Auditory Brainstem Response Evaluation In-Depth

What is an ABR Evaluation?

An Auditory Brainstem Response (ABR) test is a sleep EEG hearing test that identifies the softest sounds your child's ears can detect at various pitches. EEG tests measure brain electrical activity.

How will the test be performed?

Your child will be asleep or sedated for the test, and you will be present in the testing room throughout. The test is very comfortable and painless, but it is necessary for your child to be asleep in order to obtain clear recordings during the test. Children over the age of six months are usually sedated with chloral hydrate. There will be three or four small stickers on your child's head, connected to leads going into a computer. Sounds will be presented through an earphone to each ear separately while a computer analyzes the changes in the brain wave pattern in response to sounds. ABR evaluations take approximately 2-3 hours, and the results are available right away. Don't worry if your child is very sleepy after the test; this is normal.

What should I bring to the test?

Maximize your child's comfort by bringing anything that helps her fall asleep, like a blanket or a toy. If you think your child will be heavy to carry afterward, bring a stroller. Your child will need to drink after the test, so bring clear liquid, like water.

What can my child eat or drink before the test?

If your child is less than six months old, please avoid solid food, milk, or formula for 4 hours before the test. If your child is older than six months, avoid solid food, milk, or formula for 6 hours before the test. Be sure to give your child plenty of clear liquids, like water, breast milk, or apple juice, up to 2 hours before the test.

What is an Auditory Brainstem Response Evaluation (ABR)?

An ABR is a type of test that evaluates how well sounds travel along the hearing nerve pathways from the ear to the brainstem.

There are two main types of hearing loss:

Conductive hearing loss—problems transmitting sound from the outer ear (where sound is collected) to the inner ear.
This is the predominant type of hearing loss that’s associated with microtia.

Sensorineural hearing loss—problems with the nerves connecting the inner ear to the brain. In the inner ear, tiny hairs on the cochlea act as a neural pathway, transmitting through the inner ear. Usually, problems with these hairs on the cochlea are responsible for sensorineural hearing loss.
Sensorineural hearing loss is present in 10 to 15 percent of children with microtia.

How does it work?

An ABR test is a sleep EEG hearing test, which shows the softest sounds your child's ears can detect at various pitches. The ABR compares changes in brain activity to the timing of repetitive sounds to determine whether the particular intensity of sound can be heard.

How is the test performed?

There will be three or four small stickers on your child's head, connected to leads going into a computer. Sounds will be presented through an earphone to each ear separately while a computer analyzes the changes in the brain wave pattern in response to sounds.

Your child should be sleeping for the duration of the test. Young children under the age of 6 months are not usually sedated, and the test is performed while your baby is naturally sleeping, following a feeding. Children older than 6 months are usually sedated.

The test is not painful or uncomfortable in any way, but it is necessary for your child to be asleep in order to obtain clear recordings during the test.

You will be in the room with your child during the test, and the results will be explained immediately afterward.

How long does an ABR test take?

ABR evaluations, both sedated and unsedated, take two to three hours to complete.

Important: Please follow these feeding instructions before your child’s ABR test.

Under 6 months of age:
no solid food, milk or formula for four hours before the test

6 months or older:
no solid food, milk or formula for six hours before the test

For all children:
Clear liquids such as water, breast milk or apple juice should be given until two hours before the test.
Please bring your child awake but very sleepy.