The exact cause of Parkinson's disease is unknown. Scientists believe that many factors may be involved, including both environmental and inherited factors. An example of an environmental factor could be exposure to a certain chemical in the environment. There are likely to be multiple genes and environmental factors involved. The general course of PD is known.
Dopamine is a chemical needed by other nerve cells that control movement.
As more and more of these neurons die, less dopamine is produced and voluntary movements become difficult to control. The area of the brain most affected in PD patients is the substantia nigra, located in the brain stem. The neurons in this area have connections with other structures deep within the brain. Dopamine is sent through these connections. The substantia nigra and the deep-brain structures affected by PD are part of the brain called basal ganglia.