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WHAT IS PARKINSON'S DISEASE?
Parkinson's disease is a progressive neurological
disorder that results from degeneration of neurons in a region of the
brain that controls movement. This degeneration creates a shortage of
the brain signaling chemical (neurotransmitter) known as dopamine,
causing the movement impairments that characterize the disease.
Parkinson's disease was first formally described in "An Essay on
the Shaking Palsy," published in 1817 by a London physician named
James Parkinson, but it has probably existed for many thousands of
years. Its symptoms and potential therapies were mentioned in the
Ayurveda, the system of medicine practiced in India as early as 5000 BC,
and in the first Chinese medical text, Nei Jing, which appeared 2500
years ago.
WHAT ARE THE SYMPTOMS OF PARKINSON'S DISEASE?
Often, the first symptom of Parkinson's disease is
tremor (trembling or shaking) of a limb, especially when the body is at
rest. The tremor often begins on one side of the body, frequently in one
hand. Other common symptoms include slow movement (bradykinesia), an
inability to move (akinesia), rigid limbs, a shuffling gait, and a
stooped posture. People with Parkinson's disease often show reduced
facial expressions and speak in a soft voice. Occasionally, the disease
also causes depression, personality changes, dementia, sleep
disturbances, speech impairments, or sexual difficulties. The severity
of Parkinson's symptoms tends to worsen over time.
HOW MANY PEOPLE ARE AFFECTED?
In the United States, at least 500,000 people are
believed to suffer from Parkinson's disease, and about 50,000 new cases
are reported annually. These figures are expected to increase as the
average age of the population increases. The disorder appears to be
slightly more common in men than women. The average age of onset is
about 60. Both prevalence and incidence increase with advancing age; the
rates are very low in people under 40 and rise among people in their 70s
and 80s. Parkinson's disease is found all over the world. The rates vary
from country to country, but it is not clear whether this reflects true
ethnic and/or geographic differences or discrepancies in data
collection.
WHAT CAUSES PARKINSON'S DISEASE?
Although there are many theories about the cause of
Parkinson's disease, none has ever been proved. Researchers have
reported families with apparently inherited Parkinson's for more than a
century. However, until recently, the prevailing theory held that one or
more environmental factors caused the disease. Severe Parkinson's-like
symptoms have been described in people who took an illegal drug
contaminated with the chemical MPTP
(1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and in people who
contracted a particularly severe form of influenza during an epidemic in
the early 1900s. Recent studies of twins and families with Parkinson's
have suggested that some people have an inherited susceptibility to the
disease that may be influenced by environmental factors. The strong
familial inheritance of the chromosome 4 gene is the first evidence that
a gene alteration alone may lead to Parkinson's disease in some people.
HOW IS PARKINSON'S DISEASE DIAGNOSED?
Parkinson's disease is usually diagnosed by a
neurologist who can evaluate symptoms and their severity. There is no
test that can clearly identify the disease. Sometimes people with
suspected Parkinson's disease are given anti-Parkinson's drugs to see if
they respond. Other tests, such as brain scans, can help doctors decide
if a patient has true Parkinson's disease or some other disorder that
resembles it. Microscopic brain structures called Lewy bodies, which can
be seen only during an autopsy, are regarded as a hallmark of classical
Parkinson's. Autopsies have uncovered Lewy bodies in a surprising number
of older persons without diagnosed Parkinson's -- 8% of people over 50,
almost 13% of people over 70, and almost 16% of those over 80, according
to one study. As a result, some experts believe Parkinson's disease is
something of an "iceberg; phenomenon," lurking undetected in
as many as 20 people for each known Parkinson's patient. A few
researchers contend that almost everyone would develop Parkinson's
eventually if they lived long enough.
WHAT TREATMENTS ARE AVAILABLE?
There is no cure for Parkinson's disease. Many
patients are only mildly affected and need no treatment for several
years after the initial diagnosis. When symptoms grow severe, doctors
usually prescribe levodopa (L-dopa), which helps replace the brain's
dopamine. Sometimes doctors prescribe other drugs that affect dopamine
levels in the brain. In patients who are very severely affected, a kind
of brain surgery known as pallidotomy has reportedly been effective in
reducing symptoms. Another kind of brain surgery, in which healthy
dopamine-producing tissue is transplanted into the brain, is also being
tested. Finally, researchers are trying to identify substances that will
prevent dopamine-producing brain cells from dying. |
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