Cochlear Implantation

Abstract

Background: Hearing impairment that is too severe to be adequately treated with conventional hearing aids can lead, in children, to severe developmental disturbances of hearing and language, and, in adults, to communicative and social deprivation. Recent advances in medical device technology and in microsurgical techniques have led to an expansion of the indications for cochlear implantation (CI) for adults with progressive hearing loss in older age, and to a restructuring of the process of care for these patients in Germany.

Methods: This review is based on pertinent publications retrieved by a selective search in PubMed, as well as on the CI guidelines and CI "white book" of the German Society of Otolaryngology and Head and Neck Surgery.

Results: Early and accurate diagnosis is crucial for the successful auditory rehabilitation of high-grade hearing impairment. In children, a key role is played by newborn auditory screening, which is mandatory in Germany and enables the provision of a CI in the first year of life when necessary. 86% of the children receiving a CI achieve linguistic comprehension of fluently spoken sentences. For adults, positive prognostic factors for hearing after the provision of a CI include a highly motivated patient, "postlingual" onset of the hearing impairment (i.e., after the acquisition of language), and a brief duration of deafness. Auditory rehabilitation is associated with significant improvement, not just of hearing and of the comprehension of spoken language, but also of quality of life, particularly in elderly patients. For patients of any age with bilateral hearing loss, CIs should be provided on both sides, if possible. The more common complications of the procedure, with a probability of 2-4% each, are technical implant defects, dizziness, and wound-healing disturbances.

Conclusion: Cochlear implantation, performed in specialized centers, is a safe and reliable technique and regularly enables the successful rehabilitation of hearing in both children and adults.

Figure

Principle of a cochlear implant The sound waves are picked up by a microphone in the audio processor (1), converted into electrical signals, and transmitted via the transmitter coil (2) to the receiver implant located beneath the skin (3). The electrical signals then stimulate—in a frequency-specific manner via the electrodes arranged on the electrode carrier (4)—the auditory nerve fibers (5).

Figure 1:

Diagnostic imaging prior to cochlea implantation a) Thin-slice petrous temporal bone computed tomography and b) magnetic resonance imaging

Figure 2: Insertion of the cochlear implant (CI) electrodes

a) Intraoperative visualization of the round window through the mastoid process and b) insertion of the CI electrode array in the scala tympani via the round window