Antibodies to dendritic neuronal surface antigens in opsoclonus myoclonus ataxia syndrome

Characteristics of Opsoclonus-Myoclonus Syndrome in Patients of the Largest Pediatric Hospital in Latin America

BACKGROUND

Opsoclonus-myoclonus syndrome (OMS) is a rare neuroinflammatory disorder characterized by ataxia, opsoclonus, and myoclonus. Clinical diagnosis of OMS has been challenging; therefore, we sought to determine the clinical and treatment profiles of patients with OMS at the largest pediatric hospital in Latin America.

METHODS

We analyzed the data of patients diagnosed with OMS between 2010 and 2020 at Pequeno Principe Hospital (Brazil) to determine the corresponding clinical profile more accurately.

RESULTS

Of the approximately 50,000 visitors to our pediatric neurology department from 2010 to 2020, 10 patients with OMS were observed. Five nontumor cases included three parainfectious and two idiopathic cases. The median time from symptom onset to diagnosis was 34 days. All patients with diagnostic OMS criteria in the idiopathic, nontumor group underwent whole-exome sequencing, with potentially pathogenic mutations identified in two cases. Nine patients were treated with methylprednisolone pulse, followed by oral steroids; eight received one or more intravenous immunoglobulin treatments; and six received azathioprine and cyclophosphamide. Complete symptomatic recovery was observed in only one patient.

CONCLUSIONS

OMS diagnosis remains challenging. Diagnostic suspicion is necessary to improve the management of these patients and allow early immunosuppressive treatment. Paraneoplastic etiology is the most prevalent. In idiopathic patients who do not respond to immunosuppressive treatment, tests, such as whole-exome sequencing, may reveal a differential diagnosis. Genetic alterations that increase the risk of tumors may be an important clue to the pathophysiology of OMS.

Clinical features and outcomes of opsoclonus myoclonus ataxia syndrome

OBJECTIVES AND METHODS

Opsoclonus myoclonus ataxia syndrome (OMAS) is a rare neuroinflammatory disorder. We aimed to retrospectively evaluate clinical and laboratory data and outcomes of 23 children diagnosed with OMAS in two children's hospitals between 2010 and 2021.

RESULTS

There were 14 boys and 9 girls aged 4-113 months, median 24 months. Ten (43.5%) children had paraneoplastic causes: neuroblastoma/ganglioneuroblastoma (n = 9), acute lymphoblastic leukemia (n = 1). Three children had a postinfectious cause (upper respiratory tract infection in 2, EBV infection in 1) and two had a history of vaccination (varicella in 1, hepatitis A and meningococcal in 1). No underlying factor was identified in 8 (34.8%) children. Speech disorders were more frequent in patients with neural tumors than in those without (p = 0.017). Intravenous immunoglobulin and steroids were effective as initial treatment in most children. Rituximab resulted in at least mild improvement in all 6 children with persistent or recurrent symptoms. Nine (39%) children experienced at least one relapse. Neurological sequelae were detected in 13 (57%) children. There was no significant correlation between clinical characteristics and outcome, except for higher risk of relapse in case of incomplete recovery after first attack (p = 0.001).

CONCLUSIONS

Acute lymphoblastic leukemia, vaccines against hepatitis A and meningococci can be included among antecedent factors in OMAS. Among clinical symptoms, speech problems might point to the likelihood of an underlying neoplasm in OMAS. Intravenous immunoglobulin and steroids may be chosen for initial treatment while rituximab can increase the chance of recovery in case of persistent or recurrent symptoms. The presence of relapse was associated with poor outcome.

Monocentric retrospective clinical outcome in a group of 13 patients with opsoclonus myoclonus syndrome, proposal of diagnostic algorithm and review of the literature

BACKGROUND

Dancing eye syndrome or opsoclonus-myoclonus syndrome (OMS) is a very rare disease (incidence <1/5,000,000 per year), which is more prevalent in young children. Although it is not usually a cause of mortality, the aftermaths are not rare.

METHODS

We performed an observational retrospective review of children diagnosed with OMS in our neuropediatric department from 1996 to 2020, with the objective of assessing the prognostic value of initial clinical features. All medical data from diagnosis to last follow-up were reviewed. We defined unfavorable evolution of OMS as persistence or worsening of symptoms. Subsequently, based on a literature review, our results and experience, a diagnostic algorithm was developed.

RESULTS

A total of 13 OMS patients were included: 61.5% were male (n = 8), median age at diagnosis was 18 months (IR = 76), median treatment delay was 14 days (IR = 146) and OMS score at onset was 8 (IR = 11). The most frequent etiologies were neuroblastoma-associated and idiopathic OMS (38.46%; n = 5) of the patients, followed by post-infectious OMS (n = 3). All the patients were treated with corticosteroids, five required a surgical intervention (neuroblastoma group), and three required adjunctive immune therapy (immunoglobulins, cyclophosphamide and/or rituximab). We detected neurodevelopmental disorders in 38.46% (n = 5) of the patients, mainly attention deficit (n = 4), and persistent sleep disturbances (n = 4). The median OMS score at the end of follow-up was 1 (IR = 3). An important diagnostic delay, OMS score of ≥10 and age >1 year at onset may correlate with a higher risk of aftermaths. We detected a better prognosis in the post-infectious OMS, with full recovery occurring in 2/3 of patients.

CONCLUSIONS

Early clinical suspicion is key to guarantee maximum response of treatment.

Diagnosis and Management of Opsoclonus-Myoclonus-Ataxia Syndrome in Children: An International Perspective

BACKGROUND AND OBJECTIVES

Opsoclonus-myoclonus-ataxia syndrome (OMAS) is a rare disorder of the nervous system that classically presents with a combination of characteristic eye movement disorder and myoclonus, in addition to ataxia, irritability, and sleep disturbance. There is good evidence that OMAS is an immune-mediated condition that may be paraneoplastic in the context of neuroblastoma. This syndrome may be associated with long-term cognitive impairment, yet it remains unclear how this is influenced by disease course and treatment. Treatment is largely predicated on immune suppression, but there is limited evidence to indicate an optimal regimen.

METHODS

Following an international multiprofessional workshop in 2004, a body of clinicians and scientists comprising the International OMS Study group continued to meet biennially in a joint professionals and family workshop focusing on pediatric OMAS. Seventeen years after publication of the first report, a writing group was convened to provide a clinical update on the definitions and clinical presentation of OMAS, biomarkers and the role of investigations in a child presenting with OMAS, treatment and management strategies including identification and support of long-term sequelae.

RESULTS

The clinical criteria for diagnosis were reviewed, with a proposed approach to laboratory and radiologic investigation of a child presenting with possible OMAS. The evidence for an upfront vs escalating treatment regimen was reviewed, and a treatment algorithm proposed to recognize both these approaches. Importantly, recommendations on monitoring of immunotherapy response and longer-term follow-up based on an expert consensus are provided.

DISCUSSION

OMAS is a rare neurologic condition that can be associated with poor cognitive outcomes. This report proposes an approach to investigation and treatment of children presenting with OMAS, based on expert international opinion recognizing the limited data available.

Acute Movement Disorders in Childhood

Acute-onset movement disorders (MDs) are an increasingly recognized neurological emergency in both adults and children. The spectrum of possible causes is wide, and diagnostic work-up is challenging. In their acute presentation, MDs may represent the prominent symptom or an important diagnostic clue in a broader constellation of neurological and extraneurological signs. The diagnostic approach relies on the definition of the overall clinical syndrome and on the recognition of the prominent MD phenomenology. The recognition of the underlying disorder is crucial since many causes are treatable. In this review, we summarize common and uncommon causes of acute-onset movement disorders, focusing on clinical presentation and appropriate diagnostic investigations. Both acquired (immune-mediated, infectious, vascular, toxic, metabolic) and genetic disorders causing acute MDs are reviewed, in order to provide a useful clinician’s guide to this expanding field of pediatric neurology.

Opsoclonus-myoclonus-ataxia syndrome in children

Opsoclonus-myoclonus-ataxia syndrome is a rare neuroimmunologic disorder typically presenting in previously healthy infants and toddlers. It is characterized by a clinical triad of (1) erratic saccadic intrusions; (2) myoclonus and/or ataxia; (3) behavioral features, typified by developmental plateauing, irritability and insomnia. About half of cases are associated with an underlying neuroblastoma and diagnostic imaging is essential once OMAS is suspected. A thorough workup, including serum, urine, and cerebrospinal fluid studies is critical to identify underlying biomarkers of OMAS itself or neuroblastoma. Historically, many children had relatively poor long-term outcomes, with residual neurologic and/or neuropsychiatry sequelae typical. More recent concepts have emphasized combined immunotherapy regimens that offer hope for better outcomes in children with this remarkable, challenging disease.

Serum Biomarkers in Neuro-Ophthalmology: When to Test

Discovery and characterization of serologic biomarkers has revolutionized the diagnostic framework of systemic and paraneoplastic autoimmune neuro-ophthalmic diseases. Expanding recognition of the multiple ocular and visual manifestations of these conditions highlights the important role of the referring provider in identifying potential cases. Increasing ease of access to serologic testing also enables these practitioners to initiate the diagnostic work-up in suspected cases. We aimed to provide an update on the current knowledge surrounding and use of relevant autoimmune biomarkers by correlating specific clinical neuro-ophthalmic manifestations with autoantibody biomarkers. The utility of select biomarkers for myasthenia gravis, neuromyelitis optica spectrum disorder, myelin oligodendrocyte glycoprotein-IgG-associated disorder, opsoclonus-myoclonus syndrome, anti-collapsin-response mediator protein-5 optic neuropathy, and glial fibrillary acidic protein-IgG-associated disease are discussed with particular focus on the clinical contexts in which to consider testing.

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.

Treatment of Movement Disorder Emergencies in Autoimmune Encephalitis in the Neurosciences ICU

Immune response against neuronal and glial cell surface and cytosolic antigens is an important cause of encephalitis. It may be triggered by activation of the immune system in response to an infection (para-infectious), cancer (paraneoplastic), or due to a patient's tendency toward autoimmunity. Antibodies directed toward neuronal cell surface antigens are directly pathogenic, whereas antibodies with intracellular targets may become pathogenic if the antigen is transiently exposed to the cell surface or via activation of cytotoxic T cells. Immune-mediated encephalitis is well recognized and may require intensive care due to status epilepticus, need for invasive ventilation, or dysautonomia. Patients with immune-mediated encephalitis may become critically ill and display clinically complex and challenging to treat movement disorders in over 80% of the cases (Zhang et al. in Neurocrit Care 29(2):264-272, 2018). Treatment options include immunotherapy and symptomatic agents affecting dopamine or acetylcholine neurotransmission. There has been no prior published guidance for management of these movement disorders for the intensivist. Herein, we discuss the immune-mediated encephalitis most likely to cause critical illness, clinical features and mechanisms of movement disorders and propose a management algorithm.

Paraneoplastic Syndromes in Neuro-ophthalmology

PURPOSE OF REVIEW

This article discusses the varied types of paraneoplastic syndromes that commonly have neuro-ophthalmologic manifestations. Diagnostic considerations and therapeutic options for individual diseases are also discussed.

RECENT FINDINGS

Paraneoplastic syndromes can affect the afferent and efferent visual systems. Paraneoplastic syndromes may result in reduced visual acuity from retinal degeneration, alterations in melanocyte proliferation and uveal thickening, or acquired nystagmus. Ocular motor abnormalities related to paraneoplastic syndromes may present with symptoms from opsoclonus or from neuromuscular junction disease. Diagnosis remains challenging, but serologic identification of some specific antibodies may be helpful or confirmatory. Treatment, in addition to directed therapies against the underlying cancer, often requires systemic corticosteroids, plasma exchange, or immunosuppression, but some specific syndromes improve with use of targeted pharmacologic therapy.

SUMMARY

Diagnosis and therapy of paraneoplastic syndromes presenting with neuro-ophthalmic symptoms remain a challenge, but strategies are evolving and new approaches are on the horizon.

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.

Clinical Profile, Prognostic Indicators, and Therapeutic Outcomes of Pediatric Opsoclonus-Myoclonus-Ataxia Syndrome: A Single-Center Experience from South India

Background:

Opsoclonus myoclonus syndrome (OMS) is a neuroinflammatory disorder. Indian literature on its clinical profile and outcome is sparse.

Objectives:

The objective of this study is to describe the clinical profile and analyze outcomes and prognostic predictors in a cohort of children with OMS.

Materials and Methods:

This was a retrospective study of children with OMS between 2007 and 2017.

Results:

Twenty-two children were included in the study. The mean age at onset of symptom was 20.9 months (standard deviation [SD]: 7.5). The mean duration of delay in diagnosis was 8.4 months (SD 1.26) with acute cerebellitis being the most common misdiagnosis. Eleven children (50%) were diagnosed with tumor during evaluation and follow-up and 11 children (50%) belonged to idiopathic/postinfectious group. Magnetic resonance imaging brain was normal in all children except for one revealing cerebellar atrophy on follow-up. One child in the paraneoplastic group (neuroblastoma) had a positive PNMA2/Ta onconeural antibody. Children in the tumor group had an earlier age of onset (mean 15.5 vs. 26.3 months), shorter time to onset of opsoclonus from initial symptom (2.54 vs. 7.27 weeks), and higher severity score at presentation (13.7 vs. 11.3) compared to the nontumor group. Children in the nontumor group attained their first remission with treatment earlier (10.9 weeks, SD: 4.5) than the children with tumor (18.72 weeks, SD: 5.8). There was no significant difference in the outcome between the groups. Children with multiple relapses (>3) and late surgical intervention for tumor (>6 months after symptom onset) had a poor outcome.

Discussion:

A high index of suspicion coupled with early diagnosis and periodic tumor surveillance (even in the initially negative cases) along with aggressive combined multimechanistic immunotherapies is the key in improving outcomes.

Conclusion:

A high index of suspicion in appropriate clinical circumstances and early aggressive immunomodulation might lead to a better outcome.

IGF-1 alleviates serum IgG-induced neuronal cytolysis through PI3K signaling in children with opsoclonus-myoclonus syndrome and neuroblastoma

BACKGROUND

Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder, usually accompanied by neuroblastoma (NB). There is no targeted treatment and animal model of OMS. We aimed to investigate whether insulin-like growth factor 1 (IGF-1)/phosphoinositide 3-kinase (PI3K) signaling alleviates neuronal cytolysis in pediatric OMS.

METHODS

Cultured rat cerebral cortical neurons and cerebellar neurons were incubated with sera or IgG isolated from sera of children with OMS and NB. Cytolysis and PI3K expression were measured by the lactate dehydrogenase assay and enzyme-linked immunosorbent assay, respectively. Using inhibitors and activators, the effects of IGF-1 and PI3K on cytolysis were investigated.

RESULTS

The incubation of sera or IgG from children with OMS and NB increased cytolysis in not only cerebellar neurons, but also cerebral cortical neurons. Furthermore, the IGF-1 receptor antagonist NVP-AEW541 exaggerated cytolysis in children with OMS and NB. IGF-1 alleviated cytolysis, which was blocked by the PI3K inhibitor LY294002. Additionally, sera or IgG from children with OMS and NB compensatively elevated PI3K expression. LY294002 exacerbated cytolysis; whereas, the PI3K activator 740 Y-P suppressed cytolysis.

CONCLUSION

IGF-1/PI3K signaling alleviates the cytolysis of cultured neurons induced by serum IgG from children with OMS and NB, which may be innovation therapy targets.

Glutamate receptor δ2 serum antibodies in pediatric opsoclonus myoclonus ataxia syndrome

Objective

To identify neuronal surface antibodies in opsoclonus myoclonus ataxia syndrome (OMAS) using contemporary antigen discovery methodology.

Methods

OMAS patient serum immunoglobulin G immunohistochemistry using age-equivalent rat cerebellar tissue was followed by immunoprecipitation, gel electrophoresis, and mass spectrometry. Data are available via ProteomeXchange (identifier PXD009578). This generated a list of potential neuronal surface cerebellar autoantigens. Live cell-based assays were used to confirm membrane-surface antigens and adsorb antigen-specific immunoglobulin Gs. The serologic results were compared to the clinical data.

Results

Four of the 6 OMAS sera tested bound rat cerebellar sections. Two of these sera with similar immunoreactivities were used in immunoprecipitation experiments using cerebellum from postnatal rat pups (P18). Mass spectrometry identified 12 cell-surface proteins, of which glutamate receptor δ2 (GluD2), a predominately cerebellar-expressed protein, was found at a 3-fold-higher concentration than the other 11 proteins. Antibodies to GluD2 were identified in 14/16 (87%) OMAS samples, compared with 5/139 (5%) pediatric and 1/38 (2.6%) adult serum controls (p < 0.0001), and in 2/4 sera from patients with neuroblastoma without neurologic features. Adsorption of positive OMAS sera against GluD2-transfected cells substantially reduced but did not eliminate reactivity toward cerebellar sections.

Conclusion

Autoantibodies to GluD2 are common in patients with OMAS, bind to surface determinants, and are potentially pathogenic.

Autoimmune Movement Disorders: a Clinical and Laboratory Approach

Autoimmune movement disorders are caused by an aberrant immune response to neural self-antigens. These disorders may be paraneoplastic, parainfectious, or (most commonly) idiopathic. The neurological presentations are diverse, and sometimes multifocal. Movement disorders can occur as part of the spectrum with phenotypes including chorea, myoclonus, ataxia, CNS hyperexcitability (including stiff-person syndrome), dystonia, and parkinsonism. Symptoms are subacute in onset and may have a fluctuating course. The best characterized disorders are unified by neural autoantibodies identified in serum or cerebrospinal fluid. The antibody specificity may predict the association with cancer and the response to immunotherapy. In this article, we review autoimmune-mediated movement disorders, associated cancers, diagnosis, and treatment.

Infection-mediated autoimmune movement disorders

Infectious diseases remain the most common cause of neurological disability in the world. A number of movement disorders can develop in adults and children in response to infections. These can occur in isolation or as part of a broader neurological illness, with movement abnormalities consequent to an encephalopathy or a broader brain dysfunction. While most infection-related movement disorders are direct consequences of an active infectious process affecting cerebral structures implied in the motor network, at times a delayed immune-mediated process in response to a previous infectious is responsible for the neurological dysfunction. This immunological response can occur as a consequence of a number of pathogens, and develop at variable times after the initial infection. The most common infection-mediated autoimmune movement disorders are chorea, which is especially common in children, and other hyperkinetic disorders, but Parkinsonism and other hypokinetic movement disorders may also occur.

Opsoclonus-Myoclonus Syndrome: A New Era of Improved Prognosis?

BACKGROUND

Opsoclonus-myoclonus syndrome is an autoimmune neurological disorder characterized by opsoclonus, myoclonus, ataxia, and behavioral changes. Although long-term outcomes have historically been poor, including motor and cognitive disabilities, the advent of new and more aggressive immunotherapy regimens may be improving prognosis in opsoclonus-myoclonus syndrome.

METHODS

We retrospectively reviewed the records of all children diagnosed with opsoclonus-myoclonus syndrome at BC Children's Hospital from 2000 to 2010. Neurological outcomes were compared with those previously reported in the literature.

RESULTS

Twelve children with opsoclonus-myoclonus syndrome were identified, four of whom had an associated neuroblastoma. Two thirds of patients received initial treatment with a combination of corticosteroids, intravenous immunoglobulin (IVIG), and an additional immunosuppressant agent. After a median follow-up of three years from diagnosis, ten patients had no or minimal neurological abnormalities. Two patients had poor outcome with significant cognitive impairment.

CONCLUSIONS

Most patients in this series were treated with early multimodal immunotherapy, and neurological outcomes were better than those in most historical reports. This finding is consistent with recent studies that suggest multimodal immunotherapy regimens may be improving the prognosis in this challenging disease. However, some individuals did well with less aggressive treatment, and further studies are required to determine optimal treatment approach.

Stiff person syndrome and other immune-mediated movement disorders - new insights

PURPOSE OF REVIEW

This review highlights the recent developments in immune-mediated movement disorders and how they reflect on clinical practice and our understanding of the underlying pathophysiological mechanisms.

RECENT FINDINGS

The antibody spectrum associated with stiff person syndrome and related disorders (SPSD) has broadened and, apart from the classic glutamic acid decarboxylase (GAD)- and amphiphysin-antibodies, includes now also antibodies against dipeptidyl-peptidase-like protein-6 (DPPX), gamma-aminobutyric acid type A receptor (GABAAR), glycine receptor (GlyR) and glycine transporter 2 (GlyT2). The field of movement disorders with neuronal antibodies keeps expanding with the discovery for example of antibodies against leucine rich glioma inactivated protein 1 (LGI1) and contactin associated protein 2 (Caspr2) in chorea, or antibodies targeting ARHGAP26- or Na/K ATPase alpha 3 subunit (ATP1A3) in cerebellar ataxia. Moreover, neuronal antibodies may partly account for movement disorders attributed for example to Sydenham's chorea, coeliac disease, or steroid responsive encephalopathy with thyroid antibodies. Lastly, there is an interface of immunology, genetics and neurodegeneration, e.g. in Aicardi-Goutières syndrome or the tauopathy with IgLON5-antibodies.

SUMMARY

Clinicians should be aware of new antibodies such as dipeptidyl-peptidase-like protein-6, gamma-aminobutyric acid type A receptor and glycine transporter 2 in stiff person syndrome and related disorders, as well as of the expanding spectrum of immune-mediated movement disorders.

Clinical and Immunological Features of Opsoclonus-Myoclonus Syndrome in the Era of Neuronal Cell Surface Antibodies

IMPORTANCE

Most studies on opsoclonus-myoclonus syndrome (OMS) in adults are based on small case series before the era of neuronal cell surface antibody discovery.

OBJECTIVE

To report the clinical and immunological features of idiopathic OMS (I-OMS) and paraneoplastic OMS (P-OMS), the occurrence of antibodies to cell surface antigens, and the discovery of a novel cell surface epitope.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study and laboratory investigations of 114 adult patients with OMS at a center for autoimmune neurological disorders done between January 2013 and September 2015.

MAIN OUTCOMES AND MEASURES

Review of clinical records. Immunohistochemistry on rat brain and cultured neurons as well as cell-based assays were used to identify known autoantibodies. Immunoprecipitation and mass spectrometry were used to characterize novel antigens.

RESULTS

Of the 114 patients (62 [54%] female; median age, 45 years; interquartile range, 32-60 years), 45 (39%) had P-OMS and 69 (61%) had I-OMS. In patients with P-OMS, the associated tumors included lung cancer (n = 19), breast cancer (n = 10), other cancers (n = 5), and ovarian teratoma (n = 8); 3 additional patients without detectable cancer were considered to have P-OMS because they had positive results for onconeuronal antibodies. Patients with I-OMS, compared with those who had P-OMS, were younger (median age, 38 [interquartile range, 31-50] vs 54 [interquartile range, 45-65] years; P < .001), presented more often with prodromal symptoms or active infection (33% vs 13%; P = .02), less frequently had encephalopathy (10% vs 29%; P = .01), and had better outcome (defined by a modified Rankin Scale score ≤ 2 at last visit; 84% vs 39%; P < .001) with fewer relapses (7% vs 24%; P= .04). Onconeuronal antibodies occurred in 13 patients (11%), mostly Ri/ANNA2 antibodies, which were detected in 7 of 10 patients (70%) with breast cancer. Neuronal surface antibodies were identified in 12 patients (11%), mainly glycine receptor antibodies (9 cases), which predominated in P-OMS with lung cancer (21% vs 5% in patients with OMS without lung cancer; P = .02); however, a similar frequency of glycine receptor antibodies was found in patients with lung cancer without OMS (13 of 65 patients [20%]). A novel cell surface epitope, human natural killer 1 (HNK-1), was the target of the antibodies in 3 patients with lung cancer and P-OMS.

CONCLUSIONS AND RELEVANCE

Patients with I-OMS responded better to treatment and had fewer relapses than those with P-OMS. Older age and encephalopathy, significantly associated with P-OMS, are clinical clues suggesting an underlying tumor. Glycine receptor antibodies occur frequently in P-OMS with lung cancer, but the sensitivity and specificity are low. The HNK-1 epitope is a novel epitope in a subset of patients with P-OMS and lung cancer.

The "neuro" of neuroblastoma: Neuroblastoma as a neurodevelopmental disorder

Neuroblastoma is a childhood cancer derived from cells of neural crest origin. The hallmarks of its enigmatic character include its propensity for spontaneous regression under some circumstances and its association with paraneoplastic opsoclonus, myoclonus, and ataxia. The neurodevelopmental underpinnings of its origins may provide important clues for development of novel therapeutic and preventive agents for this frequently fatal malignancy and for the associated paraneoplastic syndromes. Ann Neurol 2016;80:13-23.