Elevated anti-streptococcal antibodies in patients with recent narcolepsy onset

Narcolepsy patients have antibodies that stain distinct cell populations in rat brain and influence sleep patterns

Narcolepsy is a chronic sleep disorder, likely with an autoimmune component. During 2009 and 2010, a link between A(H1N1)pdm09 Pandemrix vaccination and onset of narcolepsy was suggested in Scandinavia. In this study, we searched for autoantibodies related to narcolepsy using a neuroanatomical array: rat brain sections were processed for immunohistochemistry/double labeling using patient sera/cerebrospinal fluid as primary antibodies. Sera from 89 narcoleptic patients, 52 patients with other sleep-related disorders (OSRDs), and 137 healthy controls were examined. Three distinct patterns of immunoreactivity were of particular interest: pattern A, hypothalamic melanin-concentrating hormone and proopiomelanocortin but not hypocretin/orexin neurons; pattern B, GABAergic cortical interneurons; and pattern C, mainly globus pallidus neurons. Altogether, 24 of 89 (27%) narcoleptics exhibited pattern A or B or C. None of the patterns were exclusive for narcolepsy but were also detected in the OSRD group at significantly lower numbers. Also, some healthy controls exhibited these patterns. The antigen of pattern A autoantibodies was identified as the common C-terminal epitope of neuropeptide glutamic acid-isoleucine/α-melanocyte-stimulating hormone (NEI/αMSH) peptides. Passive transfer experiments on rat showed significant effects of pattern A human IgGs on rapid eye movement and slow-wave sleep time parameters in the inactive phase and EEG θ-power in the active phase. We suggest that NEI/αMSH autoantibodies may interfere with the fine regulation of sleep, contributing to the complex pathogenesis of narcolepsy and OSRDs. Also, patterns B and C are potentially interesting, because recent data suggest a relevance of those brain regions/neuron populations in the regulation of sleep/arousal.

CD4+ T cell autoimmunity to hypocretin/orexin and cross-reactivity to a 2009 H1N1 influenza A epitope in narcolepsy

Narcolepsy, a disorder strongly associated with human leukocyte antigen (HLA)-DQA1*01:02/DQB1*06:02 (DQ0602), is characterized by excessive daytime sleepiness, cataplexy, and rapid eye movement sleep abnormalities. It is caused by the loss of ~70,000 posterior hypothalamic neurons that produce the wake-promoting neuropeptide hypocretin (HCRT) (orexin). We identified two DQ0602-binding HCRT epitopes, HCRT56-68 and HCRT87-99, that activated a subpopulation of CD4(+) T cells in narcolepsy patients but not in DQ0602-positive healthy control subjects. Because of the established association of narcolepsy with the 2009 H1N1 influenza A strain (pH1N1), we administered a seasonal influenza vaccine (containing pH1N1) to patients with narcolepsy and found an increased frequency of circulating HCRT56-68- and HCRT87-99-reactive T cells. We also identified a hemagglutinin (HA) pHA1 epitope specific to the 2009 H1N1 strain, pHA1275-287, with homology to HCRT56-68 and HCRT87-99. In vitro stimulation of narcolepsy CD4(+) T cells with pH1N1 proteins or pHA1275-287 increased the frequency of HCRT56-68- and HCRT87-99-reactive T cells. Our data indicate the presence of CD4(+) T cells that are reactive to HCRT in narcolepsy patients and possible molecular mimicry between HCRT and a similar epitope in influenza pH1N1, pHA1275-287.

Narcolepsy as an autoimmune disease: the role of H1N1 infection and vaccination

Narcolepsy is a sleep disorder characterised by loss of hypothalamic hypocretin (orexin) neurons. The prevalence of narcolepsy is about 30 per 100 000 people, and typical age at onset is 12-16 years. Narcolepsy is strongly associated with the HLA-DQB1*06:02 genotype, and has been thought of as an immune-mediated disease. Other risk genes, such as T-cell-receptor α chain and purinergic receptor subtype 2Y11, are also implicated. Interest in narcolepsy has increased since the epidemiological observations that H1N1 infection and vaccination are potential triggering factors, and an increase in the incidence of narcolepsy after the pandemic AS03 adjuvanted H1N1 vaccination in 2010 from Sweden and Finland supports the immune-mediated pathogenesis. Epidemiological observations from studies in China also suggest a role for H1N1 virus infections as a trigger for narcolepsy. Although the pathological mechanisms are unknown, an H1N1 virus-derived antigen might be the trigger.

Quality of life in children with narcolepsy

AIMS

To evaluate the health-related quality of life (HRQL) and its correlates in children and adolescents with narcolepsy.

METHODS

We compared the clinical characteristics of control subjects and patients with primary narcolepsy from data collected at the National Reference Centers for Narcolepsy.

RESULTS

The cohort included 69 control subjects (29 boys) and 117 patients (65 boys; 59 de novo patients). Cataplexy was present in 81% and DQB1*0602 was positive in 91%. The control children were older (13.5±3.2 vs. 11.6±3.1 years, P<0.001) and less obese (1.4% vs. 60%, P<0.001). Twenty-five percent of the patients and 15.6% of the control subjects had clinically significant depressive feelings on Children's Depression Inventory (CDI≥16) (NS). Fifty-three narcoleptic and 43 control adolescents, 31 narcoleptic children and 23 control children filled out the HRQL questionnaires as well as 83 parents of patients and 60 parents of control subjects. Narcolepsy seriously impacts HRQL in terms of vitality, physical well-being, relations with friends and leisure activities, especially in adolescents. Depression was the factor that most affected HRQL in both narcoleptic and control subjects. For the control subjects and the narcoleptic patients, when the CDI score was entered into the multivariable regression model adjusted for gender and age, no other continuous independent variable could significantly increase the likelihood of the model. When the CDI score increased by 1, the mean HRQL score decreased by 1.7 for narcoleptic patients and 1.5 for control subjects. Apnea-hypopnoea index, diagnosis delay, disease duration, obesity, the presence of cataplexy or treatment had no effects on HRQL.

CONCLUSIONS

Narcoleptic children and adolescents were at high risk for poor HRQL. Depressive symptoms had a major impact on HRQL. We recommend a more thorough assessment and management of psychological health in this population.

Narcolepsy: a clinical review

Despite the classic tetrad of clinical features that typify it, narcolepsy remains much under-diagnosed, in part, because of the wide spectrum of clinical phenotypes, but also because of its insidious onset, usually in a young person. The median time to diagnosis from first symptoms remains very long, around 10 years in the UK. Conversely, in the specialist setting, it is likely over-diagnosed, largely because of failure to exclude other causes of hypersomnia. There is an over-reliance on a biological marker of the condition, the multiple sleep latency test (MSLT), which, like many tests, has a significant false-positive and false-negative rate. This review aims to discuss some of the difficulties in achieving a diagnosis, interpretation of investigations, differential diagnosis, and appropriate management of patients with narcolepsy.

History of narcolepsy at Stanford University

Although narcolepsy was first described in the late nineteenth century in Germany and France, much of the research on this disorder has been conducted at Stanford University, starting with Drs. William C. Dement and Christian Guilleminault in the 1970s. The prevalence of narcolepsy was established, and a canine model discovered. Following the finding in Japan that almost all patients with narcolepsy carry a specific HLA subtype, HLA-DR2, Hugh Mac Devitt, F. Carl Grumet, and Larry Steinman initiated immunological studies, but results were generally negative. Using the narcoleptic canines, Dr. Nishino and I established that stimulants increased wakefulness by stimulating dopaminergic transmission while antidepressants suppress cataplexy via adrenergic reuptake inhibition. A linkage study was initiated with Dr. Grumet in 1988, and after 10 years of work, the canine narcolepsy gene was cloned by in 1999 and identified as the hypocretin (orexin) receptor 2. In 1992, studying African Americans, we also found that DQ0602 rather than DR2 was a better marker for narcolepsy across all ethnic groups. In 2000, Dr. Nishino and I, in collaboration with Dr. Lammers in the Netherlands, found that hypocretin 1 levels in the cerebrospinal fluid (CSF) were undetectable in most cases, establishing hypocretin deficiency as the cause of narcolepsy. Pursuing this research, our and Dr. Siegel's group, examining postmortem brains, found that the decreased CSF hypocretin 1 was secondary to the loss the 70,000 neurons producing hypocretin in the hypothalamus. This finding revived the autoimmune hypothesis but attempts at demonstrating immune targeting of hypocretin cells failed until 2013. At this date, Dr. Elisabeth Mellins and I discovered that narcolepsy is characterized by the presence of autoreactive CD4(+) T cells to hypocretin fragments when presented by DQ0602. Following reports that narcolepsy cases were triggered by vaccinations and infections against influenza A 2009 pH1N1, a new pandemic strain that erupted in 2009, our groups also established that a small epitope of pH1N1 resembles hypocretin and is likely involved in molecular mimicry. Although much remains to be done, these achievements, establishing hypocretin deficiency as the cause of narcolepsy, demonstrating its autoimmune basis, and showing molecular mimicry between hypocretin and sequences derived from a pandemic strain of influenza, are likely to remain classics in human immunology.

Narcolepsy with cataplexy and comorbid immunopathological diseases

Evidence suggests that autoimmune diseases tend to co-occur so that patients with an autoimmune disorder are at higher risk of a second autoimmune disease. The association between allergic and autoimmune diseases is also of considerable interest. There are no reports on the association between sporadic or familial narcolepsy with cataplexy and other non-neurological immune-mediated diseases. This study reported on the comorbid immunopathological diseases associated with narcolepsy. One-hundred and fifty six narcoleptic patients with a mean age at diagnosis of 39.1 ± 17.8 years (range, 6-70 years) were assessed using the clinical history, physical and neurological examinations, sleep questionnaires, neuroimaging and human leucocyte antigen typing. Diagnosis was confirmed by polysomnography followed by a multiple sleep latency test or by measuring hypocretin-1 levels. Patients with immunopathological diseases were matched for gender and age at the onset of narcoleptic symptoms with narcoleptic patients without immunopathological diseases. Twenty-six patients (16.6%; 50% women; one familial, 25 sporadic) had one or more immunopathological diseases associated: autoimmune diseases, such as idiopathic thrombocytopenic purpura, multiple sclerosis, systemic lupus erythematosus, psoriasis, Crohn's disease, ulcerative colitis, autoimmune thyroid disease, Peyronie's disease and idiopathic recurrent facial palsy; other immunopathological diseases, like atopic dermatitis, allergic asthma and allergic rhinitis. Although not significant, the age at diagnosis of narcolepsy was 9.3 years earlier in patients with narcolepsy + immunopathological diseases. The results demonstrate that the prevalence of comorbid immunopathological diseases is high in narcolepsy, and cataplexy is significantly more severe in patients with narcolepsy + immunopathological diseases.

Narcolepsy with cataplexy after A/H1N1 vaccination – A case reported from Cuba

Narcolepsy with cataplexy is a rare sleep disorder with a neurological basis which has been recently linked to H1N1 vaccination either in children or adults. Cases from Europe, United States and Brasil were registered. Authors describe a case report of a 15 years old boy who developed narcolepsy with cataplexy after H1N1 vaccination in Havana. As far as it is concerned this is the first case reported from Cuba.

Narcolepsy in pediatric age - Experience of a tertiary pediatric hospital

Narcolepsy, a chronic disorder of the sleep–wake cycle of multifactorial etiology, is characterized by excessive daytime sleepiness, often associated with cataplexy, hypnagogic/hypnopompic hallucinations and sleep paralysis. Both early clinical suspicion and therapeutic approach are essential for promotion of cognitive development and social integration of these children. The authors present a descriptive retrospective study of a series of eight children in whom symptoms first started between 6.8 and 10.5 years of age. Diagnostic delay ranged from 4 months to 2 years. One child had H1N1 flu vaccination eight months before the clinical onset. The first multiple sleep latency test was positive in 6 of 8 cases. All cases were treated with methylphenidate, and venlafaxine was associated in 4 of them. In one case the initial therapy was exclusively behavioral. In all cases, symptomatic improvement, better school performance and social integration were achieved after therapeutic adjustment.

Cerebrospinal fluid and serum cytokine profiles in narcolepsy with cataplexy: a case-control study

Recent advances in the identification of susceptibility genes and environmental exposures provide strong support that narcolepsy-cataplexy is an immune-mediated disease. Only few serum cytokine studies with controversial results were performed in narcolepsy and none in the cerebrospinal fluid. We measured a panel of 12 cytokines by a proteomic approach in the serum of 35 patients with narcolepsy-cataplexy compared to 156 healthy controls, and in the cerebrospinal fluid of 34 patients with narcolepsy-cataplexy compared to 17 non-narcoleptic patients; and analyzed the effect of age, duration and severity of disease on the cytokine levels. After multiple adjustments we reported lower serum IL-2, IL-8, TNF-α, MCP-1 and EGF levels, and a tendency for higher IL-4 level in narcolepsy compared to controls. Significant differences were only found for IL-4 in cerebrospinal fluid, being higher in narcolepsy. Positive correlations were found in serum between IL-4, daytime sleepiness, and cataplexy frequency. The expression of some pro-inflammatory cytokines (MCP-1, VEGF, EGF, IL2, IL-1β, IFN-γ) in either serum or CSF was negatively correlated with disease severity and duration. No correlation was found for any specific cytokine in 18 of the patients with narcolepsy with peripheral and central samples collected the same day. Significant decreased pro/anti-inflammatory cytokine profiles were found at peripheral and central levels in narcolepsy, together with a T helper 2/Th1 serum cytokine secretion imbalance. To conclude, we showed some evidence for alterations in the cytokine profile in patients with narcolepsy-cataplexy compared to controls at peripheral and central levels, with the potential role of IL-4 and significant Th1/2 imbalance in the pathophysiology of narcolepsy.

Narcolepsy as an immune-mediated disease

Narcolepsy is a neurological disorder characterized by excessive daytime sleepiness, cataplexy, hypnagonic hallucinations, sleep paralysis, and disturbed nocturnal sleep patterns. This disease is secondary to the specific loss of hypothalamic hypocretin (orexin)-producing neurons in the lateral hypothalamus. An autoimmune basis for the disease has long been suspected based on its strong association with the genetic marker DQB1∗06:02, and current studies greatly support this hypothesis. Narcolepsy with hypocretin deficiency is associated with human leukocyte antigen (HLA) and T cell receptor (TCR) polymorphisms, suggesting that an autoimmune process targets a peptide unique to hypocretin-producing neurons via specific HLA-peptide-TCR interactions. This concept has gained a lot of notoriety after the increase of childhood narcolepsy in 2010 following the 2009 H1N1 pandemic (pH1N1) in China and vaccination with Pandemrix, an adjuvanted H1N1 vaccine that was used in Scandinavia. The surge of narcolepsy cases subsequent to influenza A H1N1 infection and H1N1 vaccination suggests that processes such as molecular mimicry or bystander activation might be crucial for disease development.

Depressive feelings in children with narcolepsy

OBJECTIVES

We aimed to evaluate depressive feelings and their correlations in children and adolescents with narcolepsy collected in national reference centers for narcolepsy.

METHODS

We compared clinical and sleep characteristics of patients with and without depressive symptoms evaluated on the Children's Depression Inventory (CDI).

RESULTS

Our study sample included 88 children (44 boys; 44 de novo patients) with a mean age of 11.9 ± 3.1 years at diagnosis (37.5% were aged ⩽ 10 years). Obesity was found in 59% of the sample and cataplexy was present in 80.7%. The DQB1*0602 allele was positive in 93.5% of our sample. There were 25% of children who had clinically depressive feelings (CDI>16), especially girls older than the age of 10 years. Bivariate associations indicated that depressive feelings were associated with fatigue (48%), hyperactivity (31%), insomnia (16%), and excessive daytime sleepiness (EDS) (14-24%). In the multivariate model adjusted for gender and age, only fatigue explained the variability of the depression score.

CONCLUSION

In our large cohort, high levels of depressive symptoms essentially expressed by fatigue affected 25% of children with narcolepsy. The girls older than 10 years of age were especially vulnerable. The similar prevalence of depressive feelings in treated vs never-treated patients suggests a specific need for diagnosing and managing this symptom in young patients with narcolepsy.

Etiopathogenesis and neurobiology of narcolepsy: a review

Narcolepsy is a chronic lifelong sleep disorder and it often leaves a debilitating effect on the quality of life of the sufferer. This disorder is characterized by a tetrad of excessive daytime sleepiness, cataplexy (brief loss of muscle tone following strong emotion), hypnogogic hallucinations and sleep paralysis. There are two distinct subgroups of Narcolepsy: Narcolepsy with cataplexy and Narcolepsy without cataplexy. For over 100 years, clinicians have recognised narcolepsy, but only in the last few decades have scientists been able to shed light on the true cause and pathogenesis of narcolepsy. Recent studies have shown that a loss of the hypothalamic neuropeptide Hypocretin/Orexincauses Narcolepsy with cataplexy and that an autoimmune mechanism may be responsible for this loss. Our understanding of the neurophysiologic aspect of narcolepsy has also significantly improved. The basic neural mechanisms behind sleepiness and cataplexy, the two defining symptoms of narcolepsy have started to become clearer. In this review, we have provided a detailed account of the key aspects of etiopathogenesis and neurobiology of narcolepsy, along with a critical appraisal of the more recent and interesting causal associations.We have also looked at the contributions of neuroimaging to the etiopathogenesis of Narcolepsy.

Narcolepsy and A(H1N1)pdm09 vaccination: shaping the research on the observed signal

Epidemiological data from several European countries suggested an increased risk of the chronic sleep disorder narcolepsy following vaccination with Pandemrix(™), an AS03-adjuvanted, pandemic A(H1N1)pdm09 influenza vaccine. Further research to investigate potential associations between Pandemrix™ vaccination, A(H1N1)pdm09 influenza infection and narcolepsy is required. Narcolepsy is most commonly caused by a reduction or absence of hypocretin produced by hypocretin-secreting neurons in the hypothalamus, and is tightly associated with HLA-II DQB1*06:02. Consequently, research focusing on CD4(+) T-cell responses, building on the hypothesis that for disease development, T cells specific for antigen(s) from hypocretin neurons must be activated or reactivated, is considered essential. Therefore, the following key areas of research can be identified, (1) characterization of hypothetical narcolepsy-specific auto-immune CD4(+) T cells, (2) mapping epitopes of such T cells, and (3) evaluating potential mechanisms that would enable such cells to gain access to the hypothalamus. Addressing these questions could further our understanding of the potential links between narcolepsy and A(H1N1)pdm09 vaccination and/or infection. Of particular interest is that any evidence of a mimicry-based mechanism could also explain the association between narcolepsy and A(H1N1)pdm09 influenza infection.

Greatly increased numbers of histamine cells in human narcolepsy with cataplexy

OBJECTIVE

To determine whether histamine cells are altered in human narcolepsy with cataplexy and in animal models of this disease.

METHODS

Immunohistochemistry for histidine decarboxylase (HDC) and quantitative microscopy were used to detect histamine cells in human narcoleptics, hypocretin (Hcrt) receptor-2 mutant dogs, and 3 mouse narcolepsy models: Hcrt (orexin) knockouts, ataxin-3-orexin, and doxycycline-controlled-diphtheria-toxin-A-orexin.

RESULTS

We found an average 64% increase in the number of histamine neurons in human narcolepsy with cataplexy, with no overlap between narcoleptics and controls. However, we did not see altered numbers of HDC cells in any of the animal models of narcolepsy.

INTERPRETATION

Changes in histamine cell numbers are not required for the major symptoms of narcolepsy, because all animal models have these symptoms. The histamine cell changes we saw in humans did not occur in the 4 animal models of Hcrt dysfunction we examined. Therefore, the loss of Hcrt receptor-2, of the Hcrt peptide, or of Hcrt cells is not sufficient to produce these changes. We speculate that the increased histamine cell numbers we see in human narcolepsy may instead be related to the process causing the human disorder. Although research has focused on possible antigens within the Hcrt cells that might trigger their autoimmune destruction, the present findings suggest that the triggering events of human narcolepsy may involve a proliferation of histamine-containing cells. We discuss this and other explanations of the difference between human narcoleptics and animal models of narcolepsy, including therapeutic drug use and species differences.

Genome wide analysis of narcolepsy in China implicates novel immune loci and reveals changes in association prior to versus after the 2009 H1N1 influenza pandemic

Previous studies in narcolepsy, an autoimmune disorder affecting hypocretin (orexin) neurons and recently associated with H1N1 influenza, have demonstrated significant associations with five loci. Using a well-characterized Chinese cohort, we refined known associations in TRA@ and P2RY11-DNMT1 and identified new associations in the TCR beta (TRB@; rs9648789 max P = 3.7×10⁻⁹ OR 0.77), ZNF365 (rs10995245 max P = 1.2×10⁻¹¹ OR 1.23), and IL10RB-IFNAR1 loci (rs2252931 max P = 2.2×10⁻⁹ OR 0.75). Variants in the Human Leukocyte Antigen (HLA)- DQ region were associated with age of onset (rs7744020 P = 7.9×10⁻⁹ beta −1.9 years) and varied significantly among cases with onset after the 2009 H1N1 influenza pandemic compared to previous years (rs9271117 P = 7.8×10⁻¹⁰ OR 0.57). These reflected an association of DQB1*03:01 with earlier onset and decreased DQB1*06:02 homozygosity following 2009. Our results illustrate how genetic association can change in the presence of new environmental challenges and suggest that the monitoring of genetic architecture over time may help reveal the appearance of novel triggers for autoimmune diseases.

Narcolepsy-hypocretin deficiency results from a highly specific autoimmune attack on hypocretin cells. Recent studies have established antigen presentation by specific class II proteins encoded by (HLA DQB1*06:02 and DQA1*01:02) to the cognate T cell receptor as the main disease pathway, with a role for H1N1 influenza in the triggering process. Here, we have used a large and well-characterized cohort of Chinese narcolepsy cases to examine genetic architecture not observed in European samples. We confirmed previously implicated susceptibility genes (T cell receptor alpha, P2RY11), and identify new loci (ZNF365, IL10RB-IFNAR1), most notably, variants at the beta chain of the T cell receptor. We found that one HLA variant, (DQB1*03:01), is associated with dramatically earlier disease onset (nearly 2 years). We also identified differences in HLA haplotype frequencies among cases with onset following the 2009 H1N1 influenza pandemic as compared to before the outbreak, with fewer HLA DQB1*06:02 homozygotes. This may be the first demonstration of such an effect, and suggests that the study of changes in GWAS signals over time could help identify environmental factors in other autoimmune diseases.

Increased risk of narcolepsy in children and adults after pandemic H1N1 vaccination in France

An increased incidence of narcolepsy in children was detected in Scandinavian countries where pandemic H1N1 influenza ASO3-adjuvanted vaccine was used. A campaign of vaccination against pandemic H1N1 influenza was implemented in France using both ASO3-adjuvanted and non-adjuvanted vaccines. As part of a study considering all-type narcolepsy, we investigated the association between H1N1 vaccination and narcolepsy with cataplexy in children and adults compared with matched controls; and compared the phenotype of narcolepsy with cataplexy according to exposure to the H1N1 vaccination. Patients with narcolepsy-cataplexy were included from 14 expert centres in France. Date of diagnosis constituted the index date. Validation of cases was performed by independent experts using the Brighton collaboration criteria. Up to four controls were individually matched to cases according to age, gender and geographic location. A structured telephone interview was performed to collect information on medical history, past infections and vaccinations. Eighty-five cases with narcolepsy-cataplexy were included; 23 being further excluded regarding eligibility criteria. Of the 62 eligible cases, 59 (64% males, 57.6% children) could be matched with 135 control subjects. H1N1 vaccination was associated with narcolepsy-cataplexy with an odds ratio of 6.5 (2.1-19.9) in subjects aged<18 years, and 4.7 (1.6-13.9) in those aged 18 and over. Sensitivity analyses considering date of referral for diagnosis or the date of onset of symptoms as the index date gave similar results, as did analyses focusing only on exposure to ASO3-adjuvanted vaccine. Slight differences were found when comparing cases with narcolepsy-cataplexy exposed to H1N1 vaccination (n=32; mostly AS03-adjuvanted vaccine, n=28) to non-exposed cases (n=30), including shorter delay of diagnosis and a higher number of sleep onset rapid eye movement periods for exposed cases. No difference was found regarding history of infections. In this sub-analysis, H1N1 vaccination was strongly associated with an increased risk of narcolepsy-cataplexy in both children and adults in France. Even if, as in every observational study, the possibility that some biases participated in the association cannot be completely ruled out, the associations appeared robust to sensitivity analyses, and a specific analysis focusing on ASO3-adjuvanted vaccine found similar increase.

Clinical and polysomnographic course of childhood narcolepsy with cataplexy

Our aim was to investigate the natural evolution of cataplexy and polysomnographic features in untreated children with narcolepsy with cataplexy. To this end, clinical, polysomnographic, and cataplexy-video assessments were performed at diagnosis (mean age of 10 ± 3 and disease duration of 1 ± 1 years) and after a median follow-up of 3 years from symptom onset (mean age of 12 ± 4 years) in 21 children with narcolepsy with cataplexy and hypocretin 1 deficiency (tested in 19 subjects). Video assessment was also performed in two control groups matched for age and sex at first evaluation and follow-up and was blindly scored for presence of hypotonic (negative) and active movements. Patients’ data at diagnosis and at follow-up were contrasted, compared with controls, and related with age and disease duration. At diagnosis children with narcolepsy with cataplexy showed an increase of sleep time during the 24 h; at follow-up sleep time and nocturnal sleep latency shortened, in the absence of other polysomnographic or clinical (including body mass index) changes. Hypotonic phenomena and selected facial movements decreased over time and, tested against disease duration and age, appeared as age-dependent. At onset, childhood narcolepsy with cataplexy is characterized by an abrupt increase of total sleep over the 24 h, generalized hypotonia and motor overactivity. With time, the picture of cataplexy evolves into classic presentation (i.e. brief muscle weakness episodes triggered by emotions), whereas total sleep time across the 24 h decreases, returning to more age-appropriate levels.

Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS): An Evolving Concept

Pediatric autoimmune neuropsychiatric disorders associated with streptococcus infections (PANDAS) originated from the observational work of Swedo and collaborators, who formalized their definition in 1998 in a set of operational criteria. The application of these criteria, which focuses on tics and obsessive-compulsive symptoms as core symptoms, has encountered difficulties, eventually leading to a high rate of misdiagnosis. In particular, the core feature represented by the association between newly diagnosed infections and neuropsychiatric symptom relapses in youths with this diagnosis could not be demonstrated by longitudinal studies. Exploratory studies aiming to identify clinical or cognitive features that could discriminate PANDAS from other pediatric obsessive-compulsive and tic disorders present methodological limitations, and therefore are not conclusive. Other behavioral features, in addition to obsessive-compulsive symptoms and tics, have been included in pediatric acute-onset neuropsychiatric syndromes (PANS) and childhood acute neuropsychiatric syndromes (CANS), two new concepts recently proposed in order to define a much broader clinical spectrum encompassing etiologically diverse entities. Given the uncertainties on the clinical definition of PANDAS, it is not surprising that evidence in support of a post-infectious, immune-mediated pathophysiology is also insufficient. Anti-dopamine receptor antibodies might be relevant to both Sydenham's chorea (SC)-the prototypical post-streptococcal neuropsychiatric disorder-and some rare forms of encephalitis targeting the basal ganglia specifically, but studies exploring their association with children fulfilling Swedo's criteria for PANDAS have been inconclusive. Moreover, we lack evidence in favor of the efficacy of antibiotic prophylaxis or tonsillectomy in patients fulfilling Swedo's criteria for PANDAS, whereas a response to immune-mediated treatments like intravenous immunoglobulins has been documented by one study, but needs replication in larger trials. Overall, the available evidence does not convincingly support the concept that PANDAS are a well-defined, isolated clinical entity subdued by definite pathophysiological mechanisms; larger, prospective studies are necessary to reshape the nosography and disease mechanisms of post-streptococcal acute neuropsychiatric disorders other than SC. Research is also under way to shed further light on a possible relationship between streptococcal infections, other biological and psychosocial stressors, and the complex pathobiology of chronic tic disorders.

No serological evidence of influenza A H1N1pdm09 virus infection as a contributing factor in childhood narcolepsy after Pandemrix vaccination campaign in Finland

BACKGROUND

Narcolepsy cataplexy syndrome, characterised by excessive daytime sleepiness and cataplexy, is strongly associated with a genetic marker, human leukocyte antigen (HLA) DQB1*06:02. A sudden increase in the incidence of childhood narcolepsy was observed after vaccination with AS03-adjuvanted Pandemrix influenza vaccine in Finland at the beginning of 2010. Here, we analysed whether the coinciding influenza A H1N1pdm pandemic contributed, together with the Pandemrix vaccination, to the increased incidence of childhood narcolepsy in 2010. The analysis was based on the presence or absence of antibody response against non-structural protein 1 (NS1) from H1N1pdm09 virus, which was not a component of Pandemrix vaccine.

METHODS

Non-structural (NS) 1 proteins from recombinant influenza A/Udorn/72 (H3N2) and influenza A/Finland/554/09 (H1N1pdm09) viruses were purified and used in Western blot analysis to determine specific antibody responses in human sera. The sera were obtained from 45 patients who fell ill with narcolepsy after vaccination with AS03-adjuvanted Pandemrix at the end of 2009, and from controls.

FINDINGS

Based on quantitative Western blot analysis, only two of the 45 (4.4%) Pandemrix-vaccinated narcoleptic patients showed specific antibody response against the NS1 protein from the H1N1pdm09 virus, indicating past infection with the H1N1pdm09 virus. Instead, paired serum samples from patients, who suffered from a laboratory confirmed H1N1pdm09 infection, showed high levels or diagnostic rises (96%) in H1N1pdm virus NS1-specific antibodies and very high cross-reactivity to H3N2 subtype influenza A virus NS1 protein.

CONCLUSION

Based on our findings, it is unlikely that H1N1pdm09 virus infection contributed to a sudden increase in the incidence of childhood narcolepsy observed in Finland in 2010 after AS03-adjuvanted Pandemrix vaccination.

Electroencephalogram paroxysmal θ characterizes cataplexy in mice and children

Astute control of brain activity states is critical for adaptive behaviours and survival. In mammals and birds, electroencephalographic recordings reveal alternating states of wakefulness, slow wave sleep and paradoxical sleep (or rapid eye movement sleep). This control is profoundly impaired in narcolepsy with cataplexy, a disease resulting from the loss of orexin/hypocretin neurotransmitter signalling in the brain. Narcolepsy with cataplexy is characterized by irresistible bouts of sleep during the day, sleep fragmentation during the night and episodes of cataplexy, a sudden loss of muscle tone while awake and experiencing emotions. The neural mechanisms underlying cataplexy are unknown, but commonly thought to involve those of rapid eye movement-sleep atonia, and cataplexy typically is considered as a rapid eye movement sleep disorder. Here we reassess cataplexy in hypocretin (Hcrt, also known as orexin) gene knockout mice. Using a novel video/electroencephalogram double-blind scoring method, we show that cataplexy is not a state per se, as believed previously, but a dynamic, multi-phased process involving a reproducible progression of states. A knockout-specific state and a stereotypical paroxysmal event were introduced to account for signals and electroencephalogram spectral characteristics not seen in wild-type littermates. Cataplexy almost invariably started with a brief phase of wake-like electroencephalogram, followed by a phase featuring high-amplitude irregular theta oscillations, defining an activity profile distinct from paradoxical sleep, referred to as cataplexy-associated state and in the course of which 1.5-2 s high-amplitude, highly regular, hypersynchronous paroxysmal theta bursts (∼7 Hz) occurred. In contrast to cataplexy onset, exit from cataplexy did not show a predictable sequence of activities. Altogether, these data contradict the hypothesis that cataplexy is a state similar to paradoxical sleep, even if long cataplexies may evolve into paradoxical sleep. Although not exclusive to overt cataplexy, cataplexy-associated state and hypersynchronous paroxysmal theta activities are highly enriched during cataplexy in hypocretin/orexin knockout mice. Their occurrence in an independent narcolepsy mouse model, the orexin/ataxin 3 transgenic mouse, undergoing loss of orexin neurons, was confirmed. Importantly, we document for the first time similar paroxysmal theta hypersynchronies (∼4 Hz) during cataplexy in narcoleptic children. Lastly, we show by deep recordings in mice that the cataplexy-associated state and hypersynchronous paroxysmal theta activities are independent of hippocampal theta and involve the frontal cortex. Cataplexy hypersynchronous paroxysmal theta bursts may represent medial prefrontal activity, associated in humans and rodents with reward-driven motor impulse, planning and conflict monitoring.

The autoimmune basis of narcolepsy

Narcolepsy is a neurological disorder characterized by excessive daytime sleepiness, cataplexy, hypnagonic hallucinations, sleep paralysis, and disturbed nocturnal sleep patterns. Narcolepsy is caused by the loss of hypocretin (orexin)-producing neurons in the lateral hypothalamus. Evidence, such as a strong association with HLA DQB1*06:02, strongly suggests an autoimmune basis targeting hypocretin neurons. Genome-wide association studies have strengthened the association between narcolepsy and immune system gene polymorphisms, including the identification of polymorphisms in the T cell receptor alpha locus, TNFSF4 (also called OX40L), Cathepsin H (CTSH) the purinergic receptor P2RY11, and the DNA methyltransferase DNMT1. Recently, attention has been raised regarding a spike in cases of childhood narcolepsy in 2010 following the 2009 H1N1 pandemic (pH1N1) in China and vaccination with Pandemrix, an adjuvanted H1N1 vaccine that was used in Europe. How the immune system may be involved in disease initiation and/or progression remains a challenge to researchers. Potential immunological pathways that could lead to the specific elimination of hypocretin producing neurons include molecular mimicry or bystander activation, and are likely a combination of genetic and environmental factors, such as upper airway infections.

Impact of obesity in children with narcolepsy

AIMS

To evaluate the impact of obesity on clinical and sleep characteristics in a population of narcoleptic children.

METHODS

Data from the children diagnosed with idiopathic narcolepsy in the National Reference Centers for Narcolepsy were collected between 2008 and 2011. Clinical and electrophysiological characteristics were compared between obese (body mass index [BMI] greater than P97) and nonobese children.

RESULTS

The 117 children (65 boys, 59 de novo patients) had a mean age of 11.6 ± 3.1 years on diagnosis. Cataplexy was present in 81%, DQB1*0602 in 91%. Mean BMI was 23.2 ± 5.2 kg/m(2) and BMI z-score was 2.9 ± 2.6. Obesity was found in 60% with a similar prevalence in treated versus de novo patients and in patients with and without cataplexy. Sleepiness and cataplexy started earlier in obese children. Obese narcoleptic children had lower sleep efficiency, higher apnea hypopnea index and respiratory arousals index (RAI) than nonobese children. BMI z-score was positively correlated with RAI. Obese children were more tired and missed more often school than nonobese children.

CONCLUSION

Obesity affects more than 50% of narcoleptic children, mostly younger at disease onset, and has a deleterious impact on sleep quality as well as on school attendance.

Narcolepsy-cataplexy: is streptococcal infection a trigger?

Narcolepsy-cataplexy is an uncommon sleep disorder which may present in childhood. We report a case of an 8-year-old presenting with narcolepsy-cataplexy following a streptococcal infection. Autoimmune etiology for narcolepsy has been suggested. In our patient increased anti-streptolysin O and anti-DNAse B titers were noted. As suggested by recent cases, the streptococcal infection was likely a trigger for narcolepsy onset in this genetically predisposed child. The patient was initially diagnosed as having Sydenham chorea due to motor movements. However, these transient movements may be due to the narcolepsy onset. Narcolepsy in childhood may present with atypical symptoms; it might be difficult to obtain accurate history and can be misdiagnosed as in the reported case. A high index of clinical suspicion is needed to diagnose these patients.

Genetic association, seasonal infections and autoimmune basis of narcolepsy

In recent years, a growing number of potential autoimmune disorders affecting neurons in the central nervous system have been identified, including narcolepsy. Narcolepsy is a lifelong sleep disorder characterized by excessive daytime sleepiness with irresistible sleep attacks, cataplexy (sudden bilateral loss of muscle tone), hypnagogic hallucinations, and abnormalities of Rapid Eye Movement sleep. Narcolepsy is generally a sporadic disorder and is caused by the loss of hypocretin (orexin)-producing neurons in the hypothalamus region of the brain. Studies have established that more than 90% of patients have a genetic association with HLA DQB1*06:02. Genome-wide association analysis shows a strong association between narcolepsy and polymorphisms in the TCRα locus and weaker associations within TNFSF4 (also called OX40L), Cathepsin H and the P2RY11-DNMT1 (purinergic receptor subtype P2Y11 to DNMT1, a DNA methytransferase) loci, suggesting an autoimmune basis. Mutations in DNMT1 have also been reported to cause narcolepsy in association with a complex neurological syndrome, suggesting the importance of DNA methylation in the pathology. More recently, narcolepsy was identified in association with seasonal streptococcus, H1N1 infections and following AS03-adjuvanted pH1N1 influenza vaccination in Northern Europe. Potential immunological pathways responsible for the loss of hypocretin producing neurons in these cases may be molecular mimicry or bystander activation. Specific autoantibodies or T cells cross-reactive with hypocretin neurons have not yet been identified, however, thus narcolepsy does not meet Witebsky's criteria for an autoimmune disease. As the brain is not an easily accessible organ, mechanisms of disease initiation and progression remain a challenge to researchers.

Pediatric narcolepsy: clinical and therapeutical approaches

Narcolepsy occurs during childhood in combination with cataplexy in one-third of the subjects. Symptoms may develop rapidly over a few weeks or months, with excessive daytime sleepiness and cataplexy being the most dramatic and observable symptoms. It can be secondary to brain tumors or several rare diseases, but in most cases narcolepsy with or without cataplexy is a primary condition, better explained by the selective loss of hypocretin neurons in posterolateral hypothalamus. A specific HLA allele, HLA-DQB1*0602, is involved and the disease is thought to be autoimmune. Tribbles 2-specific antibodies have been identified. Recent medications have greatly improved the symptoms and wellbeing of young patients. However, these treatments are delivered off-label in the pediatric population. There is an absolute necessity for well-conducted clinical trials in order to improve treatment in children and adolescents with narcolepsy and to evaluate clinical efficacy and good tolerance of medications. Nonpharmacological approaches are certainly helpful and should be promoted systematically, especially in very young children. Narcolepsy of recent onset in children or adolescents should be considered a therapeutic emergency, even though immunotherapy is still controversial.

Hypocretin deficiency develops during onset of human narcolepsy with cataplexy

STUDY OBJECTIVES

Although hypothesized through animal studies, a temporal and causal association between hypocretin deficiency and the onset of narcolepsy with cataplexy (NC) has never been proven in humans.

SETTING

Paediatric Department, Blekinge Hospital, Sweden, and Danish Center for Sleep Medicine, Glostrup Hospital, Denmark.

PATIENT AND RESULTS

Two weeks after his second Pandemrix-vaccination, a 10 year old HLA-DQB1*0602-positive boy developed NC. The CSF hypocretin-1 level was 10 pg/ml. However, CSF saved from a pre-narcolepsy episode of Lyme disease revealed a normal hypocretin-1 level (318 pg/ml).

CONCLUSIONS

We confirm that hypocretin deficiency develops in parallel to the onset of human narcolepsy with cataplexy.

Control of sleep and wakefulness in health and disease

Sleep and wake are actively promoted states of consciousness that are dependent on a network of state-modulating neurons arising from both the brain stem and hypothalamus. This network helps to coordinate the occurrence of a sleep state in billions of cortical neurons. In many neurological diseases, there is a specific disruption to one of the components of this network. Under conditions of such disruptions, we often gain an improved understanding of the underlying function of the specific component under nonpathological conditions. The loss or dysfunction of one of the hypothalamic or brain stem regions that are responsible for promotion of sleep or wake can lead to disruptions in sleep and wake states that are often subtle, but sometime quite pronounced and of significant medical importance. By understanding the neural substrate and its pathophysiology, one can more appropriately target therapies that might help the specific sleep disruption. This chapter reviews what is currently understood about the neurobiological underpinnings of sleep and wake regulation and how various pathologies evoke changes in these regulatory mechanisms.

The incidence of narcolepsy in Europe: before, during, and after the influenza A(H1N1)pdm09 pandemic and vaccination campaigns

BACKGROUND

In August 2010 reports of a possible association between exposure to AS03 adjuvanted pandemic A(H1N1)pdm09 vaccine and occurrence of narcolepsy in children and adolescents emerged in Sweden and Finland. In response to this signal, the background rates of narcolepsy in Europe were assessed to rapidly provide information for signal verification.

METHODS

We used a dynamic retrospective cohort study to assess the narcolepsy diagnosis rates during the period 2000-2010 using large linked automated health care databases in six countries: Denmark, Finland, Italy, the Netherlands, Sweden and the United Kingdom.

RESULTS

Overall, 2608 narcolepsy cases were identified in almost 280 million person years (PY) of follow up. The pooled incidence rate was 0.93 (95% CI: 0. 90-0.97) per 100,000 PY. There were peaks between 15 and 30 year of age (women>men) and around 60 years of age. In the age group 5-19 years olds rates were increased after the start of pandemic vaccination compared to the period before the start of campaigns, with rate ratios (RR) of 1.9 (95% CI: 1.1-3.1) in Denmark, 6.4 (95% CI: 4.2-9.7) in Finland and 7.5 (95% CI: 5.2-10.7) in Sweden. Cases verification in the Netherlands had a significant effect on the pattern of incidence over time.

CONCLUSIONS

The results of this incidence study provided useful information for signal verification on a population level. The safety signal of increased narcolepsy diagnoses following the start of the pandemic vaccination campaign as observed in Sweden and Finland could be observed with this approach. An increase in narcolepsy diagnoses was not observed in other countries, where vaccination coverage was low in the affected age group, or did not follow influenza A(H1N1)pdm09 vaccination. Patient level analyses in these countries are being conducted to verify the signal in more detail.

Pediatric sleep pharmacology

This article reviews common sleep disorders in children and pharmacologic options for them. Discussions of pediatric sleep pharmacology typically focus on treatment of insomnia. Although insomnia is a major concern in this population, other conditions of concern in children are presented, such as narcolepsy, parasomnias, restless legs syndrome, and sleep apnea.

HLA-DQ association and allele competition in Chinese narcolepsy

In Japanese, Koreans and Caucasians, narcolepsy/hypocretin deficiency is tightly associated with the DRB1*15:01-DQA1*01:02-DQB1*06:02 haplotype. Studies in African-Americans suggest a primary effect of DQB1*06:02, but this observation has been difficult to confirm in other populations because of high linkage disequilibrium between DRB1*15:01/3 and DQB1*06:02 in most populations. In this study, we studied human leucocyte antigen (HLA) class II in 202 Chinese narcolepsy patients (11% from South China) and found all patients to be DQB1*06:02 positive. Comparing cases with 103 unselected controls, and 110 and 79 controls selected for the presence of DQB1*06:02 and DRB1*15:01, we found that the presence of DQB1*06:02 and not DRB1*15:01 was associated with narcolepsy. In particular, Southern Chinese haplotypes such as the DRB1*15:01-DQA1*01:02-DQB1*06:01 and DRB1*15:01-DQA1*01:02-DQB1*05 were not associated with narcolepsy. As reported in Japanese, Koreans, African-Americans and Caucasians, additional protective effects of DQA1*01 (non-DQA1*01:02) and susceptibility effects of DQB1*03:01 were observed. These results illustrate the extraordinary conservation of HLA class II effects in narcolepsy across populations and show that DRB1*15:01 has no effect on narcolepsy susceptibility in the absence of DQB1*06:02. The results are also in line with a previously proposed 'HLA-DQ allelic competition model' that involves competition between non-DQA1*01:02, non-DQB1*06:02 'competent' (able to dimerize together) DQ1 alleles and the major DQα*01:02/ DQβ*06:02 narcolepsy heterodimer to reduce susceptibility.

Control of sleep and wakefulness

This review summarizes the brain mechanisms controlling sleep and wakefulness. Wakefulness promoting systems cause low-voltage, fast activity in the electroencephalogram (EEG). Multiple interacting neurotransmitter systems in the brain stem, hypothalamus, and basal forebrain converge onto common effector systems in the thalamus and cortex. Sleep results from the inhibition of wake-promoting systems by homeostatic sleep factors such as adenosine and nitric oxide and GABAergic neurons in the preoptic area of the hypothalamus, resulting in large-amplitude, slow EEG oscillations. Local, activity-dependent factors modulate the amplitude and frequency of cortical slow oscillations. Non-rapid-eye-movement (NREM) sleep results in conservation of brain energy and facilitates memory consolidation through the modulation of synaptic weights. Rapid-eye-movement (REM) sleep results from the interaction of brain stem cholinergic, aminergic, and GABAergic neurons which control the activity of glutamatergic reticular formation neurons leading to REM sleep phenomena such as muscle atonia, REMs, dreaming, and cortical activation. Strong activation of limbic regions during REM sleep suggests a role in regulation of emotion. Genetic studies suggest that brain mechanisms controlling waking and NREM sleep are strongly conserved throughout evolution, underscoring their enormous importance for brain function. Sleep disruption interferes with the normal restorative functions of NREM and REM sleep, resulting in disruptions of breathing and cardiovascular function, changes in emotional reactivity, and cognitive impairments in attention, memory, and decision making.