What is Parkinson's disease?
Parkinson's disease is a chronic progressive neurological disease that affects
nerve cells (neurons) in an area of the brain near the neck, known as the
substantia nigra. These cells normally produce dopamine, a chemical
(neurotransmitter) that transmits signals between areas in the brain. These
signals, when working normally, coordinate smooth and balanced muscle movement.
Parkinson's disease, however, causes neurons in the substantia nigra cells to
die, leading to a lack of dopamine in the brain, especially in the part of the
brain known as the basal ganglia. The basal ganglia are responsible for
organizing movement commands from other parts of the brain. The loss of dopamine
causes patients to lose the ability to control their body movements.
Who gets Parkinson’s disease?
Approximately one million Americans have Parkinson's disease. More than 50,000
Americans are diagnosed with Parkinson's disease each year. There is increasing
evidence that Parkinson's disease may be inherited. Men after the age of 60 are
more likely to develop the disease than women. The average age at the onset of
symptoms is 60. However, 10 percent of patients are diagnosed before age 40.
What are the symptoms of Parkinson's?
The major symptoms of Parkinson’s disease include:
- Muscle stiffness (rigidity)
- Bradykinesia (the slowing down of movement and the gradual loss of
- Changes in walking pattern and posture
- Changes in speech and handwriting
- Loss of balance and increased falls
How is Parkinson’s disease diagnosed?
Diagnosing Parkinson's disease is sometimes difficult, since early features may
be difficult to assess and may mimic other disorders. For example, tremor may
not be apparent as a person is sitting at rest, or posture changes may be
written off as osteoporosis or simply a sign of aging.
There are currently no sophisticated blood or
laboratory tests available to diagnose the disease. Some imaging tests, such as
CT (computed tomography) or MRI (magnetic resonance imaging) scans, may be used
to rule out other disorders that cause similar symptoms. Given these
circumstances, a physician may need to observe the patient over time to
recognize signs of tremor and rigidity, and pair them with other characteristic symptoms.
The physician will also compile a comprehensive
history of the patient's symptoms, activity, medications, other medical problems
and exposures to toxic chemicals. This will likely be followed up with a
rigorous physical examination with concentration on the functions of the brain
and nervous system. Tests are conducted on the patient's reflexes, coordination,
muscle strength and mental function.
Because the diagnosis is based on the physician’s
examination of the patient, it is very important that the physician be
experienced in evaluating and diagnosing patients with Parkinson’s disease. If
there is any question whether or not a patient has Parkinson’s disease, the
patient should see a specialist, preferably a Movement Disorders trained
neurologist. The treatment decisions made early in the illness can have profound
implications on the long-term success of the treatment.
Common symptoms of Parkinson's disease include tremor,
or a shaking that begins on one side of the body. In some cases, this tremor is
confined to only one body part, such as the hand or foot. However, it may spread
as the disease progresses and it can worsen with stress. Tremor rarely disables
a patient and often disappears during sleep and when the arm or leg is being moved.
Bradykinesia, another common symptom, is a generalized
slowness of movement. Common activities, such as getting dressed or bathing, may
take a patient several hours to complete.
Most patients with Parkinson's disease develop some
degree of rigidity, or stiffness of limbs. This rigidity is caused by
uncontrolled tensing of muscles and results in the patient being unable to move
about freely. Also, patients may experience aches or pains from affected muscles.
Balance and coordination problems are additional
symptoms of advancing Parkinson's disease. Patients typically develop a forward
or backward lean that makes them more likely to fall when bumped. Additionally,
a posture is often developed in which the head is bowed and shoulders are
slumped (stooped posture).
Other symptoms include:
- Decreased facial expressions
- Speech changes
- Handwriting changes
- Urinary problems
- Skin problems, such as dandruff
- Sleeping problems
It is important to note that the symptoms of
Parkinson's disease can be highly variable between patients, sometimes making it
hard to diagnose. In fact, as many as 25 percent are misdiagnosed.
What treatment options are available?
A variety of other medications are available for the treatment of Parkinson's
disease symptoms. The most powerful drug for treatment of Parkinson’s symptoms
is levodopa, a chemical found naturally in plants and animals. Nerve cells can
use levodopa to make dopamine, which replenishes the low amount in the brain.
Levodopa is often used in combination with carbidopa (Sinemet®) to
prevent or diminish some of the side effects of the medication. However, there
are concerns about the long-term side effects of levodopa, especially the
development of involuntary movements (dyskinesias) which can be disabling. Newer
medications, such as the dopamine agonists, are much less likely to produce
dyskinesias. Consequently, most experts recommend against using levodopa early
in the course of the disease and to use dopamine agonists instead. If the
patient cannot get sufficient relief with the dopamine agonists, particularly
the newer generation of dopamine agonists, levodopa/carbidopa (Sinemet) can be added.
Dopamine agonists, such as the newer generation
ropinirole (Requip®) and pramipexole (Mirapex®) and the
older agent, bromocriptine (Parlodel®), are agonist drugs used to
treat Parkinson's disease. These drugs mimic the role of dopamine in the brain
and work by stimulating certain parts of the brain and nervous system. They can
also be used in combination with levodopa, but are generally less effective in
controlling rigidity and bradykinesia. Most experts will use these medications
first and only add levodopa if the symptoms cannot be controlled sufficiently.
Another class of drugs used to treat the symptoms of
Parkinson’s disease is called COMT inhibitors because they block an enzyme that
breaks down levodopa and dopamine. Examples of these are tolcapone (Tasmar®)
and entacapone (Comtan®). Alone, the medications aren’t helpful, but
they work well in combination with levodopa. Tolcapone and entacapone slow the
body's ability to get rid of levodopa, so it lasts longer and is more
consistent. Because they increase the effectiveness of levodopa, tolcapone and
entacapone may also increase its side effects, such as involuntary movements.
Tolcapone has been associated with liver failure and is thus rarely used. When
tolcapone is used, regular blood monitoring for liver damage is required. Other
medications include amantadine (Symmetrel®), selegiline (deprenyl),
and rasagiline (Azilect®). These drugs can be used in early
Parkinson’s disease on their own or can be combined with levodopa later in the
course of the illness.
There are now a number of safe and effective surgical options available for the
treatment of Parkinson's disease. Generally, surgery is only considered when
medication cannot provide adequate control.
Deep brain stimulation involves placing an electrode
permanently in one of three locations deep in the brain. The electrode is then
connected to a type of pacemaker implanted under the skin on the chest. Once
activated, the device sends continuous electrical pulses to the targets,
blocking the impulses that cause tremors. Deep brain stimulation has many
significant advantages. First, it does not require purposeful destruction of any
part of the brain and therefore, has few complications. Deep brain stimulation
is adjustable and can be changed as the patient’s disease or response to
medications change. If deep brain stimulation is causing excessive side effects,
the stimulator can be turned off and the effects reverse, which is not the case
with older destructive surgeries.
Older surgeries required the purposeful destruction of
parts of the brain and had a higher risk of complications. They are rarely done
today. In pallidotomy, a small section of the brain that is overactive due to
Parkinson's disease is permanently destroyed using surgical techniques. This
treatment can eliminate rigidity and significantly reduce tremor, bradykinesia,
and balance problems. Thalamotomy is a similar procedure where a section of the
thalamus, the part of the brain that controls messaging, is destroyed using
surgical techniques. This treatment is used only to control tremors and is not
generally recommended because of better targets.
Clinical Trial Participation
There are now several treatment options being tested for Parkinson’s disease. These include:
- medications that slow the progression of disease or alleviate the
symptoms of Parkinson’s
- surgical procedures that look into other brain targets or test new devices
- non-pharmacological interventions such as exercise, physical,
behavioral, and cognitive therapy
Most of these "clinical trials" allow the Parkinson
patient to continue with their usual medications while participating in the
study. During clinic visits, patients and their caregivers should ask their
health care provider if some of these clinical trials are available and an
option. Participating may improve their own care while contributing to the
advancement of Parkinson’s disease treatment.
What is the outlook?
Although research is ongoing, to date there is no known cure or preventative
measure for Parkinson's disease. It is important to realize that the patient's
and physician's efforts should be focused on management of the disease. Through
identifying individual symptoms and determining a proper course of action, most
people with Parkinson's disease can live enjoyable, fulfilling lives. The good
news is that physicians have a much clearer profile of the condition, and are
closer than ever to finding a cause—which may help find a cure.
National Institute of Neurological Disorders and Strokes. NINDS Parkinson’s Disease Information Page.
www.ninds.nih.gov Accessed 10/7/2010
American Parkinson Disease Association, Inc. Basic Information About Parkinson’s Disease.
www.apdaparkinson.org Accessed 10/7/2010
Parkinson’s Disease Foundation. Understanding Parkinson’s. What is Parkinson’s Disease?
www.pdf.org Accessed 10/17/2010
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