PHILADELPHIA (AP) - In a study that could help change how Parkinson's disease is diagnosed, researchers have discovered that the disease affects nerves in the heart as well as the brain.
It has been known for many years that the tremors and movement problems associated with Parkinson's result from a loss of nerve endings in part of the brain.
Researchers at the National Institute of Neurological Disorders and Stroke report in Tuesday's issue of the Annals of Internal Medicine that people with Parkinson's disease also have a decreased number of nerve endings in the heart.
That suggests that Parkinson's may effect the entire nervous system.
''This may change the viewpoints about what Parkinson's disease is,'' said the institute's David S. Goldstein, author of the study. ''What these findings indicate is that Parkinson's disease is associated with a loss of nerves outside the brain and, in particular, in the heart.''
Goldstein said it appears that other organs' nerve systems are not affected, but further research is needed.
''If it turns out that the loss of these cells (happens only) in the heart, then the key question is, what it is about the nerves in the heart and the system in the brain that appears to make those the systems that are destroyed.''
The heart nerve damage differentiates Parkinson's from conditions with similar symptoms, such as multiple system atrophy, according to the study. Goldstein said that may help doctors determine whether a patient has Parkinson's or some other disease.
However, Dr. Fred Wooten, chairman of the department of neurology at the University of Virginia, said that while the study was intriguing, putting it into practice in diagnosis may be difficult because researchers used specialized imaging equipment to see the nerves around the heart.
''I don't see this becoming a widely used standard of diagnosis,'' Wooten said. ''It's expensive. The equipment necessary wouldn't be widely available. I'm skeptical that it will be useful.''
Wooten said few Parkinson's patients exhibit noticeable heart problems.
''More often than not, there's no major problem with blood pressure control,'' Wooten said. ''It's rarely a problem early and can become a problem later on, but only for some patients.''
The study also found that the breakdown of heart nerves was related to the disease itself, not to drugs taken to treat Parkinson's.
Some patients with Parkinson's have difficulty maintaining adequate blood pressure while standing up. The study concluded that such problems happen as a result of the nerve damage, not the drug levodopa, which is given to Parkinson's patients because of the loss of certain brain chemicals.
What the nerve damage in the heart means is hard to determine.
''There are functional consequences, but I don't think anyone knows what those consequences are,'' Goldstein said.
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On the Net:
Annals of Internal Medicine: http://www.annals.org
Nat'l Institute of Neurological Disorders and Stroke: http://www.ninds.nih.gov
Parkinson's Disease Association: http://www.apdaparkinson.com