Intraoperative auditory steady state response measurements during Vibrant Soundbridge middle ear implantation in patients with mixed hearing loss: preliminary results.

Objective: To optimize intraoperatively the coupling of the floating mass transducer (FMT) of the Vibrant Soundbridge middle ear implant to the round or oval cochlear window in patients with mixed hearing loss.

Study Design: Intraoperative measurement of objective hearing thresholds using auditory steady state responses (ASSRs).

Setting: Radboud University Nijmegen Medical Centre, tertiary referral hospital.

Patients: Four individuals with mixed hearing loss and, at least no incus, in need for a middle ear implant.

Intervention: Surgical placement of the Vibrant Soundbridge. ASSR thresholds were measured intraoperatively, whereas FMT coupling to the cochlea was manipulated to find the most effective coupling of the FMT.

Main Outcome Measure: Differences in ASSR thresholds between different FMT coupling options within patients.

Results: With ASSR, we assessed placement of the FMT in the round window niche, loosely or tightly packed in the niche; creation of a mobile window in case of a fixed stapes footplate; and FMT position coupled to the stapes that afforded vibration in the natural vibration direction or perpendicular to it. Furthermore, test-retest variations in ASSR thresholds were studied. It was shown that differences in ASSR thresholds could be detected, while manipulating the FMT couplings, which were statistically significant.

Conclusion: Intraoperative ASSR measurement is a good method to study different positions of the FMT and to determine the best position of the FMT for a patient.