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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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 Published by Elsevier Ltd on behalf of European Paediatric Neurology Society.)

Introduction: Flow cytometric cerebrospinal fluid (CSF) lymphocyte subset analysis has improved the diagnosis of neuroinflammation and identified multiple markers of inflammation in opsoclonus-myoclonus syndrome (OMS). The aim of this exploratory, retrospective study was to analyze the effect of immunotherapy on these markers to determine which agents are disease modifying., Methods: Cross-sectional immunological observations were made in an IRB-approved case-control study, and patients were treated empirically. Ten different CSF lymphocyte subpopulations from 18 children with persistent OMS had been measured by flow cytometry before and after clinical treatment with cyclophosphamide/ACTH/IVIG combination (n = 7) or ACTH/IVIG alone (n = 11). Clinical severity of OMS was scored from videotapes by a blinded observer using the OMS Evaluation Scale., Results: Only cyclophosphamide combination therapy (mean dose 26 ± 3 mg/kg or 922 ± 176 mg/m 2 x 6 cycles) significantly decreased the percentage of CSF B cells. The mean reduction was 65%, with CSF B cell frequency normalized at 7-8 months in 70%. Other abnormalities of the CSF immunophenotype, such as the low CD4/CD8 T cell ratio, persisted, and there were no therapeutic changes in T cell activation/maturation markers. Effects on relative and absolute size of PBMC subsets were similar. Clinical improvement was 70% and 55% in respective treatment groups. The relapse rates of the two groups did not significantly differ., Discussion: The main effect of cyclophosphamide combination therapy on neuroinflammation in OMS was moderate reduction in CSF B cell expansion. Though exploratory, it may provide a steroid sparer option in partially-responsive OMS., (Copyright © 2018 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

Non ketotic hyperglycinemia is a rare inborn error of glycine metabolism due to deficient activity of glycine cleavage system, a multienzymatic complex consisting of four protein subunits: the P-protein, the H-protein, the T-protein and the L-protein. The neonatal form of non ketotic hyperglycinemia presents in the first days of life with encephalopathy, seizures, multifocal myoclonus and characteristic "hiccups". Rapid progression may lead to intractable seizures, coma and respiratory failure requiring mechanical ventilation. Clinical trial with scavenges drugs decreasing glycine levels such as sodium benzoate, and with drugs reducing NMDA receptors excitatory properties, such as ketamine and dextromethorphan, have been tried but the outcome is usually poor; antiepileptic therapy, moreover, is unable to control epileptic seizures. Ketogenic diet has been successfully tried for refractory epilepsy in pediatric patients. We report three cases affected by neonatal non ketotic hyperglycinemia and early myoclonic encephalopathy treated with ketogenic diet. In our patients ketogenic diet, in association with standard pharmacological therapy, determined dramatic reduction of seizures and improved quality of life., (Copyright © 2012 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

We report the 1 year follow-up of 3 children affected by non-paraneoplastic Opsoclonus-Myoclonus Syndrome (OMS) resistant to conventional therapies (steroids, ACTH and intravenous immunoglobulins) who were treated with an anti CD20 monoclonal antibody (rituximab). Treatment response was recorded on the basis of an international score at 0, 3, 6, 9 and 12 months. Despite the long disease duration and the numerous previously administered treatments, all patients underwent rapid and persistent neurological recovery following rituximab administration, thus suggesting a potential role of this drug even in pre-treated patients., (Copyright © 2011 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

Objective: To compare the clinical data at diagnosis, treatment and neurological outcome in 34 children with opsoclonus-myoclonus syndrome (OMS) associated with a detected neuroblastoma or not., Study Design: This is a multicentric retrospective study of 34 children presenting with OMS from four pediatric centers diagnosed between 1988 and 2008., Results: Twenty-two patients had OMS associated with a neuroblastoma. These patients all had neuroblastomas with favourable prognostic features; all underwent surgery, six received chemotherapy. Twelve children had OMS without a detected neuroblastoma. For OMS, the main treatment in all children was corticotherapy (n=33), but immunoglobulins (n=13), cyclophosphamide (n=4) and rituximab (n=4) were also given. In the 27 OMS patients with or without neuroblastoma whose follow up was greater than two years, the neurological outcome was evaluated: 59.3% had neurological sequelae, including motor, praxic and/or language sequelae (n=9), persistent ataxia (n=6) and moderate motor deficit (n=3). No significant difference in neurological outcome was noted between the two patient groups., Conclusion: Our retrospective study provides further evidence that OMS with or without a detected neuroblastoma is the same disease, whose major challenges are the neurological sequelae. An international collaboration is required to improve the knowledge about OMS, the treatment and the outcome in this rare disorder., (Copyright (c) 2009 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

Five patients with spontaneously recovering Dancing Eye Syndrome/Opsoclonus Myoclonus Syndrome are described. Age at presentation ranged from 4 to 19 months. Four had symptoms of fever and a coryzal illness within days to a few weeks prior to the onset. One of the 4 also had varicella zoster 4 weeks before presentation. All had opsoclonus, myoclonus/ataxia and irritability. Associated infective agents identified were Coxsackie virus and rotavirus. Spontaneous improvement of symptoms started within 9 days of presentation and total duration of illness ranged from 10 to 24 days. Developmental progress at follow-up was normal in all cases. A range of immunomodulatory therapies have been advocated for the treatment of Dancing Eye Syndrome/Opsoclonus Myoclonus Syndrome. However, in some children, early spontaneous recovery may occur, an observation which should be borne in mind when designing therapeutic trials in this condition., (2009 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

Opsoclonus-myoclonus syndrome (OMS) is a rare and debilitating disorder of unknown etiology affecting children and adults. Outcome is unfavourable; approximately 80% of children with OMS suffer from mild to severe neurological handicaps, mainly cognitive impairment. A standard therapy does not exist. Due to the possible immune-mediated mechanisms, treatment with steroids, ACTH, plasmapheresis and immunoglobulins can be successful. However, some children become steroid dependent and symptoms may reoccur after treatment has been finished. We present two girls with OMS, who had a prolonged clinical course lasting 4 and 9 years with many relapses. Both children developed symptoms around the age of two years. Diagnostic work-up to exclude neuroblastoma was negative. Several treatment modalities including oral steroids, dexamethasone pulses, immunoglobulin and cyclosporine were used without lasting success. In addition, cognitive impairment developed in both children. In order to prevent further clinical and mental deterioration, 6 pulses of cyclophosphamide in combination with dexamethasone pulses every 4 weeks were administered. Both children showed significant improvement of OMS symptoms. One girl is still symptom free 18 months after treatment, mild ataxia developed in the other after 12 months. Both children are mentally handicapped and in special need schools. We conclude that combination of cyclophosphamide pulses and dexamethasone pulse therapy is a therapeutic option even after a long clinical course to improve symptoms of OMS.