Estimating the Coupling Efficiency of the Fully Implantable Middle Ear Implant CARINA^® Using ABR Methods

Background:
The Carina^® from Cochlear is the only fully implantable middle ear implant in the European market. It can be coupled to different structures of the middle ear, depending on the hearing loss and middle ear amoralities. Hearing outcomes are dependent of sufficient coupling of the actuator to the vibrating structure. Especially in patients with high hearing losses, close to the indication limits of the Carina implant, sufficient coupling is necessary to achieve adequate results. Currently, the coupling between middle ear structure and the actuator is monitored indirectly via electrical impedance measurements. Nevertheless, it is still not possible to get an estimate about the ability of the implant system to stimulate the auditory pathway effectively.

Objective:
In this study it is planned to test 10 patients intraoperatively (so far five are already included) connecting the Actuator of the Carina directly to the ABR machine. The stimulation was performed using broadband chirp stimuli, which were presented starting from suprathreshold levels to below the registration threshold. Preoperatively standard bone conduction thresholds were evaluated and postoperatively OC-direct measurements via the Cochlear Carina Fitting Software were determined.

Results:
The first patient data show that it is possible to record intraoperative ABR via the Carina. Comparing them to the preoperative bone conduction threshold and the postoperative OC-Direct gives an insight about the reliability of this method.

Conclusions:
This method can be used to test the coupling efficiency intraoperatively and test the integrity of the implant at the end of surgery.

Sponsored by Cochlear ltd.