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The Carina® implant system is a fully implantable active middle ear implant, which can be coupled to various structures in the middle ear, depending on the nature of the hearing loss and the middle ear anatomy. Currently, there is only one method for determining the coupling efficiency of the actuator of this implant system, and this is limited to incus coupling. The proposed method is based on the intraoperative recording and evaluation of auditory brainstem responses (ABRs) while directly stimulating the hearing system via the actuator. The acoustic stimulation was achieved using an optimised broadband chirp stimulus (CE-Chirp®). This study included 10 subjects having moderate to severe sensorineural or mixed hearing loss. The intraoperative ABR measurements show, that it is possible to derive reliable AEP thresholds via the actuator of the implant. The ABR thresholds correlate well with preoperative BC PTA4 thresholds (r = 0.87) while the postoperative OC-direct thresholds (in situ audiogram via the implant) correlate with r = 0.77. The results demonstrated that the direct actuator stimulation allow for reliable intraoperative ABR measurements and that the proposed method can be used to estimate the coupling efficiency of the actuator and facilitate its positioning. [ABSTRACT FROM AUTHOR]

Objective: Active middle ear implants are widely used to treat adults and children with sensorineural, conductive, or mixed hearing loss. Currently, there is no adequate method to determine the performance of active middle ear implant systems. Design: The proposed method is based on measuring the auditory brainstem response while stimulating the hearing system via the active middle ear implant (Vibrant SoundbridgeTM, VSB; MEDEL, Austria). The acoustic stimulation was achieved via an optimised chirp stimulus (CE-Chirp), implemented in the Eclipse system (Interacoustics, Denmark). To compensate for the frequency-specific delays in the VSB system, the underlying model function of the CE-Chirp was adjusted accordingly (VSB-CE-Chirp). Study samples: The study includes 12 subjects having mild to profound sensorineural, conductive or mixed hearing loss. Results: The use of an optimised VSB-CE-Chirp instead of the CE-Chirp increases significantly the ABR wave V amplitudes (1.63 times) and so also increases their identifiability (by 15.2%). On average, wave V could be identified at a 7.5 dB lower stimulation level. Conclusion: The constructed VSB-CE-Chirp stimulus, after it had been transmitted through the VSB system, follows well the shape of the original CE-Chirp. Preliminary measurements in VSB patients demonstrated a significantly improved ABR amplitude with the VSB-CE-Chirp. [ABSTRACT FROM AUTHOR]