A cochlear implant is an electronic device that provides sound perception to patients with severe to profound sensorineural (nerve) hearing loss in both ears. The principle benefits of a cochlear implant are:
- Aid in lipreading
- Perception of environmental sounds
- Aid in monitoring one's own voice.
In some patients, the implant may also allow understanding of speech without lipreading. Common to all cochlear implants is a bundle of fine wires, the electrode array, that is surgically implanted into the hearing portion of the inner ear -the cochlea. The external device includes the sound processor, a cable and a microphone that is housed in a head piece. The sound processor analyzes incoming sounds and converts those sounds into patterns of electrical current. The current is carried along the cable and delivered to the electrode array by radio wave transmission to an antenna and receiver implanted under the skin with the electrodes. The current from the electrode array then stimulates the fibers of the auditory nerve with the electric current and produces the perception of sound. The sound processor is individually programmed to best meet the needs of each patient.
Who benefits from a cochlear implant?
Cochlear implants can help patients with severe to profound sensorineural hearing loss in both ears who cannot benefit adequately from the use of hearing aids. Normally, when sound vibrations enter the ear canal, they are collected by the ear drum, conducted through the middle ear by three small bones (ossicles), and converted to pressure waves in the fluid of the cochlea (the snail shaped structure of the inner ear). These pressure waves travel through the inner ear fluid, bending the fibers at the top of the hair cells that convert the pressure waves to electrical signals. These signals are then carried by the auditory nerve to the brain.
Sensorineural hearing loss is defined as any abnormality of the inner ear that prevents the conversion of the pressure waves to electrical signals on the auditory nerve. In many cases of sensorineural hearing loss, the problem is due to hair cell damage. However, a significant number of auditory nerve fibers are still functional. Since the cochlear implant sends an electrical signal that stimulates the nerve fibers, directly bypassing the inner ear, these patients may perceive sound with the implant despite the damage in the inner ear.
If you have specific questions which are not answered here, please feel free to call the Infirmary's General Ear, Nose, and Throat Service at 617-573-4101 or schedule an appointment for an examination by an Infirmary otolaryngologist.