Newborn Hearing Screenin : Part 2

by CDC

(Page 2 of 3)

What is an Otoacoustic Emissions (OAE)?

Otoacoustic Emissions - is a test that checks the inner ear response to sound and is measured by placing a very sensitive microphone in the ear canal to measure the ear's response to sound.

What is the difference between Auditory Brainstem Response testing and Behavioral Audiometry Evaluation?

To understand the difference between Auditory Brainstem Response (ABR) testing and Behavioral Audiometry Evaluation (please see below for an explanation), it is important to understand a little about how the ear works.

The ear has three main parts: the outer ear, the middle ear, and the inner ear.

1. The outer ear includes the visible portion of the ear and the ear canal. Sound waves travel through these two areas of the outer ear.

2. The middle ear includes the eardrum (the tympanic membrane) and three small bones (ossicles). The movement of the tympanic membrane makes the ossicles vibrate.

3. The inner ear includes a snail-shaped fluid-filled cochlea, which contains thousands of sound receptors (hair cells). The inner ear is responsible for changing the sound vibrations into electrical signals. The electrical signals are picked up by the hearing (acoustic) nerve. The acoustic nerve sends the sound to the brain.

When an adult or child has a hearing loss, one or more of these parts are not working in the usual way. In order to fully test hearing, all parts of the ear, the acoustic nerve, and the brain pathways that are involved in hearing must be tested for proper functioning.

Auditory Brainstem Response (ABR) testing focuses only on the function of the inner ear, the acoustic nerve, and the brain pathways that are associated with hearing. This test is used for babies, children, and adults. For this test, electrodes are placed on the individual's head (similar to electrodes placed around the heart when an electrocardiogram is done), and brain wave activity in response to sound is recorded. Because this test does not rely on behavior, the adult or child being tested can be sound asleep during the test.

Behavioral Audiometry Evaluation tests the function of all parts of the ear, including the acoustic nerve and the brain pathways involved in hearing. Infants and toddlers are observed for changes in their behavior such as sucking a pacifier, quieting, or searching for the sound. They are rewarded for the correct response by getting to watch an animated toy (this is called visual reinforcement audiometry). Sometimes older children are given a more play-like activity (this is called conditioned play audiometry). The child being tested must be awake and cooperative during this test.

Why is more than one hearing screening test necessary?

Hearing loss in an infant or child cannot be confirmed with one test alone. Several tests must be done to check different parts and different functions of the ear. Audiologists refer to a group of tests as a "battery of tests". Because Behavioral Audiometry Evaluation tests the function of all parts of the ear, it is considered fundamental to the battery of tests used to evaluate older infants and children for hearing loss. However, because this test relies on behavior and the cooperation of the infant, it is not reliable until the child reaches the developmental age, of 5 to 6 months. For children younger than 5 to 6 months of age and for children who are developmentally delayed, ABR testing is considered the most important of these tests.

About the Author

www.cdc.gov
The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.