Acute Flaccid Myelitis Caused by West Nile Virus: A Case Report and Neuroimaging Correlate.

West Nile virus (WNV) is the most common mosquito-borne illness in the United States. Most cases remain asymptomatic or may be associated with a mild febrile illness; however, it can invade the central nervous system and cause meningoencephalitis, or rarely, acute flaccid paralysis (AFP). Here, we describe a case of WNV-associated paralysis in a previously healthy male presenting with asymmetric weakness and absent deep tendon reflexes. Magnetic resonance imaging (MRI) of the spine displayed a hyperintensity lesion restricted to the central gray matter, preferentially affecting the ventral horns, which is reflected by his clinical features. This case contributes to mounting evidence that WNV can cause selective injury to the ventral gray matter of the spinal cord and demonstrates that WNV should be considered a unique causative agent in patients presenting with AFP.