West Nile Neuroinvasive Disease With Atypical CSF Findings: A Case Report.

West Nile Neuroinvasive Disease (WNND) is a rare complication of West Nile Virus infection with the capability of mimicking other neurologic diseases. This infection should be considered in the differential diagnosis for patients presenting in the late summer months with altered mentation, fever, and focal neurologic deficits without an otherwise clear etiology. A 63-year-old male presented with acute onset fever, confusion, falls, ataxia, vertical nystagmus, and right leg weakness. Although magnetic resonance imaging of the brain and cervical spine were unremarkable, the lumbar spine revealed enhancement of ventral nerve roots in the cauda equina. Cerebrospinal fluid (CSF) analysis was significant for elevated protein without pleocytosis, which was more suggestive of albuminocytologic dissociation. Both serum and CSF IgM labs testing for West Nile Virus were positive. Despite a 5 day course of immunoglobulin therapy, his symptoms did not significantly improve. He eventually was transferred to inpatient rehabilitation for several days prior to returning home. This case highlights the variable presentations of acute West Nile Virus infection in the rare setting of neuroinvasive disease, which can make diagnosis difficult. The CSF analysis may also not always show results consistent with an acute viral infection, which can make determining the underlying etiology more challenging.