Hearing and Otoacoustic Emissions Outcome of Stapedotomy: Does the Prosthesis Diameter Matter?

OBJECTIVE: To compare the hearing and otoacoustic emissions (OAE) outcome of stapedotomy employing 0.4 and 0.6 mm diameter prostheses.

MATERIALS AND METHODS: In total, 18 patients with otosclerosis participated in a prospective, double-armed, randomized cohort study. All the patients underwent small fenestra drill stapedotomy employing the Causse fluroplastic large loop piston prostheses. The patients were randomly assigned to groups of 0.4 mm (n=9) and 0.6 mm (n=9) diameter prostheses. The results of pure tone air and bone audiometries, speech audiometry, and OAE conducted 12 months post operatively were compared within and between the groups.

RESULTS: The within-group analysis showed significant post-stapedotomy improvements in the average air conduction pure tone thresholds in both groups (52.9±9.6 vs. 25.6±5.2 dB HL; p<0.0001 and 54.6±10.4 vs. 22.2±8.2 dB HL; p<0.0001 for the 0.4 and 0.6 mm groups, respectively) and average air-bone gap (ABG; 37.1±8.5 vs. 8.1±3.9 dB HL; p<0.0001 and 38.3±7.5 vs. 9.9±4.5 dB HL; p<0.0001 in the 0.4 and 0.6 mm groups, respectively). No significant differences were found between the groups in these outcome measures, as well as in the rate of ABG closure within 10 dB HL and the word recognition scores. Favorable outcome in the post-stapedotomy bone conduction (BC) was found for the 0.6 mm prosthesis group, reflecting superior cancellation of the Carhart phenomenon for the 500-3000 Hz pure tone thresholds average (-1.7±3.7 vs. 3.9±6.2 dB HL for the 0.4 and 0.6 mm groups, respectively; p<0.04) and 1000, 2000, and 4000 Hz average (-2.6±4.33 vs. 3.9±7.8 dB HL for the 0.4 and 0.6 mm groups, respectively; p<0.05). Small signal-to-noise ratio (SNR) values of the transient-evoked OAE (TEOAE) and distortion product OAE (DPOAE) were found at baseline and follow-up evaluation with no consistent changes post stapedotomy.

CONCLUSION: Similar post-stapedotomy hearing results were found for the 0.4 and 0.6 mm prostheses with small but statistically significant advantage in BC gain and the overclosure parameter for the 0.6 mm prosthesis. OAE testing was not found to be of clinical value in the evaluation of stapedotomy hearing outcome.