Parkinson’s disease is a disorder of the brain that causes symptoms such as impaired motor control, tremors, rigidity, and difficulty with balance. The symptoms of Parkinson’s disease occur because of the death or impairment of neurons in the brain that control the production and release of the neurotransmitter dopamine. When the brain becomes sufficiently deprived of dopamine-producing cells, the physical symptoms of Parkinson's begin to appear, generally starting with a tremor in the hands or feet.