Which statement best describes the pathophysiology of Parkinson disease and a medication used to treat it?

Which statement best describes the pathophysiology of Parkinson disease and a medication used to treat it?

• A. Degeneration of nigrostriatal dopaminergic neurons causing bradykinesia, resting tremor, and rigidity; levodopa replenishes dopamine
• B. Autoimmune destruction of acetylcholine neurons; acetylcholine antagonists
• C. Hyperactivity of the GABAergic system; benzodiazepines
• D. Demyelination of CNS neurons; interferon-beta

Answer: (A)

Parkinson disease is driven by loss of dopamine-producing neurons in the nigrostriatal pathway, from the substantia nigra to the striatum. This dopaminergic deficit disrupts the balance of the basal ganglia circuits, shifting activity toward the indirect pathway and producing the characteristic motor symptoms: bradykinesia, resting tremor, and rigidity. Levodopa works best here because it is a precursor to dopamine that can cross the blood-brain barrier. Once inside the brain, it is converted to dopamine, helping to restore the depleted neurotransmitter levels in the striatum and improve movement. To maximize brain dopamine and minimize peripheral side effects, it is usually given with a peripheral decarboxylase inhibitor (such as carbidopa), which prevents large amounts of levodopa from being converted to dopamine outside the brain. The other choices describe different diseases or mechanisms that don’t capture the main pathophysiology of Parkinson disease.

Parkinson disease is driven by loss of dopamine-producing neurons in the nigrostriatal pathway, from the substantia nigra to the striatum. This dopaminergic deficit disrupts the balance of the basal ganglia circuits, shifting activity toward the indirect pathway and producing the characteristic motor symptoms: bradykinesia, resting tremor, and rigidity.

Levodopa works best here because it is a precursor to dopamine that can cross the blood-brain barrier. Once inside the brain, it is converted to dopamine, helping to restore the depleted neurotransmitter levels in the striatum and improve movement. To maximize brain dopamine and minimize peripheral side effects, it is usually given with a peripheral decarboxylase inhibitor (such as carbidopa), which prevents large amounts of levodopa from being converted to dopamine outside the brain.

The other choices describe different diseases or mechanisms that don’t capture the main pathophysiology of Parkinson disease.