Regional anaesthesia: obturator nerve block: practice question

A Anaesthesia 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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Anaesthesia · Regional anaesthesia: obturator nerve block

Sample item

During transurethral resection of a tumour on the lateral bladder wall under spinal anaesthesia, sudden violent adduction of the thigh occurs. Which nerve block would prevent this?

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

The answer and the reasoning

D. Obturator nerve block

Diathermy near the lateral bladder wall stimulates the obturator nerve, causing sudden adductor contraction that can lead to bladder perforation. Spinal anaesthesia does not reliably prevent this reflex, so an obturator block or muscle relaxation is used. The obturator nerve supplies the adductor muscle group.

Option by option

  • A. Lateral femoral cutaneous nerve block

    The lateral femoral cutaneous nerve is purely sensory.

  • B. Sciatic nerve block

    The sciatic nerve supplies the hamstrings and structures below the knee.

  • C. Femoral nerve block

    The femoral nerve supplies the quadriceps and not the adductors.

  • D. Obturator nerve block (correct)

    Correct. The obturator nerve supplies the thigh adductors that cause the jerk.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is D, Obturator nerve block. Diathermy near the lateral bladder wall stimulates the obturator nerve, causing sudden adductor contraction that can lead to bladder perforation.

Why is "Lateral femoral cutaneous nerve block" not the answer?

The lateral femoral cutaneous nerve is purely sensory.

Why is "Sciatic nerve block" not the answer?

The sciatic nerve supplies the hamstrings and structures below the knee.

Why is "Femoral nerve block" not the answer?

The femoral nerve supplies the quadriceps and not the adductors.

What concept does this question test?

It tests Regional anaesthesia: obturator nerve block in Anaesthesia. Spinal anaesthesia does not reliably prevent this reflex, so an obturator block or muscle relaxation is used. The obturator nerve supplies the adductor muscle group.

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 Regional anaesthesia: obturator nerve block?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.