Neuroanatomy: ventricular system: 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: ventricular system

Sample item

A 35-year-old man has sudden severe headaches that appear on changing head position and ease on lying down, with brief drop attacks. CT shows a round hyperdense mass at the anterior roof of the third ventricle, enlarged lateral ventricles and normal third and fourth ventricles. Which pathway is obstructed?

AForamen of MagendieBCerebral aqueduct of SylviusCArachnoid granulationsDInterventricular foramina of Monro

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

The answer and the reasoning

D. Interventricular foramina of Monro

A colloid cyst sits at the anterior roof of the third ventricle and can intermittently block both interventricular foramina, causing positional headaches and dilatation of both lateral ventricles only. The third and fourth ventricles are normal because they lie downstream of the block. Sudden blockage can cause herniation and death, so surgical removal is required.

Option by option

A. Foramen of Magendie
Foramen of Magendie obstruction dilates the fourth ventricle also.
B. Cerebral aqueduct of Sylvius
Aqueduct obstruction would dilate the third ventricle as well as the lateral ventricles.
C. Arachnoid granulations
Arachnoid granulation failure causes communicating hydrocephalus with all ventricles dilated.
D. Interventricular foramina of Monro (correct)
Correct. Blockage at the foramina of Monro dilates only the lateral ventricles.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Interventricular foramina of Monro. A colloid cyst sits at the anterior roof of the third ventricle and can intermittently block both interventricular foramina, causing positional headaches and dilatation of both lateral ventricles only.

Why is "Foramen of Magendie" not the answer?

Foramen of Magendie obstruction dilates the fourth ventricle also.

Why is "Cerebral aqueduct of Sylvius" not the answer?

Aqueduct obstruction would dilate the third ventricle as well as the lateral ventricles.

Why is "Arachnoid granulations" not the answer?

Arachnoid granulation failure causes communicating hydrocephalus with all ventricles dilated.

What concept does this question test?

It tests Neuroanatomy: ventricular system in Anatomy. The third and fourth ventricles are normal because they lie downstream of the block. Sudden blockage can cause herniation and death, so surgical removal is required.

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: ventricular system?

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.