Cochlear Implants: Facts, Benefits and Risks
- Publish Date: 2012/03/28 - (Rev. 2017/02/27)
- Author: Thomas C. Weiss
- Contact : Disabled World
Outline: Benefits and information regarding cochlear implants an implanted hearing device designed to produce hearing sensations useful to people with profound nerve deafness.
A cochlear implant is a type of implanted electronic hearing device, one that is designed to produce hearing sensations that are useful to a person who experiences profound nerve deafness.
A cochlear (koe-klee-er) implant is defined as an electronic medical device that replaces the function of the damaged inner ear. Unlike hearing aids, which make sounds louder, cochlear implants do the work of damaged parts of the inner ear (cochlea) to send sound signals to the brain. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. For manufacturers to sell cochlear implants in the United States, they must first show the FDA that their implants are safe and effective.
The device works by electrically stimulating nerves inside the person's inner ear. Cochlear implants usually include two main components. The first is an externally worn microphone, sound processor, and transmitter system. The second is an implanted receiver and electrode system; something that contains electronic circuits that receive signals from the external system, and send electrical currents to the person's inner ear.
Cochlear implant devices that are currently available have a magnet that holds the external system in place next to the implanted internal system. The external system can be worn behind the person's ear, or its parts can be placed in a person's pocket, in a belt pouch, or in a harness. Cochlear implants are designed to help adults and children who are profoundly deaf who receive little or no benefit from using hearing aids. Even people who experience severe or profound nerve deafness might be able to benefit from using cochlear implants.
A number of different things determine the successful use of cochlear implant use by a person. Among these are:
- The age of the person when they received the cochlear implant: People who are younger as a group do better than people who are older and have been deaf for longer periods of time.
- The age of the person when they became deaf: The person's age when they became deaf may determine whether they could speak or not.
- The health and structure of the person's cochlea: The number of nerve cells the person has is important and has bearing on the successful use of a cochlear implant.
- The length of time a person has been deaf: As a population, people who have been deaf for a short period of time do better with cochlear implants than people who have been deaf for long periods of time.
- Implantation variables: These variables include the depth and type of implanted electrode and signal processing technique.
Additional factors bearing on the successful use of a cochlear implant include the following:
- How rapidly the person learns to use the implant
- The communicativeness and intelligence of the person
- The length of time the person has used the implantation
- The quality and dedication of the person's learning support structure
How Cochlear Implants Work
Fig 1. Diagram of a cochlear implant
A cochlear implant receives sound from the person's outside environment, processes the sound, and then sends small electric currents near the person's auditory nerve. The electric currents activate the person's nerve, sending a signal to their brain. The person's brain learns to recognize the signal and the person experiences the signal as, 'hearing.' The cochlear implant simulates hearing to a degree, with sound creating an electric current that stimulates the person's auditory nerve. The first commercially available types of implant devices were approved by the FDA in the 1980's, although research regarding them started all the way back in the 1950's.
The Reason for Different Types of Implants:
Current thought in the medical realm is that a person's inner ear responds to sound in at least two separate ways. According to the, 'place,' theory - cochlea respond more readily to a simple tone at one place along its length. Another theory suggests a person's ear responds to the timing of the sounds presented to it.
Researchers following the place theory devised implants that separate sound into groups. For example; the devices they created sent sounds with lower pitches to the area of a person's cochlea where it seemed to respond more readily to lower pitches. The researchers sent higher pitches to areas that respond more readily to high pitches. Following the place theory, the researchers used a number of channels and electrodes spaced out inside a person's cochlea. Due to timing theories, researchers also created implants that made sound signals into pulses in order to find out if a person's cochlea would respond more readily to different kinds of pulses.
The majority of modern cochlear implants are versatile and are somewhat capable of being adjusted to respond to sound in a number of ways. Audiologists attempt a variety of adjustments to find out what works best for each person.
The Risks of Cochlear Implant Surgery
The risks of pursuing a cochlear implantation surgical procedure involve a number of different things. The surgical procedure itself, as with any surgical procedure, present risks to the person. What follows are some of the risks involved.
- Injury to the person's facial nerve:
A person's facial nerve goes through their middle ear to provide movement to the muscles of their face. The nerve lies close to where a surgeon needs to place the implant and might be injured during surgery. An injury to the nerve may cause a temporary or permanent weakening or even full paralysis on the same side of a person's face as the implant.
- General Anesthesia:
General anesthesia is drug-induced sleep and involves the use of drugs such as anesthetic gases and injected drugs. The drugs used might affect people differently, although for most people the risk of using these drugs is very low. Some people with certain medical conditions; however, are at higher risk where the use of these drugs is concerned.
- Cerebrospinal fluid leakage:
A person's brain is surrounded by fluid that might leak from a hole created in their inner ear, or from somewhere else, through a hole in the covering of their brain as a result of the surgery.
Meningitis is a form of infection involving the lining surface of a person's brain. People who experience a differently formed inner ear structure seem to also experience a higher risk of meningitis.
- Taste disturbances:
The nerve that provides a person with taste sensations to their tongue also goes through their middle ear and may be injured during the surgical procedure.
- Perilymph fluid leak:
A person's inner ear or cochlear contain fluid; the fluid might leak through the hole that was created in order to place the implant.
- Reparative granuloma:
Reparative granuloma is the result of localized inflammation, and can happen if a person's body rejects the implant itself.
Additional surgical risks include:
- Vertigo or dizziness
- A skin wound infection
- Numbness in the area around the person's ear
- Blood or fluid collection at the surgery location
- Unforeseen complications due to the surgical procedure
Difficulties with the Everyday Use of Cochlear Implants
People with a cochlear implant might experience various difficulties with their implant. A long list of potential issues have been noted in relation to the use of a cochlear implant, involving hearing, language, medical issues, the implant itself, technology, life activities, and more. What follows is a listing of the issues people have experienced with the everyday use of cochlear implants.
Inability to pursue certain medical examinations and forms of treatments, for example; MRI scans. MRI scans have become a routine diagnostic method related to the early detection of medical problems; however, even being close to an MRI imaging unit is dangerous for a person with a cochlear implant because it has the potential to dislodge their implant or demagnetize its internal magnet.
The FDA has approved some types of implants; however, that are safe in some types of MRI studies under controlled conditions. Additional medical treatments that are dangerous for persons with cochlear implants include ionic radiation therapy, electroconvulsive therapy, electrical surgery, and neuro-stimulation.
A person with a cochlear implant might have to pursue changes in their lifestyle for a number of reasons, particularly in relation to electronics. A person's implant may:
- Set off theft detection systems
- Set of metal detectors or other security systems
- Be affected by cell phones or radio transmitters
- Interact in unpredictable ways with computer systems
- Have to be turned off during airplane take offs and landings
Hearing sounds differently:
Sound impressions from an implant differ from average hearing according to statements by people who could hear prior to becoming deaf. At first, people describe the sounds they hear as being, 'technical,' 'mechanical,' or, 'synthetic.' Their perceptions changed over a period of time, with the majority finding they did not notice the artificial quality of the sounds after a few weeks or using their implant.
Inability to upgrade the implant:
A person might not be able to upgrade their implant when new external components become available. Implanted parts are usually compatible with improved external parts. As advances in technology develop, a person can upgrade their implant through exchanges in external parts. Sometimes this doesn't work, and a person's implant needs to be changed.
Potential implant damage:
Car accidents, contact sports, slips and falls, as well as other types of impacts near to the person's ear with the cochlear implant all have the potential to damage the implant. What this might mean is the need for a new implant, along with another surgery and the risks involved with it. It is also unknown whether a new implant will work as well as the one the person had.
People with cochlear implants have to be careful of static electricity, something that can temporarily or even permanently damage their implant. A good practice may be to remove the processor and headset prior to making contact with static-generating items such as television screens, synthetic fabric, plastic play equipment, or computer monitors.
The external parts of a cochlear implant cannot get wet. Damage from water might be expensive to repair and a person would be without hearing until their implant is repaired. It is therefore important for a person with an implant to remove the external parts of their implant before showering, bathing, swimming, or participating in water sports.
Longevity of the implant:
A person will use their cochlear implant for the remainder of their life. During a person's lifespan, the manufacturer of their implant might go out of business. The question of whether or not a person will be able to obtain replacement parts, or additional customer services in the future, is something that cannot be answered.
Infection requiring temporary or permanent removal of the implant:
If a person experiences an infection after implant surgery, they may have to have the implant removed either temporarily or permanently; although the complication is rare.
Unknown or uncertain effects:
A cochlear implant stimulates a person's nerves directly with electrical currents. While this type of stimulation seems to be safe, the long-term effects of using these electrical currents on a person's nerves is unknown.
Decreased ability to hear soft and loud sounds without changing the sensitivity of the implant:
The design of cochlear implants requires a person to manually change the sensitivity setting as their sound environment changes.
Should this occur, a person would need to undergo an additional surgery to resolve the issue and would be exposed to the risks of another surgical procedure.
Inability to understand language well:
No test exists that a person can take prior to surgery that will predict how well they will understand language after implantation surgery.
A person may experience skin irritation where the external part of the implant rubs on their skin and they might have to remove it for a period of time.
A person might hear strange sound caused by interactions with magnetic fields, such as ones near airport screening machines.
Different hearing outcomes:
A person might not hear as well as other people who experience successful outcomes with their implants.
Potential loss of residual hearing:
Cochlear implants might destroy any remaining hearing in the ear that has the implant.
Dependency on batteries for hearing:
Some devices require new or recharged batteries on a daily basis.
The costs involved:
Surgery, recovery, and the replacement of lost or damaged parts can be expensive.
The Benefits of Using Cochlear Implants
The use of a cochlear implant can also provide a number of benefits. Adults; for example, many times receive an immediate hearing benefit and continue to improve over a period of around three months after their initial tuning sessions. After this period of time, their performance continues to improve, although at a slower rate. The performances of people who use cochlear implants can continue to improve over a period of several years. Other benefits can include the following.
- Most people are able to perceive soft, medium, and loud sounds:
People who use cochlear implants have reported the ability to perceive a variety of different sounds, such as ringing telephones, slamming doors, barking dogs, the sounds of engines, the sound of a light switch turning on or off, rustling leaves, a whistling tea kettle and more.
- Many people can understand speech without lip-reading:
Even when this is not possible, using a cochlear implant helps people with lip-reading.
- Many people can make phone calls:
A number of people find they can make phone calls and understand familiar voices over the phone. Some people can make phone calls and understand others they are not familiar with.
- Watching Television:
A number of people can watch television more easily, particularly when they are able to see a person's face.
- Enjoying Music:
Some people with cochlear implants enjoy the sounds of certain instruments, such as guitar or piano, as well as certain voices.
People who are deaf and are pondering whether or not to pursue surgery to receive a cochlear implant have a number of different things to think about before they receive one. There are risks involved, as well as benefits. It is important to research cochlear implants, speak with a doctor, as well as an audiologist before making the decision.