Case Presentation: A 78 year old previously healthy male presented to the hospital with 1 week of worsening confusion, shuffling gait, headache, and diarrhea. On admission, he was only oriented to person with no focal neurological deficits. Initial vitals were significant for a temperature of 49.2 oC. Imaging on admission including a chest x-ray, CT abdomen/pelvis, and CT brain were unremarkable. A lumbar puncture was performed that demonstrated 154 nucleated cells with 74% neutrophils, 6,000 RBCs, protein of 69 mg/dL, glucose of 74 mg/dL, and an opening pressure of 18 cmH2O. CSF analysis revealed positive oligoclonal bands, negative varicella zoster IgM/IgG, and initially negative West Nile IgG. The patient was started on acyclovir, ampicillin, ceftriaxone, azithromycin, and dexamethasone for empiric treatment of presumed HSV encephalitis and bacterial meningitis. On hospital day five the West Nile IgM serum and CSF tests were both found to be positive. Antimicrobials were discontinued, and the patient was transitioned to supportive care. On hospital day six the patient was obtunded, repeat MRI demonstrated debris in bilateral occipital horns suspicious for purulence and transependymal edema consistent with ventriculitis. Vancomycin, meropenem, acyclovir, and fluconazole were initiated. Neurosurgery was consulted and an external ventricular drain was placed. On hospital day 13, the CSF cultures grew Propionibacterium acnes. On hospital day 23, the patient was started on a 5 day course of IVIG, but had no clinical improvement. The patient continued to deteriorate and on hospital day 38 was transitioned to home hospice care.
Discussion: The West Nile Virus (WVN) is a flavivirus and is most frequently spread by mosquito transmission with birds as an intermediate host [1, 2]. Roughly 1% of WNV infections develop into severe neurologic disease [2]. According to CDC data in 2021, Arizona, Colorado, and Nebraska have the greatest number of WNV cases [3]. The best diagnostic test is an IgM specific ELISA test of the serum collected 8 to 21 days after symptom onset, which was positive on hospital day 5 [2]. There has been one previously published case of pyogenic ventriculitis in a patient with WNV encephalitis [4]. While rare in WNV encephalitis, radiologic evaluation for ventriculitis causing elevated intracranial pressure should be explored as one possible etiology along with possible concomitant bacterial meningitis. It was unclear in our case if the Propionibacterium acnes that grew from the CSF culture was a contaminant or pathological organism. Treatment of WNV is supportive, there is no antiviral treatment [1, 2]. One study showed lack of efficacy for high titered anti-WNV antibodies combined with IVIG in neuroinvasive WNV infections [5]. One case report described response to IVIG and systemic steroids after a patient was diagnosed with glycine receptor post-infectious autoimmune encephalitis secondary to WNV infection [6].
Conclusions: History of residing in an area with high WNV transmission in the setting of fever, headache, and patients that engage in outdoor activities should raise suspicion of WNV encephalitis. Although waxing and waning altered mental status is a common feature of WNV encephalitis, there should be a low threshold for repeat imaging in patients with progressively worsening mental status to explore other underlying etiologies. The treatment of WNV is primarily supportive, however IVIG should be considered if post-infectious autoimmune encephalitis is suspected.
