Cochlear Implants and Hearing Preservation Advances in Oto-Rhino-Laryngology

Hearing preservation after cochlear implantation and combined electric acoustic stimulation (EAS) in the same ear has reduced the gap between prosthetic hearing rehabilitation with hearing aids and cochlear implants. This has increased the possibility of successful hearing rehabilitation for patients. This paper describes the history of hearing preservation after cochlear implantation. Indications and criteria for combined electric acoustic stimulation are described, and hearing preservation surgery and outcomes achieved with combined EAS are discussed. EAS has led to a new era in prosthetic hearing rehabilitation providing new understanding of basic physiological, psychoacoustic and medical aspects of the inner ear. Copyright © 2010 S. Karger AG, Basel Inclusion criteria for electric stimulation of the auditory nerve via cochlear implantation have significantly broadened over the years. Encouraged by promising results in traditional cochlear implant (CI) patients, the application of cochlear implantation has been used in patients with increasing amounts of residual hearing. Most of these patients are able to achieve considerably good speech reception after cochlear implantation, and in some cases residual hearing could even be preserved. Combined electric acoustic stimulation (EAS) of the auditory system is the concept of using CI technology and acoustic amplification in the same ear and is a relatively new treatment for patients with a considerable amount of residual hearing in the low-frequency range. In EAS the aim is to preserve low-frequency hearing after cochlear implantation which can be used for acoustic amplification, while a CI provides electric stimulation to the auditory system in the high-frequency range to compensate for the hearing loss in the high frequencies (fig. 1). In 1999, von Ilberg et al. [1] first discussed the possibility of using electric and acoustic stimulation simultaneously in patients without losing functional residual hearing in the low frequencies. Evidence in animal experiments demonstrated the possibility of using electric and acoustic stimulation of the central auditory system simultaneously without interferences and the first patient with a considerable amount of residual low-frequency hearing was implanted for EAS. Long-term experience with EAS shows that preserved residual hearing after cochlear implantation remains stable over time in most patients, and encouraging results in speech reception are reported with the use of combined electric and acoustic stimulation [2–4].