Neuroanatomy: hindbrain malformations: 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: hindbrain malformations

Sample item

An infant has an enlarging head. MRI shows a large cystic dilatation of the fourth ventricle, an absent or hypoplastic cerebellar vermis and an elevated tentorium. What is the diagnosis?

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

The answer and the reasoning

B. Dandy-Walker malformation

Dandy-Walker malformation combines cystic enlargement of the fourth ventricle, vermis agenesis or hypoplasia and an elevated tentorium and torcula, often with hydrocephalus. It results from defective development of the roof of the fourth ventricle.

Option by option

  • A. Aqueduct stenosis

    Aqueduct stenosis enlarges the lateral and third ventricles but leaves the fourth ventricle small.

  • B. Dandy-Walker malformation (correct)

    Correct. A cystic fourth ventricle with a deficient vermis is the defining triad with the high tentorium.

  • C. Chiari II malformation

    Chiari II shows a small posterior fossa with the vermis and medulla pushed downward, usually with a myelomeningocele.

  • D. Holoprosencephaly

    Holoprosencephaly is a failure of forebrain cleavage and does not cause a cystic posterior fossa.

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, Dandy-Walker malformation. Dandy-Walker malformation combines cystic enlargement of the fourth ventricle, vermis agenesis or hypoplasia and an elevated tentorium and torcula, often with hydrocephalus.

Why is "Aqueduct stenosis" not the answer?

Aqueduct stenosis enlarges the lateral and third ventricles but leaves the fourth ventricle small.

Why is "Chiari II malformation" not the answer?

Chiari II shows a small posterior fossa with the vermis and medulla pushed downward, usually with a myelomeningocele.

Why is "Holoprosencephaly" not the answer?

Holoprosencephaly is a failure of forebrain cleavage and does not cause a cystic posterior fossa.

What concept does this question test?

It tests Neuroanatomy: hindbrain malformations in Anatomy. It results from defective development of the roof of the fourth ventricle.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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: hindbrain malformations?

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.