Parkinson's disease may go far beyond the brain in its damage to nerve cells,
researchers
have
discovered. While it has long been known that the disease involves a loss of
nerve endings in part
of
the brain, new research shows that it also damages related nerves in the heart.
This discovery could lead to new ways of predicting or even preventing
Parkinson's, according
to
investigators at the National Institute of Neurological Disorders and Stroke
(NINDS). In a study of
29
Parkinson's patients, Dr. David S. Goldstein and his colleagues found that most
had lost heart
nerve
endings that produce the chemical norepinephrine. Norepinephrine is related to
dopamine, the
chemical
that declines in the brains of Parkinson's patients. This suggests, according to
Goldstein's team,
that
whatever triggers the loss of dopamine-producing nerve endings in the brain also
depletes
nerve
endings in the heart.
Their findings were published in the September 5 issue of the Annals of Internal
Medicine.
Parkinson's is a chronic, progressive disease that strikes the motor system,
gradually robbing
patients
of muscle control, balance and coordination. Many patients also experience a
drop in blood
pressure
when they stand--a condition called orthostatic hypotension. Doctors had
believed the Parkinson's
drug
levodopa was behind this blood pressure abnormality.
But according to the NINDS researchers, the explanation may instead lie in nerve
damage to the
heart.
Among their study patients, nine had orthostatic hypotension. All nine, as well
as 11 without the
blood
pressure condition, showed a loss of nerve endings in the heart. When the
researchers looked at
a
group of patients with a disorder similar to Parkinson's--multiple system
atrophy--they found
normal
heart nerve endings.
Goldstein's team is currently studying whether other organs show similar
nerve-ending loss
in
Parkinson's. According to Goldstein, damage to the hearts of Parkinson's
patients may involve a toxin
in
the blood that prematurely wears out nerve endings. Because this hypothesis may
also apply to
the
brain, according to NINDS, the new findings could "point to a way of predicting
and ultimately
preventing
the disorder."
About 500,000 Americans have Parkinson's. The disease usually appears when
people are in their
50s
and 60s, but it can also strike young adults.
SOURCE: Annals of Internal Medicine 2000;133:338-347, 382-384.
Reuters Health
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