Parkinson's Disease

What Is It?

Parkinson's disease is a disease of the central nervous system that causes problems with body motions, including tremor (shakiness), rigidity (muscle stiffness), slowed body movements, unstable posture and difficulty walking. It happens when nerve cells (neurons) in a part of the brain called the substantia nigra gradually die. These cells normally produce a chemical called dopamine that helps to relay messages between areas of the brain that control body movement. The death of cells in this area of the brain leads to abnormally low levels of dopamine, which makes it difficult for a person with Parkinson's disease to control muscle tension and muscle movement, both at rest and during periods of activity.

Parkinson's disease affects about 500,000 people in the United States, with approximately 50,000 new cases diagnosed each year. It usually occurs in middle age, typically beginning around age 60. However, about 5% of patients have early onset Parkinson's disease and are younger than 40 years old when symptoms begin. Internationally, Parkinson's disease affects about 1 to 2 of every 1,000 people. It affects Europeans and North Americans more often than Asians or Africans. It is more common in men than in women.

So far, scientists have not determined why some people develop Parkinson's disease and others do not. The genetics are complex and the influence of family history depends on the age when the disease started. A person who has a parent or sibling that was diagnosed with the disease at a younger age is at higher risk of getting Parkinson's, but not if the affected family member was older when diagnosed.

Symptoms

Parkinson's disease usually begins as a slight tremor or stiffness in the arm or leg on one side of the body. The tremor is most obvious at rest and is regular, typically occurring three to six times per second. The Parkinson's disease tremor usually worsens under stress, improves when the arm or leg is moved voluntarily, and may disappear entirely during sleep. In the earliest stages, Parkinson's disease may be evident only as a tremor involving the thumb and index finger. This tremor sometimes is called "pill-rolling" tremor because it looks as if the person is manipulating a small object such as a pill.

As the illness worsens, the tremor may become more widespread and eventually affect limbs on both sides of the body. Handwriting may become small, shaky and eventually illegible. In addition to the classic tremor, Parkinson's disease often causes stiffness or rigidity in the muscles of the arms or legs and a slowing of body movements, called bradykinesia