Neuroanatomy: Chiari II malformation: 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: Chiari II malformation

Sample item

A newborn with a lumbosacral myelomeningocele develops progressive hydrocephalus. Which finding on MRI is characteristic of the associated hindbrain malformation?

AAbsent vermis with a large cystic fourth ventricleBVermis and medulla displaced below the foramen magnumCSingle midline ventricle with fused thalamiDAbsent corpus callosum with dilated occipital horns

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

The answer and the reasoning

B. Vermis and medulla displaced below the foramen magnum

The Chiari II malformation includes a small posterior fossa with caudal displacement of the cerebellar vermis, medulla and fourth ventricle through the foramen magnum. It is closely linked to open neural tube defects and causes hydrocephalus by obstructing CSF outflow.

Option by option

A. Absent vermis with a large cystic fourth ventricle
Vermis agenesis with a cystic fourth ventricle describes Dandy-Walker malformation.
B. Vermis and medulla displaced below the foramen magnum (correct)
Correct. Caudal herniation of the vermis and medulla through the foramen magnum defines this malformation.
C. Single midline ventricle with fused thalami
A single ventricle with fused thalami is the alobar form of holoprosencephaly.
D. Absent corpus callosum with dilated occipital horns
Absent corpus callosum with colpocephaly is a separate midline malformation not tied to a myelomeningocele.

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 B, Vermis and medulla displaced below the foramen magnum. The Chiari II malformation includes a small posterior fossa with caudal displacement of the cerebellar vermis, medulla and fourth ventricle through the foramen magnum.

Why is "Absent vermis with a large cystic fourth ventricle" not the answer?

Vermis agenesis with a cystic fourth ventricle describes Dandy-Walker malformation.

Why is "Single midline ventricle with fused thalami" not the answer?

A single ventricle with fused thalami is the alobar form of holoprosencephaly.

Why is "Absent corpus callosum with dilated occipital horns" not the answer?

Absent corpus callosum with colpocephaly is a separate midline malformation not tied to a myelomeningocele.

What concept does this question test?

It tests Neuroanatomy: Chiari II malformation in Anatomy. It is closely linked to open neural tube defects and causes hydrocephalus by obstructing CSF outflow.

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: Chiari II malformation?

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.