Electrodiagnostic Testing May Be the Key to Early Identification of West Niles Virus

Newswise — A case report from the University of Colorado Denver, School of Medicine shows that in patients with weakened immune systems, electrodiagnostic testing may be the key to early identification of West Nile virus (WNV). Because patients who have weakened immune systems may not be able to produce the antibodies that are the early detectors for WNV, it can result in delayed diagnosis with potentially fatal consequences.

A mosquito bite may seem like a familiar sign of summer to most people, but to patients with weakened immune systems, a bite from a mosquito infected with the WNV could result in serious nerve and muscle complications and even death. In a Colorado hospital, a 57-year-old woman with a prior lung transplant was seen for fever, malaise, fatigue, and weakness she had for five days. Complete paralysis and severe brain damage developed within ten days after she was admitted to the hospital. Electrodiagnostic testing indicated abnormalities in the woman's right arm and leg and suggested the possibility of early anterior horn cell disease and the diagnosis of WNV.

Testing for WNV antibodies were repeatedly negative. Further testing was conducted to determine if there was even a minimal antigen response. Two weeks into the illness, the WNF test was finally positive. The patient died within one month of the original symptoms. Autopsy of the spinal cord confirmed severe anterior horn inflammation and loss of motor neurons.

Researchers, Drs. Paramjit Kaur and Dianna Quan, of the Department of Neurology at the University of Colorado Denver School of Medicine stated, "In endemic areas, rapidly progressive fever, encephalopathy, and electrodiagnostic findings consistent with anterior horn cell disease should prompt strong consideration of WNV infection. Patients with weakened immune systems may develop antibodies later than expected, or may never develop antibodies, contributing to severe illness. Electrodiagnostic testing of nerve function could lead to early diagnosis of WNV and decrease the chances of fatal complications of the disease."

The complete findings and results of this study are being presented at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) 55th Annual Meeting in Providence, Rhode Island, Sept. 17-20, 2008. The AANEM is the largest organization worldwide, with over 5,000 members dedicated to advancing neuromuscular, musculoskeletal, and electrodiagnostic medicine.