Newborn Infant Hearing Screening (cont.)
John Mersch, MD, FAAP
Dr. Mersch received his Bachelor of Arts degree from the University of California, San Diego, and prior to entering the University Of Southern California School Of Medicine, was a graduate student (attaining PhD candidate status) in Experimental Pathology at USC. He attended internship and residency at Children's Hospital Los Angeles.
Jillyen E. Kibby, MA, CCC-A
Ms. Kibby received her master's degree in Audiology with honors from California State University, Long Beach, and is currently pursuing her doctorate at the University of Florida. She completed her clinical fellowship and spent seven years at Texas Children's Hospital in Houston, where she trained for her pediatric specialty.
James K. Bredenkamp, MD, FACS
Dr. Bredenkamp recieved his medical degree from the University of California, San Francisco School of Medicine. He then went on to serve a six year residency at the University of California, Los Angeles School of Medicine in the department of Surgery.
In this Article
- What is a newborn infant hearing screening program?
- Why is it important to screen for hearing loss in all newborn infants?
- How common is hearing loss in infants?
- What are some of the causes of hearing loss in the newborn?
- How is hearing in infants tested?
- What is an ABR test?
- What is an OAE evaluation?
- OAEs and ABRs, is one test better than the other?
- What does it mean when an infant does not pass the hearing screen?
- What is the difference between a hearing screen and a diagnostic hearing test?
- If an infant does not pass a hearing screen in the hospital, what happens next?
- If an infant has a hearing loss, what is the next step?
- Find a local Pediatrician in your town
What is an OAE evaluation?
An otoacoustic emission test (OAE) measures an acoustic response that is produced by the inner ear (cochlea), which in essence 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 infant's ear. As the infant rests quietly, sounds are generated in the probe. 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 infant'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 determine which sounds yielded a response/emission and the strength of those responses. If there is an emission present for those sounds that are critical to speech comprehension, then the infant has "passed" the hearing screen. Testing generally takes about five to eight minutes.
OAEs and ABRs, is one test better than the other?
Both tests have advantages and disadvantages when used for screening, and depending on the program and experience of the audiologist, either one can be utilized successfully. The OAE is easy and cost-effective. However, the false-positive rate (for example, an infant fails a hearing test but actually has normal hearing) may be higher for an OAE than for an ABR. The false-positive rate for ABR testing is approximately 4% when testing is done during the first three days of life. The false positive rate for OAE testing is 5%-21% for testing done during the first three days of life. This large variation between ABR and OAE testing is commonly felt to reflect the OAE testing device's increased sensitivity to residual amniotic fluid and vernix that is commonly found in the neonate's ear canal.
The two tests, however, rely on different mechanisms of hearing for the screening. For in-depth testing and a complete hearing evaluation of infants, these tests work best together as a complement to each other.
What does it mean when an infant does not pass the hearing screen?
A newborn who fails an initial hearing screen may not necessarily have a permanent hearing loss or a hearing loss at all. There are many possible reasons why an infant may fail a hearing screening test. One common reason is that fluid from the birth may still be present in the ear canal. This fluid blocks the sound stimulus, preventing it from reaching the inner ear, and therefore causes the newborn to fail. Similarly, fluid in the middle-ear space behind the eardrum (a common site for infection in children) can also block the sound stimulus and lead to a false failed test. After these problems resolve, the infant usually passes the rescreen. Therefore, it is important to have at least one week between the initial hearing screen and the rescreen to allow the newborn a chance to "dry out."
Another possible reason for a false failure is excessive noise or movement from the infant during the test. The responses that are recorded with an ABR or OAE are very, very small. Any movement or crying from the infant can prevent the equipment from detecting the response. Therefore, it is important that the newborn is quiet or sleeping for the hearing screen. Feeding the infant just prior to the screening is often very helpful. Although neither test is painful, they are novel experiences for the newborn and can be momentarily upsetting.
If it becomes evident that an infant has a hearing loss, then a full diagnostic exam is necessary to determine the type and amount of hearing loss.
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