Neuroanatomy: 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

Sample item

A man has sudden severe back pain with saddle anaesthesia, early urinary retention, symmetrical bilateral leg weakness with brisk reflexes and prominent upper motor neurone signs. Which lesion is most likely?

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

The answer and the reasoning

C. Conus medullaris lesion

The conus medullaris ends at L1 to L2, and its lesions cause early bladder and bowel dysfunction, symmetrical saddle loss and a mix of upper and lower motor signs. Cauda equina lesions are asymmetrical, root-like and entirely lower motor.

Option by option

  • A. Femoral nerve palsy

    Femoral nerve palsy affects thigh flexion and the knee jerk on one side only.

  • B. Lumbar root avulsion

    Root avulsion is unilateral and lower motor in type.

  • C. Conus medullaris lesion (correct)

    Correct. The conus lesion gives symmetrical early sphincter loss with mixed motor signs.

  • D. Peripheral neuropathy

    Peripheral neuropathy is length dependent and does not cause saddle loss.

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, Conus medullaris lesion. The conus medullaris ends at L1 to L2, and its lesions cause early bladder and bowel dysfunction, symmetrical saddle loss and a mix of upper and lower motor signs.

Why is "Femoral nerve palsy" not the answer?

Femoral nerve palsy affects thigh flexion and the knee jerk on one side only.

Why is "Lumbar root avulsion" not the answer?

Root avulsion is unilateral and lower motor in type.

Why is "Peripheral neuropathy" not the answer?

Peripheral neuropathy is length dependent and does not cause saddle loss.

What concept does this question test?

It tests Neuroanatomy in Anatomy. Cauda equina lesions are asymmetrical, root-like and entirely lower motor.

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?

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.