Cochlear Implant Surgery Benefits and Risks
Cochlear Implant
A cochlear implant is a medical device that can be implanted to restore hearing or to electrically stimulate the cochlear nerve (auditory nerve). Cochlear implants help people with hearing loss regain or improve their ability to hear and understand speech.
They are different from traditional hearing aids, which amplify sounds without significantly improving speech understanding.
When a person has difficulty understanding speech using traditional hearing aids, a cochlear implant should be considered. Once properly adjusted, cochlear implants can significantly improve hearing in adults and help infants and young children hear and learn to speak.
There are two main components to a cochlear implant: an internal component and an external component.
Internal Component
The internal component is surgically implanted. It consists of an electronic package placed under the skin behind the ear. It includes an electrode array that is precisely inserted into the inner ear.
External Component
This is also known as the speech processor and sits on the ear similar to a traditional hearing aid. It transmits sound information to the internal component via a coil that is magnetically positioned.
Types of Cochlear Implants
The types of cochlear implants vary depending on the location of the external sound processor. The external sound processors are one of the pieces of equipment used in cochlear implants. The processor may be:
- Behind the ear.
- Attached to your clothing.
- On your scalp.
How Cochlear Implants Work
To understand how cochlear implants work, it may help to know more about how you hear. Hearing starts with sound traveling from your outer ear and middle ear to your inner ear. Your inner ear contains the cochlea, which supports hearing.
A part of the cochlea contains very small hair cells. These hair cells connect to the auditory nerve. Sound that travels from your outer ear to your inner ear strikes the cochlea, creating an electrical signal that the auditory nerve carries to the temporal lobe in your brain. The temporal lobe perceives the electrical signal as sound, which your brain interprets as speech, music, or other noise.
The external component or speech processor detects speech and other sounds and divides each sound into frequencies. This information is then transmitted to the internal component.
The electrode array inside the inner ear has many individual electrodes spaced along the inner ear. The inner ear nerve fibers for each frequency are located in a predictable pattern. Thus, the implant can stimulate the appropriate nerve fibers for each frequency at an appropriate intensity.
Cochlear implants do not restore normal hearing. However, in the vast majority of cases, hearing, especially speech perception, is significantly improved.
Cochlear implants essentially bypass the structure of your inner ear, creating a new pathway for sounds to reach your brain. The process works as follows:
- You wear a sound processor that captures incoming sounds to your outer ear.
- The sound processor sends signals to a transmitter attached to your scalp with a magnet.
- The transmitter converts the signals into electrical pulses that are sent to electrodes placed in the cochlea.
- The electrodes in the cochlea collect the pulses and send them to the auditory nerves.
- The auditory nerves inform your brain that sounds are incoming.
Who Can Benefit from a Cochlear Implant?
Cochlear implant technology has improved rapidly over the past 10 years. Initially, cochlear implants were only intended for people with nearly complete bilateral hearing loss.
As technology improved, it was found that people with less severe hearing loss could also benefit.
In fact, in many cases, current technology allows for cochlear implantation with good preservation of residual natural hearing in the implanted ear.
With older implants, this was not the case, and the recipient relied entirely on hearing from the cochlear implant. Combining residual natural hearing with implant hearing works very well.
Recently, it was found that cochlear implants can also be beneficial for people with normal hearing in one ear and significant hearing loss in the other. In the past, this was not the case, and to be a candidate for cochlear implantation, one needed bilateral hearing loss.
Nowadays, cochlear implantation may be a viable option for people with moderate to severe unilateral deafness.
In cases of unilateral deafness, a cochlear implant will improve speech perception in noise, sound localization, and often provide a richer auditory experience.
In summary, a cochlear implant may be potential for significant unilateral or bilateral hearing loss. It is usually considered only when traditional hearing aids provide little or no benefit.
Tests Conducted Before Cochlear Implantation
Before the cochlear implantation procedure, the following are performed:
- Hearing tests: An audiologist may perform tests to check the extent of hearing loss, including your ability to hear sound and understand speech with and without hearing aids.
Hearing tests may include auditory brainstem response. This test checks the connections between your inner ear and your brain. Audiologists may use this test to check hearing in children and people who cannot complete pure tone tests. - Vestibular test battery: Your inner ear also manages balance. Vestibular tests are another way to assess the health of your inner ear.
- Imaging tests: Providers may conduct an MRI or CT scan to examine the structure of your inner ear.
What Happens During Cochlear Implant Surgery?
The Procedure
Cochlear implants are performed in a hospital under general anesthesia. A 5 cm incision is made behind the ear. It is performed using a high-powered microscope.
The bone behind the ear is called the mastoid. Using a drill, this area is opened, and space is created in the middle ear from the back, preserving the eardrum and ear canal skin.
Once in the middle ear, the inner ear is carefully identified and opened. The electrode array is gently developed into the inner ear or cochlea. The electronic package is placed in the pocket behind the mastoid and above the ear. The wound is then closed, and a dressing is applied.
The surgery generally takes between one and two hours.
After Surgery
In most cases, a one-day hospital stay after surgery is standard. To administer intravenous antibiotics. It is also not uncommon to be a little off-balance for a few days.
After 24 hours, most people are well enough to go home. Generally, a week at home recovering and resting is advised, after which returning to normal activities should be fine.
Pain Management
Pain is not a major feature in most cases. Usually, paracetamol is sufficient, but Panadeine Forte is also prescribed if needed.
Doctors typically prescribe antibiotics to use for one week.
Telemetry
Either during the operation or a few days after surgery, a telemetry check is conducted. This is a simple process where the cochlea is connected to a computer to check that all electrodes are functioning normally.
Switch-On Process
Two to three weeks after surgery, the switch-on process begins. This process takes several weeks and involves programming the device during several visits to audiologists.
How Long Do Cochlear Implants Last?
This depends on the device. Generally, the internal parts – the transmitter and electrodes – last indefinitely. The external parts – the sound processor and microphone – typically last from five to ten years.
Benefits of Cochlear Implants
There are many benefits of cochlear implants, whether you are someone with complete hearing loss or someone who can still hear with the help of hearing aids but wants to hear better.
People with hearing loss who have cochlear implants can use phones and often enjoy participating in conversations in groups or in noisy places.
Some benefits of cochlear implants include:
- Improved hearing: Cochlear implants can significantly improve hearing and speech perception in people with severe to profound hearing loss who do not benefit from traditional hearing aids.
- Enhanced communication: With cochlear implants, individuals can better communicate with others, engage in conversations, and participate more effectively in social interactions.
- Increased quality of life: Improved hearing can lead to a better quality of life, increased independence, and improved relationships with family and friends.
- Ability to hear a variety of sounds: Cochlear implants can help individuals hear a wider range of sounds, including speech, music, and ambient noises.
- Long-term solution: Cochlear implants are a long-term solution for people with severe hearing loss and can provide continued improvement in hearing abilities over time.
- Adaptability: Cochlear implants allow for customization and adaptation according to the individual’s needs, enabling adjustments to improve hearing performance.
Overall, cochlear implants provide a life-changing solution for individuals with severe hearing loss, enhancing their ability to hear, communicate, and fully participate in daily activities.
Risks or Complications of This Treatment
All surgeries come with risks, including those associated with general anesthesia and infection. The benefits of cochlear implants far outweigh the risks of surgery. Specific risks of cochlear implant surgery include:
- Nerve damage: Rarely, cochlear implant surgery can damage the nerves that run through your middle ear and near the area where the surgeon needs to place the implant. If this happens, you may have taste problems, weakness on the side of your face with the implant, or numbness around your ear.
- Meningitis: Rarely, people with unusual inner ear structures develop meningitis. Providers may recommend vaccination against meningitis to reduce the risk of this condition.
- Cerebrospinal fluid leak: Rarely, people with differently shaped cochleas develop this issue. You have fluid in the tissues surrounding your brain and spinal cord, including the subarachnoid space. The subarachnoid space connects to part of your inner ear. Cochlear implant surgery involves making holes in your inner ear. When this happens, you may develop a cerebrospinal fluid leak.
- Loss of residual hearing: Residual hearing is the hearing you still have despite severe or profound hearing loss. Cochlear implant surgery may damage some of the remaining cochlear hair cells.
- Dizziness: Cochlear implants also affect balance management. The surgery may affect your sense of balance.
- Tinnitus: Cochlear implants can cause tinnitus. Tinnitus is ringing in your ears. Some people experience worse tinnitus after surgery.
Overall, the benefits of cochlear implants outweigh the potential risks and complications, making them a valuable option for individuals with severe hearing loss seeking to improve their hearing and communication abilities.
How long will it take for hearing to improve?
It may take some time before you notice a significant improvement. This is because your brain needs time to get used to receiving information from the auditory nerve. Generally, people’s hearing improves about a month after cochlear implantation. In some cases, it takes three to six months for people to reach their full hearing potential.
Factors affecting the success of cochlear implantation
There are factors that affect the success of cochlear implantation, including:
- Duration of hearing loss: The shorter the duration of hearing loss, the higher the chances of success.
- Age at the time of hearing loss: The age at which the patient experienced hearing loss can affect the outcomes of the surgery.
- Age at the time of surgery: Results are better when the surgery is performed on younger children.
- Number of nerves in the inner ear: A higher number of nerves in the inner ear can make the procedure more effective.
Based on these factors, the medical team can determine the suitability of cochlear implantation and the potential expectations for success.
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