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

PURPOSE: Evaluating the effectiveness of intraoperative auditory brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant for quantifying the implant's floating mass transducer (FMT) coupling quality. METHODS: In a diagnostic multicentric study, patients (> 18 years) who received a VSB with different coupling modalities were included. Pre- and postoperative bone conduction thresholds, intraoperative VSB-evoked ABR thresholds (VSB-ABR) using a modified audio processor programmed to preoperative bone conduction thresholds, postoperative vibrogram thresholds, and postoperative VSB-ABR thresholds were measured. Coupling quality was calculated from the difference between the pure tone average at 1000, 2000, and 4000 Hz (3PTA) vibrogram and postoperative 3PTA bone conduction thresholds. RESULTS: Twenty-three patients (13 males, 10 females, mean age 56.6 (± 12.5) years) were included in the study. Intraoperative VSB-ABR response thresholds could be obtained in all except one patient where the threshold was > 30 dB nHL. Postoperatively, an insufficient coupling of 36.7 dB was confirmed in this patient. In a Bland-Altman analysis of the intraoperative VSB-ABRs and coupling quality, the limits of agreement exceeded ± 10 dB, i.e., the maximum allowed difference considered as not clinically important but the variation was within the general precision of auditory brainstem responses to predict behavioral thresholds. Five outliers were identified. In two patients, the postoperative VSB-ABR thresholds were in agreement with the coupling quality, indicating a change of coupling before the postoperative testing. CONCLUSION: The response thresholds recorded in this set-up have the potential to predict the VSB coupling quality and optimize postoperative audiological results.

Dyna-CT of the temporal bone for case-specific three-dimensional rendering of the stapedial muscle for planning of electrically evoked stapedius reflex threshold determination during cochlear implantation directly from the stapedius muscle via a retrofacial approach: a pilot study.

PURPOSE: Evaluation of 3D Dyna-CTs to improve cochlear implantation (CI) planning and intraoperative electrically elicited stapedius reflex threshold (ESRT) measurements. METHODS: A prospective observational cohort study was performed. Anonymized data collection of Dyna-CTs and CI surgeries in which a retrofacial approach was implemented to access the stapedius muscle. 3D Dyna-CTs of 30 patients and the intraoperative confirmation of the predication in 5/30 patients during CI surgery were evaluated. Inter-rater reliability was also analyzed along with the predictive value of this evaluation. RESULTS: 36 representative structures of the middle and inner ear and 3D renderings of the Dyna-CTs were evaluated by four otoneurological surgeons. Fleiss' kappa values for the evaluation of the visibility were high (> 0.7) for most of the anatomical structures. The stapedius muscle was visible in 90% of the cases. Using the 3D data, the retrofacial access to the stapedius muscles was estimated as feasible in 86.7%. Fleiss' kappa value of the evaluation of the accessibility was 0.942. The intraoperative exploration of the stapedius muscle confirmed the preoperative prediction in all five selected patients (four patients with predicted accessibility and one patient with predicted inaccessibility). CONCLUSIONS: The use of Dyna-CT and 3D rendering is a helpful tool for preoperative planning of cochlear implantations and ESRT measurements from the stapedius muscle via the retrofacial approach.

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

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.