The Sleep Disorder in Anti-lgLON5 Disease

Neuroimmunology and Sleep

The immune system and sleep are inextricably linked in both health and pathological conditions. Tightly regulated neuroimmune processes are critical for the physiological maintenance of healthy sleep. Reciprocally, sleep disturbances can detrimentally affect immune homeostasis and predispose to increased risk of autoimmune conditions, which themselves are bidirectionally associated with a higher risk of sleep disturbances. Autoimmune diseases of the central nervous system (CNS), particularly conditions that affect neuroanatomical regions involved in sleep homeostasis and nocturnal respiration, are associated with an increased risk sleep disorders that may impact diagnosis, clinical course, and management. This review summarizes the bidirectional relationship between sleep and immunity and highlights several exemplar autoimmune conditions of the CNS that include sleep disorders as a consequence or diagnostic feature of the disorder.

Distinctive sleep complaints and polysomnographic findings in antibody subgroups of autoimmune limbic encephalitis

INTRODUCTION

Sleep disturbances are being increasingly recognized in association with autoimmune encephalitis (AIE). We investigated the prevalence of sleep-related symptoms and polysomnographic features of patients with AIE and the long-term outcomes in these patients in a multi-center, prospective study from Turkey.

METHODS

We prospectively evaluated patients with definite AIE in a common database including demographics, AIE-related and sleep-related symptomatology. Maximum and latest modified Rankin scores (mRS) and Liverpool Outcome Score (LOS) were noted.

RESULTS

Of 142 patients, 87 patients (61.3%) fulfilled the criteria for definite AIE (mean age, 46.8+18.8 years; 51.7% women; mean disease duration, 21.0+38.4 months). 78.9% of patients had at least one or more new onset or worsened sleep-related symptomatology: insomnia (55.3%), excessive daytime sleepiness (EDS, 28.0%), sleep apnea (18.7%), REM sleep behavior disorder (RBD, 17.3%), restless legs syndrome (10.7%) and oneiric stupor (9.3%). Sleep efficiency, N3 and REM sleep were decreased and N1 sleep was increased in patients with Ab[+] AIE. LOS points were highest in those with insomnia and sleep apnea, and lowest in those with EDS, RBD and oneiric stupor. RBD and sleep apnea were more common in anti-LG1 Ab[+] group than anti-NMDAR Ab[+] group. Index of periodic leg movements was highest in anti-LG1 Ab[+] group. Patients with EDS and oneiric stupor had more common memory problems. Maximum and latest mRS scores were positively correlated with EDS and oneiric stupor. EDS, RBD and oneiric stupor were negatively correlated with LOS points.

CONCLUSION

Our study emphasizes the presence and importance of early diagnosis of sleep disturbances in AIE in regard to their deteriorative influences on disease prognosis.

Clinical presentations and antibody mechanisms in anti-IgLON5 disease

Anti-IgLON5 disease is a rare neurological disease, identified just ten years ago, where autoimmunity and neurodegeneration converge. The heterogeneity of symptoms, sometimes mimicking pure neurodegenerative diseases or motor neuron diseases, in addition to lack of awareness, represents a diagnostic challenge. Biomarkers of neuronal damage in combination with in vivo visualization of tau deposition using positron emission tomography (PET) scanning could represent a major advance in monitoring disease progression. Recent studies with more autopsies available have helped refine the knowledge of the pathological features of the disease and strengthen the autoimmune hypothesis of the disease. Although the pathogenesis of anti-IgLON5 disease remains unclear, the irreversible antibody-mediated decrease of IgLON5 clusters from the cell surface and alterations produced in the cytoskeleton, as well as the behavioural abnormalities and signs of neuroinflammation and neurodegeneration observed in the brains of animals infused with antibodies from patients by passive transfer, which have recently been published, support the autoimmune hypothesis of the disease. This review aims to summarize these important aspects and recent advances in the pathophysiology of anti-IgLON5 disease.

Upper airway manifestations of anti-IgLON5 disease: Otorhinolaryngological point of view

INTRODUCTION

Anti-IgLON5 disease is a recently described neurological disorder with multisystemic features. The disease is characterized by the presence of IgLON5 antibodies in serum and cerebrospinal fluid. Our objective is to describe in detail the otorhinolaryngological manifestations of this disease, which are frequent and may include dysphagia, dysarthria, vocal cord paralysis and laryngospasm.

METHODS

In this study, we present a series of 9 patients with anti-IgLON5 disease and otolaryngological manifestations. Patients were evaluated between July 2012 and March 2022 by video-polysomnography, fiber-optic laryngoscopy, and functional endoscopic evaluation of swallowing.

RESULTS

The median age was 71 years, and 5 (56%) were female. Video-polysomnography showed a NREM/REM parasomnia in 6 patients (67%), obstructive sleep apnea in 8 (88%), stridor during sleep in 7 (78%) and central apneas in 1 (11%). Six out of the 9 patients (67%) presented episodes of acute respiratory failure that required mechanical ventilation, 6 had vocal fold palsy with 4 of them requiring tracheostomy (3 had to be performed on an emergency basis). Dysphagia occurred in 8 patients (89%). Prominent upper airway secretion and sialorrhea was also present in 3 cases.

CONCLUSION

The anti-IgLON5 disease exhibits extensive otolaryngological symptoms, mainly affecting the upper airway. These symptoms affect the quality of life and can be life-threatening. Prompt acute management is essential for stridor, dyspnea, and dysphagia. Given the potential severity of the symptoms and rarity of the disease, it is important for otolaryngologists to be familiar with anti-IgLON5 disease.

LEVEL OF EVIDENCE

Level 4.

Phenotypic Insights Into Anti-IgLON5 Disease in IgLON5-Deficient Mice

BACKGROUND AND OBJECTIVES

Anti-IgLON5 disease is an autoimmune neurodegenerative disorder characterized by various phenotypes, notably sleep and movement disorders and tau pathology. Although the disease is known to be associated with the neuronal cell adhesion protein IgLON5, the physiologic function of IgLON5 remains elusive. There are conflicting views on whether autoantibodies cause loss of function, activation of IgLON5, or inflammation-associated neuronal damage, ultimately leading to the disease. We generated IgLON5 knockout (-/-) mice to investigate the functions of IgLON5 and elucidate the pathomechanism of anti-IgLON5 disease.

METHODS

IgLON5 knockout (-/-) mice underwent behavioral tests investigating motor function, psychiatric function (notably anxiety and depression), social and exploratory behaviors, spatial learning and memory, and sensory perception. Histologic analysis was conducted to investigate tau aggregation in mice with tauopathy.

RESULTS

IgLON5-/- mice had poorer performance in the wire hang and rotarod tests (which are tests for motor function) than wild-type mice. Moreover, IgLON5-/- mice exhibited decreased anxiety-like behavior and/or hyperactivity in behavior tests, including light/dark transition test and open field test. IgLON5-/- mice also exhibited poorer remote memory in the contextual fear conditioning test. However, neither sleeping disabilities assessed by EEG nor tau aggregation was detected in the knockout mice.

DISCUSSION

These results suggest that IgLON5 is associated with activity, anxiety, motor ability, and contextual fear memory. Comparing the various phenotypes of anti-IgLON5 disease, anti-IgLON5 disease might partially be associated with loss of function of IgLON5; however, other phenotypes, such as sleep disorders and tau aggregation, can be caused by gain of function of IgLON5 and/or neuronal damage due to inflammation. Further studies are needed to elucidate the role of IgLON5 in the pathogenesis of anti-IgLON5 diseases.

Sleep Disturbances in Autoimmune Neurological Diseases

PURPOSE OF REVIEW

To summarize the current evidence on the associations between autoimmune neurological diseases (e.g., multiple sclerosis, myasthenia gravis) and sleep disturbances (e.g., insomnia, parasomnias), as well as to review the main characteristics of sleep disorders with an immune-related pathophysiology (e.g., narcolepsy, anti-IgLON5 disease).

RECENT FINDINGS

An immune-mediated damage of the areas in the central nervous system that control sleep and wake functions (e.g., hypothalamus, brainstem) can lead to sleep disorders and sleep symptoms. Sleep disturbances are the reason to seek for medical attention in certain neuroimmunological conditions (e.g., narcolepsy, anti-IgLON5 disease) where sleep-related alterations are the main clinical feature. The assessment of sleep-related symptomatology and disorders should be included in the routine evaluation of patients with autoimmune neurological diseases. Clinicians should be aware of the typical clinical presentation of certain neuroimmunological disorders mainly affecting sleep.

Sleep disorders and polysomnography findings in patients with autoimmune encephalitis

BACKGROUND

Sleep disorders in patients with autoimmune encephalitis (AE) are increasingly reported. Early recognition and treatment have significant importance regarding the potential of sleep disorders' effect on morbidity and even mortality. There are a limited number of studies related to polysomnography (PSG) in these patients. Here, we report the clinical and PSG data of patients with AE and sleep disorders, with a particular interest in sleep-related breathing disorders (SRBD).

METHODS

Seventeen patients with diagnosed AE and acute or subacute onset sleep complaints who underwent video-electroencephalography-PSG recordings in our tertiary center were investigated.

RESULTS

The mean age was 50, with eight females and nine males. The detected antibodies were against leucine-rich glioma-inactivated 1(LGI-1) in 6, anti-contactin-associated protein-2(CASPR2) in 3, voltage-gated potassium channel complex antigens(VGKC) in 1, anti-glycine in 1, dipeptidyl-peptidase-like protein-6(DPPX) in 1, anti-Hu in 1, and anti-amphiphysin in 1. All commercially available and known autoimmune encephalitis-related antibodies were negative in 3 of the patients. Final diagnosis after PSG was circadian rhythm sleep disorder (n = 3), periodic limb movement disorder (n = 3), insomnia (n = 5), central apnea with or without Cheyne-Stokes breathing (CSB) (n = 4), obstructive sleep apnea (OSA) (n = 4), non-rapid eye movement (NREM) and REM parasomnia (n = 8), faciobrachial dystonic seizures (n = 2), and subclinical seizures (n = 1). Sleep microstructure was disrupted in 9, REM periods without atonia occurred in 4, and brief sleep fragments consisting of theta activity interspersed with faster rhythms existed in 7 patients. Nearly half of our patients (47%) had SRBD, and the mean apnea-hypopnea index (AHI) was 14.

CONCLUSIONS

Sleep disorders are frequent and essential components of AEs. Systematic clinical questionnaires and routine PSG assessments would significantly impact the correct diagnosis and proper treatment of SRBD and the overall prognosis of AE.

Clinical, serological and genetic predictors of response to immunotherapy in anti-IgLON5 disease

Anti-IgLON5 disease is a newly defined clinical entity characterized by a progressive course with high disability and mortality rate. While precise pathogenetic mechanisms remain unclear, features characteristic of both autoimmune and neurodegenerative diseases were reported. Data on immunotherapy are limited, and its efficacy remains controversial. In this study, we retrospectively investigated an anti-IgLON5 disease cohort with special focus on clinical, serological and genetic predictors of the immunotherapy response and long-term outcome. Patients were recruited from the GENERATE (German Network for Research on Autoimmune Encephalitis) registry. Along with clinical parameters, anti-IgLON5 immunoglobulin (Ig)G in serum and CSF, anti-IgLON5 IgG1-4, IgA and IgM in serum, neurofilament light chain and glial fibrillary acidic protein in serum as well as human leukocyte antigen-genotypes were determined. We identified 53 patients (symptom onset 63.8 ± 10.3 years, female:male 1:1.5). The most frequent initial clinical presentations were bulbar syndrome, hyperkinetic syndrome or isolated sleep disorder [at least one symptom present in 38% (20/53)]. At the time of diagnosis, the majority of patients had a generalized multi-systemic phenotype; nevertheless, 21% (11/53) still had an isolated brainstem syndrome and/or a characteristic sleep disorder only. About one third of patients [28% (15/53)] reported subacute disease onset and 51% (27/53) relapse-like exacerbations during the disease course. Inflammatory CSF changes were evident in 37% (19/51) and increased blood-CSF-barrier permeability in 46% (21/46). CSF cell count significantly decreased, while serum anti-IgLON5 IgG titre increased with disease duration. The presence of human leukocyte antigen-DRB1*10:01 [55% (24/44)] was associated with higher serum anti-IgLON5 IgG titres. Neurofilament light chain and glial fibrillary acidic protein in serum were substantially increased (71.1 ± 103.9 pg/ml and 126.7 ± 73.3 pg/ml, respectively). First-line immunotherapy of relapse-like acute-to-subacute exacerbation episodes resulted in improvement in 41% (11/27) of patients and early initiation within the first 6 weeks was a predictor for therapy response. Sixty-eight per cent (36/53) of patients were treated with long-term immunotherapy and 75% (27/36) of these experienced no further disease progression (observation period of 20.2 ± 15.4 months). Long-term immunotherapy initiation during the first year after onset and low pre-treatment neurofilament light chain were significant predictors for a better outcome. In conclusion, subacute disease onset and early inflammatory CSF changes support the primary role of autoimmune mechanisms at least at initial stages of anti-IgLON5 disease. Early immunotherapy, prior to advanced neurodegeneration, is associated with a better long-term clinical outcome. Low serum neurofilament light chain at treatment initiation may serve as a potential biomarker of the immunotherapy response.

Sleep disturbances in autoimmune encephalitis

Autoimmune encephalitis is an inflammatory neurological disorder characterized by psychiatric symptoms, cognitive impairment, and focal neurological deficits or seizures. Sleep disturbances are not a major consideration in the diagnosis and treatment of patients with autoimmune encephalitis. Various types of sleep disturbances are frequent, severe, and long-lasting, which can compromise the recovery and quality of life in patients with autoimmune encephalitis. Sleep disorders in patients with autoimmune encephalitis have received limited attention, and the prevalence and pathophysiological mechanisms of sleep disorders remain unclear. Recent studies have suggested that early recognition of specific sleep disturbances may provide clues for diagnosing autoimmune encephalitis. Furthermore, early diagnosis and treatment of sleep disturbances can promote recovery and improve long-term outcomes in patients with autoimmune encephalitis. In this report, we aimed to provide a comprehensive and extensive understanding of the clinical relevance of autoimmune encephalitis and specific related sleep disorders.

Anti-IgLON5 Disease with Isolated Hemichorea: A Case Report and Review of the Literature

Background

Anti-IgLON5 disease is an autoimmune encephalopathy with sleep disturbances as a hallmark in the majority of reported cases. Additional clinical symptoms are heterogenous and include movement disorders, bulbar dysfunction, autonomic disorders, and neurocognitive impairment.

Case

Here, we report the case of an 87-year-old woman presenting with isolated progressive hemichorea. An extensive diagnostic work-up revealed antibodies against IgLON5 in the serum. Neither history nor polysomnography (PSG) unveiled signs and features of sleep dysfunction typically reported in anti-IgLON5 disease.

Literature Review

In an extensive literature review we identified twelve other studies reporting about patients with confirmed anti-IgLON5 disease and chorea as extrapyramidal movement disorder in their clinical phenotype. Subsequently, clinical characteristics of these patients were carefully evaluated.

Conclusions

Our results support the diversity of clinical phenotypes in anti-IgLON5 disease, adding isolated hemichorea to the spectrum of presenting symptoms. As sleep-related disorders are often not the leading reason for consultation and only revealed by PSG examination, we suggest that screening for antibodies against IgLON5 should be considered in patients presenting with unexplained movement disorders, including isolated hemichorea.

Sleep medicine: Practice, challenges and new frontiers

Sleep medicine is an ambitious cross-disciplinary challenge, requiring the mutual integration between complementary specialists in order to build a solid framework. Although knowledge in the sleep field is growing impressively thanks to technical and brain imaging support and through detailed clinic-epidemiologic observations, several topics are still dominated by outdated paradigms. In this review we explore the main novelties and gaps in the field of sleep medicine, assess the commonest sleep disturbances, provide advices for routine clinical practice and offer alternative insights and perspectives on the future of sleep research.

Sleep Dysfunction in Movement Disorders: a Window to the Disease Biology

PURPOSE OF REVIEW

To comprehensively summarize the sleep pathologies associated with movement disorders, focusing on neurodegenerative diseases.

RECENT FINDINGS

Mounting evidence has further implicated both sleep and circadian disruption in the pathophysiology of many movement disorders. In particular, recent data illuminate the mechanisms by which poor sleep quality and circadian dysfunction can exacerbate neurodegeneration. In addition, anti-IgLON5 disease is a recently described autoimmune disease with various symptoms that can feature prominent sleep disruption and parasomnia. Many movement disorders are associated with sleep and circadian rhythm disruption. Motor symptoms can cause sleep fragmentation, resulting in insomnia and excessive daytime sleepiness. Many neurodegenerative movement disorders involve brainstem pathology in regions close to or affecting nuclei that regulate sleep and wake. Further, commonly used movement medications may exacerbate sleep concerns. Providers should screen for and address these sleep symptoms to improve function and quality of life for patients and caregivers.

Recognizing New-Onset Sleep Disorders in Autoimmune Encephalitis Often Prompt Earlier Diagnosis

SUMMARY

Sleep/wake disorders are common in patients with autoimmune encephalitis, sometimes the most prominent or sole initial symptom, then delaying diagnosis. Sleep/wake disorders in autoimmune encephalitis vary and include severe sleeplessness, hypersomnia, central and/or obstructive sleep apnea, rapid eye movement sleep behavior disorder, indeterminate sleep/wake states, and loss of circadian sleep/wake rhythms. N-methyl- d aspartate receptor encephalitis (NMDAR) is often associated with insomnia, then hypersomnia and sleep-related central hypoventilation. Profound sleeplessness and rapid eye movement sleep behavior disorder are seen in patients with voltage-gated potassium channel-complex antibodies. Fragmented sleep and hypersomnia are common in paraneoplastic syndromes associated with anti-MA protein encephalitis; rapid eye movement sleep behavior disorder in those with antibodies against leucine-rich glioma inactivated protein (LGI1) or contactin-associated protein 2 (CASPR2) antibodies. Antibodies against a cell adhesion protein IGLON5 may result in obstructive sleep apnea, inspiratory stridor, disorganized nonrapid eye movement sleep, and excessive movements and parasomnias fragmenting nonrapid and rapid eye movement sleep. Recognizing a particular sleep/wake disorder is often a presenting or prominent feature in certain autoimmune encephalitis permit for earlier diagnosis. This is important because reduced morbidity and better short- and long-term outcomes are associated with earlier diagnosis and immunotherapies.

Epileptic Seizures and Right-Sided Hippocampal Swelling as Presenting Symptoms of Anti-IgLON5 Disease: A Case Report and Systematic Review of the Literature

Background and Objective

Anti-IgLON5 disease is an uncommon neurological disorder characterized by diverse clinical manifestations. Although many relevant cases have been reported, our understanding of this disorder is still quite restricted. We present a rare case of anti-IgLON5 disease and performed a comprehensive systematic review of all published cases to expand the clinical spectrum of this disorder.

Methods

We report a 61-year-old woman with an atypical presentation of epileptic seizures with abnormal signals in her right hippocampus on brain magnetic resonance imaging (MRI). A systematic review was performed of electronic databases, including PubMed, EMBASE, China National Knowledge Infrastructure (CNKI), WanFang and VIP China Science.

Results

We identified 161 cases from 65 publications. With heterogeneous clinical manifestations, we found that bulbar dysfunction, sleep apnea, gait instability and neurocognitive and behavioral symptoms are the most common symptoms of anti-IgLON5 disease. Anti-IgLON5 antibodies presented a higher positive rate and titer in the serum than in the cerebrospinal fluid (CSF). Haplotype DRB1*10:01-DQB1*05:01 is highly correlated with anti-IgLON5 disease. Only 38 patients have presented distinctive MRI alterations (26.2%). Approximately half of the cases are responsive to immunosuppressive or immunomodulatory treatment.

Conclusion

Anti-IgLON5 disease is characterized by various clinical manifestations and laboratory findings. Immunotherapy may be effective in treating anti-IgLON5 disease, but the results are far from satisfactory. Studies with larger sample sizes are required to improve the current understanding of this disorder.

Anti-IgLON5 Disease - The Current State of Knowledge and Further Perspectives

Anti-IgLON5 disease is a relatively new neurological entity with the first cases reported in 2014. So far, less than 70 articles on this topic have been published. Due to its unspecific symptomatology, diverse progression, novelty and ambiguous character, it remains a difficulty for both clinical practitioners and scientists. The aim of this review is to summarize the current knowledge concerning anti-IgLON5 disease; mechanisms underlying its cause, symptomatology, clinical progression, differential diagnosis and treatment, which could be helpful in clinical practice and future research.

[Clinical features of anti-IgLON5 disease]

Anti-IgLON5 diseases were first reported in 2014 as sleep disorders such as parasomnia and obstructive sleep apnea. The pathological findings were suggestive of tauopathies and eight clinical subtypes have been reported so far. Serum and cerebrospinal fluid anti-IgLON5 antibodies should be measured in patients with sleep-related disorders with parasomnia as well as in patients with movement disorders, motor neuron disease or dementia with characteristic parasominia. The prognosis is generally poor, but some patients have been reported to improve with immunotherapy. Early diagnosis and early immunotherapy may improve the prognosis.

Measuring Sleep, Wakefulness, and Circadian Functions in Neurologic Disorders

Neurologic disorders impact the ability of the brain to regulate sleep, wake, and circadian functions, including state generation, components of state (such as rapid eye movement sleep muscle atonia, state transitions) and electroencephalographic microarchitecture. At its most extreme, extensive brain damage may even prevent differentiation of sleep stages from wakefulness (eg, status dissociatus). Given that comorbid sleep-wake-circadian disorders are common and can adversely impact the occurrence, evolution, and management of underlying neurologic conditions, new technologies for long-term monitoring of neurologic patients may potentially usher in new diagnostic strategies and optimization of clinical management.

Sleep Disturbances in Autoimmune Neurologic Diseases: Manifestation and Pathophysiology

Autoimmune neurologic diseases are a new category of immune-mediated disease demonstrating a widely varied spectrum of clinical manifestations. Recently, sleep disturbances in patients with autoimmune neurologic diseases have been reported to have an immense negative impact on the quality of life. Excessive daytime sleep, rapid eye movement sleep behavior disorder (RBD), and narcolepsy are the most frequent sleep disorders associated with autoimmune neurologic diseases. Sleep disturbances might be the initial symptoms of disease or persist throughout the course of the disease. In this review, we have discussed sleep disturbances in different autoimmune neurologic diseases and their potential pathophysiological mechanisms.

Sleep in Patients With Neurologic Disease

PURPOSE OF REVIEW

This article provides a discussion of the current evidence and contemporary views on the relationship between sleep disorders and neurologic disease.

RECENT FINDINGS

Disrupted or disordered sleep can be associated with increased morbidity and mortality, the risk of cardiovascular events, increased seizure frequency, and altered immune responses. Studies have implicated disrupted sleep and circadian rhythm dysfunction with both amyloid-β (Aβ) deposition and tau deposition. A bidirectional relationship exists between disrupted sleep and the progression of Alzheimer disease pathology. Insomnia has been reported as a prodromal symptom in autoimmune encephalitis. Primary sleep disorders have now been increasingly recognized as a common comorbid condition in multiple sclerosis, making it imperative that neurologists feel comfortable differentiating multiple sclerosis fatigue from excessive daytime sleepiness caused by primary sleep disorders to optimally treat their patients.

SUMMARY

Sleep disorders are common across the population. By recognizing sleep disorders in patients with neurologic conditions, neurologists can provide comprehensive care and, in some cases, reduce neurologic disease burden.

Neurodegeneration Induced by Anti-IgLON5 Antibodies Studied in Induced Pluripotent Stem Cell-Derived Human Neurons

Anti-IgLON5 disease is a progressive neurological disorder associated with autoantibodies against a neuronal cell adhesion molecule, IgLON5. In human postmortem brain tissue, the neurodegeneration and accumulation of hyperphosphorylated tau (p-tau) are found. Whether IgLON5 antibodies induce neurodegeneration or neurodegeneration provokes an immune response causing inflammation and antibody formation remains to be elucidated. We investigated the effects of anti-IgLON5 antibodies on human neurons. Human neural stem cells were differentiated for 14–48 days and exposed from Days 9 to 14 (short-term) or Days 13 to 48 (long-term) to either (i) IgG from a patient with confirmed anti-IgLON5 antibodies or (ii) IgG from healthy controls. The electrical activity of neurons was quantified using multielectrode array assays. Cultures were immunostained for β-tubulin III and p-tau and counterstained with 4′,6-Diamidine-2′-phenylindole dihydrochloride (DAPI). To study the impact on synapses, cultures were also immunostained for the synaptic proteins postsynaptic density protein 95 (PSD95) and synaptophysin. A lactate dehydrogenase release assay and nuclei morphology analysis were used to assess cell viability. Cultures exposed to anti-IgLON5 antibodies showed reduced neuronal spike rate and synaptic protein content, and the proportion of neurons with degenerative appearance including p-tau (T205)-positive neurons was higher when compared to cultures exposed to control IgG. In addition, cell death was increased in cultures exposed to anti-IgLON5 IgG for 21 days. In conclusion, pathological anti-IgLON5 antibodies induce neurodegenerative changes and cell death in human neurons. This supports the hypothesis that autoantibodies may induce the neurodegenerative changes found in patients with anti-IgLON5-mediated disease. Furthermore, this study highlights the potential use of stem cell-based in vitro models for investigations of antibody-mediated diseases. As anti-IgLON5 disease is heterogeneous, more studies with different IgLON5 antibody samples tested on human neurons are needed.

Sleep Disturbances Associated with Neurological Autoimmunity

Associations between sleep disorders and neurological autoimmunity have been notably expanding recently. Potential immune-mediated etiopathogenesis has been proposed for various sleep disorders including narcolepsy, Kleine-Levin syndrome, and Morvan syndrome. Sleep manifestations are also common in various autoimmune neurological syndromes, but may be underestimated as overriding presenting (and potentially dangerous) neurological symptoms often require more urgent attention. Even so, sleep dysfunction has been described with various neural-specific antibody biomarkers, including IgLON5; leucine-rich, glioma-inactivated protein 1 (LGI1); contactin-associated protein 2 (CASPR2); N-methyl-D-aspartate (NMDA)-receptor; Ma2; dipeptidyl-peptidase-like protein-6 (DPPX); alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R); anti-neuronal nuclear antibody type-1 (ANNA-1, i.e., Hu); anti-neuronal nuclear antibody type-2 (ANNA-2, i.e., Ri); gamma-aminobutyric acid (GABA)-B-receptor (GABA-B-R); metabotropic glutamate receptor 5 (mGluR5); and aquaporin-4 (AQP-4). Given potentially distinctive findings, it is possible that sleep testing could potentially provide objective biomarkers (polysomnography, quantitative muscle activity during REM sleep, cerebrospinal fluid hypocretin-1) to support an autoimmune diagnosis, monitor therapeutic response, or disease progression/relapse. However, more comprehensive characterization of sleep manifestations is needed to better understand the underlying sleep disruption with neurological autoimmunity.

Sleep disorders in autoimmune encephalitis

Sleep disorders in people with autoimmune encephalitis have received little attention, probably overshadowed by the presence of other neurological and psychiatric symptoms in this group of conditions. However, sleep disorders are frequent, often severe, and usually persist beyond the acute disease stage, interfering with patients' recovery and quality of life. Because autoimmune encephalitis can affect any brain network involved in sleep initiation and regulation, all types of sleep disorders can occur, with varying distinct associations, frequency, and intensity. Anti-IgLON5 and anti-NMDA receptor encephalitis exemplify two diseases in which sleep disorders are prominent. In anti-IgLON5 disease, sleep disorders were the core symptoms that led to the description of this disease, whereas in anti-NMDA receptor encephalitis, sleep disorders vary according to the disease stage along with other neuropsychiatric symptoms. Comprehensive, systematic, multicentre studies are needed to characterise sleep disorders and their mechanisms in autoimmune encephalitis.

Rare Case of Late-Onset Narcolepsy Type 1

A 69-year-old male developed symptoms typical of the diagnosis of narcolepsy type 1 without any previous triggering events. First, daytime sleepiness occurred, soon followed by cataplexy. Nocturnal polysomnography revealed rapid eye movement (REM) sleep behavior disorder, a apnea-hypopnea index of 25.8 events/h, and no sleep-onset REM. Multiple Sleep Latency Test showed a mean sleep latency of 2.1 min and REM sleep in 3 tests. HLA DQB1*06:02 was positive and hypocretin-1 in cerebrospinal fluid unmeasurable. A treatment with 50 mg clomipramine controlled the cataplexy; excessive daytime sleepiness was sufficiently managed by repeated naps. The administration of 0.25 mg of clonazepam subjectively improved REM sleep behavior disorder. Bilevel Positive Airway Pressure improved the apnea-hypopnea index without important influence on sleepiness. Our unique case demonstrates that even elderly subjects can develop narcolepsy type 1.

Tauopathy and Movement Disorders-Unveiling the Chameleons and Mimics

The spectrum of tauopathy encompasses heterogenous group of neurodegenerative disorders characterized by neural or glial deposition of pathological protein tau. Clinically they can present as cognitive syndromes, movement disorders, motor neuron disease, or mixed. The heterogeneity in clinical presentation, genetic background, and underlying pathology make it difficult to classify and clinically approach tauopathy. In the literature, tauopathies are thus mostly highlighted from pathological perspective. From clinical standpoint, cognitive syndromes are often been focussed while reviewing tauopathies. However, the spectrum of tauopathy has also evolved significantly in the domain of movement disorders and has transgressed beyond the domain of primary tauopathies. Secondary tauopathies from neuroinflammation or autoimmune insults and some other "novel" tauopathies are increasingly being reported in the current literature, while some of them are geographically isolated. Because of the overlapping clinical phenotypes, it often becomes difficult for the clinician to diagnose them clinically and have to wait for the pathological confirmation by autopsy. However, each of these tauopathies has some clinical and radiological signatures those can help in clinical diagnosis and targeted genetic testing. In this review, we have exposed the heterogeneity of tauopathy from a movement disorder perspective and have provided a clinical approach to diagnose them ante mortem before confirmatory autopsy. Additionally, phenotypic variability of these disorders (chameleons) and the look-alikes (mimics) have been discussed with potential clinical pointers for each of them. The review provides a framework within which new and as yet undiscovered entities can be classified in the future.

Characterization of the sleep disorder of anti-IgLON5 disease

STUDY OBJECTIVE

To characterize the sleep disorder of anti-IgLON5 disease.

METHODS

We reviewed 27 video-polysomnographies (V-PSG), 6 multiple sleep latency tests (MSLT), 2 videsomnoscopies with dexmedetomidine, and 10 actigraphies recorded during the disease course of five patients. Due to severe sleep architecture abnormalities, we used a novel modified sleep scoring system combining conventional stages with a descriptive approach in which two additional stages were identified: undifferentiated-NREM (UN-NREM) and poorly structured N2 (P-SN2) sleep that were characterized by abnormal motor activation and absence or sparse elements of conventional NREM sleep.

RESULTS

Sleep-related vocalizations, movements, behaviors, and respiratory abnormalities were reported by bed-partners. In all patients, NREM sleep onset and sleep reentering after an awakening occurred as UN-NREM (median: 29.8% of total sleep time [TST]) and P-SN2 sleep (14.5% TST) associated with vocalizations and simple and quasi-purposeful movements. Sleep initiation was normalized in one patient with a high dose of steroids, but NREM sleep abnormalities reappeared in subsequent V-PSG. In all patients, if sleep continued uninterrupted, there was a progressive normalization with normal N2 (11.7% TST) and N3 (22.3% TST) sleep but stridor and obstructive apnea emerged. REM sleep behavior disorder (RBD) occurred in four patients. Sleep initiation was also altered in MSLT and dexmedetomidine-induced sleep. Actigraphy showed a 10-fold increase of nocturnal activity compared with controls. Sleep abnormalities remained stable during the disease.

CONCLUSIONS

The sleep disorder of anti-IgLON5 disease presents as a complex sleep pattern characterized by abnormal sleep initiation with undifferentiated NREM sleep, RBD, periods of normal NREM sleep, stridor, and obstructive apnea.

Figural Memory Impairment in Conjunction With Neuropsychiatric Symptoms in IgLON5 Antibody-Associated Autoimmune Encephalitis

BACKGROUND

IgLON5 disease is an autoimmune disorder that shares neuropathological aspects with a tauopathy. Its clinical spectrum is heterogeneous, and figural memory impairment as an initial phenomenon of IgLON5 syndrome has not yet been described. The rationale of this report is to highlight symptoms related to IgLON5 disease that have not been reported to date. This case report will thereby emphasize how important it is to initiate thorough diagnostic methods including cerebrospinal fluid analysis (CSF) before starting early immunotherapy.

METHODS

We examined a 65-year-old Caucasian male via neuropsychological tests, magnetic resonance imaging (MRI), electroencephalography (EEG), neurography and polysomnography. He also underwent two lumbar punctures from which we determined specific autoantibodies in cerebrospinal (CSF) and peripheral blood (PB).

RESULTS

The patient presented initially complaining of memory loss, gradual dysphagia and sleeping dysfunction. Neuropsychological testing at first presentation and follow-up revealed subtle figural and working memory impairment. At onset and at his 6-month follow-up, we detected IgLON5 antibodies in CSF and PB. Furthermore, we identified in the CSF a blood-brain barrier disturbance at disease onset and follow-up, and markers of neuroaxonal damage such as mildly elevated phosphorylated Tau-181 protein with 86 pg/ml (normal range ≤ 61 pg/ml) at onset. Three months after his initial presentation, he was suffering from axonal neuropathy and transient ataxia in the extremities. Assuming a definitive autoimmune encephalitis-associated with anti-IgLON5 antibodies, we applied high-dose steroids monthly (1g methylprednisolone i.v. for five consecutive days) and his memory complaints, ataxia of extremities and peripheral neuropathy as well as sleeping dysfunction decreased.

CONCLUSIONS

Our findings broaden IgLON5 disease's clinical spectrum to include predominant and discrete figural memory impairment together with sleeping dysfunction at disease onset. In addition, our report illustrates how important taking an elaborated diagnostic approach is to assuring an accurate diagnosis and the appropriate therapy if a patient presents with a persisting figural memory impairment and sleeping abnormalities so as to avoid overlooking IgLON5 disease and a potentially poor outcome.

Sleep disorders in anti-NMDAR encephalitis

Objective

To describe the sleep disorders in anti–NMDA receptor encephalitis (anti-NMDARe).

Methods

Patients recovering from anti-NMDARe were invited to participate in a prospective observational single-center study including comprehensive clinical, video-polysomnography (V-PSG) sleep assessment, and neuropsychological evaluation. Age- and sex-matched healthy participants served as controls.

Results

Eighteen patients (89% female, median age 26 years, interquartile range [IQR] 21–29 years) and 21 controls (81% female, median age 23 years, IQR 18–26 years) were included. In the acute stage, 16 (89%) patients reported insomnia and 2 hypersomnia; nightmares occurred in 7. After the acute stage, 14 (78%) had hypersomnia. At study admission (median 183 days after disease onset, IQR 110–242 days), 8 patients still had hypersomnia, 1 had insomnia, and 9 had normal sleep duration. Patients had more daytime sleepiness than controls (higher Barcelona Sleepiness Index, p = 0.02, and Epworth Sleepiness Score, p = 0.04). On V-PSG, sleep efficiency was similar in both groups, but patients more frequently had multiple and longer confusional arousals in non-REM (NREM) sleep (videos provided). In addition, 13 (72%) patients had cognitive deficits; 12 (67%) had psychological, social, or occupational disability; and 33% had depression or mania. Compared with controls, patients had a higher body mass index (median 23.5 [IQR 22.3–30.2] vs 20.5 [19.1–21.1] kg/m2; p = 0.007). Between disease onset and last follow-up, 14 (78%) patients developed hyperphagia, and 6 (33%) developed hypersexuality (2 requiring hospitalization), all associated with sleep dysfunction.

Conclusions

Sleep disturbances are frequent in anti-NMDARe. They show a temporal pattern (predominantly insomnia at onset; hypersomnia during recovery), are associated with behavioral and cognitive changes, and can occur with confusional arousals during NREM sleep.

HLA and microtubule-associated protein tau H1 haplotype associations in anti-IgLON5 disease

OBJECTIVES

We investigated the associations with HLA and microtubule-associated protein tau (MAPT) H1 haplotype in anti-IgLON5 disease, a recently identified disorder characterized by gait instability, brainstem dysfunction, and a prominent sleep disorder in association with IgLON5 antibodies and pathologic findings of a novel neuronal-specific tauopathy.

METHODS

We compared the HLA alleles and MAPT H1/H1 genotype of 35 patients with anti-IgLON5 with healthy controls. The on-line server tool NetMHCIIpan 3.1 was used to predict the IgLON5 peptide binding to HLA Class II molecules.

RESULTS

The HLA-DRB1*10:01-DQB1*05:01 haplotype was overrepresented in patients with anti-IgLON5 disease (OR = 54.5; 95% CI: 22.2-133.9, p < 0.0001). In addition, HLA-DQA was genotyped in 27 patients, and 25 (92.6%) of them had DQ molecules composed by DQA1*01 and DQB1*05 chains compared with 148/542 (27.3%) controls (OR = 43.9; 95% CI: 10.4-185.5, p < 0.0001). Patients DRB1*10:01 positive developed more frequently sleep or bulbar symptoms than those carrying other HLA alleles (70.0% vs 26.7%; p = 0.011). Prediction algorithms identified 2 IgLON5 peptides (1 located in the signal sequence) that showed strong binding to HLA-DRB1*10:01 and other HLA-DRB1, but not to HLA-DQA and HLA-DQB molecules. The MAPT H1/H1 homozygous genotype was present in 20/24 (83.3%) anti-IgLON5 Caucasian patients compared with 54/116 (46.5%) healthy controls (p = 0.0007).

CONCLUSIONS

The robust association of anti-IgLON5 disease with distinct HLA Class II molecules supports a primary autoimmune origin. The significant association of MAPT H1 haplotype also suggests that an underlying neurodegenerative process could be involved in anti-IgLON5 disease.

Anti-IgLON5 Disease: A Case With 11-Year Clinical Course and Review of the Literature

Background: Anti-IgLON5 disease is a novel disorder with a complex interplay between inflammation and neurodegeneration. Patients develop antibodies against IgLON5 but also deposition of neuronal tau protein. Symptoms often have an insidious onset, slow progression and mimic other neurological disorders. Here we report a case with severely prolonged 11-year disease course and provide a review of current reported cases with focus on presentation, work-up, treatment, and outcome. Method: All reported cases of anti-IgLON5 disease were evaluated. Cases reported twice (in case series and as single case reports), were carefully excluded. Results: Most patients display a characteristic sleep disorder with severe insomnia, non rapid eye movement (NREM) parasomnia, with finalistic movements and sleep disordered breathing (stridor and obstructive sleep apnea). Other symptoms are bulbar involvement, gait instability, movement disorders, oculomotor abnormalities, dysautonomia, and peripheral symptoms. Antibodies are present in both serum and CSF and there is a strong correlation with human leukocyte antigen (HLA) DRB1^*10:01 and HLA-DQB1^*05:01. Neuropathological examination reveals neurodegeneration with neuronal tau deposits in regions that correlate with the clinical presentation (e.g., predominantly hypothalamus and tegmentum of the brain stem). Majority of cases respond partially to immunotherapy. Cases, who received no treatment or treatment with IV corticosteroids alone, had a higher mortality than cases treated with more potent immunotherapy. Conclusion: The clinical spectrum of Anti-IgLON5 disease continues to expand. Further studies are needed to elucidate the pathophysiology, therapeutic strategies and outcome in this novel disorder. Aggressive immunotherapy seems to increase survival.

Non-REM Parasomnia: The Promise of Precision Medicine

Our understanding of non-REM parasomnias is just beginning to unfold the potential biomarkers and underlying pathophysiologic processes that lead to these events. Biomarkers need further investigation and will help us to understand better ways to develop risk models and possible mechanisms. Similarly, as we develop more accurate pathophysiologic-based diagnostic testing for non-REM parasomnias, we will begin the evolution toward a physiologic-based classification scheme that aids the application of precision medicine. This article explores currently known characteristics and exploratory features that may aid in this transition to better understanding our individual patients with non-REM parasomnias and tailoring their treatments.

Autoimmune encephalitis with anti-IgLON5 and anti-GABAB-receptor antibodies: A case report

RATIONALE

Anti-IgLON5 disease is a complex neurological illness which is characterized by progressive sleep and movement disorders and defined by specific autoantibodies to IgLON5. We here describe the first case of a patient with coexisting anti-IgLON5 as well as anti-γ-aminobutyric acid B (GABAB)-receptor antibodies and predominant clinical features of anti-IgLON5 disease.

PATIENT CONCERNS

The patient initially presented with subacute symptoms of severe sleep disorder, gait stability, dysarthria, cognitive impairment, depressive episode and hallucinations.

DIAGNOSES

The patient was diagnosed with autoimmune encephalitis, based on clinical features and positive anti-IgLON5 antibodies in serum as well as in cerebrospinal fluid and anti-GABAB-receptor antibodies in serum only.

INTERVENTIONS

Initially, the patient was treated with high dosages of methylprednisolone and subsequently with plasmapheresis. Due to the lack of clinical improvement immunosuppressive treatment with intravenous cyclophosphamide was initiated.

OUTCOMES

Following the first year of cyclophosphamide treatment, neurological examination revealed an improvement in gait instability, visual and acoustic hallucinations and sleep disorder.

LESSONS

The case report demonstrates that anti-IgLON5 and anti-GABAB-receptor antibodies can coexist in the same patient whereas clinical leading symptoms are determined by those antibodies that were tested positive in cerebrospinal fluid.