What is Parkinson's disease?
Parkinson's disease is a disorder of certain nerve cells in a
part of the brain (substantia nigra) that produces dopamine.
Dopamine is a chemical messenger, or neurotransmitter, that the
brain uses to help direct and control movement. In Parkinson's
disease, these dopamine-producing nerve cells break down,
dopamine levels drop, and brain signals directing movement
What causes Parkinson's disease?
The cause of Parkinson's disease is unknown. Symptoms of the
disease are caused by low levels of dopamine, a chemical in the
brain that helps control movement. While abnormal genes do seem
to be a factor in the development of Parkinson's disease,
studies aimed at finding a genetic cause for the disease have
not yet yielded any evidence strong enough to prove that the
disease is inherited.
What are the symptoms of Parkinson's disease?
The classic symptoms of Parkinson's disease are shaking
(tremor), stiff muscles (rigidity), and slow movement (bradykinesia).
A person with advanced Parkinson's disease also may have stooped
posture, a fixed facial expression, speech problems, and
problems with balance or walking, as well as a decline in
Tremor is usually the first symptom people notice. Unlike most
other tremors, the “resting” tremor of Parkinson's disease is
most severe when the person is awake but not moving around. The
tremor improves with purposeful movement or when the person is
completely relaxed or asleep. In contrast, tremors caused by
other conditions typically get worse during movement and improve
when the person is at rest.
Many people who have tremor do not have Parkinson's disease.
Up to 25% of people with Parkinson's disease do not have tremor.
Who is affected by Parkinson's disease?
It is estimated that about 1 million people (or about 4 in every
1,000) in the North America have Parkinson's disease.
The number of new cases increases with age:
1 in 100 people over age 65 have Parkinson's disease.
1 in 10 people over age 80 have the disease.
Symptoms of Parkinson's disease most often first appear during
a person's 50s or 60s. The disease progresses gradually over 10
to 15 years, resulting in increasing disability. Early-onset
disease (before age 30 to 40) is not common; among the total
number of Parkinson's disease cases, 5% to 10% are early-onset
Parkinson's disease seems to occur more often in men than in
women (a 3-to-2 ratio), but the reason for this is unknown.
How is Parkinson's disease diagnosed?
A diagnosis of Parkinson's disease is based on a medical history
and a thorough neurological exam.
There are no lab tests that can diagnose the disease. Sometimes
an imaging test called positron emission tomography (PET) can
detect low levels of dopamine in the brain, but this test is not
commonly used to diagnose Parkinson's disease because it is
expensive and not widely available.
How is Parkinson's disease treated?
There is no known cure for Parkinson's disease. Several
different types of medication may be used to relieve symptoms.
Brain surgery or deep brain stimulation also may be used to
control symptoms in some people.