Objective: To report a rare presentation of adult-onset opsoclonus-myoclonus-ataxia syndrome (OMAS) after West Nile virus infection, highlighting the overlap between OMAS semiology and functional movement disorders during early evaluation and the importance of examination over reliance on diagnostic tests for favorable outcomes.

Background: Distinguishing functional and organic eye movement disorders is critical in diagnosing rare presentations of OMAS. Opsoclonus is marked by multidirectional saccades without intersaccadic intervals.[1] Functional eye movement disorders may mimic organic pathology, presenting as eye fluttering, oculogyric movements, or effortful facial expressions.[1,2].

Method: We describe the evaluation, management, and outcomes.

Results: A 70-year-old female presented with abnormal eye movements three days after fever, nausea, and vomiting. Examination showed chaotic multidirectional conjugate saccades (end-to-end without intersaccadic intervals) of variable amplitude that fluctuated with fixation, facial dyskinesias, resting and postural limb tremor, and myoclonus, which were absent during sleep. MRI brain and CSF studies were unrevealing. Initial differential diagnoses included functional movement disorder versus infectious, autoimmune, or paraneoplastic etiologies. On day 6, serum West Nile virus IgG and IgM were positive. Repeat lumbar puncture showed lymphocytic pleocytosis and elevated protein. After a course of IVIG and IV steroids, she required inpatient rehabilitation where she had ataxic gait with scissoring and evidence of cognitive impairment (MoCA score 12/30). She returned to baseline by her 9-month follow-up.

Conclusion: Adult-onset OMAS may mimic functional movement disorders due to overlapping features including symptom variability, anxiety-limited examination, and absence of movements in sleep, providing a diagnostic challenge. Recognition of chaotic multidirectional saccades without intersaccadic intervals maintained suspicion for opsoclonus despite initial normal studies. This case underscores the importance of detailed eye movement phenomenology and serial examination when testing is unrevealing, and consideration of infectious etiologies such as West Nile virus in atypical hyperkinetic movement disorders. Distinguishing OMAS from functional movement disorders is critical as accurate diagnosis can guide intervention[3] and influence outcomes.

References: References
1. Teodoro T, Cunha JM, Abreu LF, Yogarajah M, Edwards MJ. Abnormal eye and cranial movements triggered by examination in people with functional neurological disorder. Neuroophthalmology. 2018;43(4):240-243. doi:10.1080/01658107.2018.1536998.
2. Baizabal-Carvallo JF, Jankovic J. Psychogenic ophthalmologic movement disorders. J Neuropsychiatry Clin Neurosci. 2016;28(3):195-198. doi:10.1176/appi.neuropsych.15050104.
3. Khuranna M, Kalkach Apricio M, Razavi M, Yi X, Amin N. Adult-onset opsoclonus-myoclonus-ataxia post–West Nile virus infection: diagnostic challenges and recovery with immunotherapy. Abstract presented at: American Academy of Neurology Annual Meeting; April 2026; Chicago, IL.

« Back to 2026 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/adult-onset-opsoclonus-myoclonus-ataxia-syndrome-associated-with-west-nile-virus-mimicking-a-functional-movement-disorder/