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New Test May Identify Genetic Risk for Parkinson's

ST. PAUL, MN -- A new test may be useful in identifying children and adults whose genetic makeup puts them at risk to develop Parkinson's disease, according to a study published in the March 10 issue of Neurology, the scientific journal of the American Academy of Neurology.

The study also provides further evidence that the most common form of Parkinson's may involve a genetic predisposition to the disease.

The study was designed to determine if a specific battery of tests can identify children and siblings (or "first-degree" relatives) of Parkinson's disease patients with no signs of the disease but who are significantly more impaired than "normal" individuals in the same age group. The tests of motor function, sense of smell and mood had proven effective in distinguishing mildly affected Parkinson's patients from normal individuals in previous studies.

The researchers tested 80 first-degree relatives of Parkinson's patients and 100 normal control individuals. Of the relatives, 22.5 percent scored in the abnormal range, while 9 percent of the control individuals achieved abnormal scores.

Among the children of Parkinson's patients who tested abnormal, there was a much higher prevalence of the affected parent being the father.

"This study provides further evidence that the typical form of Parkinson's involves a genetic predisposition to the disease," said neurologist and study author Erwin Montgomery Jr., MD, of the Cleveland Clinic Foundation. "Now that we can identify first-degree family members who may carry the abnormality but don't have the actual phenotype (physical manifestation) of the disease, that will be of significant help in doing genetic studies. Even if you have the gene, you may not develop the disease.

"With this test, we can identify people who have the gene but don't have the disease, which will allow us to do genetic linkage studies," he said. "This greatly improves our chances of finding the type of genetic abnormality that underlies the vast majority of Parkinson's patients we treat everyday.

"Our test battery also shows there may be different forms of the disease. Parkinson's disease in the very old may be somewhat different from the usual form of Parkinson's which strikes earlier in life."

Montgomery says the researchers' findings seem consistent with recently published research indicating that in older Parkinson's patients, environmental causes may play more of a role than genetic factors. "We have evidence showing that may very well be the case. We're beginning to realize there may be different types of Parkinson's. And that understanding is obviously going to be very important to understanding its causes."

The study was supported in part by grants from the National Institutes of Health, Arizona Chapter of the American Parkinson Disease Association, the Jane K. Pelton Fund for Movement Disorders and the Arizona Disease Control Research Commission.

Improving care for patients with neurological disorders is the goal of the American Academy of Neurology, an association of more than 15,000 neurologists and neuroscience professionals.

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