How do we test the hearing of a baby?
Our primary means of learning speech and language is passively. This means as babies/children are exposed to language, they “eavesdrop” and naturally absorb how to pronounce words and the sentence structure of the language they hear.
How do we test the hearing of a baby? They are not able to tell us when they hear a sound. We can watch their behavior after we present a sound, but the reliability is not good. What we do is a screening test called an OAE (otoacoustic emissions) to determine how the hair cells inside the hearing organ react to sound. A small probe or sound-producing device is placed in the tiny ear canal. This probe creates a clicking sound that varies in loudness and pitch or frequency. This way, we can understand what the hearing organ does with soft sound at different frequencies. Testing as many frequencies as possible is important to determine if the entire hearing organ is working well. Most hospitals offer this test prior to the baby going home. If a baby is born at home, a hearing test can be scheduled at an outpatient office. If a baby does not pass the test in both ears, a referral is made to an outpatient testing facility.
It is important to have the follow-up test completed as quickly as possible. Once babies are three months old or so, they recognize strangers and will not sleep during the test. They want to know what is going on! So, we strongly encourage parents to have the follow-up test within a few weeks of leaving the hospital. One trick for helping the test to be as successful as possible is to play with your infant’s ears while feeding or other cuddle time. This way, the infant associates ear touching with comfort time. This is a good habit to continue through two years of age. Babies that are accustomed to people touching their ears will not react negatively when the doctor looks in the ear canal during a well visit. Another recommendation for the newborn is to gently massage the ears and canal opening. This helps move the natural vernix that may be trapped in the canal. The excessive vernix may be plugging up the canal, causing the hearing to be reduced. Doing these two pre-appointment actions will help ensure the best possible follow-up test.
If the follow-up OAE screening indicates a hearing loss, the next step is to have a diagnostic hearing test. This is called an ABR (auditory brainstem response.) This test traces how sound goes into the brain and where any interruption might be. An audiologist does this test. Again, the younger the baby, the better. Babies need to sleep and be perfectly still during these procedures, so it is important to take advantage of how much a very young baby sleeps. There is absolutely zero pain in both tests and the sound is pleasant, so usually babies will sleep in the caregivers’ arms right through these tests. The audiologist will place a few electrodes on the head with tape and put soft ear tips in the canal opening. The ABR is the gold standard for diagnostic hearing evaluations. This test will be able to differentiate between a hearing loss caused from something blocking the ear canal, a sound restriction from middle ear fluid or other middle ear issues as well as a permeant nerve hearing loss in the inner ear.
The earlier we know about hearing loss, the better the outcome for speech and language learning. Time is critical when it comes to stimulating the area of the brain that receives the speech signal. We want to put hearing aids on children as soon as we identify a hearing loss. As an audiologist with more than 25 years of experience diagnosing and working with newborns through teenagers, I can attest to the success of the students who sought hearing aids as infants. QCBN
By Karon Lynn
Trinity Hearing Center is located at 1330 N. Rim Dr., Suite B in Flagstaff. For more information, visit TrinityHearing.net.
Karon Lynn, Au.D., is a doctor of audiology with 30 years of experience working with hearing impaired individuals. She may be reached at 928-522-0500 or at audio@trinityhearing.net.
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