Overview of Cochlear Implants
A cochlear implant is a special tool used to help people who have severe hearing loss. It works by getting around the damaged parts of the ear and stimulating the auditory nerve, which is the nerve that sends sounds to our brains. This device has two parts: one is outside the body and the other is inside. Together, they change sound into electric signals, which are sent to a part of the ear called the cochlea. This allows sounds to reach the auditory nerve, helping the person to hear.
This is an important development in technology, and it improves the hearing and overall quality of life of people with severe hearing loss. For children, these implants help with speech development, allows them to go to regular schools, and reduces the need for other ways of communication. For adults, cochlear implants help with communication, navigating safely, and reduce feelings of being isolated and cognitive decline that come with not treating hearing loss. For older adults, this device may even lessen the risk of dementia and improve their overall quality of life.
But deciding who should get a cochlear implant is a challenge. These devices are relatively new and are still being improved. To choose who is suitable for a cochlear implant, doctors consider their medical history, specific hearing tests, and assessments using imaging technology. The decision often depends on how severe the hearing loss is, the age of the patient, and if they have any physical conditions. However, the guidelines for who can get these devices, particularly for children, are limited. Doctors work as a team to take care of patients who get these implants. To place the implant, surgeons use special techniques and monitor nerves closely during the procedure to avoid damaging important structures like the facial nerve.
Despite their many benefits, individuals who get cochlear implants need continued care after the surgery. This includes adjusting the device and rehabilitation. Teams of health professionals, like audiologists, people who study hearing disorders, and speech-language pathologists, people who help with communication disorders, work together to make sure the patient gets the best care. Advances in technology continue to bring positive changes to cochlear implants, giving new hope to patients with complicated hearing problems. This pushes what we can do for improving hearing.
Anatomy and Physiology of Cochlear Implants
A cochlear implant is a device that helps transmit sound directly to the cochlear nerve in the ear. It transforms noises from the outside world into electrical signals. These signals then stimulate parts of the auditory nerve, which is the nerve responsible for hearing. This is different from a hearing aid, which simply makes sounds louder. A cochlear implant bypasses certain parts of the ear and transmits sound straight to the cochlea, the part of the inner ear responsible for hearing.
The cochlea is a spiral-shaped part of your ear located inside the bone at the side of your skull. On average, it spirals around about 2.5 times. There are three parts to a normal cochlea: the scala tympani, scala media, and scala vestibuli. The organ of Corti is located in the scala media and is the part of the ear responsible for hearing. Typically, sound travels from the outside, through the ear canal, hits the eardrum, and moves along three small bones in your ear (malleus, incus, and stapes). It enters the cochlea via the oval window and travels through the spiral parts. These vibrations stimulate the organ of Corti and trigger the cochlear nerve, allowing you to hear.
A cochlear implant can be placed surgically in one of two ways. One option, known as a cochleostomy, involves creating a small opening and inserting the electrode into the scala tympani. The other method involves inserting the electrode directly into the round window of the cochlea. This may or may not involve additional drilling.
The cochlear nerve is also called the eighth cranial nerve (or vestibulocochlear nerve), which originates from the brainstem and connects directly to the cochlea. This nerve runs alongside the facial nerve (seventh cranial nerve). Knowing these details helps your doctors plan the best approach for cochlear implant surgery.
Why do People Need Cochlear Implants
When a person wants to get a hearing implant, they have to undergo an extensive checkup. This includes taking a detailed medical history that focuses on any ear-related issues. They also need to undergo hearing tests and scans. This checkup helps doctors determine the cause of the hearing loss and if the patient is suitable and eligible to get a hearing implant according to the FDA’s criteria and insurance requirements.
A hearing implant is generally recommended for the following situations:
- Hearing loss that affects the nerves (also known as sensorineural hearing loss) – these individuals may have been born with the loss (prelingual deafness), developed it after learning language (postlingual deafness), or it may occur either in both ears or just one. Infants and young children with certain genetic mutations who experience deafness often see the best results when the implant is performed within the first two years of their life. However, results for teenagers who were born deaf are generally poorer.
- Children above six months old typically benefit the most from the implant.
- Another important factor are radiologic findings which involve using images (like X-rays or MRIs) to diagnose diseases. The absence of conditions which would contraindicate an implant such as:
- Absence of certain parts of the ear on imaging,
- Hardening of a part of the ear,
are favorable for this procedure. An MRI scan helps to check
if fluid-filled cochlear ducts (part of the inner ear) are present to receive the electrode and that the nerves of the cochlea (a part of the ear) are present to take the signal to the brain. - The patient should also be able to reliably follow up with healthcare professionals for check-ups following surgery, and the patient’s health should permit them to handle the general anesthesia and surgery required for the implant
Insurance generally covers the charges for the implant when the patient has hearing loss greater than 40 dB in adults and severe to profound hearing loss (greater than 70 dB) in children aged between 2 to 18 years, who have not benefited from using hearing aids. Infants under 2 years with hearing loss greater than 90 dB are also considered for insurance coverage.
Additional situations also considered for implant include children with a disorder that affects how well they can hear different sounds (known as auditory neuropathy spectrum disorder), individuals with damage to their ear structures, or a certain type of tumor known as vestibular schwannoma. However, the FDA does not currently encourage implanting for single-sided deafness, but that might change in the future.
Some more complicated cases, like those with inflammation of the dura mater (a membrane that envelops the brain and spinal cord) or people with a history of radiation treatment to the nervous system, may also be considered for an implant.
When a Person Should Avoid Cochlear Implants
Some people might not be suitable for cochlear implants, which are devices that help provide a sense of sound to people with severe hearing loss. This could be because they meet the necessary criteria but decide not to have the surgery. If sign language or other forms of communication work better for these individuals, they might not need a cochlear implant and this should be explained to them.
After getting a cochlear implant, a person needs a lot of therapy to help them understand the sounds they’re hearing. The result of this therapy differs; not everyone will gain the same level of hearing ability. During this process, individuals work with hearing and speech specialists known as audiologists and speech-language therapists.
Certain conditions like being born without a cochlear (a part of the inner ear called cochlear aplasia) or without a cranial nerve VIII (which carries sound information from the ear to the brain), mean that the person is not able to get a cochlear implant. However, less severe conditions where the cochlea is not completely developed (a condition like Mondini malformation) don’t stop a person from getting an implant.
People who can’t be put to sleep for surgery (called general anesthesia) can’t get cochlear implants. Similarly, those who have other types of hearing loss (one-sided sensorineural hearing loss, conductive hearing loss, or hearing loss treated effectively with hearing aids), may be better helped with other treatments. These treatments can be recommended by an ear, nose, and throat doctor, called an otolaryngologist.
It’s important to know that cochlear implants can’t treat all types of hearing loss. So, an individual must get a thorough check-up by an otolaryngologist and an audiologist. These checks will identify the type and how severe the hearing loss is. That will help decide the best way to improve hearing.
Equipment used for Cochlear Implants
A cochlear implant is a device made up of parts that sit both inside and outside the ear (see the related image labeled “Cochlear Implant Components”). The parts on the outside are a microphone, a unit that processes sound, and a system that sends signals. On the inside, the implant has a device that receives and stimulates signals and an array of electrodes.
The microphone on the outside picks up sounds and speech around you and sends this information to the sound processing unit. The sound processor turns these sounds into signals that are like electric pulses. These signals are then sent through your skin via radio waves to the internal receiver/stimulator. For this transmission to be successful, the magnet on the outside transmitter needs to be lined up correctly with the magnet on the internal receiver/stimulator.
The receiver/stimulator inside the ear picks up these electric signals and sends them off to the electrode array sitting within the cochlea, the part of your ear responsible for hearing. The electrodes stimulate the hearing nerve, which allows the signals to travel to the hearing area in your brain.
Different companies in the United States make cochlear implants and each one has various options to personalize devices according to an individual’s needs. Each company has particular specifications for their devices and a set of criteria they use to decide if a patient is suitable. For more detailed information about their products, please refer to these companies.
Who is needed to perform Cochlear Implants?
When a person needs a cochlear implant, which is a device that helps people with severe hearing loss or deafness hear, they receive care from an entire team of medical and educational professionals. This team can include doctors, nurses, hearing specialists, speech therapists, school counselors and even people who work for the company that makes the cochlear implant. Each person on the team has a special job, and what they do can change depending on the person’s age, when they lost their hearing, and the type of cochlear implant they receive.
Doctors that specialize in hearing and balance disorders (otolaryngologists, otologists, and neurotologists) play a crucial role in this process. They use their training and experience to figure out if a person should get a cochlear implant. During this process, they use their knowledge about surgery, anatomy of the ear and brain, understanding of potential issues that might arise during the surgery, and their ability to assess hearing. Their goal for people who lost their hearing before learning to speak (prelingually deaf) is for them to develop speech and communicate effectively. For those who lost their hearing after learning to speak (postlingually deaf), the aim is to restore communication to a level that they can function in daily activities.
An audiologist, who is a professional trained in hearing tests, works closely with the person after the cochlear implant is placed. They provide therapy to help the person hear as well as possible with the implant. They can also make adjustments to the device to suit the person’s specific needs. Another crucial part of the team is the speech-language pathologist, a professional trained in helping people with speech sounds, language, and social communication. They provide specialized help to patients whose hearing impairment might have affected their ability to communicate.
These medical professionals take care of you before and after you get a cochlear implant. After the surgery, you’ll have some follow-up appointments to make sure the implant is working properly and is set at the right volume level for you. It’s essential to keep these appointments, as they are crucial to ensuring the success of the cochlear implant.
The frequency of these follow-up visits varies. For adults, they usually occur once a year. For children, however, they need check-ups at least twice a year. If the medical team has any concerns about a child’s listening skills or if the device needs adjustments, they might schedule more frequent visits.
Preparing for Cochlear Implants
Before starting the preparation for a cochlear implant, which is a device that can help people who are deaf or hard of hearing, doctors need to make sure that the hearing loss isn’t caused by any other problems. These could include a ruptured eardrum, a middle ear infection, or a blocked ear canal. If these issues are present, they need to be treated first. The doctors also make sure that the patient’s loss of hearing can’t be improved with hearing aids.
To do this, doctors usually perform a few different tests. One is called pure tone audiometry, which measures how soft sounds can be before they’re no longer heard. Another test is called tympanometry – it checks how the ear reacts to changes in pressure. For children who might not be able to understand or respond to the tests, or in cases where it’s not clear if the hearing loss is real, an auditory brainstem response test can be used. This test looks at the nerve paths from the ear to the brain by playing sounds and measuring electrical activity in the brain.
Once doctors are sure that the hearing loss is real and can’t be treated with hearing aids, they start planning for the cochlear implant procedure. This might mean taking scans of the ear and brain areas, to get a clearer picture of what’s going on inside. These scans can also show the condition of the main auditory nerve and provide information needed for the implant surgery.
Before surgery, it’s important that patients understand all their options. This includes how the cochlear implant works, what the risks and benefits are, and any other treatment options.
The time between deciding to get a cochlear implant and the actual surgery can vary. For babies, hearing aids are usually tried first for about six months. If the baby still can’t hear well enough with them, a cochlear implant might be considered. This waiting period is usually shorter in adults.
In the US, not all health insurance plans cover cochlear implants for both ears, which can make deciding which ear to operate on difficult. Doctors usually consider how long a patient has been deaf, how severe the hearing loss is in each ear, and which hand the patient uses more. They also look at which side is best for surgery and has no abnormalities. Sometimes, it doesn’t matter much which ear gets the implant; either one can usually provide good results.
How is Cochlear Implants performed
Having cochlear implant surgery means you’ll be in the hospital or a specialized surgical center’s operating room, under the careful watch of a medical team. This team could include nurses, anesthesiologists (doctors that will put you to sleep during the surgery) and the otolaryngology team (ear, nose, and throat doctors). They will explain their roles in the operation and make sure all your questions are answered. They also need your permission called consent before we can start the process in the operating room.
The surgery usually takes between 1 to 2 hours. Most people are ready to leave the hospital the same day or the next morning. You likely won’t feel much pain and can usually go back to your normal routine within 2 to 3 days. Some might feel a little dizzy for a few weeks after. The hearing device (cochlear implant) won’t be turned on until the surgery cut has fully healed, which usually takes about 4 weeks.
The surgery is done in a super clean environment, and before starting, the medical team does a final check on the patient’s identity and the exact place where the surgery will be performed. You will be put to sleep using what’s called general anesthesia, with a tube to help you breathe. Often the facial nerve is monitored during the operation to avoid any injuries. A standard mastoidectomy procedure, involves using a special drill to make space on the bone behind your ear based on what your doctor prefers. This space will be where the electrode for the cochlear implant will be placed.
Next, it is crucial to get a clear view of a part of your inner ear called the cochlea’s round window. The surgeon will insert the cochlear implant into this area. If necessary, the surgeon may make another opening called a cochleostomy. The cochlear implant device, which looks like a tiny computer, is then secured beneath the skin or in a small hole made in the bone behind your ear. The electrode is inserted through the opening in the cochlea based on the guidance provided by the manufacturer of the device. Modern cochlear implants have between 12 and 22 electrodes to stimulate the hearing nerve.
An audiologist (a hearing specialist) or a representative from the device company should be there during the surgery to make sure the device is positioned properly within the cochlea. An x-ray is taken to double-check its placement before the skin is closed. The surgery cut is then closed in layers, to make sure it heals nicely and looks good. Finally, a temporary dressing is used to apply pressure to the area where the surgery was performed for the first 24 to 48 hours.
Possible Complications of Cochlear Implants
Cochlear implantation is a procedure completed by an expert ear, nose, and throat doctor (otolaryngologist). The purpose of this surgery is to improve hearing. It is generally a safe and reliable procedure, but like all surgeries, it can have complications during and after the operation. However, these complications are rare given the procedure is performed by a highly experienced physician.
Some possible complications during or soon after surgery could include bleeding, which can sometimes be life-threatening, a buildup of blood or fluid (seroma or hematoma) around where the surgery took place, a stroke, an infection, increased risk of meningitis, discomfort or pain, and skin breaking down over the area of the magnet. The device inserted during surgery could also fail, including broken parts of the device, the device not working, or it not being placed correctly in the cochlea (part of the inner ear). There might also be injury to the skull base, brain trauma, leaks of cerebrospinal fluid (fluid found in your brain and spine), facial nerve paralysis or weakness, loss of taste on the side of the tongue where the surgery happened, dizziness or a spinning sensation (vertigo), and loss of residual hearing or complete deafness in some people.
In rare cases, this procedure can cause death, but this is very unusual.
There are also possible long-term complications, although these are not as clearly understood. These might include skin infections, mastoiditis (an infection of a part of the skull behind the ear), issues with the electrode of the device, the body rejecting the device, recurring ear infections, the device moving from its original placement, a skin growth in the ear (cholesteatoma), a hole in the eardrum, chronic headaches, and leaks of cerebrospinal fluid from the ear.
What Else Should I Know About Cochlear Implants?
In the medical world, making sure the patient is comfortable and informed about their treatment is essential. To make this happen, a team of medical professionals like doctors, nurses, and health specialists, all need to work together smoothly. This collaboration ensures the patient’s journey from the diagnosis of the problem to the treatment is smooth-sailing. For example, if a person is diagnosed with a hearing issue that needs a cochlear implant surgery (a surgery to implant a device that helps deaf or hard-of-hearing people), everyone from the surgeon doing the surgery, the nurses assisting, to the audiologist (hearing specialist) who will help the patient adapt to the device after the surgery, needs to work in harmony.
In order to catch hearing problems as soon as possible, it’s important to get your hearing tested regularly. For newborns, there are special programs in 43 states called Early Hearing Detection and Intervention (EHDI). These programs aim to diagnose and treat hearing loss as early as possible, ensuring the best possible outcome for your child. If a baby or child is found to have hearing issues, they might also see a geneticist, who can figure out if the problem is due to a genetic condition and if there are any related health problems that need attention.
Cochlear implants are lifesavers for many people. Not only do they bring back the sense of hearing, but they also have an impact on the overall quality of life. People of different ages, from infants to the elderly, can benefit differently from these implants. For older adults with severe hearing loss, they often develop dementia earlier than those without hearing loss. Hearing loss can lead to social isolation and a decline in the quality of life, which contributes to cognitive decline. In such cases, hearing aids can help slow down dementia or even reverse mild cognitive impairment. When hearing aids are not enough, cochlear implants can also be considered.
Finding out about hearing loss early in adults can lead to timely treatment, which helps the person get back to their normal life, like going back to work, and also reduces the risk of accidents due to hearing impairment.
For children who are born deaf, these implants greatly help them in developing speech, which may reduce their need to learn other forms of communication, such as sign language. It is important to respect the choices of those who choose or require alternative communication methods. These implants, while at first might seem expensive, actually lead to overall savings by helping the child attain educational independence. Goals are set to provide a bilateral (both ears) cochlear implant to children as it improves their learning outcomes and provides a natural listening experience.
Cochlear implants greatly improve speech development, allow people who lost their hearing after learning languages to regain their speech, and obviously restore hearing. They have a multitude of benefits such as preventing accidents by making navigation safe, enriching the quality of life such as enjoying music and facilitating integration into normal classroom environments for children, leading to better pay later in life. Each implant can be customized according to the needs of each individual. There is a dedicated team of professionals who make sure the operation is successful and the device works perfectly for each patient. This team also takes care of any issues that arise during the recovery process, ensuring that the patients get the maximum benefit from the device.
