Objectives: To analyze changes in bone conduction (BC) thresholds before and after stapedotomy in patients with clinical otosclerosis with a focus on the Carhart notch, which is defined as a significant loss of BC at a certain audiometric frequency.
Methodology: Retrospective case review of pure tone audiometry (PTA) in 213 patients who underwent a stapedotomy at a tertiary referral center between 2004 and 2011. The patients were grouped by age and the frequency of the Carhart notch. The non-operated ear was also evaluated.
Results: The Carhart notch was present on pre-operative audiometry in 158 (74%) patients at 0.5 (n = 18, 8.45%), 1 (n = 25, 11.70%), or 2 kHz (n = 115, 54.0%). We measured a mean postoperative improvement in BC of 7.5, 8.4, and 8.8 dB HL. Pre-operatively, 55 (25.8%) patients did not exhibit a typical notch configuration. The mean gain in BC, defined on PTA according to the AAO-HNS criteria (0.5, 1, 2 and 3, or 4 kHz), was 1.8 dB HL after stapedotomy.
Conclusion: The Carhart notch was not solely related to the 2 kHz frequency. The greatest gain in BC after stapedotomy for otosclerosis occurred at the notch frequency.