West Nile Virus Arachnoiditis: A Case Report of Progressive Lower Extremity Weakness

Case Diagnosis: West Nile Virus Arachnoiditis

Case Description or Program Description: A 70 year-old female with hypertension and Bell's palsy was admitted for dizziness and progressive lower extremity weakness. Neurology workup revealed leptomeningeal enhancement of the spinal cord from T10 to the conus medullaris on MRI with lumbar puncture demonstrating lymphocytic pleocytosis. Subsequent serum and CSF studies showed elevations of West Nile Virus IgG and IgM. The patient received IVIG and high-dose intravenous steroids then was transferred to the IRF. Her rehabilitation course was complicated by neurogenic bladder and bilateral lower extremity neuropathic pain.

Setting: Inpatient Rehabilitation Facility (IRF)

Assessment/Results: The patient presented with neurogenic bladder, characterized by retention and decreased urge. Intially, she required intermittent catheterizations and failed trial of bethanechol. Prior to IRF discharge, the patient was volitionally voiding with low post-void residuals. She was started on gabapentin for neuropathic pain, eventually finding relief with the addition of duloxetine.

Discussion (relevance): West Nile Virus (WNV) is a mosquito-borne member of the Flavivirus family endemic to North America, and much of the world, since the early 2000s. While the virus commonly presents as asymptomatic or mild infection, elderly and immunocompromised individuals are at risk of serious manifestations including neuroinvasive disease. About 1% of WNV cases are neuroinvasive, with the most common symptoms including abrupt fever, headache, and fatigue, with variable malaise, anorexia, nausea, myalgia, lymphadenopathy, and nonpruritic generalized maculopapular rash. Uncommonly, the virus may infiltrate the arachnoid mater of the spinal cord, causing WNV arachnoiditis. Due to the scarcity of WNV arachnoiditis, only a handful of case reports have been published. WNV should be included in the differential for viral etiologies of spinal cord injury (SCI).

Conclusions: WNV arachnoiditis is a rare cause of SCI. In this case, the thoracic spinal cord to the cauda equina was affected resulting in neurogenic bladder with lower extremity weakness and neuropathic pain.