A:
|
A DISCUSSION OF HEARING PROBLEMS
IN CHILDREN
Five thousand children are born profoundly deaf each year
in the United States alone. Another 10 to 15 percent of newborns
have a partial hearing handicap.
FUNCTION OF THE NORMAL EAR
The ear is divided into three parts: an external ear, a middle
ear and an inner ear. Each part performs an important function
in the process of hearing.
The external ear consists of an auricle and ear canal. These
structures gather sound and direct it toward the eardrum.
The middle ear chamber lies between the external an inner
ear. This chamber is connected to the back of the throat by
the eustachian tube, which serves as a pressure equalizing
valve. The middle ear consists of the eardrum and three small
ear bones (ossicles): malleus (hammer), incus (anvil) and
stapes (stirrup). These structures transmit sound vibrations
to the inner ear. In so doing, they act as a transformer,
converting sound vibrations in the external ear canal into
fluid waves in the inner ear.
The inner ear chamber contains the microscopic hearing nerve
endings bathed in fluid. Fluid waves stimulate the delicate
nerve endings which in turn transmit sound energy to the brain,
where it is interpreted.
TYPES OF HEARING IMPAIRMENT
The outer and middle ears conduct and transform sound; the
inner ear receives it. When there is some difficulty in the
outer or middle ear, a conductive hearing impairment occurs.
When there is trouble in the inner ear, a sensorineural or
hair cell impairment is the result. Difficulty in both the
middle and inner ear results in a mixed hearing impairment.
CONDUCTIVE IMPAIRMENT
A conductive type of hearing impairment occurs when sound
is not conducted efficiently through the ear canal, eardrum,
or tiny bones of the middle ear. Conductive losses reduce
the loudness of sound that is heard.
A conductive impairment may occur from blockage of the outer
ear canal, from a perforation (hole) in the eardrum, from
middle ear infection or fluid due to blockage of the eustachian
tube, or from a congenital defect or disease of any of the
three middle ear bones. This type of impairment is usually
correctable through surgery.
The child with a conductive hearing loss will never go deaf.
He will always be able to hear, either through ear surgery
or by use of properly fitted hearing aid.
SENSORINEURAL IMPAIRMENT
A sensorineural hearing loss is used to describe hearing impairments
which result from disturbances or defects in the inner ear
and transmission of electrical signals from the hair cells.
These impairments may be congenital (i.e. present at birth),
hereditary, developmental, or a combination of these. In addition,
these impairments may result from infections, injuries, ototoxic
drug therapy, or lack of oxygen.
Hearing loss may be divided further due to the cause of the
hearing handicap.
A. Congenital hearing loss
1. Genetic - In the genetic type there is
an actual defect in your child's genes which results in an
abnormal development of the ear.
2. Non-genetic - This is a hearing loss which
is due to some problem which occurred during the fetal development
or the immediate birth period.
B. Acquired hearing loss - This is a hearing
impairment which occurs sometime after birth and is not transmitted
to future children.
CONGENITAL FACTORS
Several viral infections, including CMV and German measles
contracted by the mother during the first three months of
pregnancy may interfere with inner ear development in the
fetus. Occasionally, other viral diseases are at fault. The
viruses of measles and mumps may cause a sensorineural hearing
loss after birth, but this happens infrequently. Immunizations
are now available for both of these diseases.
PROBLEMS AT BIRTH
A very difficult and complicated labor or premature birth
may also result in an inner ear hearing impairment on occasion.
This may be due to lack of oxygen. These are many syndromes
which can also result in a hearing impairment at birth. One
can have a hearing loss at birth without any hereditary relationship.
Jaundice occurring at or shortly after birth is capable of
damaging the inner ear. This is most often due to Rh incompatibility
between the mother's and the child's blood. Fortunately, this
is not a common occurrence.
HEREDITARY IMPAIRMENT
The development and function of the ear is dependent upon
hundreds or even thousands of genes interacting with each
other and with the inter-and extrauterine environment. A major
cause of late-onset hearing loss is genetic. There are several
patterns of inheritance. In autosomal dominant disorders,
one parent expresses the trait, which he transmits to 50 percent
of his children. In autosomal recessive inheritance, the parents
of the children are clinically normal, but carry the recessive
gene to 25 percent of their children. X-link inheritance traits
are transmitted from a carrier mother to 50 percent of her
sons.
Most cases of hereditary childhood deafness are sensorineural
rather than conductive in nature. Most examples of hereditary
hearing loss are recessive. Recessive deafness characteristically
is associated with retention of hearing of low frequency sounds
since most of these cases are associated with abnormalities
primarily affecting the first turn or the cochlea (i.e. the
Scheibe inner ear abnormality). In dominant inherited deafness,
the audiogram generally is flat. However, there are other
dominant types of mid-frequency sensorineural hearing loss.
In X-link recessive deafness, some retention of hearing is
usually seen in all frequencies.
Hereditary sensorineural hearing loss may be present at birth,
or may develop later in life. This may be due to inner ear
malformations or to other associated syndromes which have
an associated inner ear hearing loss. One may see a genetic
sensorineural hearing loss with or without associated abnormalities.
INFECTIONS
The most common type of acquired sensorineural loss is meningitis.
Frequently this may affect both ears, but can involve one
ear. Other types of infections would include viral diseases,
such as mumps, rubella and otitis media.
HEARING IMPAIRMENT IN ONE EAR
A hearing impairment that is confined to one ear deprives
a person of the ability to distinguish the direction of sound.
He will also have difficulty hearing from the involved side
in a noisy background. These are minor problems to a young
child. When this hearing impairment in one ear is conductive,
surgery will usually be able to restore the hearing, giving
a better balance of hearing. This is usually done in a child
who is in his teens. When the impairment is sensorineural,
it is often possible when the child grows older to restore
some of this balance of hearing through the use of a special
hearing aid (i.e. CROS hearing aid).
TREATMENT
There is no known medical or surgical treatment that will
restore normal hearing in patients with sesorineural hearing
impairments. We, therefore, rely on rehabilitation through
the use of a hearing aid and special training. Fortunately,
many children with this type of hearing impairment will not
show progression of the impairment as they get older.
THE HARD-OF-HEARING CHILD
If your child's hearing impairment is in the range of 35-70
dB HL, he or she should do well with a properly fitted
hearing aid. He or she will probably be able to attend
school with normal hearing children. He or she will need preschool
speech therapy and auditory training in order that communication
abilities will be at the optimal level when regular school
starts.
HEARING AID EVALUATION
Evaluation of the hearing in a young child may require several
visits with the audiologist.
It is important to determine an accurate measurement of both
the type and the degree of hearing impairment in order to
select the proper hearing aid.
An aid that is too powerful for a young child may be uncomfortable
and cause the child to reject it. On the other hand, if the
aid is not strong enough, a child may receive little or no
benefit from it and therefore object to wearing it.
SPEECH READING (LIP READING)
Speech reading is very important whatever the type of degree
of impairment. This skill enables a person with impaired hearing
to understand conversation by attentively observing the speaker.
All of us, whether we have a hearing loss or not, employ the
sense of sight as well as the sense of hearing in ordinary
conversation. We find it easier to comprehend if we can watch
the speaker's facial expressions, lip movements and gestures.
Just as the visually handicapped learns to use his sense of
hearing to compensate for his impaired sight, the person with
defective hearing must learn to use his eyes to assist him
in hearing. A study of the fundamentals of lip reading or
of speech reading, as it is called, will make communication
less of an effort and therefore more pleasant for both the
speaker and the listener.
Speech reading has its limitations. For example, when the
distance between the speaker is great or when there is inadequate
lighting or defective vision, one may not always be able to
see the speaker's lips clearly enough to speech read adequately.
Some persons do not open their mouths very far when they speak
and, consequently, their lip movements are very limited. Others
have beards, hold their hands over their mouths, or smoke
as they talk, making speech reading difficult if not impossible.
It is important to tell other family members and friends to
get the child's attention before speaking. The child with
a hearing impairment must recognize characteristics of the
English language. Many sounds and many words look the same
on the lips. The hearing impaired child will find it impossible
to see certain words on the lips and therefore needs to continuously
fill in the "gaps" of words and sentences. Two thirds
of all sounds in the English language are not visible on the
lips. Because of the difficulties presented by sounds, the
speech reader is encourage to follow the contact or thought
of what is being said rather than to try to lip-read each
word.
The child, who is learning to speech read, learning to use
a hearing aid, or both, should have help from a professional
person trained to teach these skills. There are many books
on the subject of speech reading. Help is also available at
various universities.
Cued speech is a phonemically-based hand supplement to speech
reading (speech is made up of sounds called phonemes). The
26 letters in our English language, either singly or in combinations,
produce 43 phonemes. Spelling does not illustrate the pronunciation
differences whereas cued speech can show the child how something
is pronounced while it is being spoken. It is comprised of
eight hand shapes used to represent groups of consonant sounds
and four positions about the face to represent groups of vowel
sounds. Combinations of these hand shapes and placements are
used to illustrate exact pronunciations in words in connected
speech. Although cueing helps recognize pronunciation, the
child will still need speech lessons with a speech therapist.
Some deaf educators find some limitations with cued speech,
but in certain specific instances this has been used with
some success.
PROFOUND SENSORINEURAL HEARING IMPAIRMENT
For those children who are not able to achieve any benefit
with a hearing aid and an oral educational program, they will
require training in manual forms of communication such as
finger spelling or American Sign Language. The type of school
depends upon the child's hearing level, progress, and communication
skills. If your child's level is greater than 70 dB, he or
she will not, in all likelihood, be able to attend classes
with normal hearing children, at least in the beginning. It
will be difficult for him or her, but with the help of a hearing
aid, training in speech reading, and attention to speech correction,
he or she may be able to progress through schools for the
hearing handicapped to normal schools, to college, and to
take his or her place in society with normal hearing people.
For those children who are not able to achieve understanding
for speech, special schools are available to train them in
the manual form of communication. The type of school a child
attends depends upon his progress in communication.
REHABILITATIVE MEASURES
There are two very important factors to be determined upon
examining the child with a suspected hearing impairment. First,
determination should be made regarding the presence of a hearing
loss and the type (i.e., conductive or sensorineural). Secondly,
once a hearing loss is found to be present, it should be determined
if this loss is progressive or stable. Therefore, your child
may require periodic audiograms to be sure that the hearing
loss is going to remain stable.
A complete otologic/audiologic examination by a competent
ear specialist and audiologist
are necessary to determine what type of hearing impairment
is present, its probable cause, and its treatment. At times
it may be necessary to obtain special x-rays of the inner
ear, a balance test or other laboratory tests to make this
decision.
A well-rounded program of rehabilitation for children with
hearing loss may include speech reading, auditory training,
speech therapy and instruction in the use of a hearing
aid. One may also consider other adjuvants to assist with
their communication skills such as cued speech or other manual
techniques. All aspects of the program do not necessarily
apply to each child with an impairment, but each individual
may be helped through some of these methods.
THE COCHLEAR IMPLANT
The cochlear implant is an electronic device that is implanted
into the inner ear of a severe to profoundly hearing impaired
child. This device is only utilized in the child who cannot
benefit with a hearing aid.
It is a device which is used to bypass the disease or nonfunctional
hair cells and converts the sounds we hear to electrical impulses
which directly stimulate the cochlear nerve. The implant consists
of an external portion comprised of a microphone, sound processor,
and external coil and an internal portion that must be surgically
implanted. The surgical procedure involves the placement of
an internal coil beneath the skin behind the ear and a stimulating
electrode which is inserted into the cochlea or inner ear.
To determine suitability for this device in the severe to
profoundly hearing impaired child, a careful examination is
required. The evaluation is performed to determine whether
or not the child can receive adequate information from a powerful
hearing aid, or whether or not the procedure can be performed
and give the expected improvement.
Currently there are several multiple channel devices which
are utilized. This is related to the number of stimulating
electrodes within the cochlea.
|