Diseases & Conditions

ABR - Brainstem Auditory Evoked Response Test


Overview & Description

The brainstem auditory evoked response test, or BAER, helps evaluate the following:

  • hearing, or auditory, structures in the brain
  • how well a person hears
  • During this test, clicking noises stimulate the hearing nerves that run between the ear and the brain. Electrodes are attached to the scalp and ear lobes to record tiny changes in brain waves from these sounds. These changes appear on a graph as peaks, or highs, and troughs, or lows.

    Because the response to BAER is involuntary, this test is used to check hearing in those who cannot respond or cooperate, such as babies, young children, and people in comas. It is also helpful in determining whether certain hearing problems are physical or psychological.

    Who is a candidate for the test?

    The test may be done on newborns to check hearing. It may also be used when a person shows the following signs:

  • a balance disorder, such as Meniere disease
  • a brain tumor that affects hearing
  • certain conditions that attack the nerves, such as multiple sclerosis
  • hearing impairments or deafness
  • hearing nerve damage
  • a stroke that affects hearing
  • How is the test performed?

    Usually the test takes less than 30 minutes. A healthcare provider may perform the test in an office, clinic, or hospital. Often, a person sits up for this test. Dabs of ointment are applied at certain spots on the person's scalp and each ear lobe. Electrodes are placed on these spots. As earphones deliver clicks to each ear, brain waves sensed by the electrodes are graphed.


    Preparation & Expectations

    What is involved in preparation for the test?

    People may be asked to wash their hair the night before the test. However, preparation for tests can vary. It is best to check with the staff where the test will be done for specific instructions.


    Results and Values

    What do the test results mean?

    The results of the test are compared to the results from people with normal hearing and brain function. Fewer peaks than normal on a person's graph suggest disorders or damage to the hearing nerves. Longer than normal delays between clicks and brain wave response suggest hearing loss due to a problem in the ear itself.


    Attribution

    Author:Francesca Coltrera, BA
    Date Written:
    Editor:Ballenberg, Sally, BS
    Edit Date:09/24/01
    Reviewer:Adam Brochert, MD
    Date Reviewed:09/25/01

    Sources

    American Academy of Otolaryngology-Head and Neck Surgery, Inc. "Clinical Indicators Auditory Brainstem Response (ABR), (BAER), (BAEP)." 1999.

    Anderson KN, Anderson LE, Glanze WD. Mosby's medical, nursing, and allied health dictionary, 5th ed. St. Louis, Missouri: Mosby-Year Book, Inc., 1998.

    Miller BF, Keane, CB. Encyclopedia and dictionary of medicine, nursing, and allied health, 4th ed. Philadelphia, Pennsylvania: WB Saunders Company, 1987.

    Pagana KD and Pagana T. Mosby's manual of diagnostic and laboratory tests, 4th ed. St. Louis: Mosby, 1998.