Early Outcomes of a Novel Middle Ear Microphone for Cochlear Implants

INTRODUCTIONTotally implantable cochlear implants should be able to address many of the problems cochlear implant users have around cosmetic appearances,discomfort and restriction of activities.The major technological challenges to solve relate to implanted microphone performance.Microphones can be implanted under the skin or act as sensors in the middle ear.Surface contact and physiological noise are the main barrier to success in subcutaneous microphones.Evidence from totally implantable active middle ear implants suggest body and contact noise can be overcome by converting ossicular chain movements into digital signals.We discuss our own cadaveric series and clinical trial assessing a new fully implantable middle-ear microphone.METHODSWe carried out 40 temporal bone dissections and established the best method of coupling a new implantable microphone to the ossicular chain via objective sensitivity and body noise measurements.This informed a subsequent 6 patient clinical trial.Patients were implanted for 6 months and a series of audiological tests regularly carried out measuring microphone performance and patient satisfaction.RESULTSOur cadaveric trial established the most robust position for microphone placement.Our presentation will discuss data from the clinical trial suggesting middle-ear microphone technology is a safe,functional and effective technology.CONCLUSIONPotential benefits of a fully implantable cochlear implant are obvious,however, implantable microphones must also produce a sound quality that matches or exceeds external counterparts.To date,most commercial products are confined to subcutaneous devices and although most have equivalent hearing thresholds,surface contact or physiological noise are barriers to successful implantation.Positioning implantable microphones in the middle-ear avoids this and potentially takes advantage of directionality cues and amplification provided by the external ear.