What causes Parkinson disease ?
What causes Parkinson disease? Parkinson disease occurs when the nerve cells in the brain that make dopamine, a chemical messenger which transmits signals within the brain to produce smooth physical movements, are slowly destroyed. Without dopamine, the nerve cells in the part of the brain known as the substantia nigra cannot properly send messages. This leads to progressive loss of muscle function. Exactly why these brain cells waste away is unknown. Recent studies have shown that people with Parkinson disease also experience damage to the nerve endings that produce the neurotransmitter norepinephrine. Norepinephrine, which is closely related to dopamine, is the main chemical messenger of the sympathetic nervous system, the part of the nervous system that controls the automatic functions of the body, including pulse and blood pressure. The loss of norepinephrine may explain some of the non-motor features seen in Parkinson disease, including fatigue and problems with blood pressure regulation.  More detailed information about the cause of Parkinson disease is available through an information page developed by the National Institute of Neurological Disorders and Stroke (NINDS). Click here to view this information.