Which combination defines Parkinson's disease diagnostic criteria?

• A. Bradykinesia in combination with resting tremor or rigidity
• B. Resting tremor alone
• C. Gait changes alone
• D. Cognitive impairment

Answer: (B)

Parkinson's disease is diagnosed when there is clear bradykinesia—slowness of movement with reduced amplitude—plus at least one of the classic parkinsonian signs: resting tremor or rigidity. Bradykinesia is the essential feature, and the presence of either resting tremor or rigidity supports the diagnosis by reflecting the underlying dopaminergic deficit in the basal ganglia circuits. Resting tremor alone can occur in other tremor disorders and gait changes or cognitive impairment can arise from many conditions, so they do not establish PD on their own. Together, the combination of bradykinesia with resting tremor or rigidity best defines the diagnostic criteria.