Parkinson's disease (or, simply, Parkinson's) is the most common form of parkinsonism, a group of motor system disorders. It is a slowly progressing, degenerative disease that is usually associated with the following symptoms, all of which result from the loss of dopamine-producing brain cells:

• Tremor or trembling of the arms, jaw, legs, and face
• Stiffness or rigidity of the limbs and trunk
• Bradykinesia (slowness of movement)
• Postural instability, or impaired balance and coordination
• Dopamine is a substance produced in the body that has many effects, including smooth and coordinated muscle movement

Facts about Parkinson's

It is a myth that Parkinson's disease was cured after the introduction of levodopa (L-dopa) in the 1960s. In fact, about 60,000 Americans are newly diagnosed with Parkinson's disease each year, and more than 1 million Americans affected at any one time. in addition, more people suffer from Parkinson's disease than multiple sclerosis, muscular dystrophy, and amyotrophic lateral sclerosis combined.

What causes Parkinson's?

The specific cause of PD is unknown. However, medical experts believe the symptoms are related to a chemical imbalance in the brain caused by brain-cell death. Parkinson's disease is chronic (persists over a long period of time), and progressive (symptoms grow worse over time).

Although the disease may appear in younger patients (even teenagers), it usually affects people in late middle age. It is not contagious.

The biggest risk factor for developing PD is advancing age. The average age for the onset of PD is 60 years. In addition, 50 percent more men are affected than women, according to the National Institute of Neurological Disorders and Stroke.

Family history is another important risk factor. Individuals with a parent or sibling who are affected have approximately two times the chance of developing PD. This increased risk is most likely because of a combination of environmental and genetic factors.

Environmental causes are being researched and the strong consistent findings are that rural living, exposure to well water, and exposure to agricultural pesticides and herbicides are related to PD. It is important to remember, however, that these factors do not guarantee the development of PD, nor does their absence prevent it. Having one or more close relatives with PD increases one's risk of developing the disease; however, unless there is a known genetic mutation for PD present, the increased risk is only 2 to 5 percent.

Currently researchers believe that in most individuals the cause of PD is a combination of genetics and environmental exposure.

What are the four primary symptoms of PD?

The following are the most common symptoms of Parkinson's disease. However, each individual may experience symptoms differently. Symptoms may include:

• Muscle rigidity. Stiffness when the arm, leg, or neck is moved back and forth.
• Resting tremor. Tremor (involuntary movement from contracting muscles) that is most prominent at rest.
• Bradykinesia. Slowness in initiating movement.
• Postural instability. Poor posture and balance that may cause falls; gait or balance problems.

The symptoms of Parkinson's disease may resemble other conditions or medical problems. Always consult your doctor for a diagnosis.

How is PD diagnosed?

Making an accurate diagnosis in the early stages of Parkinson's disease can be difficult, as the beginning signs and symptoms may be considered to be indications of other conditions or the effects of normal aging. For this reason, observation of the patient may be required for some time until the symptoms are consistently present.

Currently, there are no blood or laboratory tests that are useful in the diagnosis of PD. Diagnosis of PD is based primarily on a medical history and thorough neurological examination. Brain scans and/or lab tests may be performed to help rule out other diseases or conditions, but brain scan generally will turn out to be normal with PD.

Methods to assist with the diagnosis of PD include:

• Neurological examination (including evaluation of symptoms and their severity)
• Trial test of drugs. When symptoms are significant, a trial test of drugs (primarily levodopa [L-dopa]) may be used to further diagnose the presence of PD. If a patient fails to benefit from levodopa, a diagnosis of Parkinson's disease may be questionable.
• Computed tomography scan (CT or CAT scan). A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.
• Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.