Mechanisms for lesion localization in neuromyelitis optica spectrum disorders

Immune-related biomarkers in the neuromyelitis optica spectrum disorder; pathogenesis and therapeutic approaches

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune inflammatory disease of the central nervous system that mostly affects the optic nerves and spinal cord. About eighty percent of patients have antibodies that are directed against the water channel aquaporin-4 (AQP4)-IgG, which is expressed on astrocytes. This protein was shown to be both a biomarker and a pathogenic cause of NMOSD. Researchers have discovered that antibodies against myelin oligodendrocyte glycoprotein (MOG) IgG can serve as a biomarker for a distinct condition known as MOG antibody-associated disease (MOGAD). This condition shares some similarities with AQP4-IgG-positive NMOSD, but it has distinct differences in terms of its underlying causes, clinical characteristics, response to treatment, and prognosis. Identifying AQP4 antibodies in the blood serum confirms the diagnosis of seropositive NMOSD. Nevertheless, it remains uncertain if there is a correlation between AQP4-IgG levels and disease activity, severity, responsiveness to medication, or long-term effects. Furthermore, there is still a need to establish and confirm biomarkers specifically for patients diagnosed with seronegative NMOSD. This study primarily examines the immunological aspects of NMOSD, which might have significant consequences for clinical practice. These implications include the possible use of new biomarkers to aid in the early and correct diagnosis of NMOSD, as well as the development of current treatment options to enhance the long-term prognosis of NMOSD patients.

The Percentage of Neutrophils is Independently Associated with Blood-Brain Barrier(BBB) Disruption in Myelin Oligodendrocyte Glycoprotein Antibody Associated Disease (MOGAD)

Purpose

This study aims to investigate the risk factors associated with blood-brain barrier(BBB) disruption in patients with myelin oligodendrocyte glycoprotein antibody associated disease(MOGAD).

Patients and Methods

We collected clinical data from 95 patients diagnosed with MOGAD at the Department of Neurology, the First Affiliated Hospital of Zhengzhou University from October 2018 to May 2024. Patients were classified into normal or damaged BBB groups based on cerebrospinal fluid (CSF) albumin/serum albumin (QAlb). Binary logistic regression analysis was used to evaluate the risk factors for BBB disruption in MOGAD patients.

Results

Our study revealed that in MOGAD patients with BBB damaged, there is a higher proportion of acute phase high EDSS scores, higher incidence of prodromal symptoms, and a higher rate of viral infections. Myelitis is the main clinical phenotype, with clinical manifestations primarily including limb weakness and bladder/bowel dysfunction. Laboratory tests showed higher levels of CSF protein, immunoglobulin (IgG), 24-hour intrathecal IgG synthesis rate, peripheral blood leukocytes, neutrophil percentage, NLR, anti-thyroglobulin antibodies(TGAbs), and fibrinogen levels, while free triiodothyronine (FT3) and lymphocyte percentage were lower. Multivariate regression analysis indicated that an increased neutrophil percentage is an independent risk factor for BBB damage in MOGAD patients (OR=1.068, 95% CI: 1.018-1.122, P=0.008).

Conclusion

Neutrophil percentage is a readily available and widely used indicator reflecting the immune system's state and the body's inflammation level. The change in neutrophil percentage is independently associated with BBB damage in MOGAD patients. This finding helps provide more reference information for personalized treatment decisions and further research into the pathogenesis of MOGAD.

Humanized-Aquaporin-4-Expressing Rat Created by Gene-Editing Technology and Its Use to Clarify the Pathology of Neuromyelitis Optica Spectrum Disorder

Conventional rodent neuromyelitis optica spectrum disorder (NMOSD) models using patient-derived immunoglobulin G (IgG) are potentially affected by the differences between the human and rodent aquaporin-4 (AQP4) extracellular domains (ECDs). We hypothesized that the humanization of AQP4 ECDs would make the rodent model lesions closer to human NMOSD pathology. Humanized-AQP4-expressing (hAQP4) rats were generated using genome-editing technology, and the human AQP4-specific monoclonal antibody (mAb) or six patient-derived IgGs were introduced intraperitoneally into hAQP4 rats and wild-type Lewis (WT) rats after immunization with myelin basic protein and complete Freund's adjuvant. Human AQP4-specific mAb induced astrocyte loss lesions specifically in hAQP4 rats. The patient-derived IgGs also induced NMOSD-like tissue-destructive lesions with AQP4 loss, demyelination, axonal swelling, complement deposition, and marked neutrophil and macrophage/microglia infiltration in hAQP4 rats; however, the difference in AQP4 loss lesion size and infiltrating cells was not significant between hAQP4 and WT rats. The patient-derived IgGs bound to both human and rat AQP4 M23, suggesting their binding to the shared region of human and rat AQP4 ECDs. Anti-AQP4 titers positively correlated with AQP4 loss lesion size and neutrophil and macrophage/microglia infiltration. Considering that patient-derived IgGs vary in binding sites and affinities and some of them may not bind to rodent AQP4, our hAQP4 rat is expected to reproduce NMOSD-like pathology more accurately than WT rats.

Inhibition of repulsive guidance molecule-a ameliorates compromised blood-spinal cord barrier integrity associated with neuromyelitis optica in rats

The influx of pathogenic aquaporin-4 antibodies (AQP4-Abs) across the blood-spinal cord barrier (BSCB) is crucial for the development and exacerbation of neuromyelitis optica (NMO). We examined whether prophylactic intravenous administration of anti-repulsive guidance molecule-a antibodies (RGMa-Abs) has disease-modifying effects on BSCB dysfunction using an NMO model elicited by peripheral administration of AQP4-Abs to rats. RGMa-Ab treatment attenuated the acute exacerbation of perivascular astrocytopathy in the spinal cord and clinical symptoms, which were highly correlated with neurofilament light chain levels in both the cerebrospinal fluid (CSF) and serum. Additionally, RGMa-Ab treatment suppressed the expression of proinflammatory cytokines/chemokines and the infiltration of inflammatory cells into the spinal cord. CSF analysis of NMO rats revealed that RGMa-Ab treatment improved the CSF/serum albumin ratio and suppressed AQP4-Abs influx. RGMa inhibition using RGMa-Abs is suggested as a potential therapeutic option for BSCB dysfunction associated with NMO.

Manifestations of Myelinating Oligodendrocyte Glycoprotein Antibody-Associated Disease: A Rare Case of Suppurative Meningoencephalitis

Myelinating oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is an inflammatory demyelinating disease of the central nervous system (CNS) mediated by MOG antibodies (MOG-IgG). It is associated with autoimmunity and encompasses various syndromes. However, manifestations presenting with symptoms of suppurative meningoencephalitis are rare. In this case, we admitted an 80-year-old male patient who presented with fever, headache, mental and behavioral abnormalities, and disturbance of consciousness. The cerebrospinal fluid (CSF) examination revealed elevated levels of leukocytes and protein, while magnetic resonance imaging (MRI) of the brain showed an abnormal signal in the parietal lobe surrounding the posterior horn of the right lateral ventricle. The patient tested positive for serum MOG-IgG, confirming the diagnosis of MOG-IgG-related meningoencephalitis. The treatment included intravenous immunoglobulin, glucocorticoids, third-generation cephalosporins, and immunosuppressants. Following the treatment, the patient experienced complete recovery.

Anti-aquaporin-4 immunoglobulin G/anti-myelin oligodendrocyte glycoprotein immunoglobulin G double-positive paraneoplastic neurological syndrome in a patient with triple-negative breast cancer

We report a rare case of paraneoplastic neurological syndrome with dual seropositivity of anti-aquaporin-4 and myelin oligodendrocyte glycoprotein antibodies in a 40 year-old woman with metastatic triple-negative breast cancer. She received multiple lines of anti-neoplastic treatment, including immunotherapy with pembrolizumab, as well as cytotoxic chemotherapy. Paraneoplastic meningoencephalomyelitis developed 2 years after diagnosis of breast cancer and 1 year after discontinuation of immunotherapy with pembrolizumab. She first developed longitudinally extending transverse myelitis followed by left optic neuritis and meningoencephalitis with new enhancing lesions in the brain and spinal leptomeninges. Cerebrospinal fluid analysis during both episodes showed normal glucose and protein, and elevated white blood cell count. Cytology was negative for malignancy. Cerebrospinal fluid was positive for neuromyelitis optica immunoglobulin G antibody anti-aquaporin-4, and autoimmune myelopathy panel was positive for myelin oligodendrocyte glycoprotein antibody. The patient had significant clinical and radiographic improvement after completion of five cycles of plasmapheresis followed by intravenous immunoglobulin. She did not have recurrence of paraneoplastic syndrome with maintenance rituximab every 6 months and daily low-dose prednisone. She succumbed to progressive systemic metastatic disease 4.5 years after her breast cancer diagnosis. This case shows that these antibodies can occur concurrently and cause clinical features, such as both neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody disease, in a patient with a singular type of cancer. We highlight the importance of testing for paraneoplastic etiology in cancer patients with radiographic menigoencephalomyelitis or meningitis with atypical symptoms of meningeal carcinomatosis and/or cerebrospinal fluid profile negative for leptomeningeal carcinomatosis.

The pathogenesis of multiple sclerosis: a series of unfortunate events

Multiple sclerosis (MS) is characterized by the chronic inflammatory destruction of myelinated axons in the central nervous system. Several ideas have been put forward to clarify the roles of the peripheral immune system and neurodegenerative events in such destruction. Yet, none of the resulting models appears to be consistent with all the experimental evidence. They also do not answer the question of why MS is exclusively seen in humans, how Epstein-Barr virus contributes to its development but does not immediately trigger it, and why optic neuritis is such a frequent early manifestation in MS. Here we describe a scenario for the development of MS that unifies existing experimental evidence as well as answers the above questions. We propose that all manifestations of MS are caused by a series of unfortunate events that usually unfold over a longer period of time after a primary EBV infection and involve periodic weakening of the blood-brain barrier, antibody-mediated CNS disturbances, accumulation of the oligodendrocyte stress protein αB-crystallin and self-sustaining inflammatory damage.

Clinical features of MOGAD with brainstem involvement in the initial attack versus NMOSD and MS

OBJECTIVE

To assess the characteristics of Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disorder (MOGAD) with brainstem involvement in the first event (BSIFE) and make comparisons with aquaporin-4-IgG seropositive neuromyelitis optica spectrum disorder (AQP4-IgG-NMOSD) and multiple sclerosis (MS).

METHODS

From 2017 to 2022, this study identified MOG-IgG-positive patients with brainstem or both brainstem and cerebellum lesions in the first episode. As a comparison group, AQP4-IgG-NMOSD (n = 30) and MS (n = 30) patients with BSIFE were enroled.

RESULTS

Thirty-five patients (35/146, 24.0%) were the BSIFE of MOGAD. Isolated brainstem episodes occurred in 9 of the 35 (25.7%) MOGAD patients, which was similar to MS (7/30, 23.3%) but was lower than AQP4-IgG-NMOSD (17/30, 56.7%, P = 0.011). Pons (21/35, 60.0%), medulla oblongata (20/35, 57.1%) and middle cerebellar peduncle (MCP, 19/35, 54.3%) were the most frequently affected areas. Intractable nausea (n = 7), vomiting (n = 8) and hiccups (n = 2) happened in MOGAD patients, but EDSS of MOGAD was lower than AQP4-IgG-NMOSD (P = 0.001) at the last follow-up. MOGAD patients with or without BSIFE did not significantly differ in terms of the ARR (P = 0.102), mRS (P = 0.823), or EDSS (P = 0.598) at the most recent follow-up. Specific oligoclonal bands appeared in MOGAD (13/33, 39.4%) and AQP4-IgG-NMOSD (7/24, 29.2%) in addition to MS (20/30, 66.7%). Fourteen MOGAD patients (40.0%) experienced relapse in this study. When the brainstem was involved in the first attack, there was an increased likelihood of a second attack occurring at the same location (OR=12.22, 95%CI 2.79 to 53.59, P = 0.001). If the first and second events were both in the brainstem, the third event was likely to occur at the same location (OR=66.00, 95%CI 3.47 to 1254.57, P = 0.005). Four patients experienced relapses after the MOG-IgG turned negative.

CONCLUSION

BSIFE occurred in 24.0% of MOGAD. Pons, medulla oblongata and MCP were the most frequently involved regions. Intractable nausea, vomiting and hiccups occurred in MOGAD and AQP4-IgG-NMOSD, but not MS. The prognosis of MOGAD was better than AQP4-IgG-NMOSD. In contrast to MS, BSIFE may not indicate a worse prognosis for MOGAD. When patients with BSIFE, MOGAD tent to reoccur in the brainstem. Four of the 14 recurring MOGAD patients relapsed after the MOG-IgG test turned negative.

Gastrointestinal Dysfunction in Multiple Sclerosis and Related Conditions

Nervous system disorders may be accompanied by gastrointestinal (GI) dysfunction. Brain lesions may be responsible for GI problems such as decreased peristalsis (e.g., lesions in the basal ganglia, pontine defecation center/Barrington's nucleus), decreased abdominal strain (e.g., lesions in the parabrachial nucleus), hiccupping and vomiting (e.g., lesions in the area postrema), and appetite loss (e.g., lesions in the hypothalamus). Decreased peristalsis also may be caused by lesions of the spinal long tracts or the intermediolateral nucleus projecting to the myenteric plexus. This review addresses GI dysfunction caused by multiple sclerosis, neuromyelitis optica spectrum disorder, and myelin oligodendrocyte glycoprotein-associated disorder. Neuro-associated GI dysfunction may develop concurrently with brain or spinal cord dysfunction or may predate it. Collaboration between gastroenterologists and neurologists is highly desirable when caring for patients with GI dysfunction related to nervous system disorders, particularly since patients with these symptoms may visit a gastroenterologist prior to the establishment of a neurological diagnosis.

The Potential Pathogenicity of Myelin Oligodendrocyte Glycoprotein Antibodies in the Optic Pathway

BACKGROUND

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an acquired inflammatory demyelinating disease with optic neuritis (ON) as the most frequent clinical symptom. The hallmark of the disease is the presence of autoantibodies against MOG (MOG-IgG) in the serum of patients. Whereas the role of MOG in the experimental autoimmune encephalomyelitis animal model is well-established, the pathogenesis of the human disease and the role of human MOG-IgG is still not fully clear.

EVIDENCE ACQUISITION

PubMed was searched for the terms "MOGAD," "optic neuritis," "MOG antibodies," and "experimental autoimmune encephalomyelitis" alone or in combination, to find articles of interest for this review. Only articles written in English language were included and reference lists were searched for further relevant papers.

RESULTS

B and T cells play a role in the pathogenesis of human MOGAD. The distribution of lesions and their development toward the optic pathway is influenced by the genetic background in animal models. Moreover, MOGAD-associated ON is frequently bilateral and often relapsing with generally favorable visual outcome. Activated T-cell subsets create an inflammatory environment and B cells are necessary to produce autoantibodies directed against the MOG protein. Here, pathologic mechanisms of MOG-IgG are discussed, and histopathologic findings are presented.

CONCLUSIONS

MOGAD patients often present with ON and harbor antibodies against MOG. Furthermore, pathogenesis is most likely a synergy between encephalitogenic T and antibody producing B cells. However, to which extent MOG-IgG are pathogenic and the exact pathologic mechanism is still not well understood.

Pathophysiology of myelin oligodendrocyte glycoprotein antibody disease

Myelin Oligodendrocyte Glycoprotein Antibody Disease (MOGAD) is a spectrum of diseases, including optic neuritis, transverse myelitis, acute disseminated encephalomyelitis, and cerebral cortical encephalitis. In addition to distinct clinical, radiological, and immunological features, the infectious prodrome is more commonly reported in MOGAD (37-70%) than NMOSD (15-35%). Interestingly, pediatric MOGAD is not more aggressive than adult-onset MOGAD, unlike in multiple sclerosis (MS), where annualized relapse rates are three times higher in pediatric-onset MS. MOGAD pathophysiology is driven by acute attacks during which T cells and MOG antibodies cross blood brain barrier (BBB). MOGAD lesions show a perivenous confluent pattern around the small veins, lacking the radiological central vein sign. Initial activation of T cells in the periphery is followed by reactivation in the subarachnoid/perivascular spaces by MOG-laden antigen-presenting cells and inflammatory CSF milieu, which enables T cells to infiltrate CNS parenchyma. CD4+ T cells, unlike CD8+ T cells in MS, are the dominant T cell type found in lesion histology. Granulocytes, macrophages/microglia, and activated complement are also found in the lesions, which could contribute to demyelination during acute relapses. MOG antibodies potentially contribute to pathology by opsonizing MOG, complement activation, and antibody-dependent cellular cytotoxicity. Stimulation of peripheral MOG-specific B cells through TLR stimulation or T follicular helper cells might help differentiate MOG antibody-producing plasma cells in the peripheral blood. Neuroinflammatory biomarkers (such as MBP, sNFL, GFAP, Tau) in MOGAD support that most axonal damage happens in the initial attack, whereas relapses are associated with increased myelin damage.

Rare variants and HLA haplotypes associated in patients with neuromyelitis optica spectrum disorders

Neuromyelitis optica spectrum disorders (NMOSD) are rare, debilitating autoimmune diseases of the central nervous system. Many NMOSD patients have antibodies to Aquaporin-4 (AQP4). Prior studies show associations of NMOSD with individual Human Leukocyte Antigen (HLA) alleles and with mutations in the complement pathway and potassium channels. HLA allele associations with NMOSD are inconsistent between populations, suggesting complex relationships between the identified alleles and risk of disease. We used a retrospective case-control approach to identify contributing genetic variants in patients who met the diagnostic criteria for NMOSD and their unaffected family members. Potentially deleterious variants identified in NMOSD patients were compared to members of their families who do not have the disease and to existing databases of human genetic variation. HLA sequences from patients from Belgrade, Serbia, were compared to the frequency of HLA haplotypes in the general population in Belgrade. We analyzed exome sequencing on 40 NMOSD patients and identified rare inherited variants in the complement pathway and potassium channel genes. Haplotype analysis further detected two haplotypes, HLA-A*01, B*08, DRB1*03 and HLA-A*01, B*08, C*07, DRB1*03, DQB1*02, which were more prevalent in NMOSD patients than in unaffected individuals. In silico modeling indicates that HLA molecules within these haplotypes are predicted to bind AQP4 at several sites, potentially contributing to the development of autoimmunity. Our results point to possible autoimmune and neurodegenerative mechanisms that cause NMOSD, and can be used to investigate potential NMOSD drug targets.

Neuropsychiatric lupus erythematosus: Focusing on autoantibodies

Patients with systemic lupus erythematosus (SLE) frequently suffer from nervous system complications, termed neuropsychiatric lupus erythematosus (NPLE). NPLE accounts for the poor prognosis of SLE. Correct attribution of NP events to SLE is the primary principle in managing NPLE. The vascular injuries and neuroinflammation are the fundamental neuropathologic changes in NPLE. Specific autoantibody-mediated central nerve system (CNS) damages distinguish NPLE from other CNS disorders. Though the central antibodies in NPLE are generally thought to be raised from the periphery immune system, they may be produced in the meninges and choroid plexus. On this basis, abnormal activation of microglia and disease-associated microglia (DAM) should be the common mechanisms of NPLE and other CNS disturbances. Improved understanding of both characteristic and sharing features of NPLE might yield further options for managing this disease.

Autoantibodies in central nervous system and neuromuscular autoimmune disorders: A narrative review

The discovery of novel autoantibodies in neurological disorders contributes to a better understanding of its pathogenesis, improves the accuracy of diagnosis, and leads to new treatment strategies. Advances in techniques for the screening and detection of autoantibodies have enabled the discovery of new antibodies in the central nervous system (CNS) and neuromuscular diseases. Cell-based assays using live or fixed cells overexpressing target antigens are widely used for autoantibody-based diagnosis in clinical practice. Common pathogenic autoantibodies are unknown in most patients with multiple sclerosis (MS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Novel pathogenic autoantibodies to aquaporin-4 and myelin oligodendrocyte glycoprotein (MOG) have been identified in neuromyelitis optica spectrum disorder and MOG antibody-associated disease, respectively. These diseases have clinical similarities to MS, but with the discovery of pathogenic autoantibodies, they are now recognized as distinct disease entities. Antibodies to paranodal membrane proteins such as neurofascin-155, contactin‑1, contactin‑associated protein‑1 in CIDP and muscle-specific kinase and low-density lipoprotein receptor–related protein 4 in myasthenia gravis were added to the profiles of autoantibodies in neurological disorders. Despite the relatively low frequency of seropositivity, autoantibody detection is currently essential for the clinical diagnosis of CNS and neuromuscular autoimmune disorders, and differential approaches to seropositive patients will contribute to more personalized medicine. We reviewed recent discoveries of autoantibodies and their clinical implications in CNS and neuromuscular disorders.

N-Methyl-D-Aspartate (NMDA)-Type Glutamate Receptors and Demyelinating Disorders: A Neuroimmune Perspective

N-methyl-D-aspartate receptors (NMDARs) are ionotropic glutamate receptors, highly important in regulating substantial physiologic processes in the brain and the nervous system, and disturbance in their function could contribute to different pathologies. Overstimulation and hyperactivity of NMDARs, termed as glutamate toxicity, could promote cell death and apoptosis. Meanwhile, their blockade could lead to dysfunction of the brain and nervous system as well. A growing body of evidence has demonstrated the prominent role of NMDARs in demyelinating disorders and anti-NMDAR encephalitis. Herein, we provide an overview of the role of NMDARs' dysfunction in the physiopathology of demyelinating disorders such as multiple sclerosis and neuromyelitis optica spectrum disorders.

Functional impairment of CD19+CD24hiCD38hi B cells in neuromyelitis optica spectrum disorder is restored by B cell depletion therapy

[Figure: see text].

Super-resolving Microscopy in Neuroscience

Fluorescence imaging techniques play a pivotal role in our understanding of the nervous system. The emergence of various super-resolution microscopy methods and specialized fluorescent probes enables direct insight into neuronal structure and protein arrangements in cellular subcompartments with so far unmatched resolution. Super-resolving visualization techniques in neurons unveil a novel understanding of cytoskeletal composition, distribution, motility, and signaling of membrane proteins, subsynaptic structure and function, and neuron-glia interaction. Well-defined molecular targets in autoimmune and neurodegenerative disease models provide excellent starting points for in-depth investigation of disease pathophysiology using novel and innovative imaging methodology. Application of super-resolution microscopy in human brain samples and for testing clinical biomarkers is still in its infancy but opens new opportunities for translational research in neurology and neuroscience. In this review, we describe how super-resolving microscopy has improved our understanding of neuronal and brain function and dysfunction in the last two decades.

Pathogenesis of autoimmune demyelination: from multiple sclerosis to neuromyelitis optica spectrum disorders and myelin oligodendrocyte glycoprotein antibody-associated disease

Autoimmunity plays a significant role in the pathogenesis of demyelination. Multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD) and myelin oligodendrocyte glycoprotein antibody‐associated disease (MOGAD) are now recognised as separate disease entities under the amalgam of human central nervous system demyelinating disorders. While these disorders share inherent similarities, investigations into their distinct clinical presentations and lesion pathologies have aided in differential diagnoses and understanding of disease pathogenesis. An interplay of various genetic and environmental factors contributes to each disease, many of which implicate an autoimmune response. The pivotal role of the adaptive immune system has been highlighted by the diagnostic autoantibodies in NMOSD and MOGAD, and the presence of autoreactive lymphocytes in MS lesions. While a number of autoantigens have been proposed in MS, recent emphasis on the contribution of B cells has shed new light on the well‐established understanding of T cell involvement in pathogenesis. This review aims to synthesise the clinical characteristics and pathological findings, discuss existing and emerging hypotheses regarding the aetiology of demyelination and evaluate recent pathogenicity studies involving T cells, B cells, and autoantibodies and their implications in human demyelination.

Aquaporin-4 Removal from the Plasma Membrane of Human Müller Cells by AQP4-IgG from Patients with Neuromyelitis Optica Induces Changes in Cell Volume Homeostasis: the First Step of Retinal Injury?

Aquaporin-4 (AQP4) is the target of the specific immunoglobulin G autoantibody (AQP4-IgG) produced in patients with neuromyelitis optica spectrum disorders (NMOSD). Previous studies demonstrated that AQP4-IgG binding to astrocytic AQP4 leads to cell-destructive lesions. However, the early physiopathological events in Müller cells in the retina are poorly understood. Here, we investigated the consequences of AQP4-IgG binding to AQP4 of Müller cells, previous to the inflammatory response, on two of AQP4's key functions, cell volume regulation response (RVD) and cell proliferation, a process closely associated with changes in cell volume. Experiments were performed in a human retinal Müller cell line (MIO-M1) exposed to complement-inactivated sera from healthy volunteers or AQP4-IgG positive NMOSD patients. We evaluated AQP4 expression (immunofluorescence and western blot), water permeability coefficient, RVD, intracellular calcium levels and membrane potential changes during hypotonic shock (fluorescence videomicroscopy) and cell proliferation (cell count and BrdU incorporation). Our results showed that AQP4-IgG binding to AQP4 induces its partial internalization, leading to the decrease of the plasma membrane water permeability, a reduction of swelling-induced increase of intracellular calcium levels and the impairment of RVD in Müller cells. The loss of AQP4 from the plasma membrane induced by AQP4-IgG positive sera delayed Müller cells' proliferation rate. We propose that Müller cell dysfunction after AQP4 removal from the plasma membrane by AQP4-IgG binding could be a non-inflammatory mechanism of retinal injury in vivo, altering cell volume homeostasis and cell proliferation and consequently, contributing to the physiopathology of NMOSD.

Magnetic resonance imaging in neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system (CNS) associated with antibodies to aquaporin-4 (AQP4), which has distinct clinical, radiological and pathological features, but also has some overlap with multiple sclerosis and myelin oligodendrocyte glycoprotein (MOG) antibody associated disease. Early recognition of NMOSD is important because of differing responses to both acute and preventive therapy. Magnetic resonance (MR) imaging has proved essential in this process. Key MR imaging clues to the diagnosis of NMOSD are longitudinally extensive lesions of the optic nerve (more than half the length) and spinal cord (three or more vertebral segments), bilateral optic nerve lesions and lesions of the optic chiasm, area postrema, floor of the IV ventricle, periaqueductal grey matter, hypothalamus and walls of the III ventricle. Other NMOSD-specific lesions are denoted by their unique morphology: heterogeneous lesions of the corpus callosum, 'cloud-like' gadolinium (Gd)-enhancing white matter lesions and 'bright spotty' lesions of the spinal cord. Other lesions described in NMOSD, including linear periventricular peri-ependymal lesions and patch subcortical white matter lesions, may be less specific. The use of advanced MR imaging techniques is yielding further useful information regarding focal degeneration of the thalamus and optic radiation in NMOSD and suggests that paramagnetic rim patterns and changes in normal appearing white matter are specific to MS. MR imaging is crucial in the early recognition of NMOSD and in directing testing for AQP4 antibodies and guiding immediate acute treatment decisions. Increasingly, MR imaging is playing a role in diagnosing seronegative cases of NMOSD.

Sporadic amyotrophic lateral sclerosis with seropositive neuromyelitis optica spectrum disorder: A case report

RATIONALE

Neuromyelitis optica spectrum disorder (NMOSD) is a severe inflammatory disorder of the central nervous system with an autoantibody against aquaporin-4 protein (AQP4), and amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. We report a female patient with ALS who had asymptomatic AQP4 antibody at the diagnosis of ALS, and NMOSD occurred 4 years later after the diagnosis of ALS.

PATIENT CONCERNS

She was already bedridden and had tracheostomy because of ALS which was diagnosed at her age of 55. At the time of her ALS diagnosis, she had no brain or spinal cord lesions, but was seropositive for AQP4 antibody. At her age of 59, new-onset complete paralysis of all extremities and severe pain on the posterior neck and both shoulders occurred and visited the hospital.

DIAGNOSIS

Longitudinally extensive transverse myelitis was diagnosed, which was the onset attack of seropositive NMOSD. The diagnosis was confirmed based on the international consensus diagnostic criteria for NMOSD with MR imaging, cerebrospinal fluid exam and laboratory work-ups with AQP4 antibody test.

INTERVENTIONS

High dose methylprednisolone was administered for 5 days. Plasma exchange as a further treatment was recommended, but she and her family refused.

OUTCOMES

Her pain was relieved after steroid treatment, but there was no improvement of her leg weakness.

LESSONS

This case is a rare combination of neuroinflammatory and neurodegenerative diseases. Considering the alterations of blood-brain barrier along with the progression of ALS, it highlights that the consequence of ALS pathogenesis might affect the development of NMOSD. And the careful follow-up is recommended even in patients with profound weakness, especially if those who were at risk of developing certain neurological disorders.

Gastrointestinal dysfunction in neuroinflammatory diseases: Multiple sclerosis, neuromyelitis optica, acute autonomic ganglionopathy and related conditions

Disorders of the nervous system can produce a variety of gastrointestinal (GI) dysfunctions. Among these, lesions in various brain structures can cause appetite loss (hypothalamus), decreased peristalsis (presumably the basal ganglia, pontine defecation center/Barrington's nucleus), decreased abdominal strain (presumably parabrachial nucleus/Kolliker-Fuse nucleus) and hiccupping and vomiting (area postrema/dorsal vagal complex). In addition, decreased peristalsis with/without loss of bowel sensation can be caused by lesions of the spinal long tracts and the intermediolateral nucleus or of the peripheral nerves and myenteric plexus. Recently, neural diseases of inflammatory etiology, particularly those affecting the PNS, are being recognized to contribute to GI dysfunction. Here, we review neuroinflammatory diseases that potentially cause GI dysfunction. Among such CNS diseases are multiple sclerosis, neuromyelitis optica spectrum disorder, myelin oligodendrocyte glycoprotein associated disorder, and autoimmune encephalitis. Peripheral nervous system diseases impacting the gut include Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, acute sensory-autonomic neuropathy/acute motor-sensory-autonomic neuropathy, acute autonomic ganglionopathy, myasthenia gravis and acute autonomic neuropathy with paraneoplastic syndrome. Finally, collagen diseases, such as Sjogren syndrome and systemic sclerosis, and celiac disease affect both CNS and PNS. These neuro-associated GI dysfunctions may predate or present concurrently with brain, spinal cord or peripheral nerve dysfunction. Such patients may visit gastroenterologists or physicians first, before the neurological diagnosis is made. Therefore, awareness of these phenomena among general practitioners and collaboration between gastroenterologists and neurologists are highly recommended in order for their early diagnosis and optimal management, as well as for systematic documentation of their presentations and treatment.

Novel insights into pathophysiology and therapeutic possibilities reveal further differences between AQP4-IgG- and MOG-IgG-associated diseases

PURPOSE OF REVIEW

This review summarizes recent insights into the pathogenesis and therapeutic options for patients with MOG- or AQP4-antibodies.

RECENT FINDINGS

Although AQP4-IgG are linked to NMOSD, MOG-IgG-associated diseases (MOGAD) include a broader clinical spectrum of autoimmune diseases of the central nervous system (CNS). Details of membrane assembly of AQP4-IgG required for complement activation have been uncovered. Affinity-purified MOG-IgG from patients were shown to be pathogenic by induction of demyelination when the blood--brain barrier (BBB) was breached and by enhancement of activation of cognate T cells. A high-affinity AQP4-IgG, given peripherally, could induce NMOSD-like lesions in rats in the absence of BBB breach. Circulating AQP4-specific and MOG-specific B cells were identified and suggest differences in origin of MOG-antibodies or AQP4-antibodies. Patients with MOG-IgG show a dichotomy concerning circulating MOG-specific B cells; whether this is related to differences in clinical response of anti-CD20 therapy remains to be analyzed. Clinical trials of AQP4-IgG-positive NMOSD patients showed success with eculizumab (preventing cleavage of complement factor C5, thereby blocking formation of chemotactic C5a and membrane attack complex C9neo), inebilizumab (depleting CD19 + B cells), and satralizumab (anti-IL-6R blocking IL-6 actions).

SUMMARY

New insights into pathological mechanisms and therapeutic responses argue to consider NMOSD with AQP4-IgG and MOGAD as separate disease entities.

Optical Coherence Tomography Angiography (OCTA) in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder

Vascular changes are increasingly recognized as important factors in the pathophysiology of neuroinflammatory disease, especially in multiple sclerosis (MS). The relatively novel technology of optical coherence tomography angiography (OCTA) images the retinal and choroidal vasculature non-invasively and in a depth-resolved manner. OCTA provides an alternative quantitative measure of retinal damage, by measuring vascular density instead of structural atrophy. Preliminary results suggest OCTA is sensitive to retinal damage in early disease stages, while also having less of a "floor-effect" compared with commonly used OCT metrics, meaning it can pick up further damage in a severely atrophied retina in later stages of disease. Furthermore, it may serve as a surrogate marker for vascular pathology in the central nervous system. Data to date consistently reveal lower densities of the retinal microvasculature in both MS and neuromyelitis optica spectrum disorder (NMOSD) compared with healthy controls, even in the absence of prior optic neuritis. Exploring the timing of vascular changes relative to structural atrophy may help answer important questions about the role of hypoperfusion in the pathophysiology of neuroinflammatory disease. Finally, qualitative characteristics of retinal microvasculature may help discriminate between different neuroinflammatory disorders. There are however still issues regarding image quality and development of standardized analysis methods before OCTA can be fully incorporated into clinical practice.

Satralizumab for the Treatment of Neuromyelitis Optica Spectrum Disorders

OBJECTIVE

To review the pharmacological characteristics, clinical evidence, and place in therapy of satralizumab for the treatment of neuromyelitis optica spectrum disorders (NMOSDs).

DATA SOURCES

A comprehensive literature search was conducted in PubMed (January 2000 to October 15, 2020). Key search terms included satralizumab and neuromyelitis optica spectrum disorders. Other sources were derived from product labeling and ClinicalTrials.gov.

STUDY SELECTION AND DATA EXTRACTION

All English-language articles identified from the data sources were reviewed and evaluated. Phase I, II, and III clinical trials were included.

DATA SYNTHESIS

NMOSD is an autoimmune disease characterized by inflammatory lesions in the optic nerves and spinal cord. Interleukin-6 is involved in the pathogenesis of the disorder. Satralizumab is a humanized monoclonal antibody targeting the interleukin-6 receptor. Phase III trials showed that protocol-defined relapse was 30% for satralizumab and 50% for placebo (P = 0.018) when patients with NMOSD were treated with satralizumab monotherapy; protocol-defined relapse was 20% for satralizumab and 43% for placebo (P = 0.02) when satralizumab was added to immunosuppressant treatment. Satralizumab is generally well tolerated, with common adverse effects including injection-related reaction.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Satralizumab has the potential to become a valuable treatment option for patients with NMOSD.

CONCLUSION

Satralizumab appears to be safe and effective as monotherapy or in combination with an immunosuppressant for patients with NMOSD and has the potential to become a valuable treatment option for these patients.

Anti-MOG antibody-associated disorders: differences in clinical profiles and prognosis in Japan and Germany

BACKGROUND

Neurological disorders with IgG antibodies against myelin-oligodendrocyte glycoprotein (MOG-IgG) have been increasingly recognised as a new type of neuroinflammatory disorder.

OBJECTIVE

The study aimed to identify regional and ethnic differences in clinical profiles of MOG-IgG-associated disorders between East Asian (Japanese) and Caucasian (German) patients.

METHODS

Demographic, clinical and therapeutic data from 68 MOG-IgG-positive adults were collected (Japanese, n=44; German, n=24).

RESULTS

Age and sex were similar between cohorts, with optic neuritis occurring most frequently at onset (Japanese: 61%; German: 58%). However, Japanese patients had a lower annualised relapse rate (0.4 vs 0.8, p=0.019; no relapse, 64% vs 25%, p=0.002) and lower Expanded Disability Status Scale score at the last visit (1.0 vs 2.0; p=0.008), despite similar follow-up periods (mean, 73.9 months vs 73.4 months), than those of German patients, respectively. Cerebral syndromes were more common (27% vs 4%; p=0.021) and myelitis less common (21% vs 50%; p=0.012) in Japanese than in German patients, respectively. Japanese patients were more commonly treated with long-term corticosteroids (73%), whereas German patients were more commonly treated with rituximab or other immunosuppressants (63%).

CONCLUSIONS

Among patients with MOG-IgG, Japanese tended to have a monophasic milder disease, whereas the majority of German patients had a relapsing course and more frequent myelitis, findings compatible with neuromyelitis optica spectrum disorder. Although the attack-prevention treatment regimens were considerably different, genetic and environmental factors may be important to determine clinical phenotypes and disease activity.

Brain structural and functional alterations in MOG antibody disease

BACKGROUND

The impact of myelin oligodendrocyte glycoprotein antibody disease (MOGAD) on brain structure and function is unknown.

OBJECTIVES

The aim of this study was to study the multimodal brain MRI alterations in MOGAD and to investigate their clinical significance.

METHODS

A total of 17 MOGAD, 20 aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorders (AQP4 + NMOSD), and 28 healthy controls (HC) were prospectively recruited. Voxel-wise gray matter (GM) volume, fractional anisotropy (FA), mean diffusivity (MD), and degree centrality (DC) were compared between groups. Clinical associations and differential diagnosis were determined using partial correlation and stepwise logistic regression.

RESULTS

In comparison with HC, MOGAD had GM atrophy in frontal and temporal lobe, insula, thalamus, and hippocampus, and WM fiber disruption in optic radiation and anterior/posterior corona radiata; DC decreased in cerebellum and increased in temporal lobe. Compared to AQP4 + NMOSD, MOGAD presented lower GM volume in postcentral gyrus and decreased DC in cerebellum. Hippocampus/parahippocampus atrophy associated with Expanded Disability Status Scale (R = -0.55, p = 0.04) and California Verbal Learning Test (R = 0.62, p = 0.031). The differentiation of MOGAD from AQP4 + NMOSD achieved an accuracy of 95% using FA in splenium of corpus callosum and DC in occipital gyrus.

CONCLUSION

Distinct structural and functional alterations were identified in MOGAD. Hippocampus/parahippocampus atrophy associated with clinical disability and cognitive impairment.

Review of approved NMO therapies based on mechanism of action, efficacy and long-term effects

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Neuromyelitis optica (NMO - including NMO spectrum disorders [NMOSD]) is a devastating disease.

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Up until recently, there was no proven agent to treat to prevent relapses.

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We now have three agents indicated for the treatment of NMO.

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We might suggest the following sequence – 1st line using eculizumab for rapid efficacy and stabilization without effect on the acquired immune system followed by satrilizumab (long term immunomodulation).

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Reserve inebilizumab (immunosuppressant) for breakthrough disease and salvage the severe with AHSCBMT.

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In NMO, control the complement, transition to modulation, and reserve suppression – and salvage the severe with AHSCBMT.

Importance

Neuromyelitis optica (NMO - including NMO spectrum disorders [NMOSD]) is a devastating disease. Eighty-three percent of patients with transverse myelitic (TM) attacks and 67% of patients with optic neuritis (ON) attacks have no or a partial recovery.

Observations

Up until recently, there was no proven agent to treat to prevent relapses. The neuro-immunological community had a dearth of indicated agents for NMOSD. We now have three agents indicated for the treatment of NMO including (eculizumab [Soliris®]), an anti-C5 complement inhibitor, satralizumab (ENSRYNG®), a monoclonal antibody against the IL-6 receptor (IL-6R) that blocks B cell antibody production and inebilizumab (Uplinza®), a monoclonal antibody that binds to the B-cell surface antigen CD19 with subsequent B and plasmablast cell lymphocytolysis with decreasing antibody production. Autologous hematopoietic stem cell bone marrow transplantation (AHSCBMT) has also been used. How do we sequence NMO therapies with the understanding of the acuteness and severity of the disease, the individual mechanism of action (MOA) and rapidity of onset of action, onset of efficacy and long-term safety of each agent?

Conclusions and Relevance

We might suggest the following sequence – 1st line using eculizumab for rapid efficacy and stabilization without effect on the acquired immune system followed by satrilizumab (long term immunomodulation). Reserve inebilizumab (immunosuppressant) for breakthrough disease and salvage the severe with AHSCBMT. In NMO, control the complement, transition to modulation, and reserve suppression – and salvage the severe with AHSCBMT.

Pain in NMOSD and MOGAD: A Systematic Literature Review of Pathophysiology, Symptoms, and Current Treatment Strategies

Neuromyelitis optica spectrum disorders (NMOSDs) and myelin oligodendrocyte glycoprotein-antibody-associated disease (MOGAD) are autoimmune inflammatory disorders of the central nervous system (CNS). Pain is highly prevalent and debilitating in NMOSD and MOGAD with a severe impact on quality of life, and there is a critical need for further studies to successfully treat and manage pain in these rare disorders. In NMOSD, pain has a prevalence of over 80%, and pain syndromes include neuropathic, nociceptive, and mixed pain, which can emerge in acute relapse or become chronic during the disease course. The impact of pain in MOGAD has only recently received increased attention, with an estimated prevalence of over 70%. These patients typically experience not only severe headache, retrobulbar pain, and/or pain on eye movement in optic neuritis but also neuropathic and nociceptive pain. Given the high relevance of pain in MOGAD and NMOSD, this article provides a systematic review of the current literature pertaining to pain in both disorders, focusing on the etiology of their respective pain syndromes and their pathophysiological background. Acknowledging the challenge and complexity of diagnosing pain, we also provide a mechanism-based classification of NMOSD- and MOGAD-related pain syndromes and summarize current treatment strategies.

Evaluation of brain and spinal cord lesion distribution criteria at disease onset in distinguishing NMOSD from MS and MOG antibody-associated disorder

OBJECTIVE

To validate the recently proposed imaging criteria in distinguishing aquaporin-4 antibody (AQP4-ab)-seropositive neuromyelitis optica spectrum disorder (NMOSD) from multiple sclerosis (MS) and myelin oligodendrocyte glycoprotein antibody-associated disorder (MOG-AD) at disease onset in a Chinese population.

METHODS

We enrolled 241 patients in this retrospective study, including 143 AQP4-ab-seropositive NMOSD, 73 MS, and 25 MOG-AD. Cacciaguerra's criteria were described as fulfillment of at least 2/5 conditions including the absence of the combined juxtacortical/cortical lesions, the presence of longitudinal extensive transverse myelitis (LETM) lesions, the presence of periependymal-lateral ventricles lesions, the absence of Dawson's fingers lesions, and the absence of periventricular lesions.

RESULTS

Fulfillment of at least 3/5 conditions was able to differentiate NMOSD from MS with a good diagnostic performance (accuracy = 0.92, sensitivity = 0.91, specificity = 0.93), yet failed to differentiate NMOSD from MOG-AD. LETM lesions showed the highest accuracy (0.78), sensitivity (0.70), and specificity (0.97) for NMSOD.

CONCLUSION

Our research suggested the utility of Cacciaguerra's criteria in a Chinese population at disease onset. A better diagnostic performance in NMOSD could be attained with at least 3/5 conditions fulfilled. Yet their utility in distinguishing NMOSD from MOG-AD was limited.

Myelin oligodendrocyte glycoprotein-associated disorders are associated with HLA subtypes in a Chinese paediatric-onset cohort

OBJECTIVE

Myelin oligodendrocyte glycoprotein-associated disorders (MOGADs) are a rare new neurological autoimmune disease with unclear pathogenesis. Since a linkage of the disease to the human leucocyte antigen (HLA) has not been shown, we here investigated whether MOGAD is associated with the HLA locus.

METHODS

HLA genotypes of 95 patients with MOGADs, assessed between 2016 and 2018 from three academic centres, were compared with 481 healthy Chinese Han individuals. Patients with MOGADs included 51 paediatric-onset and 44 adult-onset cases. All patients were seropositive for IgG targeting the myelin oligodendrocyte glycoprotein (MOG).

RESULTS

Paediatric-onset MOGAD was associated with the DQB1*05:02-DRB1*16:02 alleles (OR=2.43; OR=3.28) or haplotype (OR=2.84) of HLA class II genes. The prevalence of these genotypes in patients with paediatric-onset MOGAD was significantly higher than healthy controls (p^adj=0.0154; p^adj=0.0221; p^adj=0.0331). By contrast, adult-onset MOGAD was not associated with any HLA genotype. Clinically, patients with the DQB1*05:02-DRB1*16:02 haplotype exhibited significantly higher expanded disability status scale scores at onset (p=0.004) and were more likely to undergo a disease relapse (p=0.030). HLA-peptide binding prediction algorithms and computational docking analysis provided supporting evidence for the close relationship between the MOG peptide subunit and DQB1*05:02 allele. In vitro results indicated that site-specific mutations of the predicted target sequence reduced the antigen-antibody binding, especially in the paediatric-onset group with DQB1*05:02 allele.

CONCLUSIONS

This study demonstrates a possible association between specific HLA class II alleles and paediatric-onset MOGAD, providing evidence for the conjecture that different aetiology and pathogenesis likely underlie paediatric-onset and adult-onset cases of MOGAD.

Comparative Analysis of T-Cell Responses to Aquaporin-4 and Myelin Oligodendrocyte Glycoprotein in Inflammatory Demyelinating Central Nervous System Diseases

Autoantibodies against aquaporin-4 (AQP4-Ab) and myelin oligodendrocyte glycoprotein (MOG-Ab) are associated with rare central nervous system inflammatory demyelinating diseases like neuromyelitis optica spectrum disorders (NMOSD). Previous studies have shown that not only antibodies, but also autoreactive T-cell responses against AQP4 are present in NMOSD. However, no study has yet analyzed the presence of MOG reactive T-cells in patients with MOG antibodies. Therefore, we compared AQP4 and MOG specific peripheral T-cell response in individuals with AQP4-Ab (n = 8), MOG-Ab (n = 10), multiple sclerosis (MS, n = 8), and healthy controls (HC, n = 14). Peripheral blood mononuclear cell cultures were stimulated with eight AQP4 and nine MOG peptides selected from previous studies and a tetanus toxoid peptide mix as a positive control. Antigen-specific T-cell responses were assessed using the carboxyfluorescein diacetate succinimidyl ester proliferation assay and the detection of granulocyte macrophage colony-stimulating factor (GM-CSF), interferon (IFN)-ɤ and interleukin (IL)-4, IL-6, and IL-17A in cell culture supernatants. Additionally, human leukocyte antigen (HLA)-DQ and HLA-DR genotyping of all participants was performed. We classified a T-cell response as positive if proliferation (measured by a cell division index ≥3) was confirmed by the secretion of at least one cytokine. Reactivity against AQP4 peptides was observed in many groups, but the T-cell response against AQP4 p156-170 was present only in patients with AQP4-Ab (4/8, 50%) and absent in patients with MOG-Ab, MS and HC (corrected p = 0.02). This AQP4 p156-170 peptide specific T-cell response was significantly increased in participants with AQP4-Ab compared to those without [Odds ratio (OR) = 59.00, 95% confidence interval-CI 2.70–1,290.86]. Moreover, T-cell responses against at least one AQP4 peptide were also more frequent in participants with AQP4-Ab (OR = 11.45, 95% CI 1.24–106.05). We did not observe any significant differences for the other AQP4 peptides or any MOG peptide. AQP4-Ab were associated with HLA DQB1^*02 (OR = 5.71, 95% CI 1.09–30.07), DRB1^*01 (OR = 9.33, 95% CI 1.50–58.02) and DRB1^*03 (OR = 6.75, 95% CI = 1.19–38.41). Furthermore, HLA DRB1^*01 was also associated with the presence of AQP4 p156-170 reactive T-cells (OR = 31.67, 95% CI 1.30–772.98). To summarize, our findings suggest a role of AQP4-specific, but not MOG-specific T-cells, in NMOSD.

Monoclonal Antibody-Based Treatments for Neuromyelitis Optica Spectrum Disorders: From Bench to Bedside

Neuromyelitis optica (NMO)/NMO spectrum disorder (NMOSD) is a chronic, recurrent, antibody-mediated, inflammatory demyelinating disease of the central nervous system, characterized by optic neuritis and transverse myelitis. The binding of NMO-IgG with astrocytic aquaporin-4 (AQP4) functions directly in the pathogenesis of >60% of NMOSD patients, and causes astrocyte loss, secondary inflammatory infiltration, demyelination, and neuron death, potentially leading to paralysis and blindness. Current treatment options, including immunosuppressive agents, plasma exchange, and B-cell depletion, are based on small retrospective case series and open-label studies. It is noteworthy that monoclonal antibody (mAb) therapy is a better option for autoimmune diseases due to its high efficacy and tolerability. Although the pathophysiological mechanisms of NMOSD remain unknown, increasingly, therapeutic studies have focused on mAbs, which target B cell depletion, complement and inflammation cascade inactivation, blood-brain-barrier protection, and blockade of NMO-IgG-AQP4 binding. Here, we review the targets, characteristics, mechanisms of action, development, and potential efficacy of mAb trials in NMOSD, including preclinical and experimental investigations.

Urinary Symptoms and Bladder Dysfunction in Patients with Neuromyelitis Optica Spectrum Disorders: Evaluation with Urodynamics and Management

Objective  To assess lower urinary tract symptoms (LUTSs) in patients with neuromyelitis optica spectrum disorders (NMOSDs) and bladder dysfunction through urodynamics (filling and voiding phase of cystometrography) and management based on findings. Patients and Methods  The study included 42 (34 females) patients admitted to the rehabilitation department. Neurologic evaluation was performed and severity of myelitis was assessed using the American Spinal Injury Association Impairment Scale. All patients underwent urodynamics, and management was based on the findings. Results  Mean age was 34.5 years (range: 11-64 years; standard deviation: 13.1). Twenty-three (54.8%) patients had a first episode of myelitis, whereas 19 patients had relapses (number of episodes varying from 2 to 7). Eleven (26%) patients had increased frequency, 16 (37%) had urgency, 12 (28%) had urge incontinence, 8 (18.6%) had stress incontinence, 22 (52.4%) had nocturia, 31 (72%) had retention of urine, 22 (52.4%) had incomplete evacuation, and 14 (33.3%) patients had mixed urinary complaints. The common urodynamic findings were neurogenic detrusor overactivity (NDO) with detrusor-sphincter dyssynergia (DSD) in 14 (33.3%) patients, NDO without DSD in 8 (19%), and acontractile detrusor in 20 (47.6%). Pharmacotherapy was advised to 22 (52.4%) patients, whereas clean intermittent catheterization (CIC)/self-catheterization was advised to 39 (92.9%) patients. Conclusions  Urinary retention was observed to be the most common urinary complaint in patients with NMOSD followed by NDO with or without sphincter dyssynergia. Urodynamics should be performed in all patients with LUTSs for best management. CIC remains the gold standard for the management of neurogenic bladder dysfunction.

Myelin oligodendrocyte glycoprotein antibodies in neurological disease

Anti-myelin oligodendrocyte glycoprotein (MOG) antibodies (MOG-Abs) were first detected by immunoblot and enzyme-linked immunosorbent assay nearly 30 years ago, but their association with multiple sclerosis (MS) was not specific. Use of cell-based assays with native MOG as the substrate enabled identification of a group of MOG-Ab-positive patients with demyelinating phenotypes. Initially, MOG-Abs were reported in children with acute disseminated encephalomyelitis (ADEM). Further studies identified MOG-Abs in adults and children with ADEM, seizures, encephalitis, anti-aquaporin-4-antibody (AQP4-Ab)-seronegative neuromyelitis optica spectrum disorder (NMOSD) and related syndromes (optic neuritis, myelitis and brainstem encephalitis), but rarely in MS. This shift in our understanding of the diagnostic assays has re-invigorated the examination of MOG-Abs and their role in autoimmune and demyelinating disorders of the CNS. The clinical phenotypes, disease courses and responses to treatment that are associated with MOG-Abs are currently being defined. MOG-Ab-associated disease is different to AQP4-Ab-positive NMOSD and MS. This Review provides an overview of the current knowledge of MOG, the metrics of MOG-Ab assays and the clinical associations identified. We collate the data on antibody pathogenicity and the mechanisms that are thought to underlie this. We also highlight differences between MOG-Ab-associated disease, NMOSD and MS, and describe our current understanding on how best to treat MOG-Ab-associated disease.

Neuromyelitis optica spectrum disorder: Patient experience and quality of life

Objective

To gain insights into NMOSD disease impact, which may negatively affect QoL of patients, their families, and social network.

Methods

The current study used validated instruments to assess physical, emotional, and socioeconomic burden of NMOSD on QoL among 193 patients.

Results

A majority of patients reported an initial diagnosis of a disease other than NMOSD. Overall, two-thirds of patients reported NMOSD as having a strong negative impact on physical health (Short Form-36 [SF-36] score 27.1 ± 39.1), whereas emotional well-being was relatively unimpaired on average (SF-36 score 54.0 ± 44.9). A subset of patients reported having the highest category of emotional health despite worse physical health or financial burden, suggesting psychological resilience. Pain (r = 0.61) and bowel/bladder dysfunction (r = 0.41) imposed the greatest negative physical impact on overall QoL. In turn, ability to work correlated inversely with worsened health (r = −0.68). Increased pain, reduced sexual function, inability to work, and reduced QoL had greatest negative impacts on emotional well-being. Dissatisfaction with treatment options and economic burden correlated inversely with QoL.

Conclusions

Collectively, the current findings advance the understanding of physical, emotional, social, and financial tolls imposed by NMOSD. These insights offer potential ways to enhance QoL by managing pain, enhancing family and social networks, and facilitating active employment.

Incidence of pediatric neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease in Denmark 2008‒2018: A nationwide, population-based cohort study

BACKGROUND

The incidence of pediatric neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease have not been reported previously. Our aim was to estimate the incidence of pediatric NMOSD and the occurrence of anti-MOG antibody-associated disease in Denmark during 2008-18, and to evaluate the diagnostic usefulness of antibodies against MOG and aquaporin-4 (AQP4) in children <18 years.

METHODS

We undertook a nationwide, population-based, multicenter cohort study using data from the Danish National Patient Register, the Danish Multiple Sclerosis Registry, and laboratories providing anti-AQP4 and anti-MOG antibody analyses. Diagnoses were confirmed by review of the medical records, including blinded MRI review in most children with acute disseminated encephalomyelitis (ADEM).

RESULTS

In children with acquired demyelinating syndromes, anti-AQP4 antibodies were detected in 4% and anti-MOG antibodies in 18%, including in the two children with ADEM who relapsed. We identified four children with NMOSD, equivalent to an incidence of 0.031/100,000 (95% confidence interval = 0.011‒0.082). In anti-MOG antibody-positive children, 32% relapsed during follow-up.

CONCLUSIONS

Pediatric NMOSD and MOG antibody-associated disease are rare, but one-third of anti-MOG-positive children relapsed. In pediatric ADEM, only anti-MOG antibody-positive children relapsed, but the overall risk of relapse after pediatric ADEM was low.

Imaging the execution phase of neuroinflammatory disease models

In vivo imaging of the rodent spinal cord has advanced our understanding of how resident cells of the central nervous system (CNS) respond to neuroinflammation. By combining two-photon imaging and experimental autoimmune encephalomyelitis (EAE), the most widely used rodent model of multiple sclerosis (MS), it has been possible, for example, to study how axons degenerate when confronted with inflammatory cells, how oligodendrocytes get damaged in inflammatory lesions, and how immune cells themselves adapt their phenotype and functionality to the changing lesion environment. Similar approaches are now increasingly used to study other forms of neuroinflammation, such as antibody/complement-mediated neuromyelitis optica spectrum disease (NMOSD). To tackle the most pressing open questions in the field, new biosensors and indicator mice that report the metabolic state and interaction of cells in neuroinflammatory lesions are being developed. Moreover, the field is moving towards new anatomical sites of inflammation, such as the cortical gray matter, but also towards longer observation intervals to reveal the chronic perturbations and adaptations that characterize advanced stages of MS.

Antibodies and venom peptides: new modalities for ion channels

Ion channels play fundamental roles in both excitable and non-excitable tissues and therefore constitute attractive drug targets for myriad neurological, cardiovascular and metabolic diseases as well as for cancer and immunomodulation. However, achieving selectivity for specific ion channel subtypes with small-molecule drugs has been challenging, and there currently is a growing trend to target ion channels with biologics. One approach is to improve the pharmacokinetics of existing or novel venom-derived peptides. In parallel, after initial studies with polyclonal antibodies demonstrated the technical feasibility of inhibiting channel function with antibodies, multiple preclinical programmes are now using the full spectrum of available technologies to generate conventional monoclonal and engineered antibodies or nanobodies against extracellular loops of ion channels. After a summary of the current state of ion channel drug discovery, this Review discusses recent developments using the purinergic receptor channel P2X purinoceptor 7 (P2X7), the voltage-gated potassium channel KV1.3 and the voltage-gated sodium channel NaV1.7 as examples of targeting ion channels with biologics.

Role of Glutamatergic Excitotoxicity in Neuromyelitis Optica Spectrum Disorders

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disorder mediated by immune-humoral responses directed against central nervous system (CNS) antigens. Most patients are positive for specific immunoglobulin G (IgG) auto-antibodies for aquaporin-4 (AQP4), a water channel present in astrocytes. Antigen-antibody binding promotes complement system cascade activation, immune system cell infiltration, IgG deposition, loss of AQP4 and excitatory amino acid transporter 2 (EAAT2) expression on the astrocytic plasma membrane, triggering necrotic destruction of spinal cord tissue and optic nerves. Astrocytes are very important cells in the CNS and, in addition to supporting other nerve cells, they also regulate cerebral homeostasis and control glutamatergic synapses by modulating neurotransmission in the cleft through the high-affinity glutamate transporters present in their cell membrane. Specific IgG binding to AQP4 in astrocytes blocks protein functions and reduces EAAT2 activity. Once compromised, EAAT2 cannot take up free glutamate from the extracellular space, triggering excitotoxicity in the cells, which is characterized by overactivation of glutamate receptors in postsynaptic neurons. Therefore, the longitudinally extensive myelitis and optic neuritis lesions observed in patients with NMOSD may be the result of primary astrocytic damage triggered by IgG binding to AQP4, which can activate the immune-system cascade and, in addition, downregulate EAAT2. All these processes may explain the destructive lesions in NMOSD secondary to neuroinflammation and glutamatergic excitotoxicity. New or repurposed existing drugs capable of controlling glutamatergic excitotoxicity may provide new therapeutic options to reduce tissue damage and permanent disability after NMOSD attacks.

Neuromyelitis optica spectrum disorder in pediatrics. Case report

Introduction: Neuromyelitis optica is an inflammatory disorder of the central nervous system that accounts for 5% of demyelinating diseases in pediatrics. Its clinical presentation is variable and associated to the involved area of the central nervous system.Case presentation: This is the case of a 15-year-old patient who consulted several times for nonspecific neurological symptoms. During his last visit to the Clínica Universitaria Colombia in Bogotá, he presented with bilateral optic neuritis, associated with frontal and parietal headache. Immunophenotyping studies were carried out, reporting positive IgG anti-aquaporin 4 antibodies (anti-AQP4 antibody), thus leading to a diagnosis of seropositive neuromyelitis optica spectrum disorder (NMOSD). Management with methylprednisolone pulses was initiated with subsequent outpatient management with rituximab that allowed stabilizing the disease.Discussion: This is an interesting case due to its insidious and uncertain onset in a pediatric patient. It was possible to evaluate clinical and diagnostic differences in relation to its presentation in adults. NMOSD mediated by anti-AQP4 is rare; brain and bone marrow MRI are essential for diagnosis. The treatment of choice for acute conditions consists of high doses of methylprednisolone.Conclusion: This disorder may result in irreversible neurological damage; for this reason, high suspicion is required for early diagnosis and timely treatment.