Parkinson Disease

Parkinson disease is a chronic and progressive movement disorder that occurs when certain neurons, nerve cells in an area of the brain called the substantia nigra, become impaired or die.

Normally, these neurons produce a vital substance called dopamine. Dopamine is the chemical messenger responsible for transmitting signals between the substantia nigra and the corpus striatum, allowing smooth, coordinated function of the body’s muscles and movement. As Parkinson’s progresses, the amount of dopamine produced in the brain decreases, leaving a person unable to control movement normally.

People who experience symptoms of Parkinson disease are generally referred to a neurologist or a movement disorder specialist. The disease is chronic and progressive, but is a very treatable neurologic disease, with the goal of treatment being to alleviate symptoms and prevent orthopedic injury.

Parkinson disease affects about 1 in 100 Americans over the age of sixty years. The average age of onset is about sixty, and while the illness is less common at younger ages, it does occur. Parkinson’s does not shorten one’s life expectancy, although there is currently no cure.

More Information

Loss of the dopamine-producing neurons in the substantia nigra causes the nerve cells in the striatum to fire out of control, resulting in an inability to control movements in a normal manner. Studies have demonstrated that the brain loses approximately 80% of the dopamine-producing cells in the substantia nigra before the cardinal features of Parkinson disease manifest. The cause of this cell death or impairment is not known, but significant findings by research scientists continue to yield important new clues.

Some scientists have suggested that Parkinson disease may occur when either an external or an internal toxin selectively destroys dopaminergic neurons. An environmental risk factor such as exposure to pesticides or toxins in the food supply is an example of the kind of the external trigger that could hypothetically cause Parkinson disease. This hypothesis is based on the fact that there are a number of toxins, such as the chemical MPTP and some drugs, known to induce parkinsonian symptoms in humans. So far, however, no research has provided conclusive proof that a toxin is the cause of the disease.

Another theory explores the role of genetic factors. Fifteen to twenty percent of people with Parkinson disease have a close relative who has experienced parkinsonian symptoms such as tremor.

Free radicals, unstable and potentially damaging molecules generated by normal chemical reactions in the body, may be another cause of Parkinson’s. Free radicals are unstable because they lack one electron; in an attempt to replace this missing electron, free radicals react with neighboring molecules (especially metals such as iron) in a process called oxidation. Oxidation is thought to cause damage to tissues, including neurons. Normally, free radical damage is kept under control by antioxidants, chemicals that protect cells from this damage.

Yet another theory proposes that Parkinson disease occurs when, for unknown reasons, the normal age-related wearing away of dopamine-producing neurons accelerates in certain individuals. This concept is supported by the knowledge that loss of antioxidative protective mechanism is associated with both Parkinson disease and increasing age.

Many researchers believe that a combination of these four mechanisms – oxidative stress, environmental toxins, genetic predisposition, and accelerated aging – may ultimately be shown to cause the disease.

Recently diagnosed patients sometimes wonder whether the onset of Parkinson symptoms could be linked to some traumatic event such as an accident, surgery, or extreme emotional distress. There is no evidence to support that concern. A significant trauma may increase a risk for Parkinson Disease but research continues to investigate this connection.

Cardinal Symptoms

Resting tremor is present in roughly half of all patients. Patients with resting tremor may have a more slowly progressive course of illness than those without tremor. Parkinson tremor has regular rate and rhythm. Tremor usually begins on one side in the hand or leg, although sometimes the jaw is affected first. It is most obvious when the affected limb is at rest or when a person is under stress. During the early stages pf the disease, the tremor usually affects only one side of the body. A Parkinson tremor is rarely disabling and usually disappears during sleep or is lessened with intentional movement, such as reaching out to shake hands or gripping the steering wheel.

Bradykinesia, profound slowness of movement and loss of spontaneous and automatic movement, is often the most disabling symptom of Parkinson disease. There may be hesitation in starting to move (“freezing”), small steps or a shuffling gait, and a loss of fine motor control affecting manual dexterity. This symptom is particularly frustrating because of its effect on function. Early signs of bradykinesia are lack of arm swing on the affected side, small handwriting, masked face, soft speech, and difficulty getting out of a couch or car.

Rigidity refers to increased muscle tone that is felt during movement of the arm, leg, and neck. Rigidity will be more pronounced on one side of the body. Rigidity of the trunk may also be present. A major premise of body movement is that all muscles have an opposing muscle. Movement is possible not just because one muscle becomes more active, but because the opposing muscle relaxes. In Parkinson disease, rigidity comes about when, in response to signals from the brain, this delicate balance of opposing muscles is disturbed. Some patients refer to this as a tightness in their limbs. Unlike arthritis, there is no pain associated with rigidity.

Postural instability, or impaired balance and coordination, causes patients to develop a forward or backward lean and to fall easily. When challenged from the front or when starting to walk, patients with a backward lean have a tendency to fall backwards. This is known as retropulsion. Postural instability can cause patients to have stooped posture, with the head bowed and the shoulders dropped. The body does this to compensate for the postural reflex changes. This can be the most serious symptom of Parkinson disease because of the risk of falls.

Secondary Symptoms

Micrographia – small, cramped handwriting may be one of the first signs.

Reduced arm swing and a slight foot drag on the affected side is an early manifestation of Parkinson disease.

Freezing – a term used to describe the phenomenon of being “stuck in place” when attempting to initiate movement. Anxiety causes freezing and is treated with anti-anxiety medication. More anti-Parkinson medication will not improve freezing.

Dysarthria – low voice volume or muffled speech.

Anxiety and depression – generally present in people with Parkinson disease, usually resulting in weight loss and disrupted sleep or early morning awakening.

Decrease in automatic reflexes such as blinking due to slowness of movement.

Seborrhea dermatitis – increase in dandruff and oily skin.

Constipation – due to slowness of movement in the colon. Anti-Parkinson medications can also be constipating.

Sleep disturbances – talking and acting out dreams are common in people with Parkinson disease.

If you have concerns that you or a loved one might be exhibiting any of the symptoms of Parkinson disease, talk to your doctor for a referral to a neurologist or movement disorders specialist. He or she will have the skills and experience to properly diagnose and treat your disease.


Manage your medications. Your medications are the key to your treatment. The timing and dose of each medication is very important. Keep a list of all of the medicines you take and learn why you take each one. Read the labels carefully, making sure you understand the instructions and doses. Ask your doctor about possible side effects, and talk to your doctor immediately if you notice any problems. Be aware that there are some medications that can interact with Parkinson’s medications. Again, talk with your doctor about all other medications you are taking before starting any new medication.


Countless studies have indicated the importance of exercise in overall health and especially for people with Parkinson disease. Exercise helps with balance, strength, flexibility, and fall prevention. Exercise has also been shown to help with the production of a variety of brain chemicals and neurotransmitters, and may help people with depression.

Thirty minutes per day of activity is recommended. Combine aerobic workouts with strength training and flexibility. Many gyms offer classes specifically designed for people with Parkinson disease. Visit the Support Group page to find classes and programs in your area.


Deep brain stimulation (DBS) is an FDA approved surgical therapy that involves implanting an electrode into a targeted area of the brain, usually the subthalamic nucleus or the globus pallidus internus. The implants can be placed on either or both sides of the brain. The electrodes are stimulated through a connection to a pacemaker-like device located under the skin in the chest. DBS will not cure PD but may help to alleviate some of your symptoms. Your doctor can tell you more about it.

Clinical Trials

Clinical trials provide an opportunity to try the newest medications and other treatments. Fox Trial Finder through The Michael J. Fox Foundation for Parkinson’s Research and the National Institutes of Health can provide information on participating clinics and current studies.

People in US with Parkinson Disease
New cases diagnosed each year in the US
WPA's years in service in WI
Connections made this year to those with PD