Ear and audiology: Carhart notch mechanism: practice question

A ENT 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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ENT · Ear and audiology: Carhart notch mechanism

Sample item

A 32-year-old woman has progressive bilateral hearing loss that worsened during pregnancy. Otoscopy is normal. The audiogram shows an air-bone gap, and the bone conduction thresholds are also depressed at 2 kHz. What explains the depressed bone conduction at 2 kHz?

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

The answer and the reasoning

A. Loss of the ossicular inertial component of bone conduction due to a fixed stapes

In otosclerosis a fixed stapes removes the ossicular inertial contribution to bone conduction, mainly around 2 kHz, so bone thresholds appear worse (the Carhart notch). It is an artefact of middle ear mechanics and the bone thresholds improve after successful stapes surgery, so it does not imply cochlear damage.

Option by option

  • A. Loss of the ossicular inertial component of bone conduction due to a fixed stapes (correct)

    Correct. Stapes fixation abolishes the inertial component of bone conduction and the notch reverses after surgery.

  • B. Selective outer hair cell loss in the mid-frequency region of the cochlea

    A true hair cell lesion would not reverse after stapes surgery and would not produce an air-bone gap.

  • C. Compression of the cochlear nerve fibres by a retrocochlear lesion

    A retrocochlear lesion gives a sensorineural pattern with poor speech discrimination, not an air-bone gap.

  • D. Noise-induced damage confined to the basal turn of the cochlea

    Noise damage classically affects around 4 kHz and is sensorineural, not conductive.

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 ENT question

What is the answer to this ENT question?

The best answer is A, Loss of the ossicular inertial component of bone conduction due to a fixed stapes. In otosclerosis a fixed stapes removes the ossicular inertial contribution to bone conduction, mainly around 2 kHz, so bone thresholds appear worse (the Carhart notch).

Why is "Selective outer hair cell loss in the mid-frequency region of the coc…" not the answer?

A true hair cell lesion would not reverse after stapes surgery and would not produce an air-bone gap.

Why is "Compression of the cochlear nerve fibres by a retrocochlear lesion" not the answer?

A retrocochlear lesion gives a sensorineural pattern with poor speech discrimination, not an air-bone gap.

Why is "Noise-induced damage confined to the basal turn of the cochlea" not the answer?

Noise damage classically affects around 4 kHz and is sensorineural, not conductive.

What concept does this question test?

It tests Ear and audiology: Carhart notch mechanism in ENT. It is an artefact of middle ear mechanics and the bone thresholds improve after successful stapes surgery, so it does not imply cochlear damage.

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 Ear and audiology: Carhart notch mechanism?

Learn tuning fork results and audiogram patterns by sketching them. Then use the flashcards and the other ENT 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.