A U of T study, published in the May issue of the quarterly Canadian Journal of Neuroscience, found that among hospitalized patients in Toronto with West Nile virus (WNV), encephalitis was the most common neurological manifestation. More surprisingly, encephalitis was an apparent risk factor for neuromuscular complications; it's very rare for this brain infection to involve other parts of the nervous system.
"It is important to keep West Nile virus in mind in the summer and early fall when faced with unexplained neurological presentations such as encephalitis and paralysis, not only to guide investigations, but to identify those who may benefit from available therapies," says Dr. Cheryl Jaigobin, a professor in the Department of Medicine at the University of Toronto and a neurologist at the University Health Network. Jaigobin co-authored the study with Dr. Jodie Burton, a senior neurology resident.
Data from the WNV outbreak in Toronto indicate that more than 50 per cent of the 26 WNV patients admitted to four Toronto tertiary-care facilities in August and September 2002 had neurological disease. Seventy-eight per cent had encephalitis and, of those, 82 per cent developed neuromuscular dysfunction within days.
The Toronto experience was similar to earlier experiences of WNV infection in New York City, Israel, Louisiana and Cleveland. In all cases, advanced age and a compromised immune system were associated with a worse outcome.
The study's authors recommend that physicians follow the currently accepted WNV testing regimen. They also suggest that electrodiagnostic testing be performed in patients with unexplained weakness and in those who are critically ill to rule out acute flaccid paralysis syndrome, a severe neuromuscular complication of the disease which may lead to prolonged disability or death.