in the group with long sleep duration (21.2 ± 11.4 years versus 28.1 ± 13.6 years, p = 0.028), their MSLT latency was longer (7.2 ± 3.7 min versus 5.1 ± 1.7 min, p = 0.005), a history of sleep inertia prevailed (p = 0.005), and daily naps were mostly non-refreshing (p = 0.014). Additionally, questionnaires in the group with long sleep duration showed more severe sleep inertia (p = 0.007), fatigue (p = 0.004), and a tendency towards evening chronotype (p = 0.001).

CONCLUSIONS

IH patients with long sleep duration differ clinically as well as by objective measures at the time of diagnosis and in long-term follow up from IH patients without long 24-h sleep time. In our opinion they represent an independent clinical entity to be considered in the revised ICSD-3 criteria.

Is Idiopathic Hypersomnia a Circadian Rhythm Disorder?

Purpose of review

The pathophysiology of idiopathic hypersomnia remains unclear, but some of its clinical features suggest the possibility of circadian dysfunction. This review will provide an overview of recent studies of circadian biology that have begun to elucidate the potential role of circadian rhythm dysfunction in idiopathic hypersomnia.

Recent findings

Clinically, people with idiopathic hypersomnia tend to have both a late chronotype and prominent sleep inertia or sleep drunkenness. Melatonin and cortisol profiles in people with IH confirm this tendency toward phase delay. More recently, it has been suggested that the night phase as defined by melatonin profile or period length as defined by BMA1 in dermal fibroblasts may also be prolonged in people with IH. Additionally, amplitude of melatonin rhythm and circadian gene expression, particularly BMAL1, PER1, and PER2, may be impaired in this disease.

Summary

Clinical features, melatonin profiles, and circadian gene expression all suggest abnormalities of the circadian system may be a contributor to the pathogenesis of IH.

Sleepiness in Adolescents

Sleepiness and sleep deprivation among adolescents are increasingly being recognized as a public health concern. Many of the determinants of this growing problem lie beyond the biomedical scope of explanation. In this article, the authors begin with a review of the prevalence and consequences of sleepiness in adolescents and then present the approach to a sleepy adolescent and the underlying cause. The topic is discussed from clinical as well as public health perspectives.

Central Disorders of Hypersomnolence: Focus on the Narcolepsies and Idiopathic Hypersomnia

The central disorders of hypersomnolence are characterized by severe daytime sleepiness, which is present despite normal quality and timing of nocturnal sleep. Recent reclassification distinguishes three main subtypes: narcolepsy type 1, narcolepsy type 2, and idiopathic hypersomnia (IH), which are the focus of this review. Narcolepsy type 1 results from loss of hypothalamic hypocretin neurons, while the pathophysiology underlying narcolepsy type 2 and IH remains to be fully elucidated. Treatment of all three disorders focuses on the management of sleepiness, with additional treatment of cataplexy in those patients with narcolepsy type 1. Sleepiness can be treated with modafinil/armodafinil or sympathomimetic CNS stimulants, which have been shown to be beneficial in randomized controlled trials of narcolepsy and, quite recently, IH. In those patients with narcolepsy type 1, sodium oxybate is effective for the treatment of both sleepiness and cataplexy. Despite these treatments, there remains a subset of hypersomnolent patients with persistent sleepiness, in whom alternate therapies are needed. Emerging treatments for sleepiness include histamine H3 antagonists (eg, pitolisant) and possibly negative allosteric modulators of the gamma-aminobutyric acid-A receptor (eg, clarithromycin and flumazenil).

Subjective symptoms in idiopathic hypersomnia: beyond excessive sleepiness

Patients with idiopathic hypersomnia never feel fully alert despite a normal or long sleep night. The spectrum of the symptoms is insufficiently studied. We interviewed 62 consecutive patients with idiopathic hypersomnia (with a mean sleep latency lower than 8 min or a sleep time longer than 11 h) and 50 healthy controls using a questionnaire on sleep, awakening, sleepiness, alertness and cognitive, psychological and functional problems during daily life conditions. Patients slept 3 h more on weekends, holidays and in the sleep unit than on working days. In the morning, the patients needed somebody to wake them, or to be stressed, while routine, light, alarm clocks and motivation were inefficient. Three-quarters of the patients did not feel refreshed after short naps. During the daytime, their alertness was modulated by the same external conditions as controls, but they felt more sedated in darkness, in a quiet environment, when listening to music or conversation. Being hyperactive helped them more than controls to resist sleepiness. They were more frequently evening-type and more alert in the evening than in the morning. The patients were able to focus only for 1 h (versus 4 h in the controls). They complained of attention and memory deficit. Half of them had problems regulating their body temperature and were near-sighted. Mental fatigability, dependence on other people for awakening them, and a reduced benefit from usually alerting conditions (except being hyperactive or stressed) seem to be more specific of the daily problems of patients with idiopathic hypersomnia than daytime sleepiness.

IgG abnormality in narcolepsy and idiopathic hypersomnia

Background

A close association between narcolepsy and the Human Leukocyte Antigen (HLA)-DQB1*0602 allele suggests the involvement of the immune system, or possibly an autoimmune process. We investigated serum IgG levels in narcolepsy.

Methodology/Principal Findings

We measured the serum total IgG levels in 159 Japanese narcolepsy-cataplexy patients positive for the HLA-DQB1*0602 allele, 28 idiopathic hypersomnia patients with long sleep time, and 123 healthy controls (the HLA-DQB1*0602 allele present in 45 subjects). The serum levels of each IgG subclass were subsequently measured. The distribution of serum IgG was significantly different among healthy controls negative for the HLA-DQB1*0602 allele (11.66±3.55 mg/ml), healthy controls positive for the HLA-DQB1*0602 allele (11.45±3.43), narcolepsy patients (9.67±3.38), and idiopathic hypersomnia patients (13.81±3.80). None of the following clinical variables, age, disease duration, Epworth Sleepiness Scale, smoking habit and BMI at the time of blood sampling, were associated with IgG levels in narcolepsy or idiopathic hypersomnia. Furthermore we found the decrease in IgG1 and IgG2 levels, stable expression of IgG3, and the increase in the proportion of IgG4 in narcolepsy patients with abnormally low IgG levels. The increase in the proportion of IgG4 levels was also found in narcolepsy patients with normal serum total IgG levels. Idiopathic hypersomnia patients showed a different pattern of IgG subclass distribution with high IgG3 and IgG4 level, low IgG2 level, and IgG1/IgG2 imbalance.

Conclusions/Significance

Our study is the first to determine IgG abnormalities in narcolepsy and idiopathic hypersomnia by measuring the serum IgG levels in a large number of hypersomnia patients. The observed IgG abnormalities indicate humoral immune alterations in narcolepsy and idiopathic hypersomnia. Different IgG profiles suggest immunological differences between narcolepsy and idiopathic hypersomnia.

Idiopathic hypersomnia with and without long sleep time: a controlled series of 75 patients

OBJECTIVE

To characterize the clinical, psychological, and sleep pattern of idiopathic hypersomnia with and without long sleep time, and provide normative values for 24-hour polysomnography.

SETTING

University Hospital.

DESIGN

Controlled, prospective cohort.

PARTICIPANTS

75 consecutive patients (aged 34 +/- 12 y) with idiopathic hypersomnia and 30 healthy matched controls.

INTERVENTION

Patients and controls underwent during 48 hours a face-to-face interview, questionnaires, human leukocyte antigen genotype, a night polysomnography and multiple sleep latency test (MSLT), followed by 24-h ad libitum sleep monitoring.

RESULTS

Hypersomniacs had more fatigue, higher anxiety and depression scores, and more frequent hypnagogic hallucinations (24%), sleep paralysis (28%), sleep drunkenness (36%), and unrefreshing naps (46%) than controls. They were more frequently evening types. DQB1*0602 genotype was similarly found in hypersomniacs (24.2%) and controls (19.2%). Hypersomniacs had more frequent slow wave sleep after 06:00 than controls. During 24-h polysomnography, the 95% confidence interval for total sleep time was 493-558 min in controls, versus 672-718 min in hypersomniacs. There were 40 hypersomniacs with and 35 hypersomniacs without long ( > 600 min) sleep time. The hypersomniacs with long sleep time were younger (29 +/- 10 vs 40 +/- 13 y, P = 0.0002), slimmer (body mass index: 26 +/- 5 vs 23 +/- 4 kg/m2; P = 0.005), and had lower Horne-Ostberg scores and higher sleep efficiencies than those without long sleep time. MSLT latencies were normal (> 8 min) in 71% hypersomniacs with long sleep time.

CONCLUSIONS

Hypersomnia, especially with long sleep time, is frequently associated with evening chronotype and young age. It is inadequately diagnosed using MSLT.

Evidence-based recommendations for the assessment and management of sleep disorders in older persons

Sleep-related disorders are most prevalent in the older adult population. A high prevalence of medical and psychosocial comorbidities and the frequent use of multiple medications, rather than aging per se, are major reasons for this. A major concern, often underappreciated and underaddressed by clinicians, is the strong bidirectional relationship between sleep disorders and serious medical problems in older adults. Hypertension, depression, cardiovascular disease, and cerebrovascular disease are examples of diseases that are more likely to develop in individuals with sleep disorders. Conversely, individuals with any of these diseases are at a higher risk of developing sleep disorders. The goals of this article are to help guide clinicians in their general understanding of sleep problems in older persons, examine specific sleep disorders that occur in older persons, and suggest evidence- and expert-based recommendations for the assessment and treatment of sleep disorders in older persons. No such recommendations are available to help clinicians in their daily patient care practices. The four sections in the beginning of the article are titled, Background and Significance, General Review of Sleep, Recommendations Development, and General Approach to Detecting Sleep Disorders in an Ambulatory Setting. These are followed by overviews of specific sleep disorders: Insomnia, Sleep Apnea, Restless Legs Syndrome, Circadian Rhythm Sleep Disorders, Parasomnias, Hypersomnias, and Sleep Disorders in Long-Term Care Settings. Evidence- and expert- based recommendations, developed by a group of sleep and clinical experts, are presented after each sleep disorder.

Effects of common medications used for sleep disorders

Sleep disorders are common and their diagnosis is becoming more widespread with improved awareness among clinicians and patients. The armamentarium for the pharmacologic treatment of sleep disorders is rapidly growing, demanding that clinicians be aware of their indications, adverse effects, and interactions. As disorders, such as narcolepsy, shift-work sleep disorder, and RLS are more readily identified, pharmacologic treatments for these conditions will also become more common.

Idiopathic hypersomnia: a study of 77 cases

STUDY OBJECTIVES

To review the clinical and polysomnographic characteristics of idiopathic hypersomnia as well as the long-term response to treatment.

SETTING

The Respiratory Support and Sleep Centre at Papworth Hospital, Cambridge, UK.

PATIENTS AND DESIGN

A large database of more than 6000 patients with sleep disorders was reviewed. A retrospective study of the clinical and polysomnographic characteristics of 77 patients with idiopathic hypersomnia was performed. Comparison with a similar group of patients with narcolepsy was performed. The response to drug treatment was assessed in 61 patients over a mean follow-up of 3.8 years.

MEASUREMENTS AND RESULTS

Idiopathic hypersomnia was 60% as prevalent as narcolepsy. Comparison with a similar group of patients with narcolepsy showed that those with idiopathic hypersomnia were more likely to have prolonged unrefreshing daytime naps, a positive family history, increased slow-wave sleep, and a longer sleep latency on the Multiple Sleep Latency Test. The results of the Multiple Sleep Latency Test were not helpful in predicting disease severity or treatment response. The clinical features were heterogeneous and of variable severity. The majority of patients with idiopathic hypersomnia had symptoms that remained stable over many years, but 11% had spontaneous remission, which was never seen in narcolepsy. Two thirds of patients with idiopathic hypersomnolence had a sustained improvement in daytime somnolence with medication, although a third needed high doses or combinations of drugs.

CONCLUSIONS

Idiopathic hypersomnolence has characteristic clinical and polysomnographic features but the prolonged latency on the Multiple Sleep Latency Test raises doubt about the validity of this test within the current diagnostic criteria. The disease often responds well to treatment and a substantial minority of patients appear to spontaneously improve.

Diagnosis of narcolepsy and idiopathic hypersomnia. An update based on the International Classification of Sleep Disorders, 2nd edition

Defining the precise nosological limits of narcolepsy and idiopathic hypersomnia is an ongoing process dating back to the first description of the two conditions. The most recent step forward has been done within the preparation of the second edition of the "International classification of sleep disorders" published in June 2005. Appointed by Dr Emmanuel Mignot, the Task Force on "Hypersomnias of central origin, not due to a circadian rhythm sleep disorder, sleep related breathing disorder, or other causes of disturbed nocturnal sleep" thoroughly revisited the nosology of narcolepsy and of idiopathic hypersomnia. Narcolepsy is now distinguished into three different entities, narcolepsy with cataplexy, narcolepsy without cataplexy and narcolepsy due to medical condition, and idiopathic hypersomnia into two entities, idiopathic hypersomnia with long sleep time and idiopathic hypersomnia without long sleep time. Nevertheless there are still a number of pending issues. What are the limits of narcolepsy without cataplexy? Is there a continuum in the pathophysiology of narcolepsy with and without cataplexy? Should sporadic and familial forms of narcolepsy with cataplexy appear as subgroups in the classification? Are idiopathic hypersomnia with long sleep time and idiopathic hypersomnia without long sleep time, two forms of the same condition or two different conditions? Is there a pathophysiological relationship between narcolepsy without cataplexy and idiopathic hypersomnia without long sleep time?

Pharmacogenetic tools for the development of target-oriented cognitive-enhancing drugs

The identification of the anatomical and physiological substrates involved in the regulation of the dorsolateral prefrontal cortex function in humans provided the basis for the understanding of mechanisms involved in cognitive and executive function under normal as well as pathological conditions. In this context, substantial evidence indicates that alterations in monaminergic function in the dorsolateral prefrontal cortex significantly contributes to the cognitive impairments present in schizophrenia, attention deficit disorders, and other neuropsychiatric conditions. The development of a number of compounds that selectively increase extracellular dopamine (DA) concentrations in the dorsolateral prefrontal cortex but not in subcortical areas by either blocking its metabolism or reuptake, or increasing its release, or that directly activate postsynaptic DA-1 receptor mechanisms provided powerful pharmacotherapeutic tools to mitigate the cognitive deficits brought about by the dopaminergic alterations of the prefrontal cortex. More recently, the findings that polymorphisms of the catecholamine-O-methyl-transferase gene may also modify the effect of these drugs on the prefrontal cortex points toward a more specific genotype-based neuropsychopharmacology for the treatment of cognitive deficits in schizophrenia as well as in a number of other neuropsychiatric conditions. The ability of these compounds to increase DA load selectively in the frontal cortex and not on subcortical systems allows a targeted intervention without the stimulant-like effects observed with older drugs used to treat those conditions.

Study of a patient population investigated for excessive daytime sleepiness (EDS)

This study included all patients referred to the out-patient department of our sleep disorders centre from 1993 to 1999 on account of excessive daytime sleepiness (EDS). As a first step, patients in whom a diagnosis was established following appropriate polysomnography were excluded: this included sleep apnea syndrome, increased upper airway resistance syndrome, narcolepsy, periodic movements during sleep or other parasomnia, and epilepsy. Patients regularly taking psychotropic substances or with psychiatric disorders were also excluded. Finally, 128 patients remained in whom no clear diagnosis had been established for EDS, 70 women and 58 men, their ages ranging from 16 to 77 years. They underwent a 48-h recording (night 1-MSLT-night 2-continuous day). The aim of the study was to establish, define and characterise different groups of undiagnosed EDS patients using clinical, electrophysiological and immunological data with the help of hierarchical cluster analysis. Eight groups were characterised: group 1: mild hypersomnia type 1 (n = 11); group 2: hypersomnia frequently associated with HLA type DR2-DQw1 (n = 11); group 3: mild hypersomnia type 2 (n = 28); group 4: morning recovery from disrupted sleep (n = 19); group 5: young "long sleepers with difficulty at waking up" (n = 17); group 6: idiopathic hypersomnia (n = 15); group 7: poor or short sleepers since childhood (n = 8); group 8: older poor sleepers with a late onset of symptoms (n = 19). Characteristic features of these different groups provided consistent and objective arguments leading to a more precise diagnosis for these patients, and helped the initiation of appropriate management and treatment.

Clinical significance of cataplexy and HLADR1501 in narcolepsy

Clinical symptoms and multiple sleep latency test (MSLT) measures among narcoleptic patients with both cataplexy and HLADR1501 were compared with cataplexy-free narcoleptic patients with a positive finding of HLADR1501 and cataplexy-free patients without HLADR1501. Both mean sleep onset latencies and rapid eye movement (REM) latencies on MSLT were shorter in the patients with cataplexy compared with the cataplexy-free patients. In four cataplexy-free patients without HLADR1501, nocturnal sleep was remarkably long and their excessive daytime sleepiness did not respond to treatment. The findings suggest that the severity and disease mechanism of narcolepsy might become heterogenous when cataplexy and HLADR1501 are considered.

Idiopathic Hypersomnia

In contrast to narcolepsy and the Kleine-Levin syndrome, idiopathic hypersomnia is a recently described sleep disorder. Absence of associated clinical features such as cataplexy or megaphagia and characteristic polysomnographic features such as sleep-onset REM episodes render positive diagnosis more uncertain in idiopathic hypersomnia than in the fwo former conditions. Consequently there has been an unfortunate tendency to label all difficult to classify cases of excessive daytime sleepiness as idiopathic hypersomnia. At present due to the description of new disorders such as upper airway resistance syndrome, narcolepsy without cataplexy, delayed sleep phase syndrome, all of which were formerly confused with idiopathic hypersomnia and the clear identification of a "polysymptomatic" or "classic" form of idiopathic hypersomnia, the limits of the disorder become more precise. Still there are a number of cases of isolated excessive daytime sleepiness with no prolonged night sleep, no difficulty waking up, which lay between narcolepsy and genuine idiopathic hypersomnia. Thus there is a definite need to further develop laboratory investigations to help identify and classify these cases. Moreover pathophysiology and pathogenesis are still in their infancy and efforts have to be pursued in this direction. Treatment has not made consistent progress except for the use of a new wake promoting compound, modafinil, which has not yet been evaluated in controlled studies.

Narcolepsy in children: a practical guide to its diagnosis, treatment and follow-up

Narcolepsy is a neurological syndrome characterised by daytime somnolence and cataplexy which often begins in childhood. Failing to recognise the condition may lead to mislabelling a child as lazy or depressed. The diagnostic criteria for narcolepsy vary with age. In children 8 years and older a Multiple Sleep Latency Test with an average latency of less than 8 minutes, and 2 or more sleep onset REM episodes supports the diagnosis. Human leucocyte antigen (HLA) marker DQbeta1 -0602 has been associated with narcolepsy. The current evidence supports the hypothesis that transmission of narcolepsy is multifactorial. with at least two genes, one of which is non-HLA related. The goal of all therapeutic approaches in narcolepsy is to control the narcoleptic symptoms and allow the patient to continue to fully participate in personal and academic activities. This usually requires a combination of behavioural therapy along with medication. Medications for patients with excessive sleepiness are usually stimulants, including amphetamines. However, a novel wake promoting agent, modafinil, is now available. Cataplexy can be controlled by medications with noradrenergic reuptake-blocking properties, such as clomipramine and fluoxetine, through their active metabolites. Increased awareness of narcolepsy is important to allow earlier diagnosis. Research on the effects different medications have, specifically on children with narcolepsy, has been very limited.