Objective: To discuss an unusual case of chorea in WNV encephalitis.

Background: The “neuroinvasive” form of human infection with West Nile virus (WNV) is known to cause meningitis, encephalitis, and poliomyelitis, particularly in the elderly and immunocompromised.  WNV has a particular tropism for extrapyramidal structures and movement disorders have been described in the acute and convalescent phases of WNV encephalitis. Tremor, myoclonus, and parkinsonism are the most commonly described [1].

Method: Case report.

Results: A 75-year-old woman with mild cognitive impairment presented to an outside hospital with encephalopathy for two weeks. Upon transfer to our institution, the patient was obtunded with subtle oromandibular dyskinesias. CSF was inflammatory: 39 WBC, 83% lymphocytes; 190 RBC with positive WNV IgM. CSF culture, HSV 1/2, enterovirus, AFB stain, listeria, varicella, VDRL, Eastern and Western Equine viruses, SLE antibodies, paraneoplastic panel, and cytology were negative. MRI of the brain with contrast showed chronic T2/FLAIR hyperintensities consistent with microvascular disease and no areas of enhancement. Forty-eight hours of EEG showed no epileptiform activity. There was no evidence of another infectious process or significant metabolic derangement. She was treated conservatively and her alertness improved, but she was disinhibited and emotionally labile which was not her baseline. One month after the onset of symptoms, her providers noticed the gradual progression of continuous flowing movements of her arms and trunk. Her examination was notable for clear truncal and appendicular chorea which gradually improved without treatment. She was discharged to a nursing facility.

Conclusion: WNV infection causes a broad spectrum of movement disorders and few cases of chorea have been reported in the literature; none have been in the setting of WNV encephalitis [2]. It should be considered on the differential diagnosis of acute-onset chorea. The course in this case suggests a self-limited condition in the recovery phase from WNV infection in the absence of MRI abnormalities.

References: 1. Sejvar JJ, Haddad MB, Tierney BC, et al. Neurologic Manifestations and Outcome of West Nile Virus Infection. JAMA. 2003; 290(4):511–515. 2. Cunha BA, Kang S and Chandrankunnem JG. West Nile Virus (WNV) infection presenting as acute chorea. Travel Medicine and Infectious Disease. 2012; 10(1): 52-53.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/convalescent-chorea-in-west-nile-virus-encephalitis/