Intraoperative Monitoring of Coupling Efficiency for the Floating Mass Transducer - Results of a Multicenter Study

The coupling efficiency of the semi-implantable active middle ear implant Vibrant Soundbridge (VSB) (MED-EL, Innsbruck, Austria) with its electromagnetically driven floating mass transducer (FMT) can only be quantified postoperatively in cooperative patients by measuring behavioral vibroplasty in situ thresholds in comparison to bone conduction (BC) thresholds. However, poor coupling efficiency, reflected by differences of 20 dB or more between these thresholds, has been shown to have a negative influence on word recognition scores (1). In order to avoid revision surgeries and suboptimal audiological outcome, there is a need for a feasible and objective intraoperative method for assessing the absolute coupling efficiency.

In a multicenter study, auditory brainstem responses (ABRs) are recorded intraoperatively and postoperatively to objectively assess the FMT coupling efficiency. Stimulation via the implant is provided by a modified AP404 audio processor (MED-EL, Innsbruck, Austria). Broadband CE-Chirps are delivered to the audio processor by an insert earphone sound tube connected to a sound tube adapter glued to the processor’s microphone aperture. The frequency specific amplification of the audio processor is programmed according to the preoperative BC thresholds of the patient. The intraoperative ABR thresholds are compared to the postoperative coupling efficiency, i.e., the difference between the vibroplasty in situ and the BC thresholds.

The first results show good correlation between the intraoperative response thresholds and the postoperative coupling efficiency, i.e., the vibroplasty in situ - BC- difference.

Poster-PDF A-1508.PDF

Publication History

Article published online:
10 June 2020