A cochlear implant is a computerized device that provides hearing to people with ‘nerve deafness’ by stimulating the hearing nerve with coded electrical signals. It by passes damaged hair cells of the cochlea (the actual cause of ‘nerve deafness’ in most people). Without a Cochlear Implant, those damaged hair cells can prevent sound from normally reaching the brain, even with the most powerful hearing aids.
Please see the section on history for more information. The U.S. Food and Drug Administration (FDA) first approved cochlear implant devices for adults in 1985 and for children in 1990. More than 40,000 individuals have received cochlear implants worldwide, approximately half children and half adults.
In general, adults who had some degree of useful hearing before becoming severely to profoundly hearing impaired and benefit minimally from hearing aids may qualify as candidates for cochlear implantation. Children as young as 12 months of age with profound hearing loss in both ears and who demonstrate little progress in the development of auditory skills may also be considered candidates. It is very important that the implant recipient (and the family, in the case of a young child) have an understanding of cochlear implants and realistic expectations regarding the use of the device.
Cochlear implant surgery usually takes about 2 hours under general anesthesia. Most patients are discharged the same day as the operation. An incision is made behind the ear and a seat is made in the bone to secure the implant package and to protect it. The mastoid bone is opened, then the cochlea is identified and a tiny opening made in it. The electrode array is placed into the cochlea through that opening, called a cochleostomy. A dressing is placed over the ear for 24 hours. The operation is minimally painful, requiring pain relief only the day of surgery in many instances.
The vast majority of patients receiving cochlear implants use them very successfully. However, recipients may experience a wide range of outcomes. For individuals who lost their hearing after learning to speak, the average implant recipient will be able to have a conversation without lipreading and to use the telephone. However, the perception of sound after implantation may initially seem different from what they remember. After using the cochlear implant for a few months, these individuals often report that they perceive speech to be natural or closer to their memory of familiar sounds. People can recognize familiar speakers but do best in one-on-one conversation in quiet. A predictive factor for implant performance for adults who are deaf is the length of time between the onset of deafness and implantation; those with duration of deafness of less than 20 years tend to experience better outcomes.
While many factors affect outcomes for children, in general, the younger a congenitally deaf (born deaf) child is implanted, the greater is the potential benefit to speech and language development. The type of communication mode and educational setting used with a child also contribute very significantly to the outcome in a child, as does the degree of parental involvement with the rehabilitation process. Children who lost hearing after three or more years of hearing should be implanted soon afterwards and results are routinely excellent.
Many patients are discharged from the hospital the same day as surgery. The surgical site is checked in about 1 week and the patient is allowed to shampoo at that time. The first programming and stimulation occurs at 3 to 4 weeks. It is important to remember that a number of programming sessions are necessary to fine tune the hearing. While sounds will be audible immediately at programming, understanding is likely to be very poor. Rapid improvement in understanding speech and recognizing environmental sounds can be expected over the first 3 months. While many individuals like to listen to music with the cochlear implant, others find that they cannot appreciate music as fully as experienced by normally hearing persons.
Getting a cochlear implant is a lifetime commitment. After surgery, it is necessary to return to the center for a follow-up services, including the fitting of the external components of the implant; activating and programming of the implant and its microphone, speech processor and transmitter; necessary adjustments and reprogramming, and annual check-ups. Children who are implanted often require years of extensive aural rehabilitation whereas adults who have been implanted due to acquired deafness usually do not need formal aural rehabilitation.
The patient may experience discomfort at the wound following surgery; this is usually temporary.
Yes, survival of ganglion cells despite insertional trauma of the cochlea may in part explain the overall good results of reimplantation. Many reimplantations have involved upgrading a single channel to a multichannel device and several authors have commented on the safety of reimplantation of multichannel devices. Hearing outcomes have been reported to be as good as or better than with the initial CI with no significant complication rate. Reimplantation success has potential implications for device upgrade in future..