Neuroinvasive West Nile Virus Disease Presenting as Opsoclonus-Myoclonus-Ataxia Syndrome

Objective Describe a case of probable Neuroinvasive West Nile Virus (WNV) disease presenting as opsoclonus-myoclonus-ataxia syndrome (OMS). Background Opsoclonus-myoclonus-ataxia syndrome is a well described condition which is thought to be often of paraneoplastic or autoimmune etiology in adults. Specific pathogenic antibodies have yet to be identified in most cases. It can also be seen in association with CNS infections, although it is unclear if the pathophysiology aligns more with an infectious or a para-infectious process. Here we describe a clinical case where a patient presented with OMS, with CSF findings indicative of a diagnosis of Neuroinvasive West Nile Virus disease. Design/Methods Case Report. Results A 65-year-old previously healthy man presented with 3 weeks of progressive generalized tremors, oscillopsia and inability to ambulate. Exam revealed opsoclonus, stimulus-induced myoclonus, and generalized ataxia. CSF showed neutrophil-predominant pleocytosis (325 WBCs with 78 neutrophils), which converted 3 days later to lymphocytic predominance (44 WBCs with 36 lymphocytes). CSF cultures, meningitis/encephalitis multiplex PCR array, brain MRI with and without contrast, body PET-CT and serum autoimmune encephalopathy panel were unrevealing. CSF WNV IgG and IgM were elevated to 2 times and 5 times the upper limit of assay respectively, concerning for Neuroinvasive WNV disease. He received 5 days of intravenous methylprednisolone and immunoglobulins with clinical improvement, and had ultimate resolution of symptoms over the next 6 months. Conclusions WNV has been associated with a wide spectrum of movement disorders, and should be considered in the differential diagnosis, especially with CSF pattern as described above. Idiopathic and paraneoplastic opsoclonus-myoclonus-ataxia syndrome remains the most common subtype, however it is important to perform an evaluation for infectious etiologies as well to guide further management and counseling regarding outcome.