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West Nile neuropathology takes three forms. (Meningitis, Encephalitis, Flaccid Paralysis).

CHICAGO -- Tremor and movement disorders in the absence of seizures may be diagnostic clues to West Nile virus, Dr. James J. Sejvar said at the annual meeting of the Infectious Diseases Society of America.

In a review of neurologic manifestations of West Nile virus, three distinct clinical pictures emerged: meningitis, encephalitis, and acute flaccid paralysis. Future surveillance should classify the three presentations separately, rather than simply referring to "meningoencephalitis," recommended Dr. Sejvar of the Centers for Disease Control and Prevention's division of viral and rickettsial diseases, Atlanta.

Previous literature has conflicted with regard to neurologic manifestations of West Nile virus, and central nervous system involvement was rarely documented prior to 1996. Meningitis and encephalitis began to be described more often following the New York City outbreak in 1999. Last summer's outbreak in St. Tammany Parish, La., presented "a unique opportunity for a prospective study" Dr. Sejvar said.

Between Aug. 1 and Sept. 2, 2002, 44 patients presenting with unexplained fever, meningitis, encephalitis, or focal weakness were enrolled in the study. Of those, 16 (3 6%) were confirmed by serology to be West Nile virus cases. Among the other 28, some of the diagnoses included viral meningitis in 6, viral encephalitis in 4, headaches in 5, and other viral illness in 4.

All 16 patients presented with fever, 15 with headache, 12 with nausea, and 12 with vomiting. Other common signs and symptoms included stiff neck (11), myalgias/body aches (11), anorexia (9), chills/rigors (9), photophobia (7), confusion/disorientation (7), and weakness/fatigue (5).

Movement disorders were common. Tremor, which was often accentuated with movement, was noted in nine patients. Myoclonus was reported in 12 patients and observed by investigators in 5. Both movement disorders occurred more than 5 days after the illness began. Parkinsonian features--including cogwheel rigidity, hypokinesia, and postural instability--were seen in 13 patients, Dr. Sejvar said at the meeting, also sponsored by Johns Hopkins University and the University of Kentucky.

The 16 patients fell into three distinct disease manifestations.

* West Nile encephalitis. Eight patients had this manifestation characterized by frequent abnormal reflexes (hyperreflexia). Three of these patients had bulbar findings, including cranial nerve abnormalities, dysphagia, and altered oculocephalics. Only one had seizures, which are common with other etiologies of encephalitis, Dr. Sejvar noted.

* West Nile meningitis. Essentially, the five patients with meningitis represented a group with somewhat milder symptoms than those with encephalitis; they experienced headache, nuchal rigidity, cerebrospinal fluid (CSF) pleocytosis, but no alteration of mental status. As a group, they generally were hospitalized for a median 5 days--somewhat longer than the national median for hospital length of stay for aseptic meningitis overall, which is 3 days. This is likely reflective of the amount of pain experienced due to the headache and dehydration associated with significant nausea and vomiting, Dr. Sejvar said.

Although these patients did not display alteration of mental status, they still displayed neurologic findings, particularly movement disorders including tremor and myoclonus, as well as subtle parkinsonism. Compared with those developing encephalitis and acute flaccid paralysis, the neurologic findings in patients with meningitis generally did not persist as long, he said.

The median age of those developing meningitis was significantly younger than the median age of those patients developing encephalitis or flaccid paralysis. This probably represents the relative absence of other age-related underlying risk factors for development of invasive neurologic disease, he said.

* Acute flaccid paralysis. The other three patients had a dramatically different presentation diagnosed as acute flaccid paralysis. Clinical hallmarks included onset of paralysis during acute infection (within 48 hours of onset), asymmetry of weakness, absence of sensory changes, elevated CSF protein levels, and increased white blood cell count.

In a subsequent analysis, several more patients have demonstrated similar symptoms, including two who presented without fever or headache, he said.

Compared with the five patients who were classified as having West Nile meningitis, the eight with encephalitis were significantly older (70 years vs. 36 years), while those with acute flaccid paralysis were in the middle (56 years). The patients with meningitis had longer hospital stays than those with encephalitis (15 days vs. 5 days). One of the patients with acute flaccid paralysis was hospitalized in the acute setting for a very short time (5 days) and then transferred to rehabilitation. All three were subsequently sent to long-term rehabilitation facilities, and one was subsequently readmitted to the acute ward for suspected worsening.

Multiple alternative diagnoses had been proposed for the patients with flaccid paralysis, including stroke, Guillain-Barre syndrome, and myopathy.

It's critical to use appropriate diagnostic testing--including CSF evaluation, electrodiagnostics (indicative of anterior horn cell damage or poliomyelitis), and neuroimaging--to avoid inappropriate treatments such as heparin or intravenous immunoglobulin, he advised.
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Author:Tucker, Miriam E.
Publication:Internal Medicine News
Date:Dec 15, 2002
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