A cochlear implant (CI) is a surgically implanted neuroprosthetic device to provide a person with moderate to profound sensorineural hearing loss a modified sense of sound. CI bypasses the normal acoustic hearing process to replace it with electric signals which directly stimulate the auditory nerve. A person with a cochlear implant receiving intensive auditory training may learn to interpret those signals as sound and speech. However, one third of deaf children do not develop language if they are on a CI program alone and have no sign language input.
The implant has two main components. The outside component is generally worn behind the ear, but could also be attached to clothing, for example, in young children. This component, the sound processor, contains microphones, electronics that include Digital Signal Processor chips, battery, and a coil which transmits a signal to the implant across the skin. The inside component, the actual implant, has a coil to receive signals, electronics, and an array of electrodes which is placed into the cochlea, which stimulate the cochlear nerve.
The surgical procedure is performed under general anesthesia. Surgical risks are minimal but can include tinnitus, facial nerve bruising and dizziness.
From the early days of implants in the 1970s and the 1980s, speech perception via an implant has steadily increased. Many users of modern implants gain reasonable to good hearing and speech perception skills post-implantation, especially when combined with lipreading. However, for pre-lingually Deaf children the risk of not acquiring spoken language even with an implant may be as high as 30% One of the challenges that remain with these implants is that hearing and speech understanding skills after implantation show a wide range of variation across individual implant users. Factors such as duration and cause of hearing loss, how the implant is situated in the cochlea, the overall health of the cochlear nerve, but also individual capabilities of re-learning are considered to contribute to this variation, yet no certain predictive factors are known.