Parkinson's disease is a complex progressive neurological disease involving the loss of neurons in a part of the brain called the “substantia nigra.” This results in a reduction in the amount of dopamine, a chemical messenger or neurotransmitter. When 50% to 70% of dopamine in the brain is depleted, the symptoms of Parkinson's disease develop. The loss of dopamine in an area of the brain called the striatum is the main chemical abnormality and there is a correlation between dopamine loss in this area of the brain and the severity of the symptoms.
There are two types of symptoms: motor (movement) and non-motor (non-movement). Common motor symptoms include: tremor, slowness of movement, stiffness and impairment of balance later. Non-motor symptoms vary from person-to-person and more so than the motor symptoms. They can include low-blood pressure, constipation, speech difficulties and depression.