Hearing and Otoacoustic Emission Outcome of Stapedotomy: Does the Prosthesis Diameter Mater?

Objective: To compare the hearing and otoacoustic emissions outcome of stapedotomy employing 0.4 and 0.6 mm diameter prostheses.

Material and Methods: 18 patients suffering from otosclerosis participated in a prospective two arms randomized single blinded cohort study. All had small fenestra drill stapedotomy employing 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 otoacoustic emissions (OAEs) conducted 12 months post-operatively were compared within and between the groups.

Results: Within the groups analysis showed significant post-stapedotomy improvements in the average air conduction pure tone thresholds and average air-bone gap in both groups. 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 and 1000, 2000 and 4000 Hz average. Small SNR values of the transient evoked OAEs (TEOAEs) and distortion product OAEs (DPOAEs) were found on the baseline and follow-up evaluation with no consistent changes post-stapedotomy.

Conclusions: Similar post stapedotomy hearing results were found for the 0.4 and 0.6 mm prostheses with small but statistically significant advantage in bone conduction gain and the over-closure parameter for the 0.6 mm prosthesis. OAEs testing were not found to be of clinical value in the evaluation of stapedotomy hearing outcome.