The decision to go for a cochlear implant is not made overnight. Numerous questions arise over weeks. Explore Life has compiled the most important ones.
7 questions about CIs answered
1. How does hearing work?
The ear can be divided into three sections: the outer ear, the middle ear and the inner ear. Every sound causes vibrations in the air, known as sound waves. These sound waves reach the outer ear first, which works in a similar way to a funnel, concentrating the sound waves. At the intersection between the outer and middle ear lies the eardrum, which vibrates with the sound waves. The ossicles in the middle ear, known as the malleus, incus and stapes – or hammer, anvil and stirrup – transmit the vibrations to the inner ear and into the cochlea, a spiral-shaped tube. The cochlea is filled with a liquid and has sensory hair cells. Any movement of the liquid activates these sensory hair cells, which then trigger neural signals that are received by the auditory nerve. The auditory nerve then sends the sound information to the brain, where it is finally interpreted.
2. What is a cochlear implant?
The cochlear implant (CI) replaces those parts of the inner ear that don’t work. In the places where the sensory hair cells are missing, the device directly stimulates the nerve fibres inside the cochlea, using an electrical impulse.
A CI system consists of two parts: the implant and the external audio or speech processor. The implant’s electrode is introduced into the cochlea and the body of the implant is placed under the skin behind the ear. The speech processor on the outside of the head is held above the implant by magnets. The processor receives sound signals and electronically sends them to the implant.
The electrode, consisting of various flexible electrode arrays, is inserted into the cochlea, where it stimulates the auditory nerve. The auditory nerve then sends sound information to the brain. The electrode arrays are covered by medicinal silicone, and ceramics and titanium are used for the case. All the materials are biocompatible, which means that the body can tolerate them very well.
3. What is the difference between a CI and a hearing aid?
Hearing aids and cochlear implants are basically both suitable to treat hearing loss. However, their technology and their fields of applications differ significantly.
Hearing aids amplify sounds and reduce ambient noise for people with mild to moderate hearing loss. Cochlear implants, on the contrary, are designed for people with severe-to-profound sensorineural hearing loss where the hair cells in the inner ear are damaged and thus can't detect sounds properly. A cochlear implant bypasses these damaged hair cells and sends electric signals to the brain, where they are interpreted as sound.
The amplification of sounds through hearing aids in the case of non-functioning parts of the ear is not enough. However, hearing implants can help restore and cover the full range of hearing.
4. Who needs a cochlear implant?
A CI is a potential solution for people with severe to profound sensorineural, or labyrinthine, hearing loss. In each case, a team of ear, nose and throat specialists and audiologists assess whether a CI might be suitable.
One precondition for an implant is good health. Otherwise, it doesn’t matter from a medical point of view if the patient is a one-year-old baby or 95. Another important factor is how long the individual has been hearing-impaired. The general rule is that the sooner someone is supplied with a CI, the better the outcome will be.
In children, a CI can only help if the brain is able to process the incoming signals. For this, the corresponding brain structures have to have formed during early development. This means that children benefit most from an early implantation between the ages of six months to two years but that doesn’t totally rule out implants at a later date.
5. How much does a cochlear implant cost?
The total cost of cochlear implantation depends heavily on your country of origin, health- and insurance system. However, the total cost including operation and rehabilitation is comparable to a mid-size car. In the UK, the costs for the cochlear implant, pre-operative assessments, surgery as well as follow-up treatment are covered by the National Health Service. Private insurers may cover all or parts of the costs of cochlear implant treatment.
Generally, it is recommended to seek for further information regarding cost absorption at your local hearing specialist and or insurance company.
6. How does the world sound with a cochlear implant?
Immediately after an implantation has been carried out, speech sounds unnatural, tinny and monotonous, and it is difficult to distinguish between individual voices, which is why auditory training is necessary after the operation. After an adaptation phase and several adjustments of the audio processor by the audiologist, hearing usually improves distinctly.
Most long-term CI users report that eventually speech sounds barely differ from ‘normal’, while some no longer notice any difference at all. Music presents a different challenge though, as the brain has to learn to differentiate between single sounds and tones. This usually takes longer than the adjustment to speech.
7. Why is auditory training essential?
While glasses correct a sight defect immediately, it’s not as simple with a CI. Carrying a CI alone doesn’t guarantee that you’ll understand speech. Hearing has to be practised first. This is done by specific auditory training, which starts after the audio processor is adjusted a few weeks after the operation. During the training, CI users learn to recognise single words and sounds, even with ambient noise, and they use the telephone and practice listening to music.
The length of each person’s rehabilitation depends on several factors, including their motivation and commitment to training. In adults, the average rehabilitation takes six to 12 months; in infants and toddlers it takes several years.
It’s important to approach an implantation with realistic expectations. Hearing implants improve hearing but cannot completely compensate for hearing loss, especially in complex situations, for instance when there’s loud background noise.