A 28-year-old man with progressive bilateral hearing difficulty shows conductive hearing loss on pure tone audiometry. Bone conduction thresholds show a dip maximal at 2000 Hz, while air conduction shows a flat rising curve. This bone conduction pattern is classically associated with:

• A Congenital stapes fixation only
• B Ossicular chain discontinuity from trauma
• C Cholesteatoma eroding the incus
• D Otosclerosis ✓

Explanation

The Carhart notch, a dip in bone conduction thresholds maximally at 2000 Hz, is characteristic of otosclerosis. It results from fixation of the stapes disrupting the normal resonant contribution of the ossicular chain to bone conduction, and it disappears after successful stapes surgery. Traumatic discontinuity and cholesteatoma produce conductive loss without this specific notch, and congenital stapes fixation is simply one presentation of stapedial otosclerosis rather than a separate audiometric entity.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.