Neuroanatomy: subfalcine herniation: 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: subfalcine herniation

Sample item

A patient with a large right frontal tumour has CT evidence of midline shift, with the cingulate gyrus displaced beneath the free edge of the falx cerebri. Which new deficit is most likely?

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

The answer and the reasoning

B. Weakness of the left leg more than the arm

In subfalcine herniation the cingulate gyrus and the right anterior cerebral artery are squeezed under the falx. Infarction of the paracentral lobule gives contralateral leg weakness greater than arm weakness.

Option by option

  • A. Respiratory arrest

    Respiratory arrest follows tonsillar herniation compressing the medulla.

  • B. Weakness of the left leg more than the arm (correct)

    Correct. Anterior cerebral artery compression affects the leg area of the opposite motor cortex.

  • C. Left homonymous hemianopia

    Hemianopia arises from posterior cerebral artery compression during uncal herniation.

  • D. Dilated right pupil with ptosis

    A dilated pupil with ptosis is oculomotor compression from uncal herniation, not subfalcine herniation.

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, Weakness of the left leg more than the arm. In subfalcine herniation the cingulate gyrus and the right anterior cerebral artery are squeezed under the falx.

Why is "Respiratory arrest" not the answer?

Respiratory arrest follows tonsillar herniation compressing the medulla.

Why is "Left homonymous hemianopia" not the answer?

Hemianopia arises from posterior cerebral artery compression during uncal herniation.

Why is "Dilated right pupil with ptosis" not the answer?

A dilated pupil with ptosis is oculomotor compression from uncal herniation, not subfalcine herniation.

What concept does this question test?

It tests Neuroanatomy: subfalcine herniation in Anatomy. Infarction of the paracentral lobule gives contralateral leg weakness greater than arm weakness.

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: subfalcine herniation?

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.