Parkinson's disease occurs when
certain neurons in an area of the brain called the substantia nigra are
damaged or destroyed. Normally, these nerve cells release dopamine — a
chemical that transmits signals between the substantia nigra and another
part of the brain, the corpus striatum. These signals cause your muscles
to make smooth, controlled movements.
Everyone loses some dopamine-producing neurons as a normal part of
aging. But people with Parkinson's disease lose at least 60 percent of
neurons in the substantia nigra. Just what causes this is a subject of
intense research. Right now scientists believe Parkinson's disease may
result from a combination of genetic and environmental factors. Certain
drugs, diseases and toxins also may cause symptoms similar to those of
Until recently, scientists believed that genes played a role primarily
in an unusual type of Parkinson's disease that affects young people. But
new research shows that a strong genetic component also occurs in older
adults. In fact, people who have a first degree relative with
Parkinson's disease, such as a parent, sibling or child, are at three
times greater risk of developing the disease themselves, regardless of
their age. And one study found that having two first degree relatives
with Parkinson's disease can increase risk as much as 10 times.
People with unusual exposure to herbicides and pesticides are three
times more likely to develop Parkinson's disease than people who don't
have this exposure. Unfortunately, researchers haven't yet been able to
connect a specific herbicide or pesticide to the disease.
number of drugs taken for long periods of time or in excessive dosages
can cause symptoms of Parkinson's disease. These include medications
such as haloperidol (Haldol, Halperon) and chlorpromazine (Thorazine,
Sonazine), which are prescribed for certain psychiatric disorders, as
well as drugs used to treat nausea, such as metoclopramide (Reglan) and
prochlorperazine (Compazine, Compro). The epilepsy drug valproate (Depacon)
may also cause some of the features of parkinsonism, especially severe
Exposure to toxins such as manganese dust or the chemical MPTP, a
byproduct of heroin production, can lead to parkinsonism. Scientists
first became aware of MPTP-induced parkinsonism in the 1980s when heroin
addicts using a street drug contaminated with MPTP developed all of the
symptoms of Parkinson's disease. These cases are rare, however.
Age is one of the main risk factors for Parkinson's disease. Although
the disease can affect adults in their 20s, it ordinarily starts in
middle or late life. The risk continues to increase with age. Some
researchers theorize that people with Parkinson's disease may have
neural damage from genetic or environmental factors that becomes worse
Other risk factors include:
Having one close relative with Parkinson's increases the chances
that you'll also develop the disease. If you have two or more close
relatives with Parkinson's, your risk increases ten-fold.
pesticides and herbicides.
Direct contact with herbicides and pesticides puts you at increased
risk of Parkinson's. The disease is also more common in people who
are involved in farming, live in a rural area or drink well water.
It's likely that herbicide and pesticide exposure plays a role in
these cases as well.
Reduced estrogen levels may increase the risk of Parkinson's
disease. This means that menopausal women who receive little or no
hormone replacement therapy (HRT) and those who have had
hysterectomies may be at higher risk. Menopausal women using HRT
appear to have a decreased risk. But not all effects of HRT are
positive. Taking HRT as a combination therapy — estrogen plus
progestin — can result in serious side effects and health risks.
Work with your doctor to evaluate the options and decide what's best
naturally occurs in dark green vegetables such as spinach, in citrus
fruits, and in whole-wheat bread. Half a cup of cooked spinach
contains about 130 micrograms of folate.
When to seek medical advice
It's important to see your doctor if you have any of the symptoms
associated with Parkinson's disease — not only to diagnose the illness
but also to rule out other causes for your symptoms. For instance,
tremors are often an early sign of Parkinson's disease yet the most
common type of tremor, known as essential tremor, isn't caused by
Although Parkinson's disease can sometimes be difficult to pin down,
getting an accurate diagnosis is the key to starting appropriate
treatment that may help delay or manage symptoms for years.
Screening and diagnosis
Because no definitive tests exist for Parkinson's, the disease can be
difficult to diagnose, especially in the early stages. What's more,
symptoms of Parkinson's disease — including an unsteady walk, trembling
and trouble speaking or writing — may be dismissed as the effects of
aging, particularly in older adults with the disease. At the same time,
doctors sometimes miss Parkinson's disease in young people because they
believe it mainly affects older adults.
diagnosis of Parkinson's disease is based on your medical history,
observations of your symptoms and a neurologic examination. As part of
your medical history, your doctor will want to know about any
medications you take and whether you have a family history of
Parkinson's. The neurologic examination includes an evaluation of your
walking, coordination and some simple tasks of dexterity. Your doctor
may also notice subtle signs of parkinsonism — such as reduced facial
expressions, a lack of gestures or a subtle tremor — when he or she
takes your history.
Approximately 40 percent of people with Parkinson's disease develop
depression. In about one in four of these people, symptoms of depression
may occur months or even years before Parkinson's disease is diagnosed.
Although physical limitations resulting from Parkinson's disease can be
frustrating and stressful, depression in someone with Parkinson's isn't
usually a reaction to physical disability. Instead, it more likely
arises from underlying brain changes associated with the disease itself.
In addition, as many as a third of people with Parkinson's disease
eventually develop dementia, a condition that can include memory loss,
impaired judgment and personality changes.
Medications for Parkinson's disease also may cause a number of
complications, including involuntary twitching or jerking movements of
the arms and legs (dyskinesia), hallucinations, sleepiness, and a drop
in blood pressure when standing up (orthostatic hypotension).
Other complications of Parkinson's disease include:
chewing and swallowing.
In the later stages of the disease, the muscles you use to swallow
may be affected, making eating difficult.
Parkinson's disease may cause either urinary incontinence or urine
retention. Certain medications used to treat the disease, especially
anticholinergic drugs, also can make it hard to urinate.
Many people with Parkinson's disease develop constipation because
the digestive tract works more slowly. Constipation may also be a
side effect of medications used to treat the disease.
People with Parkinson's disease often have trouble falling asleep
and may wake up frequently throughout the night. They also may
experience restless sleep and even act out their dreams (rapid eye
movement sleep behavior disorder). Some of the problems with sleep
may be related to depression.
Some people with Parkinson's disease may notice a
decrease in sexual desire (libido). This may stem from a combination
of psychological and physical factors, or it may be the result of
physical factors alone.
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