A Case of West Nile Encephalitis: Neuroimaging Findings and Clinico-Radiological Mismatch

West Nile Virus, an arthropod-borne RNA virus, may result in severe neurological disease. West Nile neuroinvasive disease is characterized by meningitis, encephalitis, and possible acute flaccid paralysis. Classically, signal intensity abnormalities on T2-weighted magnetic resonance images are associated with poor outcomes. Herein, we present a case of previous West Nile encephalitis with diffuse leukoencephalopathy on imaging that demonstrates a favorable clinical outcome with limited neurologic sequelae. A 53-year-old male presented to the hospital with one month of headaches, dizziness, generalized weakness, and a seizure. His initial neurologic exam was notable for wide-based gait and imbalance. Magnetic resonance imaging (MRI) of the brain demonstrated diffuse bilateral white matter signal hyperintensities without contrast enhancement, suggestive of leukoencephalopathy. His lumbar puncture revealed lymphocytic pleocytosis and infectious studies demonstrated positive West Nile Virus immunoglobulin G (IgG) in the cerebrospinal fluid (CSF) and serum with negative immunoglobulin M (IgM) in both CSF and serum, suggestive of previous infection. A diagnosis of sequelae of West Nile neuroinvasive disease was made. He was started on anti-seizure medications without further seizures. At his subsequent nine-month follow-up visit, he remained asymptomatic without weakness, headaches, or confusion. Repeat MRI demonstrated interval improvement of white matter signal change. This case report highlights that West Nile neuroinvasive disease may present with profound white matter changes on MRI with limited clinical symptoms and long-term neurologic sequelae. Further research is needed to identify imaging correlation with symptom severity in this disease.