Which chronic, progressive neurological disease is characterized by tremor, rigidity, and reduced dopamine production in the brain?

Which chronic, progressive neurological disease is characterized by tremor, rigidity, and reduced dopamine production in the brain?

• A. Parkinson disease
• B. Lewy body dementia
• C. Alzheimer disease
• D. Huntington disease

Answer: (A)

The key idea is that these motor symptoms arise from a loss of dopamine-producing neurons in a specific brain pathway. In Parkinson’s disease, degeneration of dopaminergic neurons in the substantia nigra reduces dopamine in the basal ganglia circuits that regulate movement. That dopamine shortfall disrupts the normal balance of activity in these circuits, leading to the classic motor signs: a resting tremor (often a pill-rolling tremor), muscular rigidity, and slowness of movement (bradykinesia) that progressively worsen over time. The other conditions don’t fit this exact pattern. Lewy body dementia can involve parkinsonian features but is defined mainly by early cognitive impairment and fluctuations. Alzheimer disease centers on memory loss and cortical decline rather than the hallmark motor triad. Huntington disease shows chorea and psychiatric symptoms from degeneration of the striatum, not the same dopamine-deficit–driven rigidity and tremor. So the combination described points most clearly to Parkinson’s disease.

The key idea is that these motor symptoms arise from a loss of dopamine-producing neurons in a specific brain pathway. In Parkinson’s disease, degeneration of dopaminergic neurons in the substantia nigra reduces dopamine in the basal ganglia circuits that regulate movement. That dopamine shortfall disrupts the normal balance of activity in these circuits, leading to the classic motor signs: a resting tremor (often a pill-rolling tremor), muscular rigidity, and slowness of movement (bradykinesia) that progressively worsen over time.

The other conditions don’t fit this exact pattern. Lewy body dementia can involve parkinsonian features but is defined mainly by early cognitive impairment and fluctuations. Alzheimer disease centers on memory loss and cortical decline rather than the hallmark motor triad. Huntington disease shows chorea and psychiatric symptoms from degeneration of the striatum, not the same dopamine-deficit–driven rigidity and tremor. So the combination described points most clearly to Parkinson’s disease.