Lower limb: L5 radiculopathy versus fibular neuropathy: 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 · Lower limb: L5 radiculopathy versus fibular neuropathy

Sample item

A 48-year-old man has right foot drop. Examination shows weak ankle dorsiflexion, weak great toe extension and weak hip abduction. Knee flexion, plantar flexion and the ankle jerk are normal. Where is the lesion most likely to be?

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

The answer and the reasoning

B. L5 nerve root

Weak hip abduction (gluteus medius and minimus, superior gluteal nerve L4 to S1) together with foot drop localises the lesion proximal to the fibular nerve, to the L5 root, which supplies the dorsiflexors, extensor hallucis longus, hip abductors and tibialis posterior. A common fibular lesion would spare the hip. A sciatic lesion would also weaken the hamstrings and plantar flexion, and cause loss of the ankle jerk.

Option by option

  • A. Common fibular nerve at the fibular neck

    A lesion at the fibular neck would not affect hip abduction because the hip abductors are supplied by the superior gluteal nerve.

  • B. L5 nerve root (correct)

    The L5 root supplies both the foot dorsiflexors and the hip abductors, which explains the combination.

  • C. Sciatic nerve in the thigh

    A sciatic lesion would weaken knee flexion and plantar flexion and abolish the ankle jerk.

  • D. Deep fibular nerve in the anterior compartment

    A deep fibular lesion would spare eversion and the hip abductors and would not explain the hip weakness.

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, L5 nerve root. Weak hip abduction (gluteus medius and minimus, superior gluteal nerve L4 to S1) together with foot drop localises the lesion proximal to the fibular nerve, to the L5 root, which supplies the dorsiflexors, extensor hallucis longus, hip abductors and tibialis posterior.

Why is "Common fibular nerve at the fibular neck" not the answer?

A lesion at the fibular neck would not affect hip abduction because the hip abductors are supplied by the superior gluteal nerve.

Why is "Sciatic nerve in the thigh" not the answer?

A sciatic lesion would weaken knee flexion and plantar flexion and abolish the ankle jerk.

Why is "Deep fibular nerve in the anterior compartment" not the answer?

A deep fibular lesion would spare eversion and the hip abductors and would not explain the hip weakness.

What concept does this question test?

It tests Lower limb: L5 radiculopathy versus fibular neuropathy in Anatomy. A common fibular lesion would spare the hip. A sciatic lesion would also weaken the hamstrings and plantar flexion, and cause loss of the ankle jerk.

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 Lower limb: L5 radiculopathy versus fibular neuropathy?

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.