To report unique MRI findings in a fulminant case of West Nile virus (WNV) neuroinvasive disease mimicking Guillain–Barré syndrome and highlight the additional diagnostic challenges in immunocompromised patients.

WNV infection manifestation is broad, ranging from asymptomatic to severe neuroinvasive disease. As an arbovirus, cases are typically diagnosed through serum/CSF serologic testing, as viremia is transient and PCR yield is low. WNV Guillain–Barré–like syndromes are uncommon and poorly characterized. We present a case of rapidly progressive WNV neuroinvasive disease with normal serology, with the diagnosis ultimately made through molecular testing. 

Case report and literature review.

63-year-old woman with mantle cell lymphoma, with recent recurrence, admitted to the hospital for 2 days of mild paraparesis. Symptoms progressed to quadriplegia, encephalopathy and respiratory failure requiring intubation. Initial differential diagnoses and workup included autoimmune causes such as Guillain-Barre syndrome variant, infectious and paraneoplastic causes. CSF notable for albumino-cytologic dissociation with normal MRI brain. West Nile IgM/IgG in serum and CSF and paraneoplastic panels were negative. She was empirically treated with plasma exchange with minimal improvement. Day 12 of hospitalization, repeat MRI brain and spine revealed bilateral FLAIR hyperintensities and diffusion restriction with symmetric involvement of superior cerebellar peduncles, corticospinal tracts and dentate nuclei with enhancement of the ventral cauda equina. Day 16 of hospitalization, CSF metagenomic sequencing detected WNV RNA.

While initially presenting with WNV polyradiculitis, she progressed to encephalomyelitis involving the superior cerebellar peduncles; a novel MRI finding in neuroinvasive WNV radiologic spectrum. Our patient’s impaired humoral response in the setting of mantle cell lymphoma limited the yield of serology as the typical diagnostic test for WNV infection and contributed to her fulminant presentation. Our case highlights the importance of a high index of suspicion and additional diagnostic complexity that is necessary for optimal care of immunocompromised patients.