West Nile Virus(WNV) infections typically result in mild symptoms, but severe cases can affect the nervous system. Neurologic manifestations vary but include encephalitis, flaccid paralysis, or meningitis. However, literature on presentation and diagnosis is limited and outdated. We describe a case of a patient with WNV encephalitis who experienced rapid clinical improvement after early treatment with high-dose steroids followed by intravenous immunoglobulin(IVIG).

35-year-old woman presented with two days of diffuse rash followed by fever and headache. Initial lumbar puncture(LP) demonstrated neutrophilic pleocytosis(506 WBC,75 RBC,glucose 70mg/dL,protein 83mg/dL). She was started on empiric antibiotics for presumed meningitis. On day four, she developed dysarthria and dysphagia, causing difficulty managing secretions and necessitating intubation. The following day, she progressed to coma with diffuse hypertonia. Repeat LP showed lymphocytic pleocytosis and elevated opening pressure that normalized after two additional taps. MRI brain demonstrated T2 signal abnormalities in bilateral basal ganglia and brainstem without enhancement. Treatment with high dose steroids was initiated on day six after no improvement on antibiotics, despite no concrete diagnosis. Rapidly, her mental status improved. She began to track and follow commands. Muscle strength initially worsened, with loss of cough and gag reflexes and onset of flaccid paralysis. She eventually regained movement in all limbs after the five-day steroid course. On day 9, CSF from initial LP returned with strongly positive IgM and negative IgG WNV antibodies. She was diagnosed with WNV encephalitis and treated with IVIG. She is now awake, oriented, and strength continues to improve.