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October 13, 2008

On Guard for Infant Hearing Loss
By Kim M. Norton
For The Record
Vol. 20 No. 21 P. 24

Early diagnosis and intervention are the keys to success.

In the womb, the sense of hearing is one of the first to connect a fetus with its mother. Infants can hear their mother’s voice while being exposed to a plethora of sounds, including what will become their native language. However, hearing loss can stunt that language exposure. To further complicate matters, hearing loss is considered a low-incidence disability—only one to two children per 1,000 are affected—that can lead to apathy among healthcare professionals about the importance of follow-up.

Historically, children with a hearing loss are not diagnosed until they are aged 2 or older, when they fail to start speaking. “In failing to diagnose these children until they are 2 or 3 years old, the critical time period for listening and language development has passed,” says Pamela Mason, AUd, director of audiology and professional practice with the American Speech-Language-Hearing Association (ASHA).

Often, it’s understandable how parents and healthcare professionals can miss hearing loss. “Children with a hearing loss are very good at ‘pretending’ to be hearing because when they appear to turn toward a sound, they are really turning toward a vibration or movement,” says Maegan Mapes, AUd-CCC-A, of REM Audiology in Medford, N.J.

To help eliminate the delay with diagnosing children, legislation was passed in 1999 that resulted in a universal newborn hearing screening (UNHS). “The goal of the [UNHS] is to screen every newborn after birth and before they are discharged from the hospital to help at-risk children to learn a language in a natural manner because there will be no lag time for them without language exposure,” says Mapes.

“Universal screenings have revolutionized hearing diagnoses, and some studies have shown that if the diagnosis is detected early enough, the parents can educate themselves to make some decisions. [Depending on the parents’ choices], something can be done around the child’s first birthday to help them hear well,” says Gregory J. Artz, MD, an otolaryngologist at Thomas Jefferson Medical Center in Philadelphia. The UNHS has been so successful that more than 90% of the children born in the United States have been screened for hearing loss, adds Mason.

The UNHS is the first step in the Early Hearing Detection and Intervention (EHDI) program. Following the initial hearing screenings, EHDI remains in touch with a newborn’s family until the proper audiological examinations have been completed. Should a hearing loss be diagnosed, EHDI would ensure that the family receives the appropriate intervention services, Mason says.

Thanks in part to the UNHS, children with hearing difficulties are being identified earlier than ever before, says Mapes. “In the past, children who were not talking by age 2 would enter early intervention with a language and/or cognitive delay. After speaking with the parents and learning that hearing loss may be in the family, the connection is made.”

Yvonne L. Collins, a special education teacher of the deaf with Early Intervention Services of Burlington County in Trenton, N.J., agrees that the UNHS has made a difference. “The influx of children who are identified early as having a hearing loss is proving to be a challenge to us because we have to adapt to having the younger children receiving services,” she says. “The role of early intervention is to help educate and support the family and the child in achieving their particular goals and to provide a framework for the building blocks of communication whether a hearing aid, the cochlear implant, ASL [American Sign Language], oral, or pidgin.”

Follow-up and early diagnosis are critical to the success of the child emotionally, socially, and academically. The UNHS, EHDI, and the Joint Committee on Infant Hearing have made great strides in their recommendations and guidelines for detecting hearing loss, educating parents and professionals, and providing intervention services when necessary.

Diagnosing the Loss
Most hospitals use one of two screening tests: otoacoustic emission (OAE) or the auditory brainstem response (ABR). “Both tests can detect a sensorineural hearing loss [SNHL] and a conductive hearing loss, but it is important to remember that these preliminary tests are just screening tests,” says Artz. Should the child refer on the screening, follow-up is necessary with an audiologist to determine if there is a problem, he adds.

The difference between the tests is a matter of sophistication. The OAE tests the function of the outer hair cells by placing a microphone in the ear canal while a computer analyzes the echo. If no echo is detected, a hearing loss may be present, and further evaluation is necessary, says Artz.

The ABR goes beyond the OAE in that it detects what kind of loss may be present by bypassing the inner ear and monitoring responses at the auditory nerve. Sensors are placed on specific spots of the skull to detect responses at the nerve level. Both the ABR and the OAE do not require the newborn’s participation to be effective, Artz says.

Both tests have a “pass” and “refer” response at their conclusion. “Patients who receive a pass require no further evaluation, but those children who refer should be retested at least two more times before they are discharged from the hospital,” Mapes says. “If the child referred each subsequent time, then there should be a two-week lag before the next test to allow for any trapped amniotic fluid to dissipate or repeat tests will be a waste of time.”

After the two-week delay, the child should see an audiologist to undergo a repeat screening and a tympanogram, which measures the ear’s response to different sounds and pressures to rule out middle ear issues. If the tympanogram is abnormal, issues such as fluid behind the eardrum must be resolved or addressed, says Mapes. A diagnostic ABR, while either sedated or unsedated, would be the next step in identifying the type of loss and the degree to which the hearing is affected.

Types of Hearing Loss
The ear is divided into three parts: outer, middle, and inner. The outer ear consists of the pinna and the ear canal; the middle ear features the eardrum, ossicles, and the Eustachian tube; and the inner ear is composed of the cochlea, cilia, and the body’s balance system. The type of hearing loss a child has correlates to a specific part of the ear.

There are three types of hearing loss: conductive, SNHL, and mixed. A conductive hearing loss is located in the outer or middle ear and can be caused by a number of issues. The outer ear, ear canal, or middle ear may be absent or malformed, or there may be fluid, earwax, or an infection in the ear that can cause a reversible hearing loss. “Someone with a conductive hearing loss will hear sounds at reduced levels, and speech may sound muffled,” says Mason. Conductive hearing loss can be surgically treated with tubes or reconstruction of the outer ear.

SNHL, a permanent condition that cannot be surgically treated or repaired, affects the inner ear, limits language development without proper intervention, and could lead to a failure to develop speech altogether, according to Mapes.

Mixed hearing loss involves all three parts of the ear. “Of the three types of losses, this can be the most frustrating because you can treat the conductive part of the loss only to discover that a SNHL is present that may not be overcome,” Mapes says. “Putting tubes in a 2-month-old’s ear can help to determine the level of loss and isolate the conductive loss before proceeding with the degree of loss due to the SNHL.”

Once the type of loss has been identified, the next step is to determine the level of hearing, including what frequencies the child may or may not hear and what interventions are necessary.

Degrees of Hearing Loss
An audiogram looks at both frequency (from 125 to 8,000 Hertz) and loudness (from 0 to 120 decibels). To understand the audiogram, each vertical line represents a frequency, with the right side being the low frequencies and the left being the high frequencies. Examples of low frequency sounds are vowel sounds, a bass drum, and a tuba. High frequency sounds include consonants, a bird chirping, and silverware scraping. Along the horizontal of the audiogram are the decibels. The top of the audiogram represents softer sounds, such as a whisper or breathing, while the lower part contains louder sounds, such as a chain saw or an airplane taking off, according to the ASHA.

“Typical hearing is considered normal when the person hears at 20 decibels or better,” explains Ted Meyer, MD, PhD, an otolaryngologist and director of the Medical University of South Carolina’s Cochlear Implant Program in Charleston. After the type of loss has been diagnosed, the task becomes determining the degree of the loss to figure out how best to proceed with intervention, amplification, or cochlear implantation, he says.

It is estimated that more than 3 million children in the United States suffer from hearing loss, with approximately 1.3 million of those under the age of 3, according to the American Academy of Otolaryngology—Head and Neck Surgery. However, Mapes says profound hearing loss is rare.

According to EHDI, the four degrees of hearing loss are the following:

• Children with a mild loss will hear between 25 and 40 decibels, meaning they will not hear soft sounds, have difficulty hearing in noisy places, ask for things to be repeated, have some speech deviations, be slow when learning to speak, and possibly have their educational progress delayed if amplification and intervention is not provided.

• With a moderate loss, a child will hear between 40 and 60 decibels, which is similar to a mild loss except that speech is more difficult to decipher. There may be articulation and voicing issues, and vocabulary, reading, and spelling may suffer. Additionally, hearing aids and lip reading may be necessary to communicate.

• In cases of severe hearing loss, which ranges from hearing 60 to 90 decibels, the child can hear only very loud noises and is unable to hear speech. The condition necessitates a hearing device and supportive services such as speech and language therapy.

• At 90 decibels and above, a profound hearing loss occurs, resulting in a child hearing little or no sound. Depending on the communication method chosen, he or she may not learn to use his or her voice and will rely on lip reading, sign language, hearing aids, or a cochlear implant to communicate.

Following the UNHS, all test information is forwarded to EHDI to follow up with those children who referred on the initial screenings. According to Joint Committee on Infant Hearing guidelines, newborns should be screened for a hearing loss at the age of 1 month. Those who do not pass the initial screening should be seen by an audiologist for further evaluation at the age of 3 months; by 6 months of age, the child should be receiving appropriate intervention.

“Follow-up for children who refer on the UNHS is and has been a big problem in South Carolina. At least one third of the children who refer on the initial screenings rarely follow up,” says Meyer. In the long run, most of these children had nothing more than wax buildup or some external issue causing a conductive hearing loss that later resolved itself. However, for those cases where the loss is not temporary, Meyer may not see them again until an annual checkup, during which the parents will question the child’s lack of language skills and behavior problems.

South Carolina is not the only state grappling with children lost to follow-up. An astonishing 51% of children nationally follow the same pattern due to a myriad of issues, says Mason. “EHDI is designed to follow up with the parents of these children, but if test information is never forwarded onto EHDI from the initial screenings, it is impossible to track these children,” she says.

Outside of relying on EHDI, there is the child’s pediatrician. However, relying on the pediatrician to follow up on a referred hearing screening is difficult. “Pediatricians do not react appropriately when a child refers on the screening test,” Mapes says. “They do not push parents to follow up because the incidence of hearing loss is so low and chances are they do not have a single patient in their practice that has or has had a hearing loss to necessitate a follow-up.”

The Missed Diagnosis
When referring to the audiogram and contemplating what a moderate, severe, or profound loss means to a child, it’s apparent that missing a diagnosis can lead to frustration down the road for all involved, says Mapes.

Robert Keegan, an ASL specialist at the Pennsylvania School for the Deaf (PSD) in Philadelphia, sees firsthand the ramifications of children who are unable to communicate. He’s witnessed cases in which a missed diagnosis meant isolation and a lack of peer relationships.

“The child with the hearing loss needs exposure to language, and parents and caregivers who have a vested interest in the success of the child can help the child succeed,” he says. “Given access to language, the child will communicate. At PSD, we encourage parents to play with language with their children to help them catch up to their hearing peers. For hearing parents with a deaf child, this is especially important because the parent can expose the child to language in a play environment through facial expressions and mimicry.”

— Kim M. Norton is a New Jersey-based freelance writer specializing in healthcare related topics for various trade and consumer publications. She can be contacted at kim_norton1@hotmail.com.