About deafness and hearing loss
Contents:
I. The Hearing System
A. Introduction – The Ear
B. The Hearing System
C. Balance
D. What is hearing loss?
Conductive deafness
Nerve deafness
Trilingual deafness.
Acquired or adventitious deafness
E. How is deafness measured?
- Hard of Hearing
- Moderate deafness
- Severe deafness
- Profound deafness
F. Kinds of Hearing Loss
- Conductive
- Sensorineural
- Mixed
- Central
G. Degrees of Hearing loss
- Mild
- Moderate
- Severe
H. Causes of Hearing Loss
I. Signs of Hearing Loss In Adults
J. Self-Test
K. Signs of Hearing Loss in Children
L. Normal Hearing and Language Development
II. Hearing Aids and Other Technology
A. Hearing Aids
B. Hearing aid styles
- Behind the ear (BTE)
- In-the-ear (ITE)
- Completely-in-the-Canal (CIC)
- Body worn
C. Hearing aid types
D. Does a hearing aid "fix" hearing?
E. Do all children with hearing loss need to wear hearing aids?
F. Why is it so important for babies to have hearing aids?
G. Hearing aid accessories
H. Looking after a hearing aid
I. How to look after behind-the-ear (BTE) hearing aids
J. How to look after in-the-ear (ITE) hearing aids
K. How to look after in-the-canal (ITC) and completely-in-the-canal (CIC) hearing aids
L. How to look after body-worn hearing aids
M. Problems with hearing aids
N. Group listening systems
- FM systems
- Infra-red systems
- Tele-coil systems
II. Cochlear Implant
A. What is a Cochlear Implant?
B. How Does a Cochlear Implant Work?
C. Who is a candidate for a cochlear implant?
D. What is the ideal age for a deaf child to receive a cochlear implant?
E. Implant Process
F. After Implementation
G. Benefits
H. How long does it take to get maximum benefit from a cochlear implant?
I. The Hearing System
A. Introduction – The Ear
There are three major parts to the ear: the outer ear, middle ear and inner ear. The outer ear is the part we see, including the ear canal. The middle ear includes the eardrum, which is technically called the tympanic membrane. It also includes the three bones or ossicles of the middle ear and the eustachian tube. The eustachian tube leads to the throat and helps equalize pressure in the middle ear. The inner ear includes the cochlea, which looks like a snail shell, and the semi-circular canals. Inside the cochlea are sensory cells which look like fine hairs and respond to sound then send nerve signals to the brain. The semi-circular canals help us maintain our balance.
B. The Hearing System
The ear is the first part of the hearing system. The pinna catches sound waves and directs them down the ear canal. The waves then cause the eardrum to vibrate. These vibrations are passed across the middle ear by three tiny bones. These are known as the malleus, incus and stapes. They are sometimes called the hammer, anvil and stirrup. The bones increase the strength of the vibrations before they pass through into the cochlea via the oval window.
The cochlea looks like a snail’s shell. It is filled with fluid and contains many thousands of tiny sound-sensitive cells. These cells are known as ‘hair cells’. As the vibrations from the bones in the middle ear enter the cochlea they cause movement in the fluid. This causes the hair cells to bend. The movement of the hair cells is like the movement of seaweed on the sea floor when waves pass over it. As the hair cells move they create a small electrical charge. These move along the auditory nerve to the brain where they are converted into signals that can be understood as sound.
For an ear to function fully and give us access to sound, all of these elements must work well. Deafness happens when at least one part of this system is not working effectively.
C. Balance
Balance is controlled by the semicircular canals. These are three tubes that are filled with liquid. As we move the fluid in our semicircular canals moves. This creates a signal that is sent to the brain. This information, along with information from other senses, allows us to be aware of our position and helps us to keep our balance.
D. What is hearing loss?
Deafness is the term applied to the total or partial inability to perceive sound.
In physiological terms there are two types of deafness.
Conductive deafness, which means that there is some difficulty in the physical structure of the ear (e.g. with the ear drum or bone structure), causing failure to properly relay sound impulses to the hearing nerve. Conductive deafness can often be helped by surgery or other clinical interventions.
Nerve deafness, which means that there is some problem in the nerves in the inner ear which relay information to the brain. There is generally little that can be done to counter the effects of nerve deafness.
Deafness can also be classified by age of onset.
Prelingual deafness, refers to deafness at birth or in the early stages of childhood, and relates to the fact that no spoken language has been acquired at the time of onset. People who are prelingually deaf often have difficulty with spoken language and literacy, and generally communicate most effectively through sign language.
Acquired or adventitious deafness is the term applied when a person who has had hearing becomes deaf at some point during their life. They have the advantage of knowing spoken or written language and are more able to deal with lip reading and text.
E. How is deafness measured?
While there are standardized “hearing tests”, there are no formal or medical measurements by which different types or deafness can be classified. Instead there are generalized categories which attempt to differentiate deafness by the way in which the hearer can or cannot cope with hearing the human voice.
There are many different degrees of hearing loss. A mild hearing loss may mean that you have difficulty hearing and understanding someone who is speaking from a distance or has a soft voice. Understanding people speaking when there is a lot of background noise may be difficult.
Some general classifications are as follows:
o Hard of Hearing
People who are hard of hearing may have a little difficulty following speech in certain circumstances, especially if there is a lot of background noise, but can generally cope if the environment is favourable.
o Moderate deafness
People with moderate deafness have some difficulty in following speech in most settings, but can generally get a lot of help from wearing a hearing aid. They may have trouble understanding conversational levels of speech even if there is not any background noise. Hearing conversations with a noisy background is very difficult.
o Severe deafness
People with severe deafness hear no speech without the help of a hearing aid. They have trouble hearing in all situations. They may hear speech only if the speaker is talking loudly or is standing very close to you.
o Profound deafness
People who are profoundly deaf hear no speech, even with the benefit of a hearing aid. They may not hear even loud speech or environmental sounds. Hearing may not be used as the primary means of communicating.
F. Kinds of Hearing Loss
There are four main types of hearing loss:
o Conductive: Hearing loss is caused by a problem in the outer ear or middle ear. Conductive losses usually affect all frequencies to the same degree. These losses are not usually severe.
o Sensorineural: Hearing loss is caused by a problem in the inner ear or auditory nerve. A sensorineural loss often affects a person's ability to hear some frequencies more than others. This means that sounds may be appear distorted, even with the use of a hearing aid. Sensorineural losses can range from mild to profound.
o Mixed: A combination of conductive and sensorineural losses.
o Central: Hearing loss caused by a problem along the pathway from the inner ear to the auditory region of the brain or in the brain itself, not by problems in the ear.
G. Degrees of Hearing loss
Determining the degree of hearing loss can be difficult, particularly with young children who do not test as well as older people who can provide more accurate results.
There are basically four degrees.
o Mild - At 26-45 db, a little difficulty hearing speech. Even a mild hearing loss can be serious for children still learning to talk.
o Moderate - At 46-65 db, more difficulty hearing speech.
o Severe - At 66-85 db, a lot of difficulty hearing speech. It is at this level that we begin to use the term "deaf."
Profound - Anything over 85 db. With this level of hearing loss, hearing aids may or may not help; cochlear implants are often an option
H. Causes of Hearing Loss
Many people experience hearing loss as they grow older. Sometimes hearing loss is the result of damage done by loud equipment, loud music or even loud movies. Heredity contributes to age-related hearing loss, and so does simple wear and tear on the inner hairs or sensory cells of the inner ear.
Heredity is the leading known cause of hearing impairment at birth. Genetic deafness is less likely to be accompanied by other health problems.
Pregnancy/birth complications are considered to be the main cause of hearing impairment. This includes Rh incompatibility, prematurely, and birth trauma. When it results in a lack of oxygen and cerebral hemorrhage, premature birth can cause damage to the nervous system and subsequent hearing loss. When there is a blood type incompatibility between mother and child, some children will be born with a hearing loss and others will be born with cerebral palsy.
The most common cause of hearing loss is ear infection.
Another cause of hearing impairment after birth is bacterial meningitis. Boys are more likely than girls to contract this disease. Children under four are most susceptible to the disease, which is an inflammation of the lining of the brain. Most children are vaccinated against one type of meningitis, but there are other strains which are equally dangerous.
I. Signs of Hearing Loss In Adults
For adults, look for these signs of hearing loss:
- shouting in conversation
- turning television or radio too loud for other family members
- continually asking others to repeat themselves
- withdrawing from social contact
- straining to hear
- misunderstanding conversations
- favoring one ear
- complaining of a ringing or buzzing in the ear
J. Self-Test
- Do you have a problem hearing over the telephone?
- Do you hear better in one ear than the other?
- Do you have trouble following the conversation?
- Do people complain that you turn the volume up too high?
- Do you have to strain to understand conversation?
- Do you have trouble hearing in a noisy background?
- Do you have trouble hearing in restaurants?
- Do you have dizziness, pain, or ringing in your ears?
- Do you find yourself asking people to repeat themselves?
- Do family members or co-workers remark about your missing what has been said?
- Do many people you talk to seem to mumble or not speak clearly?
- Do you misunderstand what others are saying and respond inappropriately?
- Do you have trouble understanding the speech of women and children?
- Do people get annoyed because you misunderstand what they say?
If you have answered "yes" to more than two of these questions, you should have your hearing checked by an audiologist. You may choose to have your hearing "screened" to determine the presence or absence of hearing loss, or have a full hearing evaluation to determine the type and extent of hearing loss.
K. Signs of Hearing Loss in Children
- not responding when someone speaks to them
- saying "what" frequently or asking for things to be repeated
- intently watching the face of the person speaking
- sitting close to the television with the volume high or turning up the volume on the stereo
- switching ears frequently on the telephone
- not being startled by loud sounds
- responds inconsistently to conversations -- sometimes hears what's been said and sometimes does not.
- a history of ear infections -- often getting earaches or runny ears
- complains of hurting ears
- prefers low pitched or high pitched sounds
- talks in a soft or loud voice
- confuses sounds that are alike
- speech is less developed than expected for age or child does not use verbal language at all
- answers questions with unrelated answers
- seems inattentive at home or school
L. Normal Hearing and Language Development
In infants and toddlers, look for these signs of normal hearing and language development. If they are lacking, consult your pediatrician immediately.
- startles, blinks eyes or other response to sudden, loud sounds (birth to 3 or 4 months)
- stops moving or stops crying when called or when hears unfamiliar noise (birth to 3 or 4 months)
- disturbed by loud sounds during sleep (3 months)
- soothed by mother's voice or shows response (3 months)
- imitates gurgling or cooing noises and responds to noise making toys (3 months)
- begins to turn eyes and head to the side in search of source of unfamiliar sound (4-5 months)
- turns head directly toward the sound of a signal, but cannot locate sounds from above or below (6-7 months)
- responds to everyday sounds such as running water, spoon rattling in cup or footsteps from behind (7-9 months)
- responds to sound of name (7-9 months)
- plug your ears! Baby should engage in loud shrieking and sustained production of vowel sounds (9 months)
- uses his or her voice to get attention (9-12 months)
- imitates sounds and simple words (12 months)
II. Hearing Aids and Other Technology
Hearing aids are available for children and adults with all degrees of hearing loss. The type of hearing aid a person selects will depend on their degree of hearing loss, ability to understand speech, the situations in which they need to hear and cosmetic concerns.
A. Hearing Aids
A hearing aid is an electronic, battery-operated device that amplifies sound to improve listening comprehension. It collects sounds from the environment via a microphone, amplifies those sounds and then directs the amplified signal into the user's ear through a tiny speaker.
Hearing aids can be programmed to fit the needs of individual hearing patterns, such as boosting intensity level for high frequency sounds that a person may not hear at all and less for low frequency sounds that a person may hear better.
Using hearing aids in both ears generally provides superior benefit compared to a monaural hearing aid and is strongly recommended for children who are learning to listen and talk.
B. Hearing aid styles
o Behind the ear (BTE) hearing aids are the most commonly dispensed hearing aids. They are available for people with mild to severe hearing losses. BTE hearing aids fit over the ear and use an earmold to send sound into the ear. They are usually easy to manipulate as the switches are larger than in some of the other hearing aids. They can usually be easily connected to an FM system so they are ideal for children in school.
o In-the-ear (ITE) hearing aids are very popular with adults who have mild to moderately-severe hearing loss because they are smaller than BTE hearing aids. They fill in the ear and usually have one or two small switches, which are used to turn the hearing aid on and off, or to change programs. Because these are small they are more difficult to manipulate and so may be difficult for people who have dexterity problems with their fingers, or for children when their ears are continuing to grow and when they will need an FM system in school.
o Completely-in-the-Canal (CIC) hearing aids are very small hearing aids that fit into the ear canal and are less visible than ITE hearing aids.
o Body worn hearing aids are used very rarely with current technology. They are about the size of an iPod and are worn in a pocket with a cord going up to the ear. They are used for patients with profound hearing losses or patients who have physical problems using other hearing aids.
C. Hearing aid types
o Digital hearing aids make use of digital technology to control the auditory signal. They are usually able to provide a cleaner signal with less background noise.
o Programmable hearing aids are hearing aids that are programmed using a computer. They may be digital or analog.
o Analog hearing aids use an analog signal to amplify sound. These hearing aids are usually less expensive then digital hearing aids and may be very good for patients with more mild hearing losses and for patients who do not rely on listening to understand speech.
D. Does a hearing aid "fix" hearing?
Hearing aids cannot restore perfect or normal hearing because a sensorineural hearing loss involves damage to some part of the inner ear (usually the cochlear). Some degree of sound distortion usually occurs. A hearing aid can amplify the loudness of the sound, but even with the most current hearing aids speech may not be completely clear. Because young children have very plastic brains, children with hearing loss can learn to listen and speak through auditory training and speech and language therapy.
K. Do all children with hearing loss need to wear hearing aids?
Children with permanent hearing loss should be properly amplified. However, some children with severe to profound hearing loss in both ears may find that they do not get enough benefit from hearing aids. These children may be candidates for a cochlear implant. Other children may have conductive hearing loss that can be corrected or improved by surgical or medical intervention. If the hearing loss cannot be medically corrected, they may benefit from hearing aids. These children need to be carefully evaluated by medical professionals.
L. Why is it so important for babies to have hearing aids?
Babies begin developing the skills necessary for language as soon as they are born. Research suggests that there is a critical learning period during which babies learn language, from birth to about three years of age. Research also shows that when infants are aided early on they have the greatest chance of developing language skills comparable to their same-aged peers. Exposure to sound actually stimulates the development of the auditory neural synapses within the brain. If a child is unaided, it is important to begin using a visual form of language early to be certain that the child has a method of communication.
M. Hearing aid accessories
These include:
o an air-puffer to help dry the earmould and tubing after you have washed them
o special tubing that is less likely to collect moisture (if this is a problem for you)
o earmoulds made with special material if the usual ones irritate your ear
o splash-proof covers for hearing aids (these enclose the whole aid but cannot be made completely watertight)
o cleaning and repair products.
N. Looking after a hearing aid
When your hearing aid is fitted you should be given written instructions about how to look after it. If you are not sure about any of the information, ask your audiologist or hearing aid dispenser for advice.
O. How to look after behind-the-ear (BTE) hearing aids
Wipe the hearing aid and earmould with a dry tissue every time you take your hearing aid off. Ideally, you should wash the earmould and tubing every night. If you can't do this, wash them at least once a week. Only wash the earmould and tubing. Do not wash the hearing aid - the part that contains the battery.
Don't unscrew the hooked part (or 'elbow') from the hearing aid. Instead, gently pull the plastic tubing off the hooked 'elbow' but don't pull it out of the earmould. Wash the earmould and tubing together in warm soapy water, and rinse them.
Blow down the tubing to get the water out, and let it dry overnight. Once it is dry, push the end of the tubing back onto the hearing aid. The tubing will need changing every three to six months before it hardens or splits and causes problems.
P. How to look after in-the-ear (ITE) hearing aids
There are two types of ITE hearing aids:
o Custom ITE aids have only one part. If you bought an ITE hearing aid privately, it is likely to be a custom one. You must not wash these. Wipe them with a dry tissue and use a soft dry brush to remove wax from the opening. Do not poke anything into the opening as you may damage the earphone. These aids often come with instructions and cleaning tools to help you.
o Modular ITE aids have an earmould attached to a hearing aid. You can separate the earmould from the hearing aid and then wash the earmould in soapy water. Wipe the hearing aid part with a dry tissue. Don't ever wash it or get it wet.
N. How to look after in-the-canal (ITC) and completely-in-the-canal (CIC) hearing aids
You must not wash these hearing aids. Wipe them with a dry tissue and use a soft brush to clean wax from the opening. ITC hearing aids often come with special instructions and cleaning tools.
O. How to look after body-worn hearing aids
If you have this type of hearing aid, wipe it all over with a dry cloth every time you take it out. Wash the earmould at least once a week.
First, gently pull the receiver, the metal piece at the end of the cord, off the earmould. Put the hearing aid (the part with the battery in), lead and receiver in a safe, dry place. Don't ever get these wet.
Wash the earmould with warm soapy water, using a soft brush to remove any wax blocking the opening in the earmould. Rinse and dry the earmould carefully.
Leave it to dry overnight before you clip it back on to the receiver.
P. Problems with hearing aids
If you are having problems with your hearing aid, your audiologist or hearing aid dispenser will be able to help you. However, there are some common problems that you may be able to sort out yourself.
If your hearing aid doesn't seem to be working:
o Check that your hearing aid is switched on properly.
o Check that you have not switched it to the 'T' setting by accident.
o Make sure that the volume is at the correct level for you and not turned right down.
o Check that the battery is the right way round. If it is, try replacing it with a new battery.
o If you have a BTE hearing aid, take it out, pull the tubing off the elbow and blow down the tubing to remove any condensation that may have collected and could be blocking the sound.
o Check that the tubing is not squashed or split.
Buzzing noises may mean that you have switched your hearing aid to the 'T' setting by accident. However, if this is not the problem, buzzing generally means your hearing aid has developed a fault and needs to be repaired.
Whistling or squeaking is caused by 'feedback', when sound amplified by your hearing aid is fed back into it. It may happen if:
o you have not put the earmould in properly - push it gently to check.
o you have excess wax in your ears - ask your ENT doctor to check your ears.
o the earmould does not fit your ear closely enough - you'll need to ask for a new one.
o the earmould, hooked 'elbow' or tubing in a BTE aid becomes loose or splits. If this is the problem, you'll need to get help from your audiologist or hearing aid dispenser.
N. Group listening systems
o FM systems
Even when using the best, most appropriate hearing aids people will have problems hearing when the talking is more than a few feet away or when there is competing noise. FM systems are used to improve the ability to hear when the talker is at a distance or in the presence of competing noise. An FM system comes in two parts. The talker uses a microphone and the listener has a receiver connected to the hearing aids. This may be connected directly or by using a small loudspeaker. An FM system will significantly improve the ability to hear in a difficult listening situation and is recommended for everyone with hearing loss.
o Infra-red systems
Infra-red systems are similar to FM systems in that they are used to improve listening at distance and in noise. The signal is transmitted using infrared waves. The listener wears an infra-red receiver either through headphones or attached to hearing aids. This system is frequently used in theatres. It can only be used indoors because the signal would be interrupted by sunlight.
o Tele-coil systems
Tele-coil systems make use of the telephone coil on a person's hearing aid. The tele-coil can be used to help people communicate on the phone and can be used for hearing in groups. Patients can use a tele-loop worn around their necks, and theatres and other meeting areas can use a tele-loop to surround a room. People turn their hearing aids to the tele-coil and they will pick up the signal coming from the talker's microphone. Not all hearing aids have equally strong tele-loops so the loudness and clarity of the signal will vary.
III. Cochlear Implant
I. What is a Cochlear Implant?
A cochlear implant is an electronic device. One part is surgically placed inside the inner ear while the other external part is worn behind the ear. The implant delivers electrical stimulation to the inner ear or cochlea and bypasses the damaged hair cells, directly stimulating the hearing nerve.
J. How Does a Cochlear Implant Work?
A cochlear implant is very different from a hearing aid. Hearing aids amplify sound. Cochlear implants compensate for damaged or non-working parts of the inner ear. In normal hearing, complicated parts of the inner ear convert sound waves in the air into electrical impulses. These impulses are then sent to the brain, where a hearing person recognizes them as sound. A cochlear implant works in a similar way. It electronically finds useful sounds and then sends them to the brain. Hearing through an implant may sound different from normal hearing, but it allows many people to communicate fully with oral communication in person and over the phone.
K. Who is a candidate for a cochlear implant?
Children and adults who have severe or profound sensorineural hearing loss and derive minimal benefit from hearing aids may be candidates for a cochlear implant.
The benefit that an adult receives from an implant depends on several factors: their degree of hearing loss, their ability to understand speech before receiving the implant, experience using a hearing aid, and the length of time they have been severely deaf. Generally the more experience a person has with hearing and the shorter the duration of their deafness, the more benefit they can expect to receive.
Young children are excellent candidates for cochlear implants because their nervous systems are able to learn easily which allows them to make use of the sound the implant provides. Children implanted early, who do not have other significant development disabilities and who receive intensive post-implantation speech, language and listening therapy, may acquire age appropriate speech, language, developmental and social skills. They are usually schooled in mainstream educational settings.
L. What is the ideal age for a deaf child to receive a cochlear implant?
There is no single ideal age for implantation in children. It depends on each family, each child, and the individual factors affecting each child. The best age for implantation is still being debated, but research has clearly indicated that children who receive cochlear implants early have the best results. Many centers will implant children as early as 7 months if there is certainty as to the audiologic indications.
In general, because it is felt that there is a window of opportunity for learning the skills necessary for spoken language, the earlier the implant the better. Speech and language development occurs, for the most part, by age six. Progress does not occur as quickly or as easily after that age. The decision about whether to implant an older child is made individually. Factors to consider include use of hearing aids and auditory skills. If an older child has not worn hearing aids, benefit received from a cochlear implant may be limited.
Children implanted after the age of three years may require more frequent and more intensive speech and language therapy to progress at rates comparable to children implanted before age three. Implantation should always be weighed carefully against the child's educational and therapy environments, level of family involvement, and use of residual hearing with amplification, among other factors.
M. Implant Process
The first stage in the management of profound sensorineural hearing loss with a cochlear implant is proper assessment. This includes audiological, ontological, medical, speech pathological and radiological evaluation. In addition, children who are being considered for implantation receive a complete speech and language evaluation and an assessment of educational support services available to them. These educational services are unique to the team and are performed by trained teachers of the deaf who visit each child's school before and after implantation. These services assure that children who receive implants can reach their optimal speech, language and educational skill level. Other tests may be required depending upon the needs of the individual. Throughout the entire implantation process, emphasis is placed on providing counseling and support for the adult or child being implanted, as well as their family members.
The surgery for the insertion of a cochlear implant requires an overnight hospital stay. After the operative wound has healed the implanted individual returns approximately one month later for the initial fitting of the speech processor and "turning on" of the device. Subsequent visits allow finer tuning of the processor.
N. After Implementation
Individuals who receive a cochlear implant require continual follow up. Children, in particular, require a long period of rehabilitation to teach them to listen to the new sounds and to optimally tune the device. All children who receive cochlear implants can learn to hear the everyday sounds we take for granted. Most children are able to hear conversation without lip-reading and use spoken language for everyday communication.
O. Benefits
Adults who have lost all or most of their hearing later in life can often benefit from cochlear implants. These older candidates can often associate the sounds made through an implant with sounds they remember. This may help them to understand speech without visual cues or systems such as lip reading or sign language.
Many young children can also be candidates for implants. Cochlear implants, coupled with intensive post-implantation therapy, can help young children to acquire speech, language, developmental and social skills. The best age for implantation is still being debated, but it appears that earlier implantation performs better. Most children who receive implants are between two and six years old. Because of research conducted at several implant centers in USA and Europe, infants as young as seven months old can now be implanted with cochlear devices.
P. How long does it take to get maximum benefit from a cochlear implant?
Many factors determine progress. It depends on how long you have had a severe to profound hearing loss and your ability to use hearing with hearing aids. Improvement is slow in the beginning and improves rapidly over the first few months. For adults, generally there are good benefits by three months and it may take about a year to achieve full benefit.
