Which statement best describes Parkinson's disease?

Which statement best describes Parkinson's disease?

• A. A loss of dopaminergic neurons in the basal ganglia causing bradykinesia, rigidity, and tremor.
• B. Increased dopaminergic activity causing hyperkinesia.
• C. Autonomic nerve degeneration only.
• D. Astrocyte proliferation only.

Answer: (A)

Parkinson's disease is a hypodopaminergic movement disorder caused by loss of dopaminergic neurons in the substantia nigra, a key part of the basal ganglia that regulates movement. When these neurons die, dopamine in the nigrostriatal pathway declines, shifting the balance of the direct and indirect pathways toward inhibited movement. The result is the classic triad of bradykinesia, rigidity, and resting tremor, often with slowed gait and reduced automatic movements. Lewy body pathology can accompany the dopamine loss in remaining neurons, reinforcing the diagnosis. Treatments that boost dopamine, like levodopa, tend to improve symptoms, which helps confirm the dopaminergic deficit aspect. Descriptions that imply increased dopaminergic activity would predict hyperkinesia rather than the slowed, stiff movements seen in this disease, and focusing only on autonomic degeneration or astrocyte proliferation misses the central dopaminergic loss driving the motor signs.

Parkinson's disease is a hypodopaminergic movement disorder caused by loss of dopaminergic neurons in the substantia nigra, a key part of the basal ganglia that regulates movement. When these neurons die, dopamine in the nigrostriatal pathway declines, shifting the balance of the direct and indirect pathways toward inhibited movement. The result is the classic triad of bradykinesia, rigidity, and resting tremor, often with slowed gait and reduced automatic movements. Lewy body pathology can accompany the dopamine loss in remaining neurons, reinforcing the diagnosis. Treatments that boost dopamine, like levodopa, tend to improve symptoms, which helps confirm the dopaminergic deficit aspect. Descriptions that imply increased dopaminergic activity would predict hyperkinesia rather than the slowed, stiff movements seen in this disease, and focusing only on autonomic degeneration or astrocyte proliferation misses the central dopaminergic loss driving the motor signs.