Neuroimaging: agenesis of the corpus callosum: practice question

A Radiology 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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Radiology · Neuroimaging: agenesis of the corpus callosum

Sample item

Prenatal imaging in a fetus shows widely separated, parallel lateral ventricles with dilated occipital horns. MRI after birth shows longitudinal white matter bundles indenting the medial ventricles. What is the diagnosis?

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

The answer and the reasoning

A. Agenesis of the corpus callosum with colpocephaly and Probst bundles

In callosal agenesis, the axons form anteroposterior Probst bundles that indent the lateral ventricles, which stay parallel and show colpocephaly. Holoprosencephaly shows a failed midline cleavage with a monoventricle. Dandy-Walker involves the posterior fossa.

Option by option

  • A. Agenesis of the corpus callosum with colpocephaly and Probst bundles (correct)

    Correct. Probst bundles with colpocephaly indicate callosal agenesis.

  • B. Holoprosencephaly

    Holoprosencephaly has a single fused ventricle and absent midline separation.

  • C. Schizencephaly

    Schizencephaly is a grey-matter lined cleft.

  • D. Dandy-Walker malformation

    Dandy-Walker has a cystic fourth ventricle and hypoplastic vermis.

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 Radiology question

What is the answer to this Radiology question?

The best answer is A, Agenesis of the corpus callosum with colpocephaly and Probst bundles. In callosal agenesis, the axons form anteroposterior Probst bundles that indent the lateral ventricles, which stay parallel and show colpocephaly.

Why is "Holoprosencephaly" not the answer?

Holoprosencephaly has a single fused ventricle and absent midline separation.

Why is "Schizencephaly" not the answer?

Schizencephaly is a grey-matter lined cleft.

Why is "Dandy-Walker malformation" not the answer?

Dandy-Walker has a cystic fourth ventricle and hypoplastic vermis.

What concept does this question test?

It tests Neuroimaging: agenesis of the corpus callosum in Radiology. Holoprosencephaly shows a failed midline cleavage with a monoventricle. Dandy-Walker involves the posterior fossa.

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 Neuroimaging: agenesis of the corpus callosum?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.