[Esophageal achalasia, sleep disorders and chorea in a tauopathy without ophthalmoplegia, parkinsonian syndrome, nor dementia (progressive supranuclear palsy?): clinicopathological study]

Dysphagia Prevalence in Progressive Supranuclear Palsy: A Systematic Review and Meta-Analysis

The objective of this systematic review was to determine the prevalence of dysphagia and aspiration in people with progressive supranuclear palsy (PSP). A search of six electronic databases was performed from inception to April 2022. No context restrictions were set. All primary research comprising figures to derive a prevalence rate were included. Two independent reviewers screened search results. Data were extracted by one reviewer. Conflicts were resolved by discussion with a third reviewer. The quality of included studies was assessed using the JBI Checklist for Prevalence Studies. From 877 studies, 12 were eligible for inclusion. Dysphagia had to be confirmed using instrumental assessments, clinical swallowing evaluation, screening, and patient-reported outcome measures (PROM). A random-effects meta-analysis calculated a pooled dysphagia prevalence in 78-89% (95% CI [60.6, 89.1], [78.9, 95.0]). depending on the chosen assessment method, and a pooled aspiration prevalence of 23.5% (95% CI [14.5, 33.7]). The included studies were of moderate quality, with high risk of selection and coverage bias and low to moderate risk of measurement bias. Dysphagia is highly prevalent in a sample of participants with mostly moderately severe PSP. Aspiration occurs in a quarter of this sample and is likely to increase as the disease progresses. Given the low general prevalence of PSP, studies remain at high risk for selection bias. Prospective research should focus on the development of dysphagia in the course of PSP and its subcategories using instrumental assessment and consider all phases of swallowing. REGISTRATION: The protocol of this systematic review was registered on the International Prospective Register of Systematic Reviews (PROSPERO) in April 2021 (registration number: CRD42021245204).

Prevalence of neurodegenerative/demyelinating disorders in patients with achalasia

Introduction

Esophageal achalasia is a primary motility disorder. Although the exact pathogenesis is unknown, autoimmune, and neurodegenerative processes seem to be involved similarly to neurodegenerative and/or demyelinating disorders (NDDs). We hypothesized that the prevalence of NDD may be higher among patients with achalasia and vice versa as the background pathogenetic mechanisms are similar.

Methods

This was a prospective, comparative questionnaire-based study. Patients with achalasia and patients with NDD were enrolled. Selected patients with achalasia were thoroughly examined by a neurologist and selected patients with NDD were examined by a gastroenterologist to confirm or rule out NDD or achalasia. We assessed the prevalence of both achalasia and NDD and compared them with their prevalence in general population.

Results

A total of 150 patients with achalasia and 112 patients with NDD were enrolled. We observed an increased prevalence of NDD among patients with achalasia (6.0% (9/150); 95% CI (confidence interval): 3.1–11.2%) as compared to the estimated 2.0% prevalence in general population (p = 0.003). Although 32 out of 112 patients (28.6%) with NDD reported dysphagia, we did not observe significantly increased prevalence of achalasia in these patients (1.8% (2/112) vs 0.8% in general population, p = 0.226).

Conclusion

The prevalence of NDD was significantly higher among patients with achalasia (6.0%) compared to general population (2.0%), suggesting an association of these disorders. Large-volume studies are necessary to confirm this finding.

Autoantibodies to Synaptic Receptors and Neuronal Cell Surface Proteins in Autoimmune Diseases of the Central Nervous System

Investigations in the last 10 years have revealed a new category of neurological diseases mediated by antibodies against cell surface and synaptic proteins. There are currently 16 such diseases all characterized by autoantibodies against neuronal proteins involved in synaptic signaling and plasticity. In clinical practice these findings have changed the diagnostic and treatment approach to potentially lethal, but now treatable, neurological and psychiatric syndromes previously considered idiopathic or not even suspected to be immune-mediated. Studies show that patients' antibodies can impair the surface dynamics of the target receptors eliminating them from synapses (e.g., NMDA receptor), block the function of the antigens without changing their synaptic density (e.g., GABAb receptor), interfere with synaptic protein-protein interactions (LGI1, Caspr2), alter synapse formation (e.g., neurexin-3α), or by unclear mechanisms associate to a new form of tauopathy (IgLON5). Here we first trace the process of discovery of these diseases, describing the triggers and symptoms related to each autoantigen, and then review in detail the structural and functional alterations caused by the autoantibodies with special emphasis in those (NMDA receptor, amphiphysin) that have been modeled in animals.

Neuropathological criteria of anti-IgLON5-related tauopathy

We recently reported a novel neurological syndrome characterized by a unique NREM and REM parasomnia with sleep apnea and stridor, accompanied by bulbar dysfunction and specific association with antibodies against the neuronal cell-adhesion protein IgLON5. All patients had the HLA-DRB1*1001 and HLA-DQB1*0501 alleles. Neuropathological findings in two patients revealed a novel tauopathy restricted to neurons and predominantly involving the hypothalamus and tegmentum of the brainstem. The aim of the current study is to describe the neuropathological features of the anti-IgLON5 syndrome and to provide diagnostic levels of certainty based on the presence of associated clinical and immunological data. The brains of six patients were examined and the features required for the neuropathological diagnosis were established by consensus. Additional clinical and immunological criteria were used to define “definite”, “probable” and “possible” diagnostic categories. The brains of all patients showed remarkably similar features consistent with a neurodegenerative disease with neuronal loss and gliosis and absence of inflammatory infiltrates. The most relevant finding was the neuronal accumulation of hyperphosphorylated tau composed of both three-repeat (3R) and four-repeat (4R) tau isoforms, preferentially involving the hypothalamus, and more severely the tegmental nuclei of the brainstem with a cranio-caudal gradient of severity until the upper cervical cord. A “definite” diagnosis of anti-IgLON5-related tauopathy is established when these neuropathological features are present along with the detection of serum or CSF IgLON5 antibodies. When the antibody status is unknown, a “probable” diagnosis requires neuropathological findings along with a compatible clinical history or confirmation of possession of HLA-DRB1*1001 and HLA-DQB1*0501 alleles. A “possible” diagnosis should be considered in cases with compatible neuropathology but without information about a relevant clinical presentation and immunological status. These criteria should help to identify undiagnosed cases among archival tissue, and will assist future clinicopathological studies of this novel disorder.

Autoimmune sleep disorders

A number of autoantibodies, some paraneoplastic, are associated with sleep disorders. Morvan syndrome and limbic encephalitis, associated with voltage-gated potassium channel-complex antibodies, principally against CASPR2 and LGI1, can result in profound insomnia and rapid eye movement sleep behavior disorder (RBD). Patients with aquaporin-4 antibodies and neuromyelitis optica may develop narcolepsy in association with other evidence of hypothalamic dysfunction, sometimes as the initial presentation. Central sleep apnea and central neurogenic hypoventilation are found in patients with anti-N-methyl-d-aspartate receptor antibody encephalitis, and obstructive sleep apnea, stridor, and hypoventilation are prominent features of a novel tauopathy associated with IgLON5 antibodies. In addition, paraneoplastic diseases may involve the hypothalamus and cause sleep disorders, particularly narcolepsy and RBD in those with Ma1 and Ma2 antibodies. Patients with antineuronal nuclear autoantibodies type 2 may develop stridor. Several lines of evidence suggest that narcolepsy is an autoimmune disorder. There is a strong relationship with the human leukocyte antigen (HLA) DQB1*06:02 haplotype and polymorphisms in the T-cell receptor alpha locus and purinergic receptor P2Y11 genes. Patients with recent-onset narcolepsy may have high titers of antistreptococcal or other antibodies, although none has yet been shown to be disease-specific but, supporting an immune basis, recent evidence indicates that narcolepsy in children can be precipitated by one type of vaccination against the 2009-2010 H1N1 influenza pandemic.

A novel non-rapid-eye movement and rapid-eye-movement parasomnia with sleep breathing disorder associated with antibodies to IgLON5: a case series, characterisation of the antigen, and post-mortem study

BACKGROUND

Autoimmunity might be associated with or implicated in sleep and neurodegenerative disorders. We aimed to describe the features of a novel neurological syndrome associated with prominent sleep dysfunction and antibodies to a neuronal antigen.

METHODS

In this observational study, we used clinical and video polysomnography to identify a novel sleep disorder in three patients referred to the Sleep Unit of Hospital Clinic, University of Barcelona, Spain, for abnormal sleep behaviours and obstructive sleep apnoea. These patients had antibodies against a neuronal surface antigen, which were also present in five additional patients referred to our laboratory for antibody studies. These five patients had been assessed with polysomnography, which was done in our sleep unit in one patient and the recording reviewed in a second patient. Two patients underwent post-mortem brain examination. Immunoprecipitation and mass spectrometry were used to characterise the antigen and develop an assay for antibody testing. Serum or CSF from 298 patients with neurodegenerative, sleep, or autoimmune disorders served as control samples.

FINDINGS

All eight patients (five women; median age at disease onset 59 years [range 52-76]) had abnormal sleep movements and behaviours and obstructive sleep apnoea, as confirmed by polysomnography. Six patients had chronic progression with a median duration from symptom onset to death or last visit of 5 years (range 2-12); in four the sleep disorder was the initial and most prominent feature, and in two it was preceded by gait instability followed by dysarthria, dysphagia, ataxia, or chorea. Two patients had a rapid progression with disequilibrium, dysarthria, dysphagia, and central hypoventilation, and died 2 months and 6 months, respectively, after symptom onset. In five of five patients, video polysomnography showed features of obstructive sleep apnoea, stridor, and abnormal sleep architecture (undifferentiated non-rapid-eye-movement [non-REM] sleep or poorly structured stage N2, simple movements and finalistic behaviours, normalisation of non-REM sleep by the end of the night, and, in the four patients with REM sleep recorded, REM sleep behaviour disorder). Four of four patients had HLA-DRB1*1001 and HLA-DQB1*0501 alleles. All patients had antibodies (mainly IgG4) against IgLON5, a neuronal cell adhesion molecule. Only one of the 298 controls, who had progressive supranuclear palsy, had IgLON5 antibodies. Neuropathology showed neuronal loss and extensive deposits of hyperphosphorylated tau mainly involving the tegmentum of the brainstem and hypothalamus in the two patients studied.

INTERPRETATION

IgLON5 antibodies identify a unique non-REM and REM parasomnia with sleep breathing dysfunction and pathological features suggesting a tauopathy.

FUNDING

Fondo de Investigaciones Sanitarias, Centros de Investigación Biomédica en Red de enfermedades neurodegenerativas (CIBERNED) and Respiratorias (CIBERES), Ministerio de Economía y Competitividad, Fundació la Marató TV3, and the National Institutes of Health.