Which of the following is NOT a cardinal sign of Parkinson disease?

• A. Tremor
• B. Bradykinesia
• C. Postural instability
• D. Headache

Answer: (D)

Parkinson disease presents mainly with motor symptoms from loss of dopamine neurons in the substantia nigra. The classic signs you look for are resting tremor, slowness of movement (bradykinesia), and difficulty with balance and posture (postural instability), with rigidity often described as part of the same motor picture. Headache, on the other hand, is not a motor symptom and is not a hallmark feature of Parkinson disease. It can arise from many other conditions and does not reflect the dopaminergic motor dysfunction that defines the disease. Therefore, headache is the one that does not fit among the cardinal signs. Tremor, bradykinesia, and postural instability align with the characteristic motor presentation.