Cochlea is a coiled tube, much like a snail and makes part of the inner ear. The function of the cochlea is to transmit sound impulses to the brain for analysis. There are thousands of slender “hair cells” within the cochlea and the function of each such cell is to pick up a different sound and relay it to the brain.
If these hair cells are somehow damaged, the ability of the ear to pick up sounds is greatly diminished. Cochlear damage results in sensorineural hearing loss or SNHL. Causes of SNHL can be exposure to loud noises for extended times, certain powerful antibiotics, certain diseases and age.
Noise-induced hearing loss (NIHL) is the most common cause of cochlear damage. In this case, loud noises can damage the sensitive and fragile hair cells of the cochlea. Unlike other “hair” on the surface of the human body, these hair cells do not grow back and once they are damaged, they are lost. And once these hair cells are lost, the person loses hearing ability corresponding to the amount of hair cells lost.
For such patients, electronic hearing aids are of little or no use. Their only chances of getting their hearing back is through a cochlear implant.A cochlear implant is essentially an electronic device that substitutes the function of the cochlea that was damaged. It bypasses the damaged hair cells and provides sound signals directly to the brain.
A small sound processor, worn behind the ears, collects external sounds and converts them into a digital code. It is battery-operated. This digitally coded sound is then passed on to the implant within the ear.
The cochlear implant then converts the digitally coded sound into electrical impulses. These impulses are then sent to the electrode array placed in the cochlea. These electrodes stimulate the hearing nerves of the cochlea, which then passes the impulses to the brain where the impulses are interpreted as sound.
People with severe to profound SNHL can greatly benefit from cochlear implants. Hearing aids merely amplify the sound. But in case of cochlear damage, the main equipment (the hair cells) that receives the sound itself is damaged.Thus the need for a cochlear implant.
Although the quality of sound is different from natural sound, technological advancements have played an important role in making the “artificial” sound more natural.Newer, better devices are allowing recipients to enjoy hearing better quality sound, music and even use the implant in water, while swimming.
The prime candidate for a cochlear implant is the one who has severe to profound SNHL in both hears and has a functioning auditory nerve. The candidate should also be willing to participate in a comprehensive post-surgery rehabilitation,which includes sessions with a speech language pathologist and auditory verbal therapist.
Hearing loss may occur due to many reasons. These could be with the functioning of any part of the ear or it may be due to problems with the region of the brain concerned with analyzing sound.