Diseases

A thorough diagnostic test also includes an evaluation of the middle-ear system. The middle ear is the space behind the eardrum and is a common site for ear infections in children. A tympanogram is a measure of the compliance of the middle-ear system mobility (including the eardrum) and is an objective method for confirming abnormalities of the eardrum or middle ear space, such as

• fluid behind the eardrum,
• a hole or perforation of the eardrum, or
• stiffness of eardrum or middle-ear bones (for example, otosclerosis).

The tympanogram is completed by inserting a probe in the ear and creating a vacuum-tight seal. The air pressure is changed in the ear canal from positive to negative, and the movement of the eardrum is recorded. The amount and shape of the movement can either exclude or signify different problems, as previously listed. The test is fast, objective, and is not painful (although sometimes the insertion of the probe may upset children). When a loud sound is presented to a healthy ear, the eardrum will contract, a sort of built-in hearing protection mechanism (although it's not very effective). This contraction of the eardrum is called the acoustic reflex. The absence of this reflex can further confirm problems of the middle ear or may help to identify or confirm a hearing loss. Acoustic reflexes are typically evaluated concurrent with the tympanogram. Many general pediatricians perform this test in their offices as a screening test and to aid in the diagnosis of ear infections or effusions (fluid in the middle ear space).

A child of any age can be tested with the appropriate hearing test. The type of test utilized depends on the child's age in years or developmental level. Some hearing tests require no behavioral response from the child, while other tests utilize games that entice a child's interest. The key is to find the right test method for each child.

Some children are unable to cooperate for hearing evaluations, either due to their age or to a developmental delay (for example, a child with severe mental retardation). Currently, there are two different types of tests that are utilized for children who are unable to cooperate. The first is the frequency-specific auditory brainstem response (ABR) evaluation. An ABR is a physiological measure of the brainstem's response to sound. It tests the integrity of the hearing system from the ear to the brainstem. The test is performed by placing four to five electrodes on the child's head, after which a variety of sounds are presented to the child through small earphones. As the hearing nerve fires, the sound stimulus travels up to the brain. The electrical activity generated by the nerve can be recorded by the electrodes and presented as waveforms on a computer screen. The audiologist can then present different loudness levels of each sound and determine the softest levels at which the child can hear. The child can be tested using all the sounds of a conventional hearing evaluation (adult hearing evaluation). The limitation of the ABR is the need for the child to be quiet and still. The electrical potential the computer is recording from the auditory nerve is very small. Any muscle movement, including something as small as an eye blink, can obliterate the hearing response; therefore, the infant or child must be sleeping during the test. Infants less than 3 months old can be tested during natural sleep. Children older than 3 months are typically sedated for about one hour (under the supervision of a physician) during the test. The most common oral sedative used is chloral hydrate. The second type of test to objectively evaluate children is the otoacoustic emission (OAE) test. This test can be done as a supplement to the ABR or as an initial screen of hearing. An otoacoustic emission test measures an acoustic response produced by the inner ear (cochlea). The acoustic response measured is in essence the response produced by the inner ear as it bounces back out of the ear in response to a sound stimulus. The test is performed by placing a small probe that contains a microphone and speaker into the child's ear. Otoacoustic Emissions (OAE) Photo - Hearing Loss in Children As the child sits or rests quietly, sounds are generated in the probe and responses that come back from the cochlea are recorded. Once the cochlea processes the sound, an electrical stimulus is sent to the brainstem. In addition, there is a second and separate sound that does not travel up the nerve but comes back out into the child's ear canal. This "byproduct" is the otoacoustic emission. The emission is then recorded with the microphone probe and represented pictorially on a computer screen. The audiologist can tell which sounds yielded a response/emission and the strength of those responses. If there is an emission present for those sounds critical to speech comprehension, then the child has "passed" the hearing screen. As a supplement to the ABR, the OAE serves as a crosscheck to either confirm normal hearing or verify the site-of-lesion for the hearing loss as the inner ear. OAE tests the integrity of the hearing organ for sound (the cochlea), but it does not evaluate the hearing beyond the cochlea. That is why the OAE is often paired with the ABR or with a behavioral test that can evaluate a child's responsiveness to sound. The results from an ABR and an OAE evaluation can predict the child's hearing, determine if there is a loss, determine the type of hearing loss, and help with decisions regarding intervention. Intervention can include medical treatment, surgery, or hearing aids and therapy.

Cooperative and alert infants or young children (ages 5 months to 2 and a half years) are frequently tested using a method called visual reinforcement audiometry (VRA). For this test, the child sits on a caregiver's lap in the center of a room. Play Audiometry Photo - Hearing Loss in Children Speakers are situated to the child's right and left side. The speakers have toys (usually mounted inside boxes) hung below, which can be animated by the tester. The child is then "conditioned" to turn his or her head toward the side from which the sound is presented. When the child turns to the correct side, the toy is lit up, providing positive reinforcement that encourages the child to continue participating in the task. Children (and adults) will instinctively turn toward a novel sound without having to think about the response, which is why this test is effective for children as young as 5 months of age. This method can also be used with small insert earphones, which allow the hearing of each ear to be tested individually. Below is a diagram of the setup for the VRA test. VRA Setup Illustration - Hearing Loss in Children There are, however, some limitations to the VRA test. For an accurate test, the child must participate and needs to be cooperative and alert. Additionally, if only speakers are used for testing, the results can only be used to predict hearing for the "better" ear. There is no way to tell if both ears are hearing the test sounds, or if only one ear is hearing all of the sounds, unless a device is utilized to isolate the ears (for example, earphones). It is not unusual, however, to achieve test results for individual ear information by having the child wear earphones during portions of the VRA test. The ability to localize sound even with one impaired ear can be quite good. Often, otoacoustic emission (OAE) tests are completed in conjunction with VRA testing to obtain some ear-specific results (OAE tests will be discussed later in this article). Children 3-5 years of age who are capable of more complicated tasks are often tested using a technique called play audiometry, in which sounds are paired with a specific response or task. For example, a child is taught to hold a peg next to his or her cheek. When the child hears the sound, the child places the peg on a Peg-Board. Play Audiometry Photo - Hearing Loss in Children Speech testing can be completed using pictures, for example, the child points to the correct picture as the tester's voice is presented at softer and softer levels. Once again, the child needs to be a willing participant. The advantage of this format is that results obtained are often as detailed as an adult test session.

There are a number of risk factors for hearing loss in children, so there are a number of special reasons why a child's hearing may need to be screened or tested. Common indications for a hearing evaluation include

• speech delay,
• frequent or recurrent ear infections,
• a family history of hearing loss (hearing loss can be inherited),
• syndromes known to be associated with hearing loss (for example, Down syndrome, the Alport syndrome, and Crouzon syndrome),
• infectious diseases that cause hearing loss (for example, meningitis, measles, and cytomegalovirus [CMV] infection),
• medical treatments that may have hearing loss as a side effect, including some antibiotics and some chemotherapy agents,
• poor school performance, and
• diagnosis of a learning disability or other disorder, such as autism or pervasive developmental disorder (PDD).

In addition, the circumstances surrounding the pregnancy and birth may be associated with subsequent hearing loss. If there is a history that includes any of the following, a child should have a hearing assessment.

• low birth weight (less than 2 pounds) and/or prematurity
• assisted ventilation (to help with breathing for more than 10 days after birth)
• low Apgar scores (numbers assigned at birth that reflect the newborn's health status)
• severe jaundice after birth
• maternal illness during pregnancy (for example, German measles [rubella])
• hydrocephalus

Some parents start to suspect that their child cannot hear normally because the child does not respond to his or her name consistently or asks for words, phrases, or sentences to be repeated. Another sign can be that the child does not seem to be paying attention to sounds or to what is being said. On the average, only half of all children diagnosed with a hearing loss actually have a known risk factor for hearing loss. This means that the cause is never known in about half of children with hearing loss. For this reason, all states in the U.S. have instituted a universal hearing screen so that all babies have their hearing screened before they go home from the newborn nursery.

When hearing loss is identified, a thorough search for its cause must be undertaken. In many situations, the hearing loss can be attributed to an ear infection or to fluid trapped in the middle-ear space. In this situation, the pediatrician can often prescribe antibiotics to treat the infection. If the infection is persistent, or the hearing loss is still present after treatment of the infection, then the child should be referred to a medical doctor who specializes in diseases of the ear and auditory system (an otolaryngologist or ENT). The otolaryngologist will often administer further testing, and in some situations, he or she may recommend additional therapy such as surgery (ear tubes). If the hearing loss is persistent or is related to a nerve or inner-ear problem, the otolaryngologist will often recommend an evaluation by an audiologist for hearing aids and rehabilitative therapy (which includes speech therapy and social integration of the hearing-impaired child).

One of the newest tests being utilized is the auditory steady state response (ASSR) evaluation. This is a test that is used in conjunction with the ABR. It is completed while the child is sleeping, or sedated, and it makes recordings from the auditory nerve as the response travels up to the brainstem. The generators for this test are commonly accepted to be similar to those of the ABR. One advantage of ASSR is that the stimuli used to test the child's hearing are more frequency-specific, which allows the audiologist to predict hearing levels for a wide range of sounds with increased accuracy. In addition, the ASSR is faster and has the ability to test at levels somewhat louder than the ABR (due to equipment limitations of the ABR), making the distinction between severe and profound losses more clear. It should be noted, however, that results for a mild hearing loss and normal hearing are indistinguishable from each other, so there is potential for a misdiagnosis for children with mild hearing loss.

A specialist who tests a person's hearing is called an audiologist. An audiologist has an advanced degree (minimum of master's degree) in diagnostic hearing testing techniques and auditory rehabilitation for children and adults. However, because testing hearing in children requires specific equipment, setup, and training, not all audiologists test children. When a child is referred for a hearing evaluation, it should be confirmed at the time of scheduling that the testing audiologist has a pediatric specialty and the appropriate setup to test hearing in children.

A child with undetected hearing loss may not be able to develop normal speech and language or acquire the cognitive abilities (knowing, thinking, and judging) needed for learning. Children whose hearing loss is not identified until, for example, 2 or 3 years of age may suffer from permanent impairment of speech, language, and learning. The early identification of hearing loss permits the initiation of treatment and rehabilitation of the hearing-impaired child at a very young age. The child can then learn more normal speech skills when hearing loss is identified early and intervention begins. Hearing loss can range from a mild impairment to profound loss. Many people think that hearing is only graded as normal or deaf. They may also think that the child is hearing normally if he or she is responding to sounds and voices. However, there are many subtle gradations between normal hearing and deafness and a child's hearing loss may not be apparent. For example, it is common for a child with moderate hearing loss to develop speech and language and yet miss over half of what is being said. A child in this situation will have a distinct disadvantage in development and learning and will often reach a point where advancement stops unless the hearing loss is detected and treatment begins. The stress on a child with hearing loss (and their family) can be enormous because the child does not understand why it is constant struggle to learn seemingly simple material (and the family is baffled as to why their bright child is not doing well). The degree of hearing loss often determines the impact it will have on the child throughout life. However, with early identification and treatment, the impact can be lessened.