In stapedectomy for otosclerosis, the small fenestra technique is preferred over total footplate removal. The prosthesis is placed between the incus long process and the oval window. Which characteristic audiometric finding BEFORE surgery distinguishes otosclerosis from ossicular fixation due to other causes?
- A Carhart's notch — a mechanical reduction in bone conduction threshold at 2000 Hz that reverses after successful stapedectomy ✓
- B Flat conductive hearing loss with absent acoustic reflexes and normal tympanometry
- C Low-frequency SNHL on audiometry with absent stapedius reflex
- D Broadband air-bone gap with flat Type B tympanogram
Correct answer: A. Carhart's notch — a mechanical reduction in bone conduction threshold at 2000 Hz that reverses after successful stapedectomy
Explanation
Carhart's notch is a pathognomonic audiometric finding in otosclerosis — a mechanical artifact causing apparent bone conduction threshold elevation at 2000 Hz (usually 5 dB at 500 Hz, 10 dB at 1000 Hz, 15 dB at 2000 Hz, 5 dB at 4000 Hz). It results from reduced resonance of the ossicular chain due to stapes fixation, not from true sensorineural involvement. After successful stapedectomy, the Carhart's notch disappears as ossicular mobility is restored. This distinguishes otosclerosis from other causes of conductive loss where Carhart's notch is absent.
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.