Which statement about Parkinson's disease is true?

• A. It is a progressive neurological disease with a slow onset after age 50 due to death of dopamine-generating cells in the substantia nigra.
• B. It primarily affects the peripheral nerves.
• C. It is caused by autoimmune demyelination of the central nervous system.
• D. It is rare to occur after age 70.

Answer: (A)

Loss of dopamine-producing neurons in the substantia nigra disrupts the balance of movement control in the basal ganglia, leading to the characteristic motor symptoms of Parkinson’s disease and a gradual, progressive course. The statement is true because it captures the key points: the disease is progressive, it typically begins after age 50, and the underlying problem is the death of dopamine-generating cells in the substantia nigra, which reduces dopamine in the nigrostriatal pathway and impairs smooth, coordinated movement.

Parkinson’s disease is a central nervous system disorder, not a primary peripheral neuropathy, so peripheral nerves aren’t the main target. It isn’t caused by autoimmune demyelination of the CNS (that describes conditions like multiple sclerosis). And while the likelihood increases with age, the condition is not rare after 70; many people develop symptoms in their 60s or 70s, reflecting the age-related rise in incidence.