Neuroanatomy: internal capsule: practice question

A Anatomy 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.

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Anatomy · Neuroanatomy: internal capsule

Sample item

A 62-year-old hypertensive man develops sudden, equal weakness of the left face, arm and leg. Sensation, vision and language are normal and there is no cortical sign. The lesion lies in the genu and posterior limb of the right internal capsule. Which small vessels are most commonly responsible?

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

The answer and the reasoning

B. Lenticulostriate branches of the middle cerebral artery

The genu and posterior limb carry corticobulbar and corticospinal fibres for the face, arm and leg in a tight bundle, so one small infarct produces pure motor hemiparesis. Chronic hypertension damages the deep perforating lenticulostriate arteries, causing lacunar infarcts at this site.

Option by option

  • A. Posterior inferior cerebellar artery

    PICA supplies the lateral medulla and part of the cerebellum, which would give crossed sensory loss and ataxia.

  • B. Lenticulostriate branches of the middle cerebral artery (correct)

    Correct. These deep penetrating branches of the MCA supply the internal capsule and are the usual site of hypertensive lacunes.

  • C. Thalamogeniculate branches of the posterior cerebral artery

    The thalamogeniculate arteries supply the sensory thalamic nuclei, so occlusion causes contralateral sensory loss and pain rather than pure motor weakness.

  • D. Recurrent artery of Heubner from the anterior cerebral artery

    The recurrent artery of Heubner supplies the anterior limb and the head of the caudate, so its occlusion gives a different pattern.

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.

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Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is B, Lenticulostriate branches of the middle cerebral artery. The genu and posterior limb carry corticobulbar and corticospinal fibres for the face, arm and leg in a tight bundle, so one small infarct produces pure motor hemiparesis.

Why is "Posterior inferior cerebellar artery" not the answer?

PICA supplies the lateral medulla and part of the cerebellum, which would give crossed sensory loss and ataxia.

Why is "Thalamogeniculate branches of the posterior cerebral artery" not the answer?

The thalamogeniculate arteries supply the sensory thalamic nuclei, so occlusion causes contralateral sensory loss and pain rather than pure motor weakness.

Why is "Recurrent artery of Heubner from the anterior cerebral artery" not the answer?

The recurrent artery of Heubner supplies the anterior limb and the head of the caudate, so its occlusion gives a different pattern.

What concept does this question test?

It tests Neuroanatomy: internal capsule in Anatomy. Chronic hypertension damages the deep perforating lenticulostriate arteries, causing lacunar infarcts at this site.

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 Neuroanatomy: internal capsule?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.