Parkinson's disease belongs to a group of conditions called motor system disorders. Parkinson's and related disorders are the result of the loss of dopamine-producing brain cells.
Dopamine is a chemical messenger responsible for transmitting signals within the brain. Parkinson's disease occurs when certain nerve cells, or neurons, die or become impaired. Normally, these neurons produce dopamine.
Loss of dopamine causes the nerve cells to fire out of control, leaving patients unable to direct or control their movement in a normal manner.
The four primary symptoms of Parkinson's are tremor or trembling in hands, arms, legs, jaw, and face; rigidity or stiffness of the limbs and trunk; bradykinesia, or slowness of movement and postural instability or impaired balance and coordination.
Patients may also have difficulty walking, talking, or completing other simple tasks. The disease is both chronic and progressive. Parkinson's is not usually inherited. Early symptoms are subtle and occur gradually.
A variety of medications provide dramatic relief from the symptoms, but no drug can stop the progression of the disease. In some cases, surgery is an appropriate treatment. Some doctors recommend physical therapy or muscle-strengthening exercises.
Reviewed by Dr Andrew Rose-Innes, MD, Department of Neurology, Yale University School of Medicine, New Haven.