To review the clinical presentation and diagnostic evaluation of a case of West Nile Virus (WNV) radiculomyelitis. 

52-year-old female with no significant medical history presenting with symptoms of headache and acute-onset persistent left arm weakness and paresthesia, fever, viral prodrome, and a resolved LUE rash. On admission, she was febrile with 4/5 strength in distal muscles and 3/5 strength in proximal muscles, primarily involving C5-C6 musculature, and areflexia of the left brachioradialis, biceps, and triceps. WNV, a member of the flavivirus family, is carried by the Culex mosquito and is endemic in the USA. Neuroinvasive disease is uncommon, but typically presents with meningitis/encephalitis. However, 5%-10% of neuroinvasive cases are associated with myelitis. WNV myelitis progresses as a prodrome including fever, rash, myalgias to meningitis/encephalitis, followed within 24-48 hours by acute, rapidly progressive, polio-like, asymmetric flaccid weakness with predilection for anterior horn cells. 

Physician assessment, laboratory data, and neuroimaging analysis for a patient admitted in a Pittsburgh, Pennsylvania tertiary care referral center in October 2018. 

·MRI cervical spine: patchy T2 hyperintensity within the L>R anterior spinal cord extending from C2-C6 with foci of enhancement

·MRI thoracic/lumbar spine: faint increased T2 signal involving mid-to-inferior thoracic cord and enhancement of the ventral nerve roots of the cauda equina and conus

·LP: WBC 233 with 72% lymphocytes/Protein 53/ Glucose 67

·CSF IgM WNV positive, CSF WNV IgG negative

This case report discusses a presentation of infectious viral myelitis secondary to WNV. Clinical presentation and MRI of the spine raised suspicion for this diagnosis, eventually confirmed with CSF findings of WNV IgM antibodies in the setting of a negative IgG. CNS involvement of WNV is an uncommon presentation of an endemic infection and bears consideration in the differential diagnosis for cases presenting with flaccid weakness in a immunocompetent patients.