A disorder of the brain characterized by shaking (tremor) and difficulty with walking, movement, and coordination. The disease is associated with damage to a part of the brain that is involved with movement.
The disease is caused by the progressive deterioration of the nerve cells of the part of the brain that controls muscle movement. Dopamine, which is one of the substances used by cells to transmit impulses, is normally produced in this area, so deterioration of this area of the brain reduces the amount of dopamine available to the body.
Insufficient dopamine disturbs the balance between dopamine and other transmitters, such as acetylcholine. Without dopamine, the nerve cells cannot properly transmit messages, and this results in the loss of muscle function.
The exact reason that the cells of the brain deteriorate is unknown. The disorder may affect one or both sides of the body, with varying degrees of loss of function. In addition to the loss of muscle control, some people with Parkinson’s disease become severely depressed. With severe Parkinson’s, people may exhibit overall mental deterioration (including dementia and hallucinations). The disease affects approximately 2 of every 1,000 people and most often develops after age 50.