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Acute Flaccid Paralysis Caused by West Nile Virus

Acute flaccid paralysis caused by West Nile virus infection may be mistaken for Guillain-Barré syndrome but more closely resembles poliomyelitis.

The complete clinical ramifications of any newly described syndrome are rarely displayed in the first patients identified. So, it appears, is the case with West Nile virus (WNV) infection in the U.S.: Clinicians and epidemiologists in Louisiana and Mississippi have just described 7 cases of acute flaccid paralysis during 2002 that they ascribe to infection with WNV.

The patients (5 men and 2 women) ranged in age from 46 to 69. Most patients had areflexic, asymmetrical paralysis. Five patients had no sensory deficits, and a sixth patient had sensory loss consistent with peripheral neuropathy; no data were provided for the seventh. Initial diagnoses included stroke, meningoencephalitis, and Guillain-Barré syndrome (GBS). GBS was considered in the differential diagnosis of nearly all cases. Laboratory findings included pleocytosis in 5 of 6 patients and elevated protein levels in the 6 who underwent lumbar punctures. Electromyography and nerve conduction studies confirmed an asymmetric process involving anterior horn cells and their axons, similar to findings in poliomyelitis infection. All patients had elevated levels of IgM against WNV. No deaths have been reported among these patients.

Comment: GBS can occur after many different infectious processes, including bacterial infection, mononucleosis, influenza, and Lyme disease. Unlike the syndrome presented in these patients, however, it is typically symmetric and ascending. In GBS, the cerebrospinal fluid classically shows albumino-cytologic dissociation with elevated protein levels and almost-normal cell counts. Clinicians in areas where WNV is endemic should be aware of the polio-like syndrome described by these authors and should confirm the diagnosis with electrophysiologic and serologic tests.

— Stephen G. Baum, MD

Published in Journal Watch Infectious Diseases October 25, 2002

Citation(s):

Leis A et al. Acute flaccid paralysis syndrome associated with West Nile virus infection -- Mississippi and Louisiana, July-August 2002. MMWR Morb Mortal Wkly Rep 2002 Sep 20; 51:825-8.

• Medline abstract (Free)

Glass JD et al. Correspondence: Poliomyelitis due to West Nile virus. N Engl J Med 2002 early release; posted 9/23. http://nejm.org/earlyrelease/index.asp