Neuroanatomy: obstructive hydrocephalus: 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: obstructive hydrocephalus

Sample item

An infant has an enlarging head. CT shows dilated lateral ventricles and a dilated third ventricle, but the fourth ventricle is of normal size. Where is the obstruction?

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

The answer and the reasoning

C. Cerebral aqueduct

CSF flows from the lateral ventricles through the interventricular foramina to the third ventricle, then through the cerebral aqueduct of the midbrain to the fourth ventricle, and exits through the median and lateral apertures. Dilation of the lateral and third ventricles with a normal fourth ventricle places the block at the aqueduct, as in aqueduct stenosis.

Option by option

  • A. Interventricular foramen of Monro

    A foramen of Monro block dilates the lateral ventricle or ventricles and leaves the third ventricle small.

  • B. Foramina of Luschka and Magendie

    Block of the fourth ventricle outlets dilates the fourth ventricle as well.

  • C. Cerebral aqueduct (correct)

    Aqueduct obstruction dilates the structures proximal to it and spares the fourth ventricle.

  • D. Arachnoid granulations

    Failure of arachnoid granulations causes communicating hydrocephalus, dilating all ventricles including the fourth.

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.

More Anatomy questions

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Cerebral aqueduct. CSF flows from the lateral ventricles through the interventricular foramina to the third ventricle, then through the cerebral aqueduct of the midbrain to the fourth ventricle, and exits through the median and lateral apertures.

Why is "Interventricular foramen of Monro" not the answer?

A foramen of Monro block dilates the lateral ventricle or ventricles and leaves the third ventricle small.

Why is "Foramina of Luschka and Magendie" not the answer?

Block of the fourth ventricle outlets dilates the fourth ventricle as well.

Why is "Arachnoid granulations" not the answer?

Failure of arachnoid granulations causes communicating hydrocephalus, dilating all ventricles including the fourth.

What concept does this question test?

It tests Neuroanatomy: obstructive hydrocephalus in Anatomy. Dilation of the lateral and third ventricles with a normal fourth ventricle places the block at the aqueduct, as in aqueduct stenosis.

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: obstructive hydrocephalus?

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.