Which term best describes rhythmic, oscillatory involuntary movement often seen in Parkinson's disease?

• A. Tremor
• B. Tics
• C. Chorea
• D. Dyskinesia

Answer: (A)

Rhythmic, oscillatory involuntary movement in Parkinson's disease is tremor. In PD, the classic rest tremor appears when the muscles are at rest and often takes on a pill-rolling feel as the thumb and forefinger move in a circular motion. It tends to lessen with intentional movement and can be worsened by stress or fatigue, with a typical frequency around 4–6 cycles per second. This pattern reflects dysfunction in the basal ganglia circuits and dopaminergic loss that disrupts the normal rhythmic output to the motor system.

Tics are brief, repetitive, stereotyped movements or sounds that can be suppressed for a while but are not characteristic of Parkinson's. Chorea involves irregular, rapid, jerky movements that flow from one part of the body to another and is more typical of Huntington's disease or certain drug states. Dyskinesia refers to abnormal involuntary movements that are often choreiform or dystonic and commonly arise as a side effect of long-term dopaminergic therapy in PD, rather than the rhythmic rest tremor described here.