On pure tone audiometry, a patient shows an air-bone gap at low frequencies (250 and 500 Hz) with a characteristic notch-shaped depression in the bone conduction curve at 2000 Hz known as the Carhart notch. This finding is MOST suggestive of:

• A Otosclerosis affecting ossicular chain mechanics ✓
• B Presbycusis with superimposed noise-induced hearing loss
• C Meniere's disease with low-frequency SNHL
• D Superior semicircular canal dehiscence

Explanation

The Carhart notch is a mechanical artefact seen on bone conduction audiometry in otosclerosis, characterized by a dip of approximately 5 dB at 500 Hz, 10 dB at 1000 Hz, 15 dB at 2000 Hz, and 5 dB at 4000 Hz. It results not from true cochlear sensorineural loss but from impaired ossicular resonance that normally enhances bone-conducted sound perception. The notch disappears after successful stapedectomy, confirming its mechanical (not cochlear) origin.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.