Embryology: neural tube defects: 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.

Try it

Anatomy · Embryology: neural tube defects

Sample item

A woman at 16 weeks has a raised maternal serum alpha-fetoprotein, and ultrasound shows absence of the cranial vault with exposed brain tissue. Which developmental event failed?

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

The answer and the reasoning

C. Closure of the anterior (rostral) neuropore

Anencephaly follows failure of the rostral neuropore to close around day 25, whereas failure of the caudal neuropore around day 27 to 28 produces spina bifida. Polyhydramnios may occur as the fetus cannot swallow. Folic acid before conception reduces the risk.

Option by option

  • A. Closure of the posterior (caudal) neuropore

    Failure of the caudal neuropore gives spina bifida in the lumbosacral region.

  • B. Migration of the somites

    Somites form the axial skeleton and muscles; their abnormal migration does not cause anencephaly.

  • C. Closure of the anterior (rostral) neuropore (correct)

    Correct. The rostral neuropore closes around day 25, and failure gives anencephaly.

  • D. Formation of the notochord

    Notochord defects do not produce open cranial vault defects of this type.

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, Closure of the anterior (rostral) neuropore. Anencephaly follows failure of the rostral neuropore to close around day 25, whereas failure of the caudal neuropore around day 27 to 28 produces spina bifida.

Why is "Closure of the posterior (caudal) neuropore" not the answer?

Failure of the caudal neuropore gives spina bifida in the lumbosacral region.

Why is "Migration of the somites" not the answer?

Somites form the axial skeleton and muscles; their abnormal migration does not cause anencephaly.

Why is "Formation of the notochord" not the answer?

Notochord defects do not produce open cranial vault defects of this type.

What concept does this question test?

It tests Embryology: neural tube defects in Anatomy. Polyhydramnios may occur as the fetus cannot swallow. Folic acid before conception reduces the risk.

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 Embryology: neural tube defects?

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.