Objective:

N/A

Background:

West Nile Virus (WNV) is a ssRNA arbovirus endemic to the United States that is known to cause neuroinvasive disease such as meningitis, encephalitis, and flaccid paralysis, typically detected through WNV-specific antibodies. However, obstructive hydrocephalus and the diagnostic pitfalls that chronic B cell depleting therapy generate in this disease have not been clearly described in the literature.

Design/Methods:

We report what proved to be a diagnostically challenging case of WNV rhombencephalitis complicated by obstructive hydrocephalus in a patient with multiple sclerosis on long term ocrelizumab. 

Results:

A 44-year-old female with PPMS on ocrelizumab, presented with acute onset of fever, fatigue, confusion, and worsening weakness. Encephalopathy progressed despite empiric antibiotics requiring intubation, with EEG demonstrating focal status epilepticus, resolving with ASMs. CSF studies showed pleocytosis (116 cells/uL) and elevated protein (85 mg/dL). Further studies, including infectious, inflammatory and autoimmune were all unremarkable, including West Nile IgG and IgM. Interval CT imaging demonstrated obstructive hydrocephalus at the level of the cerebral aqueduct requiring EVD placement. MRI of the brain further demonstrated extensive bilateral cerebellar, midbrain, medial temporal and thalamic T2 FLAIR hyperintensities, suggestive of a rhombencephalitis. She was treated with a five-day course of methylprednisolone and IVIG without meaningful improvement. Ultimately, CSF metagenomic next-generation sequencing (NGS) detected WNV RNA, antimicrobials were discontinued and she was discharged to LTAC.

Conclusions:

The development of severe rhombencephalitis with obstructive hydrocephalus requiring EVD placement represents an extremely rare manifestation of WNV infection. Prior reports have shown similar T2 FLAIR hyperintensities in the thalami, midbrain, and cerebellum, suggesting a predilection for subcortical structures, but no cases of obstructive hydrocephalus readily exist in the literature. Furthermore, its occurrence in the setting of B cell depleting immunotherapy illustrates the limitations of traditional antibody testing in this patient population and highlights the early adoption of metagenomic NGS for accurate diagnosis and treatment.