Intraoperative Monitoring of Hearing Improvement during Ossiculoplasty by LDV-ABR-ECochG Technique

Abstract

Objectives:

Assess utility of combined electrophysiological and laser-Doppler Vibrometry (LDV) technique for intraoperative monitoring (IM) of hearing threshold (HT) improvement during ossiculoplasty.

Methods:

Study Design: A prospective, feasibility study. Setting: Academic, tertiary referral center. Ten patients underwent two-stage canal wall-up tympanoplasty due to chronic otitis media with cholestaetoma. During the second look surgery performed 6 to 9 months later, ossiculoplasty was monitored intraoperatively by LDV to assess prosthesis movability and by electrocochleography from the round window (RW-ECochG), and by auditory brainstem responses (ABR) to evaluate HT improvement. The ear was stimulated acoustically by tone-bursts: 0.5kHz, 1.0kHz, 2.0kHz, and 4.0kHz. Intraoperative HT, defined as the last intensity for which RW-ECochG and ABR wave V was present, were tested for various configurations of prosthesis placement. Simultaneously for the same stimulation, LDV measured prosthesis moveability. In all subjects, pre- and postoperative pure tone audiometry was performed to evaluate postoperative air-bone gap closure (ABG-C).

Results:

Postoperative ABG-C ranged between 10 and 45 dB. HT improvement evaluated intraoperatively correlated with postoperative ABG-C. Various prosthesis configurations and placements resulted in measurable changes mostly in the RW-ECochG thresholds. LDV appeared sensitive mostly to prosthesis position changes manifesting by movability improvement at 0.5 and 1.0kHz.

Conclusions:

RW-ECochG was found to be better than ABR for IM of HT improvement, showing the best correlations with postoperative ABG-C. RW-ECochG and LDV showed their usefulness to control prosthesis position changes by confirming better acoustic energy transfer through the reconstructed ossicular chain.