Absence of GluD2 Antibodies in Patients With Opsoclonus-Myoclonus Syndrome.

OBJECTIVE: A recent study showed glutamate receptor delta 2 antibodies (GluD2-ab) in sera of patients with opsoclonus-myoclonus syndrome (OMS). Inconsistencies between cerebellar immunoreactivity and expression of GluD2 led us to hypothesize that these antibodies are not biomarkers of OMS. METHODS: Serum of 45 children with OMS (10 [22%] with neuroblastoma), 158 adults with OMS (53 [34%] with tumors), and 172 controls including 134 patients with several types of neurologic disorders, 18 with neuroblastoma without OMS, and 20 healthy participants were investigated. Antibodies were determined with 3 different techniques: (1) rat brain immunohistochemistry, (2) a live cell-based assay using a standard secondary antibody (2-step CBA), and (3) a similar CBA with a secondary and tertiary antibodies (3-step CBA). Two plasmids were used in the CBA studies. Three commercial GluD2-ab and 2 human sera with GluD2-ab served as controls for expression of GluD2. RESULTS: The 3 commercial GluD2-ab showed predominant reactivity with the molecular and Purkinje cell layers (where GluD2 is highly enriched), and were also positive with the indicated CBAs. Substantially milder reactivity with brain tissue and CBA was obtained with the 2 control human sera containing GluD2-ab. None of the 203 patients with OMS and 172 controls showed immunoreactivities consistent with GluD2-abs. Compared with a standard 2-step CBA, the 3-step assay did not improve antibody detection and showed more frequent nonspecific reactivity that was not immunoabsorbed with GluD2. CONCLUSION: We did not find GluD2-ab in a large cohort of patients with OMS. GluD2-ab should not be considered diagnostic biomarkers of OMS.

NK Cell-mediated Neuroblastoma Cell Lysis is Enhanced by IgG From Patients With Pediatric Opsoclonus-Myoclonus Syndrome.

Pediatric opsoclonus-myoclonussyndrome (OMS) is a rare autoimmune disorder of which 50% are associated with neuroblastoma (NB). We investigated whether surface-binding autoantibodies in OMS can enhance natural killer (NK) cell-mediated cytotoxicity in these patients. OMS immunoglobulin G (IgG) bound to NB cell lines and NK cell-mediated cytotoxicity to NB cells was enhanced after preincubation with OMS-IgG, but not IgG from NB without OMS or healthy controls. Activation of NK cells by surface-binding autoantibodies may be an additional mechanism of antitumor immunity in children with NB and OMS.

The Treatment of Opsoclonus-Myoclonus Syndrome Secondary to Neuroblastic Tumours-Single-Centre Experience and Literature Review.

Background and Objectives: The opsoclonus-myoclonus syndrome (OMS) is characterised by opsoclons, myoclons and impaired balance, often concomitant with sleep disorder and behavioural difficulties. The symptoms develop as a result of autoimmune response triggered by a neuroblastic tumour (NT). OMS can also develop secondarily to a viral infection or as an immune response triggered by an unknown agent. This leads to the activation of B- and T-cells, which produce and release autoantibodies or cytokines directly within the central nervous system (CNS), thus damaging the neurons within the cerebellum and the brain stem. The available OMS treatments aim at decreasing lymphocyte, cytokine and autoantibody production or accelerating the utilisation of the latter. Another treatment option for OMS involves using cytostatic agents, which damage T- and B-cells causing their depletion and impaired function, which reduces their ability to produce antibodies and cytokines. Materials and Methods: We present a single-centre experience in treating OMS secondary to NT in 7 children. Results: The combined treatment with cyclophosphamide plus dexamethasone resulted in a complete resolution of OMS symptoms in 4 children, and a significant improvement in the 3 children. Two of them periodically present hyperactivity, and one girl requires an additional support at school due to special educational needs (SEN). Conclusions: NT resection does not resolve OMS in children with OMS secondary to NT. The combined treatment with dexamethasone plus cyclophosphamide seems to be an effective treatment of OMS.

Serum IgG-induced microglial activation enhances neuronal cytolysis via the NO/sGC/PKG pathway in children with opsoclonus-myoclonus syndrome and neuroblastoma.

BACKGROUND: Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disease. Some children with OMS also have neuroblastoma (NB). We and others have previously documented that serum IgG from children with OMS and NB induces neuronal cytolysis and activates several signaling pathways. However, the mechanisms underlying OMS remain unclear. Here, we investigated whether nitric oxide (NO) from activated microglias and its cascade contribute to neuronal cytolysis in pediatric OMS. METHODS: The activation of cultured cerebral cortical and cerebellar microglias incubated with sera or IgG isolated from sera of children with OMS and NB was measured by the expression of the activation marker, cytokines, and NO. Neuronal cytolysis was determined after exposing to IgG-treated microglia-conditioned media. Using inhibitors and activators, the effects of NO synthesis and its intracellular cascade, namely soluble guanylyl cyclase (sGC) and protein kinase G (PKG), on neuronal cytolysis were evaluated. RESULTS: Incubation with sera or IgG from children with OMS and NB increased the activation of cerebral cortical and cerebellar microglias, but not the activation of astrocytes or the cytolysis of glial cells. Moreover, the cytolysis of neurons was elevated by conditioned media from microglias incubated with IgG from children with OMS and NB. Furthermore, the expression of NO, sGC, and PKG was increased. Neuronal cytolysis was relieved by the inhibitors of NO signaling, while neuronal cytolysis was exacerbated by the activators of NO signaling but not proinflammatory cytokines. The cytolysis of neurons was suppressed by pretreatment with the microglial inhibitor minocycline, a clinically tested drug. Finally, increased microglial activation did not depend on the Fab fragment of serum IgG. CONCLUSIONS: Serum IgG from children with OMS and NB potentiates microglial activation, which induces neuronal cytolysis through the NO/sGC/PKG pathway, suggesting an applicability of microglial inhibitor as a therapeutic candidate.

An upfront immunomodulatory therapy protocol for pediatric opsoclonus-myoclonus syndrome.

BACKGROUND: Treatment of opsoclonus-myoclonus syndrome (OMS) has historically involved corticosteroids and intravenous immunoglobulin (IVIG) for a duration of 6-12 months or longer. This study evaluated whether a brief upfront immunomodulatory therapy protocol with rituximab reduces the duration of OMS therapy without adversely affecting OMS outcomes. PROCEDURE: Retrospective chart review was performed for consecutive children diagnosed with OMS from 2006 to 2019 at The Hospital for Sick Children (Toronto, Canada). Children treated within 3 months of diagnosis with a treatment protocol involving pulse methylprednisolone (3-5 days, followed by an oral steroid taper), IVIG and/or plasma exchange, and rituximab (protocol group, n = 7) were compared to a historical group treated primarily with prednisone and IVIG (n = 8). RESULTS: The duration of corticosteroid treatment was shorter in the protocol (median 4.5 [range 3-12] months) compared to that in the historical group (median 21.5 [range 6-70] months, P = .005), and subjects in the protocol group received fewer cycles of IVIG (median 1 [range 0-7] cycle vs 7 [range 1-70] cycles, P = .01). The proportion of children with OMS relapse was similar between the protocol and historic groups (2/6 vs 5/8, P = .59). OMS symptom rating scales at 12-month follow-up were similar in the protocol group (median 2.5, range 0-3) compared to that in the historical group (median 1, range 0-7; P = .66). CONCLUSIONS: An upfront immunomodulatory therapy protocol with rituximab permits reduction in the duration of corticosteroid and IVIG therapy without a detrimental effect on OMS outcomes. Future studies with longer follow-up will have to determine whether neurocognitive and psychosocial outcomes are improved by this approach.

Update on opsoclonus-myoclonus syndrome in adults.

Opsoclonus-myoclonus syndrome in adults is a rare and heterogeneous disorder with the clinical features of opsoclonus, myoclonus, ataxia, and behavioral and sleep disturbances. The pathophysiology is thought to be immunological on the basis of paraneoplastic or infectious etiologies. Immunomodulatory therapies should be performed although the response may be incomplete. A number of autoantibodies have been identified against a variety of antigens, but no diagnostic immunological marker has yet been identified. This review focuses on underlying mechanisms of opsoclonus-myoclonus syndrome, including findings that have been identified recently, and provides an update on the clinical features and treatments of this condition.

NMDA receptor antibody in teratoma-related opsoclonus-myoclonus syndrome.

Opsoclonus-myoclonus syndrome (OMS) is a brainstem/cerebellar syndrome producing disabling multi-directional saccadic oscillations with oscillopsia, with or without somatic myoclonus and cerebellar ataxia (Wong et al., 2001; Armangué et al., 2016). OMS is presumed to have an autoimmune basis and patients with it are tested for antineuronal antibodies and have imaging to locate any tumors. Here we report a unusual case of a young woman who had NMDAR antibody (NMDAR-ab) positive, teratoma-related, isolated OMS without encephalopathy. Removal of her ovarian teratoma, and immunotherapy with steroids, intravenous immunoglobulin (IVIg), plasma exchange (PLEX), and ultimately with B-cell depletion with rituximab resulted in total recovery after 3 months. Patients with teratoma-related OMS very rarely have NMDAR-ab which suggests that it is not the NMDAR-ab per se that causes the OMS.

Multifactorial analysis of opsoclonus-myoclonus syndrome etiology ("Tumor" vs. "No tumor") in a cohort of 356 US children.

BACKGROUND: Pediatric opsoclonus-myoclonus syndrome (OMS) presents a paradox of etiopathogenesis: A neuroblastic tumor (NB) is found in only one half of the cases, the others are ascribed to infections or designated as idiopathic. METHOD: From an IRB-approved observational study of 356 US children with OMS, secondary analysis of "etiology" and related factors was performed on a well-characterized cohort. The "Tumor" (n = 173) and "No Tumor" groups (n = 183), as defined radiologically, were compared according to multiple factors considered potentially differentiating. Data were analyzed retrospectively using parametric and nonparametric tests as indicated. RESULTS: Patients with NB were not distinguishable by prodromal symptoms, OMS onset age, gender, race/ethnicity, OMS severity, rank order of neurological sign appearance, or geographic distribution. Various CSF immunologic biomarker abnormalities of OMS did not vary in the presence or absence of a detectable tumor: frequency of six lymphocyte subsets, or concentrations of 18 cytokines/chemokines, cytokine antagonists, chemokine receptors, cell adhesion molecules, or neuronal/glial markers. Prior responsiveness to conventional immunotherapy was not contingent on tumor/no tumor designation. CONCLUSIONS: Multiple convergent factors provide compelling empirical evidence and rationalize the concept that OMS is one neurological disorder, regardless of apparent etiology. Limitations to the current clinical etiologic classifications as paraneoplastic, parainfectious/post-infectious, and idiopathic etiology require antigen-based biological solutions to tease out the molecular pathophysiology of viral/tumoral mechanisms. Systematic studies, regardless of presumed etiology, will be necessary to find the highest-yield combination of imaging approaches, screening for infectious agents, and new biomarkers. Two testable hypotheses for future research are presented.

Cerebrospinal fluid γδ T cell frequency is age-related: a case-control study of 435 children with inflammatory and non-inflammatory neurological disorders.

Studies of cerebrospinal fluid (CSF) γδ T cells in children are limited, due especially to the lack of control data. In adults, gamma/delta T cells (TCR-γδ) residing in the intrathecal space are sometimes involved in neuroinflammation. To evaluate the possible role of γδ T cells in paediatric neuroinflammation, we immunophenotyped cerebrospinal fluid (CSF) and blood lymphocytes using flow cytometry in a case-control study of 100 children with non-inflammatory neurological disorders (NIND), 312 with opsoclonus-myoclonus (OMS) and 23 with other inflammatory neurological disorders (OIND). In NIND, the negative correlation between CSF γδ T cell frequency and patient age was striking: median frequency of 27% in infants and 3·3% in teens. Interindividual variations were largest in the youngest. There was no gender effect. In all OMS, after correcting for age, only a small effect of OMS severity remained. Measurement of markers for γδ T cell activation [human leucocyte antigen D-related (HLA-DR)], maturation (CD45RA, CD45RO) or intracellular cytokine staining [interleukin (IL)-4, interferon (IFN)-γ] failed to discriminate OMS and NIND groups. Of seven OMS immunotherapies/combinations, none altered the frequency of total CSF γδ T cells or subsets significantly. In OIND, the CSF γδ T cell frequency was < 10% for single samples of other paraneoplastic disorders [anti-neuronal nuclear antibody (ANNA)-1, PCA-1, teratoma-associated syndrome], cerebellar ataxia (post-infectious, ataxia-telangiectasia), acute disseminated encephalomyelitis, neuroborreliosis and encephalitis. This study provides new insights into CSF γδ T cells in the paediatric population. Although their role in CSF remains elusive, the negative age correlation, resistance to immunotherapy and our age cut-off references for NIND are important findings for the design of future paediatric studies.

HIV-associated opsoclonus-myoclonus-ataxia syndrome: early infection, immune reconstitution syndrome or secondary to other diseases? Case report and literature review.

Opsoclonus-myoclonus-ataxia (OMA) syndrome is a debilitating autoimmune neurological disorder. Post-infectious opsoclonus-myoclonus-ataxia syndrome has been described with varying bacterial, spirochetal, and viral infections including several patients with HIV. However, specific immunopathological mechanisms that may lead to opsoclonus-myoclonus in HIV-positive patients are unknown.We report a case of HIV-associated opsoclonus-myoclonus and early HIV infection. A review of published literature shows opsoclonus-myoclonus can occur during early infection, in immune reconstitution syndrome or in association with other infections, especially tuberculosis.

Cancer and Autoimmunity: Paraneoplastic Neurological Disorders Associated With Neuroblastic Tumors.

Cancer and autoimmunity come together in paraneoplastic syndromes (PNS), which reflect the remote, not direct, effects of cancer. In the pediatric population, a variety of PNS have been described, but the most common of these rare disorders are instigated by neuroblastic tumors, such as neuroblastoma, ganglioneuroblastoma, and ganglioneuroma. The main pediatric-onset neurological PNS are ROHHAD syndrome, anti-ANNA1 (anti-Hu), and opsoclonus-myoclonus syndrome. They manifest distinctive neurological features, which aid the diagnosis, though under-recognition still poses serious challenges and risks. In each clinical syndrome, a large subgroup of patients had no demonstrated tumor. Most neurological PNS are immunologically mediated, and CSF neuroimmunological studies show common elements of immune involvement in PNS as well as important differences. Future immunotherapy strategies may be able to take advantage of these abnormalities.

Adult-onset opsoclonus-myoclonus syndrome due to West Nile Virus treated with intravenous immunoglobulin.

A 63-year-old female with no significant past medical history was presented with a 5-day history of progressive opsoclonus-myoclonus, headaches, and fevers. Her workup was significant only for positive West-Nile Virus serum serologies. She received a 2-day course of intravenous immunoglobulin (IvIG). At an 8-week follow up, she had a complete neurological remission. Adult-onset opsoclonus-myoclonus syndrome is a rare condition for which paraneoplastic and infectious causes have been attributed. To our knowledge, this is the first case reported of opsoclonus-myoclonus secondary to West-Nile Virus treated with intravenous immunoglobulin monotherapy.

Adult-onset Opsoclonus-Myoclonus Syndrome Associated With Ganglionic Acetylcholine Receptor Autoantibody.

INTRODUCTION: Opsoclonus-myoclonus syndrome (OMS) may have a toxin induced, parainfectious, or paraneoplastic etiology. Several autoantibodies have been associated with adult-onset OMS, most commonly antineuronal nuclear antibody 2 (Ri), and it is most frequently associated with breast or small cell lung cancer. The nicotinic ganglionic acetylcholine receptor autoantibody (α3-AChR Ab) has not been described in association. CASE REPORT: A 46-year-old woman was evaluated for symptoms of oscillopsia, tremor, gait imbalance, and mild cognitive deficits that began 6 weeks prior. Neurological examination demonstrated opsoclonus, myoclonus, and mild gait ataxia. Laboratory evaluation revealed an elevated α3-AChR Ab at 0.27 nmol/L (normal ≤0.02 nmol/L) with no other autoantibodies or infectious etiology detected. Thorough screening revealed no evidence of associated malignancy. Immunotherapy with weekly methylprednisolone led to significant improvement. CONCLUSIONS: This first reported case of α3-AChR Ab positivity in the setting of adult-onset OMS expands the spectrum of associated autoantibodies. The mechanism of disease may be linked to cholinergic nuclei within the brainstem. This case suggests including α3-AChR Ab in the evaluation of adult-onset OMS, and highlights the importance of further understanding α3-AChR within the brain.

Immunoproteomic studies on paediatric opsoclonus-myoclonus associated with neuroblastoma.

We aimed to identify new cell-membrane antigens implicated in opsoclonus-myoclonus with neuroblastoma. The sera of 3 out of 14 patients showed IgG electron-microscopy immunogold reactivity on SH-SY5Y neuroblastoma cells. Immunoprecipitation experiments using rat brain synaptosomes and SH-SY5Y cells led to the identification of: (1) thirty-one nuclear/cytoplasmic proteins (including antigens HuB, HuC); (2) seven neuronal membrane proteins, including the Shaw-potassium channel Kv3.3 (KCNC3), whose genetic disruption in mice causes ataxia and generalized muscle twitching. Although cell-based assays did not demonstrate direct antigenicity, our findings point to Shaw-related subfamily of the potassium voltage-gated channels complexed proteins as hypothetical antigenic targets.

Childhood opsoclonus-myoclonus syndrome: diagnosis and treatment.

Opsoclonus-myoclonus syndrome (OMS) is a rare and primarily immune-mediated disease in children and adults. The main symptoms include opsoclonus, myoclonus and ataxia. In children, the symptoms also include irritability, and, over a long-term course, learning and behavioural disturbances. OMS can be idiopathic, parainfectious or occur as a paraneoplastic (tumour-associated) syndrome. Paraneoplastic OMS in children is almost exclusively associated with neuroblastoma, whereas in adults, small cell lung cancer and breast cancer are the main underlying tumours. An autoimmune pathophysiology is suspected because childhood OMS patients have functionally active autoantibodies, proinflammatory changes in the cytokine network and immunotherapy responses. Children appear to respond regularly to immunosuppressive treatment. However, although the neurological symptoms show a good response, most children continue to show neuropsychological disturbances.