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Narcolepsy with cataplexy is a sleep disorder caused by deficiency in the hypothalamic neuropeptide hypocretin/orexin (HCRT), unanimously believed to result from autoimmune destruction of hypocretin-producing neurons. HCRT deficiency can also occur in secondary forms of narcolepsy and be only temporary, suggesting it can occur without irreversible neuronal loss. The recent discovery that narcolepsy patients also show loss of hypothalamic (corticotropin-releasing hormone) CRH-producing neurons suggests that other mechanisms than cell-specific autoimmune attack, are involved. Here, we identify the HCRT cell-colocalized neuropeptide QRFP as the best marker of HCRT neurons. We show that if HCRT neurons are ablated in mice, in addition to Hcrt, Qrfp transcript is also lost in the lateral hypothalamus, while in mice where only the Hcrt gene is inactivated Qrfp is unchanged. Similarly, postmortem hypothalamic tissues of narcolepsy patients show preserved QRFP expression, suggesting the neurons are present but fail to actively produce HCRT. We show that the promoter of the HCRT gene of patients exhibits hypermethylation at a methylation-sensitive and evolutionary-conserved PAX5:ETS1 transcription factor-binding site, suggesting the gene is subject to transcriptional silencing. We show also that in addition to HCRT, CRH and Dynorphin ( PDYN ) gene promoters, exhibit hypermethylation in the hypothalamus of patients. Altogether, we propose that HCRT , PDYN , and CRH are epigenetically silenced by a hypothalamic assault (inflammation) in narcolepsy patients, without concurrent cell death. Since methylation is reversible, our findings open the prospect of reversing or curing narcolepsy.

Background and ObjectivesRecent studies fueled doubts as to whether all currently defined central disorders of hypersomnolence are stable entities, especially narcolepsy type 2 and idiopathic hypersomnia. New reliable biomarkers are needed, and the question arises of whether current diagnostic criteria of hypersomnolence disorders should be reassessed. The main aim of this data-driven observational study was to see whether data-driven algorithms would segregate narcolepsy type 1 and identify more reliable subgrouping of individuals without cataplexy with new clinical biomarkers.MethodsWe used agglomerative hierarchical clustering, an unsupervised machine learning algorithm, to identify distinct hypersomnolence clusters in the large-scale European Narcolepsy Network database. We included 97 variables, covering all aspects of central hypersomnolence disorders such as symptoms, demographics, objective and subjective sleep measures, and laboratory biomarkers. We specifically focused on subgrouping of patients without cataplexy. The number of clusters was chosen to be the minimal number for which patients without cataplexy were put in distinct groups.ResultsWe included 1,078 unmedicated adolescents and adults. Seven clusters were identified, of which 4 clusters included predominantly individuals with cataplexy. The 2 most distinct clusters consisted of 158 and 157 patients, were dominated by those without cataplexy, and among other variables, significantly differed in presence of sleep drunkenness, subjective difficulty awakening, and weekend-week sleep length difference. Patients formally diagnosed as having narcolepsy type 2 and idiopathic hypersomnia were evenly mixed in these 2 clusters.DiscussionUsing a data-driven approach in the largest study on central disorders of hypersomnolence to date, our study identified distinct patient subgroups within the central disorders of hypersomnolence population. Our results contest inclusion of sleep-onset REM periods in diagnostic criteria for people without cataplexy and provide promising new variables for reliable diagnostic categories that better resemble different patient phenotypes. Cluster-guided classification will result in a more solid hypersomnolence classification system that is less vulnerable to instability of single features.

BackgroundThe short-term and long-term outcome of inflammatory neuropsychiatric SLE (NPSLE) with immunosuppressive treatment is largely unknown. We used clinical data from our tertiary referral centre for NPSLE to investigate the type of inflammatory NPSLE manifestations, type of immunosuppressive treatment prescribed for these manifestations and clinical outcomes.MethodsAll patients with SLE visiting the Leiden University Medical Centre NPSLE clinic between 2007 and 2021 receiving immunosuppressive therapy for neuropsychiatric symptoms were included. Clinical, immunological and radiological information was collected in as standardised way during a 1-day multidisciplinary assessment. In a multidisciplinary consensus meeting, the presence of NPSLE and the type of NPSLE manifestations and treatment were determined. For this study, short-term (0–6 months) and long-term outcomes (7–24 months) of the NP symptoms were assessed by two independent readers and scored on a 7-point Likert scale, ranging from death to resolved.ResultsIn total, 95 out of 398 (24%) patients visiting the NPSLE clinic between 2007 and 2021 received any form of immunosuppressive treatment for 101 separate NPSLE events. The most common NP manifestation was cognitive dysfunction (50%) as identified by formal cognitive assessment, often present in combination with other NPSLE manifestations. Treatment modalities were induction (24%), induction and maintenance (73%) and other therapy (3%). The treatments mostly consisted of (combinations of) prednisone (97%), methylprednisolone (53%), azathioprine (generally 2 mg/kg daily) (49%) and cyclophosphamide (generally induction 750 mg/m2every 4 weeks for 24 weeks or 500mg biweekly for 12 weeks) (42%). Short-term outcome showed improvement on the Likert scale in 73% (improved: 22%, much improved: 29%, resolved: 22%), no change in 21% and worsening in 6% of patients. Long-term outcome was available for 78 out of 101 events and showed improvement in 70% (improved: 14%, much improved: 28%, resolved: 28%), no change in 17%, worsening in 10% and death in 3% of patients (none directly NPSLE-related).ConclusionThe outcome of inflammatory NPSLE after immunosuppressive treatment is generally good, with improvement of neuropsychiatric symptoms occuring in approximately 70% of events.

Introduction Current prophylactic drugs for cluster headache are associated with limited efficacy, serious side effects and poor tolerability. Greater occipital nerve injection (GON-injection) has been proven effective and safe as a single, one-time injection in episodic (ECH), and to a lesser extent, chronic cluster headache (CCH). We aim to analyse the effectiveness and safety of repeated GON-injections in medically intractable chronic cluster headache (MICCH). Methods Clinical data of all cluster headache patients who had received at least one GON-injection between 2014 and 2018 in our tertiary headache centre were retrieved from patients’ medical records. Clinical history was taken as part of routine care shortly before and 6 weeks after GON-injection. Results We identified 47 MICCH patients (79 injections), and compared results with 22 non-MI CCH patients (30 injections) and 50 ECH patients (63 injections). Nineteen MICCH patients received repeated injections (32 in total, range 2–8). Rates of clinical relevant improvement to a first injection were similar in all groups (MICCH: 60%, non-MICCH 73%, ECH 76%; attack freedom: MICCH: 30%, non-MICCH 32%, ECH 43%). Furthermore, no difference in response to the first and second injection was shown between groups (all p > 0.29). Median effect duration in MICCH was 6 weeks (IQR 2.8–12 weeks). Side effects were only mild and local. Conclusion In this retrospective analysis, first and repeated GON-injections were well-tolerated and equally effective in MICCH as in non-MICCH, and ECH.

Background The pathophysiology of cluster headache and how cluster episodes are triggered, are still poorly understood. Recurrent inflammation of the trigeminovascular system has been hypothesized. It was noted that some long-term attack-free cluster headache patients suddenly developed a new cluster episode shortly after COVID-19 vaccination. Methods Cases are described from patients with cluster headache who reported a new cluster episode within days after COVID-19 vaccination. All cases were seen in a tertiary university referral center and a general hospital in the Netherlands between March 2021 and December 2021, when the first COVID-19 vaccinations were carried out in The Netherlands. Clinical characteristics of the previous and new cluster episodes, and time between the onset of a new cluster episode and a previous COVID-19 vaccination were reported. Results We report seven patients with cluster headache, who had been attack-free for a long time, in whom a new cluster episode occurred within a few days after a COVID-19 vaccination. Interpretation COVID-19 vaccinations may trigger new cluster episodes in patients with cluster headache, possibly by activating a pro-inflammatory state of the trigeminocervical complex. COVID-19 vaccinations may also exacerbate other neuroinflammatory conditions.

Study Objectives The most sensitive and specific investigative method for the diagnosis of narcolepsy type 1 (NT1) is the determination of hypocretin-1 (orexin-A) deficiency (≤110 pg/mL) in cerebrospinal fluid using a radioimmunoassay (RIA). We aimed to assess the reliability of the Phoenix Pharmaceuticals hypocretin-1 RIA, by determining the lower limit of quantification (LLOQ), the variability around the cutoff of 110 pg/mL, and the inter- and intra-assay variability. Methods Raw data of 80 consecutive hypocretin-1 RIAs were used to estimate the intra- and inter-assay coefficient of variation (CV). The LLOQ was established and defined as the lowest converted concentration with a CV Results The mean intra-assay CV was 4.7%, while the unconverted inter-assay CV was 28.3% (18.5% excluding 2 outliers) and 7.5% when converted to international values. The LLOQ was determined as 27.9 pg/mL. The intra-assay CV of RIAs with lower specific radioactive activity showed a median of 5.6% (n = 41, range 1.6%–17.0%), which was significantly higher than in RIAs with higher specific activity (n = 36; median 3.2%, range 0.4%–11.6%, p = .013). The CV around the 110 pg/mL cutoff was Conclusions Hypocretin-1 RIAs should always be harmonized using standard reference material. The specific activity of an RIA has a significant impact on its reliability, because of the decay of 125I radioactivity. Values around the hypocretin-1 cut-off can reliably be measured. Hypocretin-1 concentrations below 28 pg/mL should be reported as “undetectable” when measured with the Phoenix Pharmaceuticals RIA. Clinical Trial Information This study is not registered in a clinical trial register, as it has a retrospective database design

Core body and skin temperatures are intimately linked to sleep and alertness. The distal-to-proximal skin temperature gradient has been described as a good physiological predictor for sleep onset. Increased ear skin temperature is often caused by increased blood flow reflected in redness, which is commonly noticed in people who are sleepy, especially anecdotally in children. Nonetheless, no prior study investigated the possible relation between sleepiness and ear skin temperature as a separate measurement. We assessed the relation between ear skin temperature and sleepiness in patients undergoing regular electroencephalographic examinations, because of suspicion of epilepsy, both without and after sleep deprivation. Subjective sleepiness was measured using the Stanford Sleepiness Scale, and objective sleepiness by determining sleep onset with electroencephalography. Distal, proximal and ear skin temperature were measured repeatedly using wireless measurement devices (iButtons). Forty-four adult patients were included. Ear skin temperature correlates weakly with distal skin temperature (r = 0.174, p < 0.001) and distal-to-proximal gradient (r = 0.160, p < 0.001), but not with proximal skin temperature (r = -0.001, p = 0.975). Ear skin temperature increased significantly in a subgroup of 13 patients, between 5 and 1 min before sleep onset (p = 0.002; eta(2) = 0.059), even though this increase was also associated with supine posture. iButtons is a valid method to measure ear skin temperature, which appears to function partly like a distal and partly like a proximal skin temperature measurement. Change in ear skin temperature is associated with sleep onset and supine posture.

Study Objectives To review the Maintenance of Wakefulness Test (MWT) as assessment of daytime sleepiness in the evaluation of treatment effects and driving fitness in central disorders of hypersomnolence (CDH). Methods We performed a scoping review of studies using the MWT in patients with CDH (i.e. narcolepsy types 1 and 2, and idiopathic hypersomnia). N = 20 articles were included, comprising 683 patients and 129 controls. MWT effect sizes were compared to the Clinical Global Impression (GCI) scale and the Epworth Sleepiness Scale (ESS). MWT sleep latency was correlated to objective driving performances. The role of motivation was evaluated by comparing MWTs of treatment studies (low motivation) to driving fitness studies (high motivation to stay awake). Healthy controls were compared to norm values. Results MWT and CGI were both impacted by the same treatment; however, the MWT has higher effect sizes and was more sensitive to measure these effects. The MWT correlated fairly to moderately (ρ = −0.26 to −0.56; p ≤ .05) to objective driving performance. Motivation played a major role on MWT sleep latencies (d = 0.76 to 1.43; p ≤ .001). Current norm values may not be valid, as sleep latency may be impacted by age. Conclusions The MWTs applicability to measure treatment effects in CDH was confirmed, but age-adjusted norm values are needed. For a more complete evaluation of EDS it should be combined with subjective measures. Its reliability for driving fitness evaluation is insufficient, and motivation plays a major role. To predict or monitor driving performance in CDH, valid and easy methods should be developed.

Rory C Monahan,1 Hannelore JL Beaart,1 Rolf Fronczek,2,3 Gisela M Terwindt,2 Liesbeth JJ Beaart-van de Voorde,1 Jeroen de Bresser,4 Margreet Kloppenburg,1,5 Nic JA van der Wee,6 Tom WJ Huizinga,1 Gerda M Steup-Beekman1,7 1Department of Rheumatology, Leiden University Medical Center (LUMC), Leiden, the Netherlands; 2Department of Neurology, LUMC, Leiden, the Netherlands; 3Sleep-Wake Center SEIN, Heemstede, the Netherlands; 4Department of Radiology, LUMC, Leiden, the Netherlands; 5Department of Clinical Epidemiology, LUMC, Leiden, the Netherlands; 6Department of Psychiatry, LUMC, Leiden, the Netherlands; 7Department of Rheumatology, Haaglanden Medical Center, The Hague, the NetherlandsCorrespondence: Rory C MonahanDepartment of Rheumatology, Leiden University Medical Center (LUMC), Leiden 2333 ZA, the NetherlandsTel +3171-5265762Fax +3171-5266752Email r.c.monahan@lumc.nlPurpose: To evaluate the use of immunosuppressive treatment, clinical outcome and diagnostic strategy in patients with systemic lupus erythematosus (SLE) presenting with clinical features of transverse myelitis (TM), but normal MRI of the spinal cord (sMRI) and normal cerebrospinal fluid (CSF) assessment, and to suggest a clinical guideline.Patients and Methods: All patients with SLE and clinical features compatible with (sub)acute TM visiting the NPSLE clinic of the LUMC between 2007 and 2020 were included. Information on baseline characteristics, investigations, treatment and outcomes was collected from electronic medical records. In addition, a systematic review of individual participant data was performed up to April 2020 in PubMed, Embase and Web of Science, identifying all patients with TM, SLE and sMRI assessment. Data regarding sMRI, CSF analysis, treatment and outcome were extracted, and outcome was compared between patients with normal sMRI and CSF (sMRI-/CSF-) and patients with abnormalities.Results: Twelve SLE patients with a clinical diagnosis of TM were identified: four sMRI-/CSF- and one sMRI- with CSF not available. All patients received immunosuppressive treatment, but outcome in sMRI-/CSF- patients was worse: no recovery (n=1) or partial recovery (n=3) compared to partial recovery (n=4) and (nearly) complete recovery (n=3) in MRI+ patients. The systematic literature review yielded 146 articles eligible for inclusion, 90% case reports. A total of 427 SLE patients with TM were identified, of which only four cases were sMRI-/CSF- (1%), showing no improvement (n=1), partial improvement (n=2) and complete recovery (n=1) after immunosuppressive treatment.Conclusion: Outcome in SLE patients presenting with clinically suspected TM with normal sMRI and CSF is less favorable, despite treatment with immunosuppressive therapy. Taking a functional neurological disorder into consideration may be helpful in order to start other therapeutic strategies. We suggest prescribing immunosuppressive treatment for a restricted period of time to evaluate its effect in cases where a functional disorder initially is considered unlikely.Keywords: lupus, neuropsychiatric, transverse myelitis, MRI, CSF

BackgroundAlthough autoantibodies are an important hallmark of systemic lupus erythematosus (SLE), most are not specific for SLE or any of its clinical manifestations. Autoantibodies against post-translationally modified (PTM) proteins have been studied extensively in rheumatoid arthritis and associate with disease progression. While PTMs have also been detected in patients with SLE, studies on anti-PTM antibodies remain scarce. We studied the presence of anti-PTM antibodies in SLE and neuropsychiatric SLE (NPSLE), a manifestation that lacks serological markers.MethodsIgG antibody responses against six PTMs (malondialdehyde–acetaldehyde adducts (MAA), advanced glycation end-products (AGE), carbamylation (CarP), citrullination, acetylation and nitration) were tested using ELISA in sera of 349 patients with SLE (mean age 44±13 years; 87% female) and compared with 108 healthy controls. Levels and positivity were correlated with clinical features and SLE manifestations.ResultsAnti-MAA, anti-AGE and anti-CarP antibodies were more prevalent in SLE compared with controls (MAA: 29% vs 3%, AGE: 18% vs 4%, CarP: 14% vs 5%, all p≤0.0001). Anti-MAA and anti-AGE antibodies correlated with clinical manifestations and serological inflammatory markers. Patients with major NPSLE showed higher positivity of anti-MAA (39% vs 24%, p=0.01) and anti-CarP antibodies (20% vs 11%, p=0.04) than patients without major NPSLE. In addition, anti-PTM antibody levels correlated with brain volumes, an objective measure of nervous system involvement.ConclusionsIn our NPSLE cohort, a subset of patients with SLE have anti-PTM antibodies against MAA, AGE and CarP modified proteins. Interestingly, anti-MAA and anti-CarP were more prevalent in NPSLE, a manifestation for which no biomarkers exist.

Background and Objectives Increased sensitivity to light and patterns is typically associated with migraine, but has also been anecdotally reported in cluster headache, leading to diagnostic confusion. We wanted to assess whether visual sensitivity is increased ictally and interictally in cluster headache. Methods We used the validated Leiden Visual Sensitivity Scale (L-VISS) questionnaire (range 0-36 points) to measure visual sensitivity in people with episodic or chronic cluster headache: (i) during attacks; (ii) in-between attacks; and in episodic cluster headache (iii) in-between bouts. The L-VISS scores were compared with the L-VISS scores obtained in a previous study in healthy controls and participants with migraine. Results Mean L-VISS scores were higher for: (i) ictal vs interictal cluster headache (episodic cluster headache: 11.9 ± 8.0 vs. 5.2 ± 5.5, chronic cluster headache: 13.7 ± 8.4 vs 5.6 ± 4.8; p Conclusion Cluster headache is associated with increased ictal and interictal visual sensitivity. In contrast to migraine, this is mostly unilateral and ipsilateral on the side of the ictal pain.

Study Objectives The diagnosis of narcolepsy type 1 (NT1) is based upon the presence of cataplexy and/or a cerebrospinal fluid (CSF) hypocretin-1/orexin-A level ≤ 110 pg/mL. We determined the clinical and diagnostic characteristics of patients with intermediate hypocretin-1 levels (111–200 pg/mL) and the diagnostic value of cataplexy characteristics in individuals with central disorders of hypersomnolence. Methods Retrospective cross-sectional study of 355 people with known CSF hypocretin-1 levels who visited specialized Sleep-Wake Centers in the Netherlands. For n = 271, we had full data on cataplexy type (“typical” or “atypical” cataplexy). Results Compared to those with normal hypocretin-1 levels (>200 pg/mL), a higher percentage of individuals with intermediate hypocretin-1 levels had typical cataplexy (75% or 12/16 vs 9% or 8/88, p Conclusion Individuals with intermediate hypocretin-1 levels or typical cataplexy more often have outcomes fitting the PSG and MSLT criteria for narcolepsy than those with normal levels or atypical cataplexy. In addition, typical cataplexy has a much stronger association with hypocretin-1 deficiency than atypical cataplexy. We suggest increasing the NT1 diagnostic hypocretin-1 cutoff and adding the presence of clearly defined typical cataplexy to the diagnostic criteria of NT1. Clinical trial information: This study is not registered in a clinical trial register, as it has a retrospective database design.

Objective We aimed to evaluate all-cause and cause-specific mortality in patients with systemic lupus erythematosus (SLE) and neuropsychiatric (NP) symptoms in the Netherlands between 2007–2018. Methods Patients visiting the tertiary referral NPSLE clinic of the Leiden University Medical Center were included. NP symptoms were attributed to SLE requiring treatment (major NPSLE) or to other and mild causes (minor/non-NPSLE). Municipal registries were checked for current status (alive/deceased). Standardized mortality ratios (SMRs) and 95% confidence intervals (CI) were calculated using data from the Dutch population. Rate ratio (RR) and 95% CI were calculated using direct standardization to compare mortality between major NPSLE and minor/non-NPSLE. Results 351 patients were included and 149 patients were classified as major NPSLE (42.5%). Compared with the general population, mortality was increased in major NPSLE (SMR 5.0 (95% CI: 2.6–8.5)) and minor/non-NPSLE patients (SMR 3.7 (95% CI: 2.2–6.0)). Compared with minor/non-NPSLE, mortality was similar in major NPSLE patients (RR: 1.0 (95% CI: 0.5–2.0)). Cause-specific mortality rates demonstrated an increased risk of death due to infections in both groups, whereas death due to cardiovascular disease was only increased in minor/non-NPSLE patients. Conclusion Mortality was increased in both major NPSLE and minor/non-NPSLE patients in comparison with the general population. There was no difference in mortality between major NPSLE and minor/non-NPSLE patients.

Narcolepsy type 1 (NT1) is a chronic sleep disorder correlated with loss of hypocretin(orexin). In NT1 post-mortem brains, we observed 88% reduction in corticotropin-releasing hormone (CRH)-positive neurons in the paraventricular nucleus (PVN) and significantly less CRH-positive fibers in the median eminence, while CRH-neurons in the locus coeruleus and thalamus, and other PVN neuronal populations were spared: i.e. vasopressin, oxytocin, tyrosine hydroxylase and thyrotropin releasing hormone-expressing neurons. Other hypothalamic cell groups, i.e. the suprachiasmatic, ventrolateral preoptic, infundibular and supraoptic nuclei and nucleus basalis of Meynert were unaffected. The surprising selective decrease in CRH-neurons provide novel targets for diagnostics and therapeutic interventions. This article is protected by copyright. All rights reserved.

Zhongxing Zhang,1 Yves Dauvilliers,2– 4 Giuseppe Plazzi,5,6 Geert Mayer,7 Gert Jan Lammers,8,9 Joan Santamaria,10 Markku Partinen,11 Sebastiaan Overeem,12,13 Rafael del Rio Villegas,14 Karel Sonka,15 Rosa Peraita-Adrados,16 Raphaël Heinzer,17 Aleksandra Wierzbicka,18 Birgit Högl,19 Mauro Manconi,20 Eva Feketeova,21 Antonio Martins da Silva,22 Jitka Bušková,23 Claudio LA Bassetti,24,25 Lucie Barateau,2– 4 Fabio Pizza,5,26 Elena Antelmi,5,6 Jari K Gool,8,9 Rolf Fronczek,8,9 Carles Gaig,10 Ramin Khatami1,24 1Center for Sleep Medicine, Sleep Research and Epileptology, Klinik Barmelweid AG, Barmelweid, Aargau, Switzerland; 2Sleep-Wake Disorders Unit, Department of Neurology, Gui-de-Chauliac Hospital, CHU Montpellier, Montpellier, France; 3National Reference Centre for Orphan Diseases, Narcolepsy, Idiopathic Hypersomnia, and Kleine-Levin Syndrome, Montpellier, France; 4Institute for Neurosciences of Montpellier INM, Univ Montpellier, INSERM, Montpellier, France; 5Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy; 6IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy; 7Neurology Department, Hephata Klinik, Schwalmstadt, Germany; 8Sleep Wake Center SEIN Heemstede, Stichting Epilepsie Instellingen Nederland, Heemstede, the Netherlands; 9Department of Neurology and Clinical Neurophysiology, Leiden University Medical Center, Leiden, the Netherlands; 10Neurology Service, Institut de Neurociències Hospital Clínic, University of Barcelona, Barcelona, Spain; 11Helsinki Sleep Clinic, Vitalmed Research Center, Helsinki, Finland; 12Sleep Medicine Center Kempenhaeghe, Heeze, the Netherlands; 13Eindhoven University of Technology, Eindhoven, the Netherlands; 14Neurophysiology and Sleep Disorders Unit, Hospital Vithas Nuestra Señora de América, Madrid, Spain; 15Neurology Department and Centre of Clinical Neurosciences, First Faculty of Medicine, Charles University and General University Hospital, Prague, Czech Republic; 16Sleep and Epilepsy Unit – Clinical Neurophysiology Service, University General Hospital Gregorio Marañón, Research Institute Gregorio Marañón, University Complutense of Madrid, Madrid, Spain; 17Center for Investigation and Research in Sleep, Lausanne University Hospital, Lausanne, Vaud, Switzerland; 18Department of Clinical Neurophysiology, Institute of Psychiatry and Neurology, Warsaw, Poland; 19Neurology Department, Sleep Disorders Clinic, Innsbruck Medical University, Innsbruck, Austria; 20Neurology Department, EOC, Ospedale Regionale di Lugano, Lugano, Ticino, Switzerland; 21Neurology Department, Medical Faculty of P. J. Safarik University, University Hospital of L. Pasteur Kosice, Kosice, Slovak Republic; 22Serviço de Neurofisiologia, Hospital Santo António/Centro Hospitalar Universitário do Porto and UMIB-Instituto Ciências Biomédicas Abel Salazar, Universidade do Porto, Porto, Portugal; 23Department of Sleep Medicine, National Institute of Mental Health, Klecany, Czech Republic; 24Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; 25Department of Neurology, Sechenov First Moscow State University, Moscow, Russia; 26Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, ItalyCorrespondence: Yves Dauvilliers, National Reference Network for Narcolepsy, Sleep-Disorders Center, Department of Neurology, Hopital Gui de Chauliac, INSERM U1061, Montpellier, UM1, France, Email ydauvilliers@yahoo.fr Ramin Khatami, Center for Sleep Medicine, Sleep Research and Epileptology, Klinik Barmelweid AG, Barmelweid, CH-5017, Switzerland, Email ramin.khatami@barmelweid.chPurpose: Narcolepsy type-1 (NT1) is a rare chronic neurological sleep disorder with excessive daytime sleepiness (EDS) as usual first and cataplexy as pathognomonic symptom. Shortening the NT1 diagnostic delay is the key to reduce disease burden and related low quality of life. Here we investigated the changes of diagnostic delay over the diagnostic years (1990– 2018) and the factors associated with the delay in Europe.Patients and Methods: We analyzed 580 NT1 patients (male: 325, female: 255) from 12 European countries using the European Narcolepsy Network database. We combined machine learning and linear mixed-effect regression to identify factors associated with the delay.Results: The mean age at EDS onset and diagnosis of our patients was 20.9± 11.8 (mean ± standard deviation) and 30.5± 14.9 years old, respectively. Their mean and median diagnostic delay was 9.7± 11.5 and 5.3 (interquartile range: 1.7− 13.2 years) years, respectively. We did not find significant differences in the diagnostic delay over years in either the whole dataset or in individual countries, although the delay showed significant differences in various countries. The number of patients with short (≤ 2-year) and long (≥ 13-year) diagnostic delay equally increased over decades, suggesting that subgroups of NT1 patients with variable disease progression may co-exist. Younger age at cataplexy onset, longer interval between EDS and cataplexy onsets, lower cataplexy frequency, shorter duration of irresistible daytime sleep, lower daytime REM sleep propensity, and being female are associated with longer diagnostic delay.Conclusion: Our findings contrast the results of previous studies reporting shorter delay over time which is confounded by calendar year, because they characterized the changes in diagnostic delay over the symptom onset year. Our study indicates that new strategies such as increasing media attention/awareness and developing new biomarkers are needed to better detect EDS, cataplexy, and changes of nocturnal sleep in narcolepsy, in order to shorten the diagnostic interval.Keywords: cataplexy, diagnostic delay, misdiagnosis, symptom onset, machine learning

Purpose of Review Idiopathic hypersomnia is an incapacitating disorder with a profound impact on daytime performance and quality of life. The most commonly used treatment modalities are lifestyle advice and pharmacological therapy. We present an update on the evidence concerning treatment options for idiopathic hypersomnia. Recent Findings Evidence for non-pharmacological interventions is lacking; improvement in symptoms on introducing these interventions is often less pronounced than in narcolepsy. Additional pharmacological treatment is therefore usually initiated. The few treatment studies that have been performed are hampered by small sample sizes and the use of variable and often insufficiently validated outcome parameters for the whole spectrum of idiopathic hypersomnia symptoms. Conclusion Evidence on treatment is scarce. Since the efficacy of modafinil is consistently described and there is much experience with this substance, it is reasonable to start with modafinil as a first choice treatment. Methylphenidate and dexamphetamine are good alternatives. In the future, newer drugs such as sodium oxybate, pitolisant, and solriamfetol might be authorized for use in idiopathic hypersomnia.

Background To compare symptoms of clinical androgen deficiency between men with migraine, men with cluster headache and non-headache male controls. Methods We performed a cross-sectional study using two validated questionnaires to assess symptoms of androgen deficiency in males with migraine, cluster headache, and non-headache controls. Primary outcome was the mean difference in androgen deficiency scores. Generalized linear models were used adjusting for age, BMI, smoking and lifetime depression. As secondary outcome we assessed the percentage of patients reporting to score below average on four sexual symptoms (beard growth, morning erections, libido and sexual potency) as these items were previously shown to more specifically differentiate androgen deficiency symptoms from (comorbid) anxiety and depression. Results The questionnaires were completed by n = 534/853 (63%) men with migraine, n = 437/694 (63%) men with cluster headache and n = 152/209 (73%) controls. Responders were older compared to non-responders and less likely to suffer from lifetime depression. Patients reported more severe symptoms of clinical androgen deficiency compared with controls, with higher AMS scores (Aging Males Symptoms; mean difference ± SE: migraine 5.44 ± 0.90, p p < 0.001) and lower qADAM scores (quantitative Androgen Deficiency in the Aging Male; migraine: − 3.16 ± 0.50, p < 0.001; cluster headache: − 5.25 ± 0.56, p < 0.001). Additionally, both patient groups more often reported to suffer from any of the specific sexual symptoms compared to controls (18.4% migraine, 20.6% cluster headache, 7.2% controls, p = 0.001). Conclusion Men with migraine and cluster headache more often suffer from symptoms consistent with clinical androgen deficiency than males without a primary headache disorder.

To compare symptoms of clinical androgen deficiency between men with migraine, men with cluster headache and non-headache male controls.We performed a cross-sectional study using two validated questionnaires to assess symptoms of androgen deficiency in males with migraine, cluster headache, and non-headache controls. Primary outcome was the mean difference in androgen deficiency scores. Generalized linear models were used adjusting for age, BMI, smoking and lifetime depression. As secondary outcome we assessed the percentage of patients reporting to score below average on four sexual symptoms (beard growth, morning erections, libido and sexual potency) as these items were previously shown to more specifically differentiate androgen deficiency symptoms from (comorbid) anxiety and depression.The questionnaires were completed by n = 534/853 (63%) men with migraine, n = 437/694 (63%) men with cluster headache and n = 152/209 (73%) controls. Responders were older compared to non-responders and more likely to suffer from lifetime depression. Patients reported more severe symptoms of clinical androgen deficiency compared with controls, with higher AMS scores (Aging Males Symptoms; mean difference ± SE: migraine 5.44 ± 0.90, p 0.001; cluster headache 5.62 ± 0.99, p 0.001) and lower qADAM scores (quantitative Androgen Deficiency in the Aging Male; migraine: - 3.16 ± 0.50, p 0.001; cluster headache: - 5.25 ± 0.56, p 0.001). Additionally, both patient groups more often reported to suffer from any of the specific sexual symptoms compared to controls (18.4% migraine, 20.6% cluster headache, 7.2% controls, p = 0.001).Men with migraine and cluster headache more often suffer from symptoms consistent with clinical androgen deficiency than males without a primary headache disorder.

Narcolepsy with cataplexy is a chronic sleep disorder characterized by hypocretin deficiency. The condition is believed to result from autoimmune destruction of hypocretin (HCRT) neurons, although direct evidence is lacking and mere Hcrt gene inactivation causes full-blown narcolepsy in mice. Here we show that the expression of another hypothalamic neuropeptide, QRFP, is lost in mouse models with HCRT cell-ablation, but tends to be even increased in Hcrt gene knockout mice, suggesting that QRFP expression can be used as a proxy for the presence or absence of HCRT neurons. Similar to Hcrt knockout mice, narcolepsy patients show intact hypothalamic QRFP expression, and cerebrospinal fluid levels of QRFP peptide are increased, suggesting their HCRT neurons are intact. We show that the human HCRT gene promoter is methylation-sensitive in vitro, and is hypermethylated in the hypothalamus of patients selectively at a putative PAX5:ETS1 binding site within the proximal HCRT promoter. Ets1-KO mice display downregulated Hcrt expression, while pax5-ets1 knockdown in zebrafish causes decreased hcrt expression, decreased activity and sleep fragmentation, similar to narcolepsy patients. Our results suggest that HCRT neurons are alive, but epigenetically silenced, in the hypothalamus of narcolepsy patients, opening the possibility to reverse or cure narcolepsy.

Hypocretin (also called orexin) regulates various functions, such as sleep-wake rhythms, attention, cognition, and energy balance, which show significant changes in schizophrenia (SCZ). We aimed to identify alterations in the hypocretin system in SCZ patients. We measured plasma hypocretin-1 levels in SCZ patients and healthy controls and found significantly decreased plasma hypocretin-1 levels in SCZ patients, which was mainly due to a significant decrease in female SCZ patients compared with female controls. In addition, we measured postmortem hypothalamic hypocretin-1-immunoreactivity (ir), ventricular cerebrospinal fluid (CSF) hypocretin-1 levels, and hypocretin receptor (Hcrt-R) mRNA expression in the superior frontal gyrus (SFG) in SCZ patients and controls We observed a significant decrease in the amount of hypothalamic hypocretin-1 ir in SCZ patients, which was due to decreased amounts in female but not male patients. Moreover, Hcrt-R2 mRNA in the SFG was decreased in female SCZ patients compared with female controls, while male SCZ patients showed a trend of increased Hcrt-R1 mRNA and Hcrt-R2 mRNA expression compared with male controls. We conclude that central hypocretin neurotransmission is decreased in SCZ patients, especially female patients, and this is reflected in the plasma.

Hypocretin-1 and 2 (or orexin A and B) are neuropeptides exclusively produced by a group of neurons in the lateral and dorsomedial hypothalamus that project throughout the brain. In accordance with this, the two different hypocretin receptors are also found throughout the brain. The hypocretin system is mainly involved in sleep-wake regulation, but also in reward mechanisms, food intake and metabolism, autonomic regulation including thermoregulation, and pain. The disorder most strongly linked to the hypocretin system is the primary sleep disorder narcolepsy type 1 caused by a lack of hypocretin signaling, which is most likely due to an autoimmune process targeting the hypocretin-producing neurons. However, the hypocretin system may also be affected, but to a lesser extent and less specifically, in various other neurological disorders. Examples are neurodegenerative diseases such as Alzheimer's, Huntington's and Parkinson's disease, immune-mediated disorders such as multiple sclerosis, neuromyelitis optica, and anti-Ma2 encephalitis, and genetic disorders such as type 1 diabetus mellitus and Prader-Willi Syndrome. A partial hypocretin deficiency may contribute to the sleep features of these disorders.

The tuberomamillary nucleus (TMN) is located within the posterior part of the hypothalamus. The histamine neurons in it synthesize histamine by means of the key enzyme histidine decarboxylase (HDC) and from the TMN, innervate a large number of brain areas, such as the cerebral cortex, hippocampus, amygdala as well as the thalamus, hypothalamus, and basal ganglia. Brain histamine is reduced to an inactivated form, tele-methylhistamine (t-MeHA), by histamine N-methyltransferase (HMT). In total, there are four types of histamine receptors (H

We reviewed current definitions of vigilance to propose a definition, applicable in sleep medicine. As previous definitions contained terms such as attention, alertness, and arousal, we addressed these concepts too. We defined alertness as a quantitative measure of the mind state governing sensitivity to stimuli. Arousal comprises a stimulus-induced upward change in alertness, irrespective of the subsequent duration of the increased level of alertness. Vigilance is defined as the capability to be sensitive to potential changes in one's environment, ie the capability to reach a level of alertness above a threshold for a certain period of time rather than the state of alertness itself. It has quantitative and temporal dimensions. Attention adds direction towards a stimulus to alertness, requiring cognitive control: it involves being prepared to process stimuli coming from an expected direction. Sustained attention corresponds to a state in which some level of attention is purposefully maintained, adding a time factor to the definition of attention. Vigilance differs from sustained attention in that the latter in addition implies a direction to which attention is cognitively directed as well as a specification of duration. Attempts to measure vigilance, however, are often in fact measurements of sustained attention. (C) 2021 The Authors. Published by Elsevier B.V.

Background: Orexin-A and -B are neuropeptides involved in sleep-wake regulation. In human narcolepsy type 1, this cycle is disrupted due to loss of orexin-producing neurons in the hypothalamus. Cerebrospinal fluid (CSF) orexin-A measurement is used in the diagnosis of narcolepsy type 1. Currently available immunoassays may lack specificity for accurate orexin quantification. We developed and validated a liquid chromatography mass spectrometry assay (LC-MS/MS) for CSF orexin-A and B.Methods: We used CSF samples from narcolepsy type 1 (n=22) and type 2 (n=6) and non-narcoleptic controls (n=44). Stable isotope-labeled orexin-A and -B internal standards were added to samples before solid-phase extraction and quantification by LC-MS/MS. The samples were also assayed by commercial radioimmunoassay (RIA, n=42) and enzymatic immunoassay (EIA, n=72) kits. Stability of orexins in CSF was studied for 12 months.Results: Our assay has a good sensitivity (10 pmol/L = 35 pg/mL) and a wide linear range (35-3500 pg/mL). Added orexin-A and -B were stable in CSF for 12 and 3 months, respectively, when frozen. The median orexin-A concentration in CSF from narcolepsy type 1 patients was Conclusions: Orexin-A concentrations measured by our LC-MS/MS assay were lower in narcolepsy type 1 patients as compared to controls. RIA yielded on average higher concentrations than LC-MS/MS.

Introduction We aimed to investigate risk factors for fatigue in patients with systemic lupus erythematosus (SLE) and neuropsychiatric symptoms in order to identify potential interventional strategies. Methods Patients visiting the neuropsychiatric SLE (NPSLE) clinic of the Leiden University Medical Center between 2007–2019 were included. In a multidisciplinary consensus meeting, SLE patients were classified as having neuropsychiatric symptoms of inflammatory origin (inflammatory phenotype) or other origin (non-inflammatory phenotype). Fatigue was assessed with the SF-36 vitality domain (VT) since 2007 and the multidimensional fatigue inventory (MFI) and visual analogue scale (VAS) since 2011. Patients with a score on the SF-36 VT ≥1 standard deviation (SD) away from the mean of age-related controls of the general population were classified as fatigued; patients ≥2 SD away were classified as extremely fatigued. Disease activity was measured using the SLE disease activity index-2000. The influence of the presence of an inflammatory phenotype, disease activity and symptoms of depression and anxiety as measured by the hospital anxiety and depression scale (HADS) was analyzed using multiple regression analyses corrected for age, sex and education. Results 348 out of 371 eligible patients filled in questionnaires and were included in this study . The majority was female (87%) and the mean age was 43 ± 14 years. 72 patients (21%) had neuropsychiatric symptoms of an inflammatory origin. Fatigue was present in 78% of all patients and extreme fatigue was present in 50% of patients with an inflammatory phenotype vs 46% in the non-inflammatory phenotype. Fatigue was similar in patients with an inflammatory phenotype compared to patients with a non-inflammatory phenotype on the SF-36 VT (β: 0.8 (95% CI −4.8; 6.1) and there was less fatigue in patients with an inflammatory phenotype on the MFI and VAS (β: −3.7 (95% CI: −6.9; −0.5) and β: −1.0 (95% CI −1.6; −0.3)). There was no association between disease activity and fatigue, but symptoms of anxiety and depression (HADS) associated strongly with all fatigue measurements. Conclusion This study suggests that intervention strategies to target fatigue in (NP)SLE patients may need to focus on symptoms of anxiety and depression rather than immunosuppressive treatment.

Aim To determine whether our E-diary can be used to diagnose migraine and provide more reliable migraine-related frequency numbers compared to patients’ self-reported estimates. Methods We introduced a self-developed E-diary including automated algorithms differentiating headache and migraine days, indicating whether a patient has migraine. Reliability of the E-diary diagnosis in combination with two previously validated E-questionnaires was compared to a physician’s diagnosis as gold standard in headache patients referred to the Leiden Headache Clinic (n = 596). In a subset of patients with migraine (n = 484), self-estimated migraine-related frequencies were compared to diary-based results. Results The first migraine screening approach including an E-headache questionnaire, and the E-diary revealed a sensitivity of 98% and specificity of 17%. In the second approach, an E-migraine questionnaire was added, resulting in a sensitivity of 79% and specificity of 69%. Mean self-estimated monthly migraine days, non-migrainous headache days and days with acute medication use were different from E-diary-based results (absolute mean difference ± standard deviation respectively 4.7 ± 5.0, 6.2 ± 6.6 and 4.3 ± 4.8). Conclusion The E-diary including algorithms differentiating headache and migraine days showed usefulness in diagnosing migraine. The use emphasised the need for E-diaries to obtain reliable information, as patients do not reliably recall numbers of migraine days and acute medication intake. Adding E-diaries will be helpful in future headache telemedicine.

OBJECTIVES Sleep-wake disorders are common in the general population and in most neurological disorders but are often poorly recognized. With the hypothesis that neurologists do not get sufficient training during their residency, the Young European Sleep Neurologist Association (YESNA) of the European Academy of Neurology (EAN) performed a survey on postgraduate sleep education. METHODS A 16-item questionnaire was developed and distributed among neurologists and residents across European countries. Questions assessed demographic, training and learning preferences in sleep disorders, as well as a self-evaluation of knowledge based on five basic multiple-choice questions (MCQs) on sleep-wake disorders. RESULTS The questionnaire was completed by 568 participants from 20 European countries. The mean age of participants was 31.9 years (SD 7.4 years) and was composed mostly of residents (73%). Three-quarters of the participants reported undergraduate training in sleep medicine, while fewer than 60% did not receive any training on sleep disorders during their residencies. Almost half of the participants (45%) did not feel prepared to treat neurological patients with sleep problems. Only one-third of the participants correctly answered at least three MCQs. Notably, 80% of participants favoured more education on sleep-wake disorders during the neurology residency. CONCLUSIONS Education and knowledge on disorders in European neurological residents is generally insufficient, despite a strong interest in the topic. The results of our study may be useful for improving the European neurology curriculum and other postgraduate educational programmes.

The tuberomamillary nucleus (TMN) is located within the posterior part of the hypothalamus. The histamine neurons in it synthesize histamine by means of the key enzyme histidine decarboxylase (HDC) and from the TMN, innervate a large number of brain areas, such as the cerebral cortex, hippocampus, amygdala as well as the thalamus, hypothalamus, and basal ganglia. Brain histamine is reduced to an inactivated form, tele-methylhistamine (t-MeHA), by histamine N-methyltransferase (HMT). In total, there are four types of histamine receptors (H1-4Rs) in the brain, all of which are G-protein coupled. The histaminergic system controls several basal physiological functions, including the sleep-wake cycle, energy and endocrine homeostasis, sensory and motor functions, and cognitive functions such as attention, learning, and memory. Histaminergic dysfunction may contribute to clinical disorders such as Parkinson's disease, Alzheimer's disease, Huntington's disease, narcolepsy type 1, schizophrenia, Tourette syndrome, and autism spectrum disorder. In the current chapter, we focus on the role of the histaminergic system in these neurological/neuropsychiatric disorders. For each disorder, we first discuss human data, including genetic, postmortem brain, and cerebrospinal fluid studies. Then, we try to interpret the human changes by reviewing related animal studies and end by discussing, if present, recent progress in clinical studies on novel histamine-related therapeutic strategies.

Publisher Copyright: © 2021 The Authors. Annals of Neurology published by Wiley Periodicals LLC on behalf of American Neurological Association. Objective: Identifying common genetic variants that confer genetic risk for cluster headache. Methods: We conducted a case–control study in the Dutch Leiden University Cluster headache neuro-Analysis program (LUCA) study population (n = 840) and unselected controls from the Netherlands Epidemiology of Obesity Study (NEO; n = 1,457). Replication was performed in a Norwegian sample of 144 cases from the Trondheim Cluster headache sample and 1,800 controls from the Nord-Trøndelag Health Survey (HUNT). Gene set and tissue enrichment analyses, blood cell-derived RNA-sequencing of genes around the risk loci and linkage disequilibrium score regression were part of the downstream analyses. Results: An association was found with cluster headache for 4 independent loci (r2 < 0.1) with genomewide significance (p < 5 × 10−8), rs11579212 (odds ratio [OR] = 1.51, 95% confidence interval [CI] = 1.33–1.72 near RP11-815 M8.1), rs6541998 (OR = 1.53, 95% CI = 1.37–1.74 near MERTK), rs10184573 (OR = 1.43, 95% CI = 1.26–1.61 near AC093590.1), and rs2499799 (OR = 0.62, 95% CI = 0.54–0.73 near UFL1/FHL5), collectively explaining 7.2% of the variance of cluster headache. SNPs rs11579212, rs10184573, and rs976357, as proxy SNP for rs2499799 (r2 = 1.0), replicated in the Norwegian sample (p < 0.05). Gene-based mapping yielded ASZ1 as possible fifth locus. RNA-sequencing indicated differential expression of POLR1B and TMEM87B in cluster headache patients. Interpretation: This genomewide association study (GWAS) identified and replicated genetic risk loci for cluster headache with effect sizes larger than those typically seen in complex genetic disorders. ANN NEUROL 2021;90:203–216.

Purpose of Review: Clinical presentation of central hypersomnolence disorders, including narcolepsy type 1 and 2 and idiopathic hypersomnia, is often similar, and determining the correct diagnosis remains challenging. Neuroimaging techniques have provided valuable insights into the pathophysiology of narcolepsy and idiopathic hypersomnia. Here, we review current structural and functional brain imaging findings in central hypersomnolence disorders and discuss the future perspectives of neuroimaging in these sleep disorders. Recent Findings: Most studies have focused on narcolepsy type 1 (or narcolepsy with cataplexy), showing inconsistent but extensive structural differences in the hypothalamus and its normally widespread projections. Functional studies have mainly focused on resting-state or emotion regulation in narcolepsy type 1 and have revealed disturbed activity in limbic and mesolimbic structures in relation to cataplexy. Finally, recent studies suggest a disruption of the default-mode network in patients with idiopathic hypersomnia. Summary: Most neuroimaging studies to date have been conducted in small samples, while narcolepsy type 2 (or narcolepsy without cataplexy) and idiopathic hypersomnia remain relatively understudied. Larger studies with consistent clinical phenotyping should be the focus of future investigations. In addition, multi-modal imaging methods will be crucial to resolve previous inconsistencies and identify reliable objective biomarkers that could aid in understanding the pathophysiology and potentially support the diagnostic process.

Narcolepsy with cataplexy (NT1) is a chronic hypothalamic disorder with a presumed immune-mediated etiology leading to a loss of hypocretin neurons. Previous studies reported conflicting results in terms of presence of auto-antibodies involved in narcolepsy pathophysiology. A total of 86 patients with primary/ idiopathic narcolepsy (74 NT1, 12 NT2) and 23 control patients with excessive daytime sleepiness due to other causes were tested for the presence of a wide range of anti-neuronal antibodies in both serum and cerebrospinal fluid (CSF). Anti-neuronal antibodies were rarely found in patients with narcolepsy (n = 2) and in controls (n = 1). Our results are in line with previous reports. We can therefore support the current evidence, that conventional anti-neuronal antibodies are not routinely detected during the workup of NT1 and other CDH patients. (c) 2020 Elsevier B.V. All rights reserved.

The classification of the central disorders of hypersomnolence has undergone multiple iterations in an attempt to capture biologically meaningful disease entities in the absence of known pathophysiology. Accumulating data suggests that further refinements may be necessary. At the 7th International Symposium on Narcolepsy, a group of clinician-scientists evaluated data in support of keeping or changing classifications, and as a result suggest several changes. First, idiopathic hypersomnia with long sleep durations appears to be an identifiable and meaningful disease subtype. Second, idiopathic hypersomnia without long sleep time and narcolepsy without cataplexy share substantial phenotypic overlap and cannot reliably be distinguished with current testing, and so combining them into a single disease entity seems warranted at present. Moving forward, it is critical to phenotype patients across a wide variety of clinical and biological features, to aid in future refinements of disease classification.

Increased incidence rates of narcolepsy type-1 (NT1) have been reported worldwide after the 2009–2010 H1N1 influenza pandemic (pH1N1). While some European countries found an association between the NT1 incidence increase and the H1N1 vaccination Pandemrix, reports from Asian countries suggested the H1N1 virus itself to be linked to the increased NT1 incidence. Using robust data-driven modeling approaches, that is, locally estimated scatterplot smoothing methods, we analyzed the number of de novo NT1 cases (n = 508) in the last two decades using the European Narcolepsy Network database. We confirmed the peak of NT1 incidence in 2010, that is, 2.54-fold (95% confidence interval [CI]: [2.11, 3.19]) increase in NT1 onset following 2009–2010 pH1N1. This peak in 2010 was found in both childhood NT1 (2.75-fold increase, 95% CI: [1.95, 4.69]) and adulthood NT1 (2.43-fold increase, 95% CI: [2.05, 2.97]). In addition, we identified a new peak in 2013 that is age-specific for children/adolescents (i.e. 2.09-fold increase, 95% CI: [1.52, 3.32]). Most of these children/adolescents were HLA DQB1*06:02 positive and showed a subacute disease onset consistent with an immune-mediated type of narcolepsy. The new 2013 incidence peak is likely not related to Pandemrix as it was not used after 2010. Our results suggest that the increased NT1 incidence after 2009–2010 pH1N1 is not unique and our study provides an opportunity to develop new hypotheses, for example, considering other (influenza) viruses or epidemiological events to further investigate the pathophysiology of immune-mediated narcolepsy.