Electrocochleography in round window vibrant soundbridge implantation

OBJECTIVE: To determine the role of intraoperative electrocochleography to optimize the fitting of the floating mass transducer of the Vibrant Soundbridge on the round window membrane in patients with conductive and mixed hearing loss. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary referral center, Otolaryngology Department, University of Verona, Verona, Italy. SUBJECTS AND METHODS: Twenty-six adult patients suffering from chronic otitis media with moderate to severe conductive and mixed hearing loss, all with previous unsuccessful functional surgery, underwent round window vibroplasty. Thirteen subjects had intraoperative compound cochlear action potentials measured to assess vibroplasty coupling during and after surgery. In these patients, surgery was modified according to electrocochleographic feedback. The other 13 had vibroplasty without electrocochleography monitoring. RESULTS: The average preoperative air conduction and bone conduction thresholds (0.5-4 kHz) were not statistically significantly different between the 2 cohorts (P > .05). Compound action potential recordings indicated specific surgical modalities to optimize coupling of the floating mass transducer with the round window membrane. The average postoperative Vibrant Soundbridge-aided air conduction threshold improvements (0.5-4 kHz) were 54.6 ± 8.9 and 41.7 ± 11.1 dB HL, respectively, in the monitored and unmonitored cohorts (P = .0032). CONCLUSION: Improved round window vibroplasty outcomes are observed when the surgeon is promptly informed of the compound action potential changes induced by the floating mass transducer round window membrane vibroplasty and alters surgery accordingly. The key point for optimal coupling is a floating mass transducer in full contact with the round window membrane, free to vibrate without any contact with the surrounding bony structures and mobile footplate.