Intraoperative Recording of Auditory Brainstem Responses for Monitoring of Floating Mass Transducer Coupling Efficacy During Revision Surgery—Proof of Concept

Abstract

Objective: The objective of the study was to measure auditory brainstem responses elicited by stimulation via a semi-implantable active middle ear implant with an electromagnetically driven floating mass transducer to quantify the coupling efficacy (=vibroplasty in situ thresholds – bone conduction thresholds) in a patient during a revision surgery. Patients: One patient, reimplanted with an active middle ear implant in a revision surgery. Intervention(s): Diagnostic. Main Outcome Measure(s): Intraoperative auditory brainstem responses evoked by stimulation via an active middle ear implant in a calibrated set-up directly indicating the coupling efficacy magnitude (auditory brainstem response threshold = coupling efficacy), as well as pre- and postoperative bone conduction and vibroplasty in situ thresholds. Results: The intraoperative auditory brainstem response threshold was detected at 0 dB nHL, i.e., the magnitude of coupling efficacy was determined intraoperatively to be 0 dB. The actual postoperative coupling efficacy (=postoperative vibroplasty in situ – postoperative bone conduction thresholds) was –2.5 dB. Conclusions: The coupling efficacy determined intraoperatively was consistent with the postoperative coupling efficacy. The described method seems to be a promising tool to objectively quantify the magnitude of coupling efficacy in active middle ear implant surgeries.

Intraoperative quantification of floating mass transducer coupling quality in active middle ear implants: a multicenter study

“…To provide such feedback, the VIB thresholds have to be measured objectively. It has been shown that the recording of auditory evoked potentials (AEPs), like auditory steady state responses (ASSRs) [20], compound action potentials (CAPs) [21][22][23], and auditory brainstem responses (ABR) [24][25][26] is possible in AMEI patients. Custom made set-ups were used in these studies for providing stimulation by the implanted transducer.…”

“…However, most of the studies lack a sufficient sound- or vibration-level calibration of the set-up allowing only a relative assessment, i.e., comparing one FMT coupling position to another. However, Fröhlich et al [ 26 ] have shown that measuring VSB-evoked ABRs using the experimental set-up already described by Radeloff et al [ 21 ] was feasible to quantify the FMT coupling quality in a VSB patient undergoing revision surgery.…”

Active Middle Ear Implant Evoked Auditory Brainstem Response Intensity-Latency Characteristics

“…Custom-made experimental set-ups were used in all studies for providing stimulus transmission by the FMT. While most studies only aimed on relative measurements, it has recently been reported that coupling efficiency could also be determined quantitatively by measuring VSB evoked ABRs ( 26 , 27 ). A modified AP404 audio processor (MED-EL, Innsbruck, Austria) programmed to preoperative BC thresholds and fitted with an insert earphone sound tube attached to the microphone aperture was used for providing stimulation by the implanted FMT.…”

“…Small differences indicate good coupling, i.e., efficient energy transmission to the inner ear without loss of energy. To determine the coupling efficiency objectively, auditory evoked potentials like auditory steady state responses (ASSRs) (19,20), compound action potentials (CAPs) (21)(22)(23), and auditory brainstem responses (ABRs) (24)(25)(26)(27) have been recorded in patients treated with a VSB. Custom-made experimental setups were used in all studies for providing stimulus transmission by the FMT.…”

“…However, standardized ABR peak V latencies as well as intensity-latency functions obtained by aided stimulation with AMEIs are currently lacking in the literature. The studies investigating VSB evoked ABRs did not report latency data but focused on thresholds to predict coupling efficiency (25)(26)(27). In electrocochleography measurements, Colletti et al found reduced CAP latencies and higher amplitudes in case of better coupling (23).…”