What is congenital hearing loss?
Congenital hearing loss is deafness that exists when a baby is born. It usually affects the inner ear and is also called congenital sensorineural hearing loss.
What causes congenital hearing loss?
A number of conditions that arise during pregnancy are associated with causing congenital hearing loss. For example, if a pregnant woman contracts German measles (rubella), particularly during the first trimester of pregnancy, the rubella virus may invade the developing baby's inner ear and destroy the nerves that transmit messages about hearing to the brain. High doses of vitamin A or the use of isotretinoin (Accutane, an antiacne medication derived from vitamin A) during pregnancy can cause serious birth defects, including ear abnormalities. Deafness may also be due to Rh incompatibility disease, a blood disorder that develops when a baby's blood is of a different Rh type than the mother's. Some babies are born with hereditary conditions that cause hearing loss. Example; include Hurler's syndrome, albinism, and Waardenburg's syndrome, all of which are relatively rare.
- Failure to respond to normal sounds.
- Failure to begin talking at the normal age.
More common causes of hearing loss occur during the birth process. For example, oxygen deprivation during labor and delivery may cause congenital deafness. Hearing loss may also be due to an injury to the base of the skull during delivery, especially if the baby is premature.
How is congenital hearing loss diagnosed and treated?
Congenital hearing loss often is not detected until the baby is several months old, at which time the parents may notice that he or she does not respond to voices or other sounds. As early as a few weeks after birth, babies react to noises. Try clapping out of the baby's sight and see if the sound produces a reaction. If not, more sophisticated hearing tests are indicated.
Early diagnosis is desirable, because children do not learn to speak normally unless they can hear language. Special education, which begins as early as 2 years of age, is crucial to a deaf child's speech development.
Depending upon the degree of hearing loss, special aids and devices may be prescribed. Babies only 8 or 9 months old can be fitted with hearing aids. The most powerful is called a body aid, which is worn in a shirt pocket or body harness. It is connected by a wire to an ear piece or receiver that is worn in the ear and attached to the ear canal with a plastic insert or ear mold. An earlevel aid fits behind the ear and is coupled to the ear mold by flexible tubing. A hearing aid can also be built into the temple of a pair of eyeglasses and connected by tubing to the ear mold, but this is only practical for children who must also wear glasses.
Some hearing aids can be fitted entirely inside the ear. A child who is deaf on one side only can use a device called the CROS aid (for contralateral routing of signals), in which a hearing aid microphone is placed on the deaf ear and sound is routed to the other ear by a wire or a miniature radio transmitter. This allows the child to hear sounds from the deaf side and to develop at least some ability to detect where sounds are coming from. A bone-conduction hearing aid is sometimes used if an ear mold or tube is not effective. In this type of hearing aid, an oscillating device conducts sound through the bones of the ear to the cochlea, the spiral tube that is located in the inner ear.
What can I do myself?
If a child needs help with speech, a speech therapist can teach parents at-home exercises to supplement formal therapy sessions.
When should I see my doctor?
If an infant does not seem to respond to a spoken voice or ordinary household sounds, a pediatrician should be consulted. Failure to babble or learn to speak should also be checked.
What will the doctor do?
Parental observations are extremely important, so the doctor will question parents closely about them. Diagnosis depends upon parental observation plus special testing that varies with the child's age. Testing the hearing of infants usually entails using audiometric devices. These devices produce different types of sounds, and the doctor then observes and measures the child's responses to them.
Children over the age of 2 are often tested with play audiometry. This involves conditioning the child to perform a task, such as placing a block in a box, when a certain tone is used.
The course of congenital hearing loss
Congenital hearing loss cannot be cured, but it can sometimes be relieved with a hearing aid. Early detection usually makes it possible to teach the child language. Lip-reading and signing are also useful. Unfortunately, some deaf children are also mentally retarded, which may limit their learning abilities.
Is congenital hearing loss dangerous?
It is not a health threat, but it can be emotionally difficult for both the parents and youngster. Also, an inability to hear sirens or other warning sounds may place a youngster in dangerous situations.
What can I do to avoid congenital hearing loss?
- A woman should make sure that she has been immunized against rubella before becoming pregnant.
- Vitamin A supplements and Accutane should be stopped several months before attempting pregnancy.