Cochlear Implants, Osseointegrated Bone Conduction Hearing Devices, and Other Implantable Devices

The cochlear implant is an electronic prosthesis that stimulates cells of the auditory spiral ganglion to provide a sense of sound to persons with hearing impairment. Although many thousands of patients have now been implanted, these represent only a fraction of the hearing-impaired individuals worldwide who would potentially benefit from implantation but do not have access to one because of failure to recognize appropriate individuals or socioeconomic reasons. Although the individual response of a patient to a cochlear implant is highly variable and depends on a number of physical and psychosocial factors, the trend toward improved performance with increasingly sophisticated electrodes and programming strategies has caused the indications for cochlear implantation to be dramatically expanded (Table 15–1). Originally, cochlear implants were thought of primarily as an aid to some sound perception for the profoundly hearing impaired. Now, it is common to find implanted patients have better unaided hearing levels and perform at levels that exceed those obtained by conventionally aided patients. Through the 1970s, devices were implanted only in adults with profound hearing loss under the FDA guidelines of the time. In 1980, the age limit was lowered to 2, and later declined to 18 months. Currently the limit for implantation is 12 months of age. Over time, the adult indications have been broadened to include patients with severe hearing