Opsoclonus-myoclonus syndrome (OMS) also known as the dancing eye syndrome is a very rare neurological disorder, affecting 1 in 10,000,000 people per year. In children, OMS was associated with neuroblastoma; in adults it may be associated with breast carcinoma or small-cell lung carcinoma, uterus or ovarian cancers, rare gall bladder, pancreas and renal cell carcinoma. It can also be consequent to toxic medication (amitriptyline, haloperidol, diazepam), metabolic disorders , hydroelectrolytic disorders, brain anoxia or autoimmune cause – Hashimoto's encephalopathy , autoantibodies against neurons and cerebellar Purkinje cells , celiac disease, and one of the paraneoplastic syndromes. Although it is not considered an infectious disease, it can be associated with some viral infections, which may trigger the debut of OMS , such as the Epstein–Barr virus, coxsackie B2, B3 virus, Saint Louis encephalitis virus, human immunodeficiency virus , hepatitis C infection , rubella, mumps , varicella-zoster virus , and West Nile virus . OMS was reported as a poststreptococcal infection associated with antibodies against a 56 kDa protein , in adolescents following an infection with Mycoplasma pneumoniae, Rickettsia and as a manifestation of acute Borrelia burgdorferi infection  and sometimes with vaccination. The conventional therapies with corticosteroids, intravenous immunoglobulin, plasmapheresis, adrenocorticotropin hormone, antiepileptic drugs are associated with long-term neurological morbidity; the combination of cyclophosphamide and dexamethasone pulse therapy  or rituximab administered in the refractory cases are promising [13, 14]. The best treatment in adults is not very clear. Steroids, baclofen, clonazepam, intravenous immunoglobulin, and immune-adsorption therapy are used currently .
We report a case of opsoclonus-myoclonus syndrome associated with West Nile encephalitis.