What to Do When Baby Fails the Newborn Hearing Screen
Can My Baby Hear?
In the United States, a newborn hearing screening test is required before a baby is released from the hospital. While most babies pass the newborn screening test, some infants will score a "refer" on the screen.
Not every infant who scores a "refer" will have a hearing problem. Some infants have extra fluid from birth, which interferes with the test results. Sometimes the test is faulty, giving a "false positive" result. The point of the newborn hearing screen is not to diagnose infants with permanent hearing loss, but to identify those infants which need further testing.
It is absolutely vital to follow up on any hearing screening test which results in a "refer." Often, the hospital will retest the baby after a period of time, to see if ear fluid was causing any problems with the test. If the baby refers on a second screening test, further testing will be required.
Infants who refer on the newborn hearing screen will be referred to an audiologist for a diagnostic auditory brainstem response test (ABR), otoacoustic emissions test (OAE), tympanometry, and bone conduction testing. These tests are painless, and give a very reliable estimation of the baby's hearing ability. If a hearing problem is found, the audiologist will determine if the hearing loss is due to a potentially correctable cause (a conductive hearing loss) or if the hearing loss is not correctable (a sensorineural hearing loss).
The diagnosis of hearing loss in infants will be made by an Ear, Nose, and Throat physician (otolaryngologist) after a full evaluation by an audiologist. Recommendations for amplification (such as hearing aids or a cochlear implant) and referral to an Early Intervention program will occur quickly after the diagnosis of permanent hearing loss is made.
If your baby refers on the newborn hearing screening test, don't despair. While many babies will not have a permanent hearing loss, it is important to follow up on all the required testing. Early intervention and amplification are vital if a child is suspected of having a permanent hearing loss.
Follow Up Testing
Once a baby has referred on the newborn hearing screening program, the child's pediatrician will write a referral to an audiology center capable of handling diagnostic newborn hearing tests. The tests that will definitively assess a baby's hearing ability include the auditory brainstem response (ABR), otoacoustic emissions (OAE), bone conduction testing, and tympanograms.
An ABR Screening Test
The Auditory Brainstem Response
An ABR test is completely painless, though the test does require a sleepy baby. Often, parents will be instructed to keep the baby awake for a few hours prior to the test, so that the child will fall asleep when it is time to run the hearing test. Infants older than 4 months will probably have to be lightly sedated for this test (movement can interfere with the test results).
This test uses electroencephalogram (EEG) readings from the auditory center of the brain. Tones are played into the sleeping baby's ear, and the audiologist looks for a neural response from the baby's brain. Using this method, the technician can determine the baby's estimated hearing thresholds at each level.
Parents can be told about the baby's hearing ability shortly after the test is completed. If a hearing loss is present, this test will diagnose the specific level of hearing loss (mild, moderate, severe, or profound). In addition, this test is able to diagnose auditory neuropathy (auditory dyssynchrony) , which may have a different course of treatment than traditional hearing loss.
The ABR test may give an abnormal response if fluid or another mechanical obstruction to sound is present. For this reason, it is important to obtain bone conduction measures and an accurate tympanogram as part of the comprehensive hearing evaluation.
Otoacoustic Emissions (OAE) are tested to determine the presence of healthy cochlear hair cells: the presence of healthy hair cells indicates a healthy inner ear. The most common OAE test performed on young infants is called the transient evoked otoacoustic emissions test. A healthy cochlea will send back an "echo" of the tone sent to the ear (this is the otoacoustic emission). A tiny microphone can pick up the emission, verifying the cochlea is healthy.
OAE have limitations: if there is middle ear fluid from the birth process, or if the middle ear is otherwise compromised (middle ear bone abnormalities), the OAE will not be present. In addition, children with auditory neuropathy will have present OAE, as the cochlea is not affected by this condition. Children with mild hearing losses will sometimes have present OAE.
It is important to obtain a full hearing evaluation, as assessing the OAE will clarify the type of hearing loss (if present), or help confirm the presence of normal hearing.
This test is very fast, and emits a small amount of air pressure against the baby's eardrum. If the eardrum is "stiff" and unresponsive to the pressure, there may be fluid in the middle ear space. This is an important part of diagnosing the type of hearing loss, if present. Hearing loss caused by fluid in the middle ear space is reversible with the placement of tympanostomy tubes (also known as "ear tubes" or "grommets"). An Ear-Nose-Throat physician (ENT) will fully evaluate and treat this condition.
If the baby has a normal tympanogram, then fluid is not likely to be the cause of any detectable hearing loss.
Bone Conduction Testing
Bone Conduction testing determines whether the hearing loss is caused by the middle ear (which is generally correctable), or the inner ear (which is permanent). This testing bypasses the middle ear system, by vibrating against the mastoid bone (or another area of the baby's head). This gentle vibration sends sound directly to the inner ear: if there is still a difficulty with hearing the sound, then the hearing problem resides in the inner ear (cochlea).
If the hearing level is normal with the bone conduction testing, then the hearing problem is caused by the middle ear: there is either fluid, or the middle ear bones are not working correctly.
Sometimes, a baby has a mixed loss. In this case, the bone conduction testing will be better than the sound received through the air, but will not reach normal levels. This means the hearing loss is caused by a combination of inner ear problems (cochlear hair cell loss) and mechanical sound transmission issues (middle ear bone malformations, fluid, or bone stiffness).
It is vital to obtain bone conduction testing on every baby, to verify the exact cause of the hearing loss.
Bone Conduction Results
Air Conduction Results
Type of Hearing Loss
Bone Conduction Results Explained.
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