DESIGN CONSIDERATIONS AND INITIAL CLINICAL EXPERIENCE WITH A PROTOTYPE TOTALLY IMPLANTABLE COCHLEAR IMPLANT RESEARCH DEVICE

Cowan RSC (1, 3), Briggs R (1, 3), Plant KL (1, 2),  Eder HC (1, 2), Seligman PM (1, 2), Dalton J (1, 2) , Money DK (1, 2), Patrick JF (1, 2).

(1)  The HEARing CRC, Melbourne, Australia; (2)   Cochlear Limited, Melbourne, Australia; (3)  The Department of Otolaryngology, University of Melbourne, Australia.

Objectives: This study aimed to evaluate the design considerations and effectiveness associated with the development and first-time-in-human (FTIH) trials of a prototype totally implantable cochlear implant research implant (TIKI).

Materials and Method: Significant biosafety and microphone bioperformance assessments were completed on a prototype totally implantable TIKI design.  Following the completion of these studies, a limited FTIH study was conducted with three adult subjects, all of whom had severe-to-profound hearing loss.  The TIKI research device incorporated a lithium ion rechargeable battery, a package-mounted internal microphone, and sound-processing electronics that enabled the use of “invisible hearing” (ie. without the use of an external device), in addition to standard functionality with an external ESPrit 3G sound processor as a conventional cochlear implant.  Postoperatively, patients used both the TIKI and conventional ESPrit 3G modes.  Assessments of speech perception were measured at 1, 3, 6 and 12 months, and performance of the internal battery and microphone were also made.

Results: No surgical or postoperative complications were found.  As expected, audiometric thresholds while using invisible hearing were higher than for ESPrit 3G, due to the subcutaneous positioning of the microphone.  However, all three subjects were able to employ invisible hearing and conventional ESPrit 3G modes.  Subjects reported some body noise interference that limited use of invisible hearing to a varying extent.  All continue to use invisible hearing on a limited daily cycle.  To date, the rechargeable battery has functioned well.

Discussion & Conclusion: The study clearly identified the many challenges to be overcome in developing a safe and effective totally implantable device. 

E-mail: r.cowan@unimelb.edu.au