Neurophysiology and special senses: Huntington disease pathway: practice question

A Physiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Physiology · Neurophysiology and special senses: Huntington disease pathway

Sample item

A 42-year-old man has choreiform movements and cognitive decline, with atrophy of the caudate nucleus on imaging. Which basal ganglia change underlies the chorea?

AEarly loss of indirect pathway neurons, which disinhibits the thalamusBLoss of nigrostriatal dopamine, which reduces direct pathway outputCLoss of dentate nucleus output from the cerebellumDDestruction of the subthalamic nucleus

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Early loss of indirect pathway neurons, which disinhibits the thalamus

In Huntington disease, the GABAergic medium spiny neurons of the indirect pathway die first. This reduces inhibition of the thalamus through the globus pallidus externa and subthalamic nucleus, and excess motor activity (chorea) results. In Parkinson disease nigrostriatal dopamine loss reduces movement.

Option by option

A. Early loss of indirect pathway neurons, which disinhibits the thalamus (correct)
Correct. Indirect pathway loss disinhibits the thalamus and causes chorea.
B. Loss of nigrostriatal dopamine, which reduces direct pathway output
Nigrostriatal dopamine loss describes Parkinson disease, with rigidity and bradykinesia.
C. Loss of dentate nucleus output from the cerebellum
Dentate nucleus lesions cause intention tremor and ataxia.
D. Destruction of the subthalamic nucleus
Subthalamic nucleus destruction produces hemiballismus on the opposite side, not chorea with caudate atrophy.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is A, Early loss of indirect pathway neurons, which disinhibits the thalamus. In Huntington disease, the GABAergic medium spiny neurons of the indirect pathway die first.

Why is "Loss of nigrostriatal dopamine, which reduces direct pathway output" not the answer?

Nigrostriatal dopamine loss describes Parkinson disease, with rigidity and bradykinesia.

Why is "Loss of dentate nucleus output from the cerebellum" not the answer?

Dentate nucleus lesions cause intention tremor and ataxia.

Why is "Destruction of the subthalamic nucleus" not the answer?

Subthalamic nucleus destruction produces hemiballismus on the opposite side, not chorea with caudate atrophy.

What concept does this question test?

It tests Neurophysiology and special senses: Huntington disease pathway in Physiology. This reduces inhibition of the thalamus through the globus pallidus externa and subthalamic nucleus, and excess motor activity (chorea) results. In Parkinson disease nigrostriatal dopamine loss reduces movement.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Neurophysiology and special senses: Huntington disease pathway?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.