Parkinson's disease belongs to a group of conditions called movement disorders. It is both chronic, meaning it persists over a long period of time, and progressive, meaning its symptoms grow worse over time.
Parkinson's disease occurs when a group of cells, in an area of the brain called the substantia nigra, that produce a chemical called dopamine begin to malfunction and eventually die. Dopamine is a neurotransmitter, or chemical messenger, that transports signals to the parts of the brain that control movement initiation and coordination. When Parkinson's disease occurs, for unexplained reasons, these cells begin to die at a faster rate and the amount of dopamine produced in the brain decreases. The four primary symptoms are:
- tremor of the hands, arms, legs, jaw, and face;
- rigidity or stiffness of the limbs and trunk;
- bradykinesia or slowness of movement, and
- postural instability or impaired balance and coordination.