Hearing Evaluation in Children

en españolEvaluación de la audición en los niños

In the first few years of life, hearing is a critical part of kids' social, emotional, and cognitive development. Even a mild or partial hearing loss can affect a child's ability to develop speech and language properly.

The good news is that hearing problems can be overcome if they're caught early — ideally by the time a baby is 3 months old. So it's important to get your child's hearing screened early and checked regularly.

Causes of Hearing Loss

Hearing loss is a common birth defect, affecting about 1 to 3 out of every 1,000 babies. Although many things can lead to hearing loss, about half the time, no cause is found.

Hearing loss can occur if a child:

• was born prematurely
• stayed in the neonatal intensive care unit (NICU)
• had newborn jaundice with bilirubin level high enough to require a blood transfusion
• was given medications that can lead to hearing loss
• has family members with childhood hearing loss
• had certain complications at birth
• had many ear infections
• had infections such as meningitis or cytomegalovirus
• was exposed to very loud sounds or noises, even briefly

When Should Hearing Be Evaluated?

Newborn hearing screening identifies most children born with a hearing loss. But in some cases, the hearing loss is caused by things like infections, trauma, and damaging noise levels, and the problem doesn't emerge until later in childhood. Researchers believe that the number of people who have hearing loss doubles between birth and the teen years. So it's important to have kids' hearing checked regularly as they grow.

Your newborn should have a hearing screening before being discharged from the hospital. Every state and territory in the United States has now established an Early Hearing Detection and Intervention (EHDI) program; the program identifies every child with permanent hearing loss before 3 months of age, and provides intervention services before 6 months of age. If your baby doesn't have this screening, or was born at home or a birthing center, it's important to have a hearing screening within the first 3 weeks of life.

If your baby does not pass the hearing screening, it doesn't necessarily mean there's a hearing loss. Because debris or fluid in the ear can interfere with the test, it's often redone to confirm a diagnosis.

If your newborn doesn't pass the initial hearing screening, it's important to get a retest within 3 months so treatment can begin right away. Treatment for hearing loss can be the most effective if it's started before a child is 6 months old.

Kids who seem to have normal hearing should continue to have their hearing evaluated at regular doctors' appointments. Hearing tests are usually done at ages 4, 5, 6, 8, and 10, and any other time if there's a concern.

But if your child seems to have trouble hearing, if speech development seems abnormal, or if your child's speech is difficult to understand, talk with your doctor.

Symptoms of a Hearing Loss

Even if your newborn passes the hearing screening, continue to watch for signs that hearing is normal. Some hearing milestones your child should reach in the first year of life:

• Most newborn infants startle or "jump" to sudden loud noises.
• By 3 months, a baby usually recognizes a parent's voice.
• By 6 months, a baby can usually turn his or her eyes or head toward a sound.
• By 12 months, a baby can usually imitate some sounds and produce a few words, such as "Mama" or "bye-bye."

As your baby grows into a toddler, signs of a hearing loss may include:

• limited, poor, or no speech
• frequently inattentive
• difficulty learning
• seems to need higher TV volume
• fails to respond to conversation-level speech or answers inappropriately to speech
• fails to respond to his or her name or easily frustrated when there's a lot of background noise 

Types of Hearing Loss

Conductive hearing loss is caused by blockage in the transmission of sound to the inner ear. Ear infections are the most common cause of this type of hearing loss in infants and young children. This loss is usually mild, temporary, and treatable with medicine or surgery.

Sensorineural hearing loss can happen when the sensitive inner ear (cochlea) has damage or a structural problem, though in rare cases it can be caused by problems with the auditory cortex, the part of the brain responsible for hearing. Cochlear hearing loss, the most common type, may involve a specific part of the cochlea such as the inner hair cells, outer hair cells, or both. It usually exists at birth, and can be inherited or come from other medical problems, though sometimes the cause is unknown. This type of hearing loss is usually permanent.

The degree of sensorineural hearing loss can be:

• mild (a person cannot hear certain sounds)
• moderate (a person cannot hear many sounds)
• severe (a person cannot hear most sounds)
• profound (a person cannot hear any sounds)

Sometimes the loss is progressive (gets worse over time) and sometimes unilateral (one ear only).

Because the hearing loss can get worse over time, audiologic testing should be repeated later on. Although medicines and surgeries cannot cure this type of hearing loss, hearing aids can help children hear better.

Mixed hearing loss happens when a person has both conductive and sensorineural hearing loss.

Central hearing loss occurs when the cochlea is working properly, but other parts of the brain are not. This rarer type of hearing loss is more difficult to treat.

Auditory processing disorder (APD) is a condition in which the ears and brain cannot fully coordinate. People with APD usually hear well when it is quiet, but cannot hear well when it is noisy. In most cases, speech-language therapy can help kids with APD.

How Hearing Is Tested

Several methods can be used to test hearing, depending on a child's age, development, and health status.

During behavioral tests, an audiologist carefully watches a child respond to sounds like calibrated speech (speech that is played with a particular volume and intensity) and pure tones. A pure tone is a sound with a very specific pitch (frequency), like a note on a keyboard.

An audiologist may know an infant or toddler is reponding by his or her eye movements or head turns. A preschooler may move a game piece in response to a sound, and a gradeschooler may raise a hand. Children can respond to speech with activities like identifying a picture of a word or repeating words softly.

Other Tests to Evaluate Hearing

If a child is too young to get behavioral hearing testing, or has other medical or developmental problems to prevent this type of test, doctors can check for hearing problems by looking at how well the ear, nerves, and brain are working.

Auditory brainstem response (ABR) test

For this test, tiny earphones are placed in the ear canals and small electrodes (sensors which look like small stickers) are placed behind the ears and on the forehead. Usually, clicking sounds are sent through the earphones, and the electrodes measure the hearing nerve's response to the sounds.

Young infants under 6 months can sleep for the entire test, but older infants may need sedation for this test. Older cooperative kids can do this testing in a silent environment while they're visually occupied.

Normal hearing has a certain appearance when test results are measured on a chart. Because of this, a normal ABR suggests that a baby's inner ear and lower part of the auditory system (brainstem) are working normally for typical speech. An abnormal ABR may be a sign of hearing loss, but it may also be due to some medical problems or measurement problems.

Auditory steady state response (ASSR) test

This test is similar to the ABR, though an infant usually needs to be sleeping or sedated for the ASSR test.

Sound passes into the ear canals, and a computer picks up the brain's response to the sound and automatically decides whether hearing loss is mild, moderate, severe, or profound. This ASSR test has to be done with (and not instead of) ABR to check for hearing.  

Central auditory evoked potential (CAEP) test

This test is similar to the ABR, and uses the same tiny earphones and small electrodes. This CAEP test allows the audiologist to see if the pathways from the brainstem to the auditory cortex are working properly. The audiologist may recommend a CAEP test for some specific types of hearing loss. This test can be done at any age and does not require participation from the child. 

Otoacoustic emissions (OAE) test

A sleeping infant or an older child who may be able to sit quietly can do this quick test. A tiny probe is placed in the ear canal, then many pulsing sounds are sent and the probe records an "echo" response from the outer hair cells in the inner ear. These recordings are averaged by a computer.

A normal recording suggests that the outer hair cells are working well. But in some cases, a hearing loss may still happen if other hearing pathways are not working normally. 

Hospitals use ABR or OAE to screen newborns. If a baby fails a screening, the test is usually repeated. If the screening is failed again, the baby is sent to an audiologist for a full hearing evaluation.

Tympanometry

Tympanometry is not a hearing test but a procedure that can show how well the eardrum moves when a soft sound and air pressure are introduced in the ear canal. It's helpful in identifying middle ear problems, such as fluid collecting behind the eardrum.

A tympanogram puts the tympanometry results into a graph. A "flat" line on a tympanogram may indicate that the eardrum can't move, while a "peaked" pattern usually suggests that the ear drum is moving normally. Doctors who do this exam should also do a visual ear examination and see the ear drum. 

Middle ear muscle reflex (MEMR)

The MEMR (also called acoustic reflex test) tests how well the ear responds to loud sounds by evoking a reflex. In a healthy ear, this reflex helps protect the ear against loud sounds. 

For the MEMR, a soft rubber tip is placed in the ear canal. A series of loud sounds are sent through the tips into the ears and a machine records whether the sound has triggered a reflex. Sometimes the test is done while the child is sleeping.

Who Performs Hearing Tests?

A pediatric audiologist specializes in testing and helping kids with hearing loss and works closely with doctors, teachers, and speech/language pathologists.

Audiologists have a lot of specialized training. They have master's or doctorate degrees in audiology, have performed internships, and are certified by the American Speech-Language-Hearing Association (CCC-A) or are Fellows of the American Academy of Audiology (F-AAA).

Hearing Aids and Other Interventions

While medical treatments and surgery can help people with certain types of hearing loss, hearing aids are the main treatment for sensorineural hearing loss. The most common type of hearing loss involves outer hair cells that do not work properly. Hearing aids can make sounds louder and overcome this problem.

A hearing aid has three basic parts: the microphone, amplifier, and receiver. Settings can be customized to make certain sounds louder.

Some hearing aid styles are worn on the body while others fit behind the ear or in the ear. If regular hearing aids can't be used — as in certain types of conductive hearing loss — specialized hearing aids that attach to the skill bone can send sound waves directly to the cochlea. 

No single style or manufacturer is best — your doctor will help you choose a hearing aid based on your child's needs. Most kids with bilateral hearing loss (in both ears) wear two hearing aids.

Because they are so technology-heavy, hearing aids are expensive. Unfortunately, health insurance companies do not usually cover hearing aids, although several states now require that insurance cover at least part of their cost. Talk to your child's doctor to look for financial assistance options for hearing aids.

A specialized amplification device called an FM system (sometimes called "auditory trainers") may help kids in school. These systems have a microphone that a teacher can speak into and a receiver help by the child, which can send the sound to the ears or directly to a hearing aid. They can work well in the classroom to improve hearing in group or noisy environments and also can be fitted for personal or home use. Other assistive listening or alerting devices may help older kids.

In addition to hearing aids or FM systems, hearing rehabilitation may include auditory or listening therapy and speech (lip) reading. Technology is improving all the time, so ask your doctor about newer tools available to help aid a child's communication.

A cochlear implant is a surgical treatment for hearing loss; this device doesn't cure hearing loss, but is a device that gets placed into the inner ear to send sound directly to the hearing nerve. It can help children with profound hearing loss who do not benefit from hearing aids.