Juvenile Parkinson's begins to develop with the loss of nerve cells in the brain which produce a chemical call dopamine. Dopamine is a chemical messenger, or neurotransmitter, that carries impulses between the nerve cells in your child's brain to control their body movements. When there is no dopamine to carry the message to the nerves that control the muscles, the muscles don't get the message and basically don't know what they are supposed to do. As the loss of nerve cells continues, the symptoms of JP set in and, over time, worsen.