To describe the case of an immunocompetent elderly man with West Nile Virus (WNV) myelitis and Guillain Barre syndrome (GBS) mimicking poliomyelitis, presenting with a protracted clinical course of severe deficits over greater than 2 years, and impressive neuroimaging demonstrating focal destruction of the anterior horn of the spinal cord.

WNV is a mosquito-borne neurotropic flavivirus, which can rarely cause central nervous system deficits, including encephalitis, meningitis, acute flaccid myelitis, and peripheral neuropathy including GBS. Most cases cause no further deficits after days to weeks; this case describes new deficits after two years.

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Patient’s initial presentation resulted in areflexic plegia of the bilateral lower extremities after he was diagnosed with WNV and GBS through EMG/NCS study, lumbar puncture. He received intravenous immunoglobulin (IVIG) and the deficits had stabilized. Two years later, he developed new right upper extremity distal greater than proximal weakness with hyporeflexia. Spinal MRI was performed which demonstrated T2 hyperintensities of the anterior horn cells extending from the level of T11 down to the conus medullaris. EMG/NCS study was repeated and it again demonstrated severe asymmetric peripheral neuropathy with both axonal and demyelinating features, similar to the study 2 years ago. CSF studies demonstrated albuminocytologic dissociation for which the patient was treated with IVIG for a potential acute inflammatory demyelinating neuropathy involving the right upper extremity. CSF also demonstrated positive WNV IgG and IgM though negative metagenomic testing. The patient had no response to IVIG this time, suggesting that this was not AIDP but potentially sequelae of WNV myelitis.

This case demonstrates a rare manifestation of neuroinvasive WNV – lifelong areflexic flaccid paralysis due to the destruction of anterior horn cells in the spinal cord, akin to a poliomyelitis. The protracted clinical course with sustained positive WNV IgM antibody is a novel finding in an immunocompetent patient.