Your ear consists of three parts: the outer ear, the middle ear, and the inner ear. The inner ear contains the cochlea, which is a small, spiral-shaped structure filled with fluid. When sound waves travel to the inner ear and cause it to vibrate, the movement of the fluid causes hair cells (which line the cochlea) to produce electrical impulses. These impulses are carried to the brain via the auditory nerve, where they are interpreted as sound.
Most hearing loss occurs due to defective hair cells. Sound waves will travel through the ear as usual, but the hair cells fail to produce electrical impulses – meaning that no impulses are sent to the brain. People with mild hearing loss often benefit from hearing aids, which amplify sound waves so that the hair cells can produce impulses again.
People who are deaf, who have profound hearing loss, or who have not had success with hearing aids may be recommended a cochlear implant, which is an electronic device that is surgically implanted into the ear.
There are two parts to a cochlear implant: external and internal. The external part of the cochlear implant is small disc-shaped device worn on the head. Its main purpose is to pick up sounds and convert them into electrical signals – this is why you may also hear it referred to as a ‘sound processor’.
The internal part of the implant, located under the scalp, receives these electrical signals via an antenna. It then converts these signals into electrical currents, which is passed down an electrode in the cochlea to stimulate the auditory nerve. The auditory nerve sends signals to the brain, which are interpreted as sound.
Cochlear implants are best suited for people who are deaf or have severe hearing loss due to inner ear damage. People who have not had success with hearing aids may also wish to consider a cochlear implant.
In children with severe hearing loss, bilateral implants are recommended to better support their hearing and speech development. Adults are not routinely offered bilateral implants, but they can be very beneficial – so many patients will opt for private care to access them.
Patients with single-sided deafness (unilateral hearing loss) can also benefit from a cochlear implant.
Before undergoing any surgery, you will have an assessment to determine your level of hearing loss and suitability for treatment. This includes hearing tests (audiometry), speech tests, balance tests, and videonystagmography (a test that evaluates your eye movements).
Adult patients will usually have a cochlear implant fitted into just one ear (unilateral). If hearing worsens with age, then a second device can be implanted into the remaining ear (bilateral). Children with severe hearing loss will often have bilateral implants to better support their hearing and speech development.
You will be placed under general anaesthetic for the procedure. Typically, the operation takes around two hours.
Your surgeon will open a small hole behind your ear, in a portion of the skull known as the mastoid. This hole allows them to reach the cochlea so that the electrodes can be placed. After placing the electrodes, an internal processor is installed between the muscle and bone behind the ear, before the incision is closed with dissolvable stitches.
Once you have healed from your procedure, you will start to attend appointments with an audiologist so that they can begin a process called ‘mapping’. Mapping is when an audiologist programs your implant by adjusting the electrodes to optimise the way in which you receive sounds.
