Case Presentation: An 86-year-old woman with history of EBV encephalitis four years prior presented for altered mental status and emesis in September. Previously, the patient was able to perform all activities of daily living. A week prior to presentation, patient developed a cough and was noted to have slow mentation. Exam was notable for fever 103.5F, inability to follow commands but no focal deficits. Initial labs and CT Head were unremarkable. Broad spectrum antibiotics were initiated for a urinary tract infection and aspiration pneumonia. Her mental status continued to deteriorate until she was unresponsive. She remained febrile with subsequent labs were notable for leukocytosis. Coarse tremor in the bilateral upper extremities was observed. EEG was negative for epileptiform activity. MRI of the brain showed bilateral hyperintensity in the caudate nuclei. Bacterial and fungal blood cultures returned negative. Patient was treated empirically for meningitis. Serum and CSF studies were positive for West Nile IgG and IgM. Her mental status slowly improved with resolution of fever and leukocytosis with supportive care. The patient continued to recover before being transferred to a skilled nursing facility.
Discussion: Encephalopathy in the geriatric population is a challenge to diagnose and treat. West Nile virus was not present in the United States until 1999; now with increasing documented cases over the last decade. Infection with West Nile virus typically causes an influenza-like illness that may progress to encephalitis, meningitis, and polyradiculitis in a minority of patients. Less than 1% of infections result in neurologic sequelae. Bilateral coarse upper extremity tremors and caudate hyperintensity suggests the presence of neuroinvasive West Nile prior to serological confirmation. We present a single case of confirmed West Nile virus with MRI findings of bilateral hyperintensity within the caudate nuclei. Similar MRI findings have been noted with other flaviviruses, such as Japanese encephalitis. The distribution and appearance of the MRI findings in our case fit well with the known pathologic information regarding this disease, and imaging could play an important role in future evaluation. The explanation for the symmetrical involvement of the deep gray matter structures by some members of the flavivirus family is unknown. The degree of white matter involvement may be due to small vessel atherosclerosis encountered in elderly patients who are at risk for neurologic complications.
Conclusions: This case illustrates how West Nile disease can present in the elderly as fever with acute encephalopathy, especially in months with mosquito activity. Patients may be initially misdiagnosed due to other confounding factors. History can be difficult to obtain in these patients however coarse upper extremity tremors and bilateral caudate hyperintensity is suggestive of West Nile virus.