Neuroanatomy: vertebrobasilar circulation: 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: vertebrobasilar circulation

Sample item

A 65-year-old man with atrial fibrillation develops sudden drowsiness, loss of upward gaze and bilateral visual loss with preserved pupillary reflexes. Embolic occlusion at the termination of which vessel best explains this?

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

The answer and the reasoning

B. Basilar artery at its bifurcation into the posterior cerebral arteries

The basilar artery forms from the two vertebral arteries and ends at the upper border of the pons by dividing into the posterior cerebral arteries. Occlusion at the top of the basilar affects the midbrain and thalami, producing drowsiness and vertical gaze palsy, and both occipital lobes, producing cortical blindness with preserved pupil reactions.

Option by option

  • A. Anterior spinal artery

    The anterior spinal artery supplies the medial medulla and cord, not the occipital lobes.

  • B. Basilar artery at its bifurcation into the posterior cerebral arteries (correct)

    Correct. The top-of-basilar territory includes the midbrain, thalami and both occipital lobes.

  • C. Internal carotid artery at the ophthalmic origin

    The ophthalmic artery occlusion causes monocular loss of vision, and the pupil reflex would not be preserved.

  • D. Both middle cerebral arteries

    Both middle cerebral arteries would cause hemispheric deficits and aphasia or neglect rather than gaze and bilateral cortical blindness.

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, Basilar artery at its bifurcation into the posterior cerebral arteries. The basilar artery forms from the two vertebral arteries and ends at the upper border of the pons by dividing into the posterior cerebral arteries.

Why is "Anterior spinal artery" not the answer?

The anterior spinal artery supplies the medial medulla and cord, not the occipital lobes.

Why is "Internal carotid artery at the ophthalmic origin" not the answer?

The ophthalmic artery occlusion causes monocular loss of vision, and the pupil reflex would not be preserved.

Why is "Both middle cerebral arteries" not the answer?

Both middle cerebral arteries would cause hemispheric deficits and aphasia or neglect rather than gaze and bilateral cortical blindness.

What concept does this question test?

It tests Neuroanatomy: vertebrobasilar circulation in Anatomy. Occlusion at the top of the basilar affects the midbrain and thalami, producing drowsiness and vertical gaze palsy, and both occipital lobes, producing cortical blindness with preserved pupil reactions.

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: vertebrobasilar circulation?

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.