Cochlear Implants: Fundamentals, Facts, and Findings

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Introduction

Cochlear implantation is a relatively new option for treating children with severe hearing impairment. Because of Universal Newborn Hearing Screening (UNHS; National Institutes of Health, 1993) and earlier implantation (12 months of age), deaf infants and toddlers can now "hear" more effectively during the most sensitive stages of language development. Cochlear implants (CIs) are electronic devices, containing a current source and electrode array, that when implanted into the cochlea, provide electrical stimulation to functioning auditory nerve fibers (Wilson, 2000). CIs increase hearing sensitivity in persons who would benefit minimally from hearing aids. These surgically implanted devices circumvent dysfunctional receptor cells in the cochlea and provide direct electrical stimulation to the eighth cranial nerve or auditory nerve (Ertmer, 2005).

Traditionally, hearing aids (HAs) have served many persons with mild, moderate, and even severe hearing losses adequately. However, HAs usually do not provide access to speech at conversation levels for those persons with profound losses (over 90 dB hearing levels). Hearing aids may be analog or digital and amplify the acoustic signal. Because CIs produce an electrical signal that bypasses damaged receptor cells to stimulate the auditory nerve directly, they facilitate greater sensitivity across a wide range of frequencies (approximately from 250 to 7000 Hz). Typically, persons with profound sensorineural hearing loss do not hear high frequency sounds, including the higher frequency sounds within the speech range (approximately 300 to 3500 Hz).

Today's CIs, when implanted early, provide an opportunity for users to lead full, productive lives within the hearing world, should they choose to do so. For those adolescents and adults whose hearing loss was acquired after development of speech and language skills (i.e., post-lingual) may also profit from CIs because the structure and form of speech, phonology, and language have already been experienced and embedded in the auditory cortex. This article provides fundamental informationincluding new technology, candidacy issues, communication options, assessment options, intervention strategies, and a review of research concerning cochlear implants.

About Cochlear Implants

Cochlear implants became commercially available in 1972 when Dr. William F. House and colleagues produced the first single-channel wearable implant for daily use. The first adult recipient indicated improved hearing for a variety of sounds (Ertmer, 2005). Contem