What is the pathogenesis of parkinson's disease?

See below:: Nerve cells use a brain chemical called Dopamine to help control muscle movement. Parkinson's disease occurs when the nerve cells in the brain that make Dopamine are slowly destroyed. Without dopamine, the nerve cells in that part of the brain cannot properly send messages. This leads to the loss of muscle function. The damage gets worse with time. Exactly why these brain cells waste away is unkno.