Objective: Present two cases of Adult-Onset parainfectious Opsoclonus-Myoclonus Syndrome with fast and good recovery

Background: Adult-Onset Opsoclonus-Myoclonus  (AOMS) is a rare disorder. Two main causes include paraneoplasic and parainfectious autoimmune etiology, with demonstrated  or non-demonstrated infection (idiopathic);  other nonparaneoplasic/nonparainfectious autoimmune rare cases have been reported . First neurological symptoms as dizziness, nausea and/or vomiting, vision abnormalities and vertigo rapidly progress in days or weeks to ataxia, opsoclonus, tremor and myoclonus; mood changes or encephalopathy are less frequent. Series and cases reviews show low consistence with serum paraneoplasic antibodies, older age and worse clinical course in paraneoplasic patients. Early immunotherapy (steroids or/ and IGIV) could be important for better  outcome especially in parainfectious  patients.

Method: Report of two cases

Results: Two adults, a 41 years old woman (case 1) and a 37 years old man (case 2) were diagnosed of Opsoclonus-Myoclonus . Both first presented dizziness, vertigo, nausea and vomiting increasing with movements. Despite symptomatic treatment 2 weeks later poor outcome with disruptive ataxia, irregular chaotic saccades, tremor and myoclonus was evident. Case 1 added headache and irritability and 1 week before first symptoms a flulike syndrome.  Laboratory tests, autoimmunity, antineurpnal and antineuropile antibodies, cerebral MRI, thoracoabdominal CT scan were normal,  plus  mammography in case 1 ant body PET in case 2. CSF tests showed lymphocytic pleocitosis. Positive IgM antibodies against R. connori were detected in case 2 and  antibiotics were given. Parainfectious etiology was postulated in case 1 because of the previous flulike syndrome despite negative microbiological tests. After iv 1 g metilprednisolone for 5 days poor improvement was detected, so they received IVIG at 2g/kg dose, with positive outcome and total recovery before 3 months. Repeated laboratory test and body CT throughout 4 years were normal in case 1.

Conclusion: AOMS must be investigated for wide autoimmune etiologies including paraneoplasic, parainfectious  and other nonparaneoplasic/nonparainfectous causes. Early immunotherapy seems to be related to better outcome. Taking into account the low consistence between paraneoplasic cases and  serum paraneoplasic antibodies, idiopathic cases should be checked throughout 25 years.

References: Klaus JP et al. Adult-Onset Opsoclonus-Myoclonus Syndrome. Arch Neurol. 2012;69(12):1598-1607. Bataller L et al. Clinical outcome in adult onset idiopathic or paraneoplasic opsoclonus-myoclonus. Brain 2001;124:437-443.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/adult-onset-parainfectious-opsoclonus-myoclonus-report-of-two-cases/