To describe and alert clinicians of longitudinally extensive transverse myelitis (LETM) associated with West Nile Virus (WNV). The diagnosis of WNV-associated LETM significantly alters the acute and long-term treatment options and prognosis.

A 22-year-old previously healthy woman presented with three days of rapidly progressive bilateral lower extremity weakness associated with urinary retention. Initially, patient reported that her legs felt heavy and weak. However, she was still able to ambulate. Her weakness soon progressed to complete paralysis of her bilateral lower extremities. On exam she had flaccid tone, 0/5 strength in bilateral lower extremities, decreased rectal tone, and a T10 sensory level. 

MRI C/T/L spine demonstrated increased T2 signal and edema of a long segment of the cervical spinal cord extending from C4 to T1. This lesion was non-enhancing but there was an additional smaller enhancing lesion visualized more superiorly. CSF results showed WBC of 195 with 95% lymphocytes, RBC of 49, glucose of 67, and protein of 48. Patient was treated for presumptive multiple sclerosis with high dose steroids for 5 days. Given lack of improvement, plasmapheresis was then initiated. Her CSF studies subsequently resulted with positivity for WNV IgM, identifying it as the LETM etiology. At discharge, patient had regained considerable strength in both of her lower extremities.

LETM associated with WNV infection has been reported but is uncommonly seen. This case illustrates the importance of considering WNV as part of the differential diagnosis when encountering a patient with clinical and radiological evidence of acute LETM during the summer and fall seasons when WNV is circulating. Currently, there is not a definitive therapy for LETM associated with WNV. Treatment remains primarily supportive. Screening for WNV in the setting of acute LETM should be considered as the diagnosis changes treatment options and prognosis.