Cochlear Implant

The cochlea is part of the inner ear and is involved in hearing. It has a spiral shape, resembling a snail (the name 'cochlea' is derived from the Ancient Greek word 'kōhlias', meaning 'spiral, snail shell').

Sound waves enter our ear canal causing the eardrum and the three bones in the middle ear (malleus, incus, and stapes) to vibrate. These vibrations move through the perilymph, a watery fluid in the cochlea. The hair cells in the cochlea perceive this motion and convert it into electrical signals that are transmitted to our nerve cells. Our brain receives these impulses and interprets them as sounds.

What are Cochlear Implants?

The cochlea converts sound from outside your body into neural signals that the brain can 'hear'. The implants essentially act as substitutes for the damaged cochlea. They generally come in two sections: an external and an internal component. The external part rests behind the ear, while the internal part must be implanted surgically.

Implants tend to include several key elements, including a microphone, processing unit, a transmitter, and electrodes to transfer electronic signals to your neural system.

How do Cochlear Implants work?

Cochlear implants are not just another form of hearing aid. Instead of simply amplifying sounds, as hearing aids do, implants directly act upon your auditory nerve, forming an extension to your auditory system.

The fitting process can take up to one year. Here’s a breakdown of what the process typically looks like:

1. Hearing Evaluation The first step is a hearing evaluation to find out whether you qualify for a cochlear implant. This typically includes an audiological evaluation and a speech perception evaluation. During an audiological evaluation, an audiogram will determine the type and degree of your healing loss. A speech perception evaluation determines how well you perceive speech sounds. This test includes a perception assessment of both single words and more complex sentences in different noise conditions.

2. Internal Implant Placement If you qualify for a cochlear implant, you will be booked in for the first surgery, where the internal implant is introduced. The surgery is performed under general anesthesia. The surgeon makes a small incision behind your ear and inserts the cochlear implant under the skin and into the cochlea. An electronic device (the 'receiver') is then placed behind the ear. The incision is then closed.

3. Placement of External Parts The incision now has to heal, which takes 4-6 weeks. You are still not able to hear at this stage. The next step is to fit the external part of the implant, which includes a microphone and a speech processor. If you have long hair, the surgeon might shave a bit of hair off, but the shaven area will be hardly noticeable. The external and internal parts of the cochlear implant are connected via a magnet.

4. Sound Calibration At this appointment, you will work with audiologists to understand different hearing levels and calibrate the device. This generally isn't achieved in one visit, and as many as 5-6 subsequent appointments may be needed.

5. Recovery and Adjustment Within one year of fitting, the process is complete, and you should experience a marked improvement in your hearing. Speech therapy might be needed - especially for children - which may last several years.

Are There Different Types of Cochlear Implants?

There are two major types of implant available: full cochlear versions and hybrid versions that incorporate some elements of conventional hearing aids.

Standard cochlear implants only include the elements discussed above: microphones, processors, transmitters and electrodes. They are mainly intended to stimulate low to mid-frequency sounds and usually have the side effect of destroying residual hearing.

Hybrid implants are more likely to be prescribed if a you suffer from high-frequency hearing loss, making you unable to process sounds such as birdsong or certain consonants in everyday speech. They tend to preserve residual hearing at lower frequencies.

Auditory brainstem implants (ABIs) are another option in some cases. These implants are suitable for patients with damaged auditory nerves, transmitting signals directly to the brain.

What Should I Expect?

When you undergo a cochlear implantation procedure, you can expect a period of 4-6 weeks in between hospital visits. In that time, patients tend to reduce their workload and activities as the healing process takes place. Some mild pain around the incision area is normal and usually lasts for a week at most, although swelling behind the ear can last for the full 6 weeks.

On the day that the implant is activated, audiologists will need to calibrate the device, so you can expect a relatively long appointment while the implant is set up. During this time, noises will be played into your ear as specialists create an auditory 'map'. This map then becomes the template for the implant's processor, governing how it transmits signals to the auditory nerve.

After the initial fitting, most patients need to return a few times for further assessments and calibrations, with gaps of one month between appointments being common.

However, as soon as the implant is activated, you can expect significant and often life-changing improvements to your hearing. Sounds may feel strange at first, but hearing tends to become normalised with further fittings. You may also be asked to keep a record of how you experience high and low-frequency sounds. Every little piece of information can help audiologists, so diligently keeping a hearing journal is recommended.

I’m Looking for a Cochlear Implant. What’s the Next Step?

The first step is determining whether a cochlear implant is right for you. You should visit an ENT physician or an audiologist who will make a first assessment. Choosing the right ENT specialist is really important. This is why you should select a physician who is board-certified and who has solid practicing experience, particularly with cochlear implant patients.

Your doctor will then refer you to a cochlear implant centre. Make sure you select a centre that meets your needs. For instance, if you are looking for the right centre for your child, find one that has proven experience in treating children. Moreover, as speech therapy and language development are part of the recovery process, especially for children, you may want to check if the centre offers these services or can connect you with reputable professionals to support you during follow-up care.