What is Parkinson’s disease? Parkinson’s disease is a gradual, progressive, degenerative disease of the basal ganglia (extrapyramidal) motor system. List the four cardinal features of Parkinson’s disease. Tremor Rigidity Bradykinesia (slowness of movement) Postural instability Describe the tremor of Parkinson’s disease. The tremor is usually a to-and-fro, pronation-supination, resting tremor that diminishes with voluntary movement. [...]