Definition: Parkinson's disease is a brain disorder involving loss of the chemical messenger dopamine. It is a progressive disorder, meaning that it typically gets worse over the years. Dopamine normally controls muscle activity so PD primarily affects movement. Its three cardinal signs are tremor (trembling which usually starts in one hand), rigidity in the trunk or limbs and slowness of movement.
Also Known As: Parkinson's disease can be shortened to Parkinson's, or simply PD.
