Objective: Analysis of number, clinical characteristics and outcome of patients admitted to our department due to OMS in the past 25 years.

Background: Opsoclonus-myoclonus-ataxia syndrome (OMS) in children is a very rare movement disorder, believed to be caused by autoimmune mechanisms. According to published reports, almost 50% of children with OMS have an underlying neuroblastoma. The Department of Child, Adolescent and Developmental Neurology of Ljubljana University Children’s Hospital is the only tertiary department in Slovenia (pediatric population of 404,430) treating children with OMS.

Method: We abstracted the data from paper and electronic medical records of patients seen between 1/1/1992 and 1/1/2019, fulfilling the diagnostic criteria for OMS. We determined their gender, age at the onset of the disease, possible etiology, pharmacotherapy and symptoms remaining at the last follow-up.

Results: During the analyzed time period, we have treated 7 children for OMS. 5 of them were girls (71%; female:male ratio of 2.5:1). Average age at onset of symptoms was 18 months (15-24 months). In 3 children symptoms appeared after a viral infection, in 1 after a streptococcal angina, in 1 after a DTPPolio revaccination, while in 2 we could not identify any potentially provoking event. In the child, that fell ill after a streptococcal angina, neuroblastoma was discovered. All children were treated with at least one form of steroids (methylprednisolone, prednisolone, ACTH, dexamethasone) and all of them received different courses of intravenous immunoglobulin therapy. In 4 children rituximab was used additionally, one of them was treated with plasmapheresis, cyclophosphamide and mycophenolate-mofetil as well. Of the supportive therapies, we often used piracetam and coenzymeQ10. On the last follow-up examination 3 children were without any remaining physical symptoms of the disease (one after a surgical removal of neuroblastoma), two were also psychologically intact. 2 children had minimal persisting ataxia. In 2 children there has been virtually no improvement of symptoms and they continue to have severe motor and cognitive problems.

Conclusion: In Slovenia we have seen one case of pediatric OMS every 3.5 years. The prevalence has been higher in girls, the average age at the onset of symptoms was also characteristic. Contrary to published reports, only one of our patients (14%) was diagnosed with neuroblastoma.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/opsoclonus-myoclonus-ataxia-syndrome-ljubljana-university-childrens-hospital-clinical-series/