Narcolepsy: a model interaction between immune system, nervous system, and sleep-wake regulation

REM sleep in narcolepsy

Narcolepsy is mainly associated with excessive daytime sleepiness, but the characteristic feature is abnormal rapid eye movement (REM) sleep phenomena. REM sleep disturbances can manifest as cataplexy (in narcolepsy type 1), sleep paralysis, sleep-related hallucinations, REM sleep behavior disorder, abnormal dreams, polysomnographic evidence of REM sleep disruption with sleep-onset REM periods, and fragmented REM sleep. Characterization of REM sleep and related symptoms facilitates the differentiation of narcolepsy from other central hypersomnolence disorders and aids in distinguishing between narcolepsy types 1 and 2. A circuit comprising regions within the brainstem, forebrain, and hypothalamus is involved in generating and regulating REM sleep, which is influenced by changes in monoamines, acetylcholine, and neuropeptides. REM sleep is associated with brainstem functions, including autonomic control, and REM sleep disturbances may be associated with increased cardiovascular risk. Medications used to treat narcolepsy (and REM-related symptoms of narcolepsy) include stimulants/wake-promoting agents, pitolisant, oxybates, and antidepressants; hypocretin agonists are a potential new class of therapeutics. The role of REM sleep disturbances in narcolepsy remains an area of active research in pathophysiology, symptom management, and treatment. This review summarizes the current understanding of the role of REM sleep and its dysfunction in narcolepsy.

Tetrad of Narcolepsy Type 1: Treatment and Management

Narcolepsy is a chronic condition that brings about excessive daytime sleepiness. It can be classified into two types: narcolepsy type 1 (presence of cataplexy, which is marked by weakness of muscles) and narcolepsy type 2 (without cataplexy). It is generally underdiagnosed, which results in delayed diagnosis of the condition. It has more prevalence in the United States of America as compared to India. The narcoleptic tetrad consists of excessive daytime sleepiness (EDS), cataplexy, sleep paralysis, and hypnagogic hallucinations. Rapid eye movement (REM) sleep behavior disorder is another characteristic feature. Research about narcolepsy has been carried out for about 145-150 years, but it is only in the last 18-20 years that there has been advancement in the underlying pathophysiology, diagnosis, and, thus, availability of better treatment. Both pharmacological and non-pharmacological methods are preferred in treating narcolepsy, yet there is no cure for it. Since the knowledge regarding this condition is very limited, it is often misunderstood, and dealing with it is mentally and socially draining, often causing anxiety in the patients, feeling of social isolation, and other significant impacts on the quality of living. Raising awareness about narcolepsy is vital to prevent further medical attention delays.

Connecting the dots: An updated review of the role of autoimmunity in narcolepsy and emerging immunotherapeutic approaches

BACKGROUND

Narcolepsy type 1 (NT1) is a chronic disorder characterized by pathological daytime sleepiness and cataplexy due to the disappearance of orexin immunoreactive neurons in the hypothalamus. Genetic and environmental factors point towards a potential role for inflammation and autoimmunity in the pathogenesis of the disease. This study aims to comprehensively review the latest evidence on the autoinflammatory mechanisms and immunomodulatory treatments aimed at suspected autoimmune pathways in NT1.

METHODS

Recent relevant literature in the field of narcolepsy, its autoimmune hypothesis, and purposed immunomodulatory treatments were reviewed.

RESULTS

Narcolepsy is strongly linked to specific HLA alleles and T-cell receptor polymorphisms. Furthermore, animal studies and autopsies have found infiltration of T cells in the hypothalamus, supporting T cell-mediated immunity. However, the role of autoantibodies has yet to be definitively established. Increased risk of NT1 after H1N1 infection and vaccination supports the autoimmune hypothesis, and the potential role of coronavirus disease 2019 and vaccination in triggering autoimmune neurodegeneration is a recent finding. Alterations in cytokine levels, gut microbiota, and microglial activation indicate a potential role for inflammation in the disease's development. Reports of using immunotherapies in NT1 patients are limited and inconsistent. Early treatment with IVIg, corticosteroids, plasmapheresis, and monoclonal antibodies has seldomly shown some potential benefits in some studies.

CONCLUSION

The current body of literature supports that narcolepsy is an autoimmune disorder most likely caused by T-cell involvement. However, the potential for immunomodulatory treatments to reverse the autoinflammatory process remains understudied. Further clinical controlled trials may provide valuable insights into this area.

The immunopathogenesis of narcolepsy type 1

Narcolepsy type 1 (NT1) is a chronic sleep disorder resulting from the loss of a small population of hypothalamic neurons that produce wake-promoting hypocretin (HCRT; also known as orexin) peptides. An immune-mediated pathology for NT1 has long been suspected given its exceptionally tight association with the MHC class II allele HLA-DQB1*06:02, as well as recent genetic evidence showing associations with polymorphisms of T cell receptor genes and other immune-relevant loci and the increased incidence of NT1 that has been observed after vaccination with the influenza vaccine Pandemrix. The search for both self-antigens and foreign antigens recognized by the pathogenic T cell response in NT1 is ongoing. Increased T cell reactivity against HCRT has been consistently reported in patients with NT1, but data demonstrating a primary role for T cells in neuronal destruction are currently lacking. Animal models are providing clues regarding the roles of autoreactive CD4+ and CD8+ T cells in the disease. Elucidation of the pathogenesis of NT1 will allow for the development of targeted immunotherapies at disease onset and could serve as a model for other immune-mediated neurological diseases.

Evaluation of Candidemia in Solid-Organ Transplant Recipients

OBJECTIVES

Solid-organ transplant recipients have high rates of invasive fungal infections. Candida species are the most commonly isolated fungi. Our aim was to identify risk factors, clinical presentations, and outcomes of candidemia in solid-organ transplant recipients.

MATERIALS AND METHODS

We evaluated adult (≥18 years old) transplant recipients seen from May 2011 to December 2022 at Baskent University Ankara Hospital. From medical records, we retrospectively reviewed age, sex, transplant type, candidemia agent, risk factors, concomitant infections, and mortality of patients with Candida detected in blood culture. We used SPSS statistics software (version 25) to analyze data.

RESULTS

There were 1080 organ transplants performed during the study period (717 kidney, 279 liver, 84 heart). There were 855 who were ≥18 years (655 kidney, 127 liver, 73 heart), of whom candidemia was detected in 26 (16 male; 11 kidney, 11 liver, 4 heart) with a median age of 47.5 years. The most common agents were Candida albicans and Candida glabrata. The most common chronic diseases were hypertension, cirrhosis, and cardiomyopathy. Eighteen patients had a concomitant focus of infection. Ten patients had pneumonia accompanying candidemia. The 30-day mortality rate was as high as 53.8%. The mean duration of candidemia after transplant was 23 months. Catheter-related candidemia was observed in 65% of patients. The 30-day mortality was found to be significantly higher in patients followed in the intensive care unit (P = .014), receiving total parenteral nutrition (P = .001), using broad-spectrum antibiotics (P = .001), and having pneumonia (P = .042) accompanying candidemia.

CONCLUSIONS

For adult solid-organ transplant recipients with candidemia, careful monitoring is essential for successful management of total parenteral nutrition, central catheter, use of broadspectrum antibiotics, and invasive interventions.

[Kleine-Levin syndrome]

Kleine-Levin syndrome (KLS) is manifested by periodic hypersomnolence with an increased appetite and psychopathological symptoms (psychomotor agitation, hallucinations, hypersexuality). The duration of the attack ranges from several days to several weeks. A forced awakening can provoke severe aggressive behavior. The disease occurs for an unknown reason, mainly in adolescence and mostly affects males. Lack of awareness among doctors about the disease leads to an incorrect diagnosis, often of a psychopathological disorder. This article presents modern data on the causes, clinical symptoms, diagnostic methods of KLS and provides a case of a 18 year-old man, whose disease manifested at the age of 16 years.

Sleep disorders during pregnancy: an underestimated risk factor for gestational diabetes mellitus

Sleep disorders are highly prevalent during pregnancy and significantly affect women's health and quality of life. Gestational diabetes mellitus (GDM) is one of the most common metabolic complications during pregnancy and constitutes a significant risk factor for both mother and fetus in the short and the long term. While the association between sleep disorders and type 2 diabetes mellitus (T2DM) is indisputable, it is not clear whether there is a link between sleep disorders and GDM. The aim of this article was to investigate the association between sleep disorders and GDM and whether the treatment of sleep disorders may prevent GDM development. Insomnia, obstructive sleep apnea (OSA), restless legs syndrome (RLS), and narcolepsy were the most common sleep disorders identified during pregnancy and were related to poor sleep quality and short or prolonged sleep duration. They were all associated with an increased risk of GDM. The ideal sleep duration for pregnant women was determined at 8-9 h daily. In conclusion, sleep disorders constitute a risk factor for GDM. It is imperative that prospective studies be conducted to evaluate the effect of the early management of sleep disorders on GDM manifestation and control. Healthcare providers should highlight the importance of sufficient sleep to reinforce pregnancy outcomes.

Pitolisant-supported bridging during drug holidays to deal with tolerance to modafinil in patients with narcolepsy

STUDY OBJECTIVES

Modafinil is a common treatment for excessive daytime sleepiness (EDS) in narcolepsy. The long-term use of modafinil can lead to tolerance with the loss of efficacy and the continuous increase of its dose. Pharmacological strategies to deal with the tolerance to modafinil are lacking. We investigated the efficacy and safety of pitolisant-supported bridging during drug holidays in patients with tolerance to modafinil.

METHODS

Narcolepsy patients on monotherapy with modafinil who developed symptoms of tolerance were eligible. The following alternating therapy regimen was established: Monday to Friday patients continued on modafinil whereas Saturday and Sunday they switched to pitolisant to "bridge" the EDS symptoms. Patients were assessed at baseline and after three months with the Epworth Sleepiness Scale (ESS) and the Ullanlinna Narcolepsy Scale (UNS). Health-related quality of life (HrQol) was evaluated by EuroQol5D. Adverse events were documented in the patients' diaries.

RESULTS

41 patients aged 30.9 ± 5.6 years were included. After three months of the alternating therapy regimen, the symptoms of tolerance decreased and the modafinil dose could be reduced by 41% (p < 0.01) resulting in better safety. The EDS improved on ESS (baseline: 18.2 ± 4.2, follow-up: 12.6 ± 4.0, p < 0.0001) and UNS (baseline: 25.8 ± 7.9, follow-up: 18.9 ± 5.9, p < 0.0001). The HrQol increased significantly.

CONCLUSION

Patients with tolerance to modafinil could benefit from pitolisant-supported bridging during drug holidays. This alternating pharmacological strategy proved to be safe and helped to reduce EDS and to decrease the modafinil dose. Further randomized controlled studies are required to evaluate the different strategies to deal with the tolerance to modafinil.

CLINICAL TRIAL REGISTRATION NUMBER

Clinical Trials.gov Identifier NCT05321355.

Larger hypothalamic volume in narcolepsy type 1

STUDY OBJECTIVES

Narcolepsy type 1 (NT1) is a neurological sleep disorder. Postmortem studies have shown 75%-90% loss of the 50 000-70 000 hypocretin-producing neurons and 64%-94% increase in the 64 000-120 000 histaminergic neurons and conflicting indications of gliosis in the hypothalamus of NT1 patients. The aim of this study was to compare MRI-based volumes of the hypothalamus in patients with NT1 and controls in vivo.

METHODS

We used a segmentation tool based on deep learning included in Freesurfer and computed the volume of the whole hypothalamus, left/right part of the hypothalamus, and 10 hypothalamic subregions. We included 54 patients with post-H1N1 NT1 (39 females, mean age 21.8 ± 11.0 years) and 114 controls (77 females, mean age 23.2 ± 9.0 years). Group differences were tested with general linear models using permutation testing in Permutation Analysis of Linear Models and evaluated after 10 000 permutations, yielding two-tailed P-values. Furthermore, a stepwise Bonferroni correction was performed after dividing hypothalamus into smaller regions.

RESULTS

The analysis revealed larger volume for patients compared to controls for the whole hypothalamus (Cohen's d = 0.71, p = 0.0028) and for the left (d = 0.70, p = 0.0037) and right part of the hypothalamus (d = 0.65, p = 0.0075) and left (d = 0.72, p = 0.0036) and right tubular-inferior (d = 0.71, p = 0.0037) hypothalamic subregions.

CONCLUSIONS

In conclusion, patients with post-H1N1 NT1 showed significantly larger hypothalamic volume than controls, in particular in the tubular-inferior subregions which could reflect several processes as previous studies have indicated neuroinflammation, gliosis, and changes in the numbers of different cell types.

Diurnal changes in blood pressure and heart rate in children with narcolepsy with cataplexy

The hypocretin neurons in the lateral hypothalamus are connected not only to brain alertness systems but also to brainstem nuclei that regulate blood pressure and heart rate. The premise is that regulation of blood pressure and heart rate is altered and affected by methylphenidate, a stimulant drug in children with narcolepsy with cataplexy. The changes in 24-hr ambulatory systolic and diastolic blood pressure and heart rate were compared among pre-treated narcolepsy with cataplexy patients (40 males, 10 females), with mean age 10.4 ± 3.5 years (M ± SD, range 5-17 years) with values from 100 archival age-sex-body mass index matched controls. Patients had a lower diurnal systolic blood pressure (-6.5 mmHg; p = 0.000) but higher heart rate (+11.0 bpm; p = 0.000), particularly evident in the waketime, while diastolic blood pressure was comparable. With methylphenidate (18 mg sustained release at 08:00 hours), patients with narcolepsy with cataplexy had higher systolic blood pressure (+4.6 mmHg, p = 0.015), diastolic blood pressure (+3.3 mmHg, p = 0.005) and heart rate (+7.1 bpm, p = 0.028) during wake time, but nighttime cardiovascular values were unchanged from pre-treated values; amplitude variation in cardiovascular values was unchanged over 24 hr. In conclusion, children with narcolepsy with cataplexy had downregulation blood pressure profile but a higher heart rate, and lesser non-dipping profiles. Daytime methylphenidate treatment increases only waketime blood pressure and further elevated heart rate values.

An Update on Kleine-Levin Syndrome

Purpose of Review

Kleine-Levin syndrome (KLS) is a rare relapsing-remitting sleep disorder distinguished by recurrent periods of severe hypersomnia accompanied by cognitive, mood, and behavioral changes. This review focuses mainly on the most recent developments and articles concerning this illness in the preceding five years while attempting to provide a basic overview of KLS.

Recent Findings

Genetic links were reported in some patients with KLS, like variation in TRANK1 in a worldwide case-control genome-wide association in patients with KLS, in addition to several uncommon variations in the LMOD3 gene, some of which are likely to be pathogenic, discovered by linkage analysis and exome sequencing in a sizable Saudi Arabian family with KLS and a European cohort of KLS patients. Additionally, recent data indicate that the amplitude of the circadian active/rest cycles significantly decreased during hypersomnia attacks, but during asymptomatic periods, it did not differ significantly from the controls. Moreover, patients with KLS are at a higher risk of developing emerging psychiatric disorders during follow-up. Recent data also points to possible discoveries of diagnostic-potential dysregulated proteomic patterns in KLS. Finally, new data suggest that functional imaging studies are often abnormal in KLS both during and between episodes.

Summary

KLS is an uncommon, severe, and uniform illness. When it comes to the diagnosis and treatment of KLS, these characteristics offer both opportunities and challenges. Over the past five years, some promising work has appeared in genetics, functional imaging, and biomarker identification; nevertheless, these areas still need more focus to advance the detection and treatment of patients suffering from KLS.