Definition of Hearing loss - infants:

Causes, incidence, and risk factors:

About 2 - 3 infants out of every 1,000 live births will have some degree of hearing loss at birth. Hearing loss can also develop in children who had normal hearing as infants. The loss can occur in one or both ears, and may be mild, moderate, severe, or profound. Profound hearing loss is what most people call deafness.

Some cases of hearing loss are progressive (they get worse over time). Other cases of hearing loss stay stable and do not get worse.

Risk factors for infant hearing loss include:

• Family history of hearing loss
• Infection with some viruses and bacteria
• Low birth weight
• Problems with the structure of the skull bones

There are four types of hearing loss:

• Conductive hearing loss (CHL)
• Sensorineural hearing loss (SNHL)
• Mixed hearing loss
• Central hearing loss

Conductive hearing loss results from a problem in the outer or middle ear, such as wax buildup, rupture of the eardrum, or repeated infections. It is usually possible to treat conductive hearing loss with medication or surgery.

Causes of conductive hearing loss in infants include:

• Abnormalities in the structure of the ear canal or middle ear
• Buildup of ear wax
• Ear infections (especially repeated infections)
• Foreign objects in the ear
• Injury
• Rupture of the eardrum
• Tumors

Sensorineural hearing loss results from a problem with the inner ear. The inner ear is responsible for sending signals to the auditory (hearing) nerve. There is no cure for sensorineural hearing loss. People with this type of hearing loss may benefit from hearing aids or a cochlear implant.

Causes of sensorineural hearing loss include:

• Exposure to certain toxic chemicals or medications while in the womb or after birth
• Genetic changes or conditions, such as Down syndrome
• Infection before birth, including cytomegalovirus infection, or infection with German measles during the early stages of pregnancy
• Infections after birth, such as bacterial meningitis
• Problems with the structure of the inner ear

Mixed hearing loss is hearing loss that results from a combination of conductive and sensorineural problems. Causes of mixed hearing loss can include any combination of the above SNHL and CHL causes.

Central hearing loss results from damage to the auditory nerve itself, or the brain pathways that lead to the nerve. Central hearing loss is rare in infants and children.

Causes of central hearing loss include:

• Diseases that affect the protective coating (myelin sheath) around nerve cells
• Tumors

Symptoms:

Signs of hearing loss in infants vary by age. For example:

• A newborn baby with hearing loss may not startle when a loud noise sounds nearby.
• Older infants, who should be responding to familiar voices, may show no reaction when spoken to.
• Children should be using single words by 15 months, and simple 2-word sentences by age 2. If they do not reach these milestones, hearing loss since infancy may be the cause.

Some children may not be diagnosed until they are in school. This is true even if they were born with hearing loss. Inattention and falling behind in class work may be the result of an undiagnosed hearing loss problem.

Signs and tests:

Hearing loss results in a baby's inability to hear sounds below a certain level. A baby with normal hearing will hear sounds below that level.

The health care provider will examine your child. The exam may show problems such as bone problems or signs of genetic changes that may cause hearing loss.

The doctor will use an instrument called an otoscope to see inside the baby's ears. This allows the doctor to see the eardrum and detect several problems that may cause conductive hearing loss.

Two common tests are used to screen newborn infants for hearing loss:

• Auditory brain stem response (ABR) test. This test uses patches, called electrodes, to determine how the auditory nerve reacts to sound.
• Otoacoustic emissions (OAE) test. Microphones placed into the baby's ears detect nearby sounds. The sounds should echo in the ear canal. If there is no echo, it is a sign of hearing loss.

Older babies and young children can be taught to respond to sounds through play. These tests, known as visual response audiometry and play audiometry, can better determine the child's range of hearing.

Treatment:

Over 30 states in the United States now have mandatory hearing screenings of newborns. Early treatment of hearing loss can allow many infants to develop normal language skills without delay. In infants born with hearing loss, treatments should start as early as possible, preferably by 6 months of age.

Treatment depends on the baby's overall health and cause of hearing loss. Treatment may include:

• Speech therapy
• Learning sign language
• Cochlear implant (for those with profound sensorineural hearing loss)

Treating the cause of hearing loss may include:

• Medications for infections
• Ear tubes for repeated ear infections
• Surgery to correct structural problems

Expectations (prognosis):

How well your baby does depends on the cause and severity of the hearing loss. Advances in hearing aid technology and speech therapy allow many children to develop normal language skills at the same age as their peers with normal hearing. Even infants with profound hearing loss will do well with the right combination of treatments.

If the baby has a disorder that affects more than hearing, the prognosis depends on the particular disorder and what other effects it has on the body.

Complications:

Complications include:

• Delays talking and being able to understand words
• Delays in the ability to make friends
• Emotional problems due to feelings of isolation
• Falling behind in school
• If hearing loss is the result of a disease or syndrome that affects other parts of the body, other complications, specific to that syndrome or disease, may also occur.

Children with cochlear implants may be at a higher risk for bacterial meningitis (inflammation around the brain, which may spread through the blood to the rest of the body). Vaccinations against several types of bacteria that cause meningitis are available, and may reduce the risk of the disease in a child with a cochlear implant. For guidelines, consult your health care provider.

Calling your health care provider:

Call your health care provider if your baby or young child displays signs of hearing loss, such as not reacting to loud noises, not making or mimicking noises, or not speaking at the expected age.

If your child has a cochlear implant, call your health care provider immediately if your child develops a fever, stiff neck, headache, or an ear infection.

Prevention:

It is not possible to prevent all cases of hearing loss in infants.

Women who are planning to become pregnant should make sure they are current on all vaccinations.

Pregnant women should check with their doctor before taking any medications. If you are pregnant, avoid activities that can expose your baby to dangerous infections such as toxoplasmosis.

If you or your partner has a family history of hearing loss, you may want to get genetic counseling before becoming pregnant.