Parkinson's Disease

What Is Parkinson’s Disease?

Parkinson’s disease (PD) is a slowly progressive condition resulting from a deficiency in the brain of a chemical called dopamine.

Dopamine is one of many chemical messengers (called neurotransmitters) in the brain that allow nerve cells to communicate with each other. Without it, messages from the brain to the muscles are disrupted. Over a period of time symptoms appear that include:

  • Tremor (shaking) when the body and limbs are at rest
  • Slowness and difficulty beginning a voluntary movement, such as standing up from a chair or turning around, and difficulty with fine precise movements such as doing up buttons. (called bradykinesia)
  • Muscle stiffness, also called rigidity, and
  • Difficulty with maintaining balance (called postural instability)

The amount of dopamine in the brain is reduced in Parkinson’s disease because some of the nerve cells that produce it are destroyed.

The small group of nerve cells affected in Parkinson’s disease nerve cells lies deep in the brain, in a region called the substantia nigra (black substance), a part of the brain involved in initiating movement. It is situated near the center of the brain and contains a clump of dark cells that manufacture dopamine.

Parkinson’s disease is named after the English physician Dr. James Parkinson, who described it in 1817. However there is a much earlier description of Parkinson’s disease among the writings of Leonardo da Vinci, in the Royal collection at Windsor Castle in England.

Facts About Parkinson’s Disease

  • The incidence of Parkinson’s disease is increasing at a rate that is faster than the population is aging.
  • Parkinson’s disease affects an estimated 1 in 1,000 people over age 55.
  • Parkinson’s disease affects about 1 in 100 people age 65 and older.
  • Some 20 percent of people with Parkinson’s disease may be diagnosed under the age of 50.
  • About 8 percent to 10 percent of people with Parkinson’s disease may be diagnosed under the age of 40. Well-known people who have had or have Parkinson’s disease include Pope John Paul II, Francisco Franco, Muhammad Ali, Yasir Arafat, Janet Reno, Sir Michael Redgrave, Adolf Hitler, Vincent Price, Morris Udall, Margaret Bourke White, Pierre Elliot Trudeau, and Michael J. Fox.
  • There has been excellent progress with research into the treatment of Parkinson’s disease. This includes stem cell technology in which very basic cells are grown in the laboratory, and can be easily cultivated into large populations. Researchers have succeeded in turning these stem cells, in the laboratory, into dopamine producing nerve cells, like those cells in the substantia nigra of the brain that produce dopamine.
  • Human trials have already begun and been published using retinal epithelial cells, and human trials using stem cells for the treatment of Parkinson’s disease should begin in the foreseeable future.


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