Ear Center: Auditory Brainstem Response Testing (ABR)
About the ABR Test
Auditory Brainstem Response (ABR, BAER, BEAR, etc.) testing is used to determine:
- Physiologic brain responses to sound
- To evaluate hearing in patients who are unable to participate in standard behavioral hearing testing (infants, mental disability, etc.),
- To assess auditory system integrity
- To assess the hearing nerves during an acoustic neuroma (vestibular schwannoma) evaluation
- To evaluate dymelinating conditions (such as multiple sclerosis, etc.)
The basis of the ABR test is the "evoked potential". Click stimuli are rapidly presented to the auditory system through head phones or insert earphones. Each stimulus causes a brain wave response from the ear being tested. Computer averaging permits time locking of the stimulus to the response, averaging, and the analysis of the brain's auditory response to the sound stimuli. By varying the intensity of the sound input, auditory generated brain waves can be evaluated. An estimate of hearing thresholds can be established for each ear. Transit times for various brain waves can be evaluated to aid in evaluating the health and integrity of the hearing nerves. In addition, the synchrony or dyssynchrony of the central auditory pathways can be evaluated.
An ABR is somewhat like having an ECG (electrocardiogram) of your heart. An ECG measures the electrical activity of the heart by using surface electrodes that are applied to the chest. Similarly, an ABR measures electrical activity of the brain that is "evoked" by sound waves and are measured by surface electrodes applied to the head. You may think of an ABR as having an "ECG of your ear."
One caveat: although ABR testing does provide a true evaluation of physiologic hearing, the standard click stimuli used during the test are high frequency clicks (4000 Hz). Therefore, ABR only tests for the presence or absence of high frequency hearing. With this limitation, it is possible to "fail" an ABR but still have intact low frequency hearing.
The ABR test is performed in a quiet room. There is no pain involved with the test. Stick-on electrodes are placed around the head and forehead. Head phones or insert earphones are placed. The patient is asked to relax and to fall asleep, if possible. The test takes approximately one hour. Sedation is not needed for adults but may be needed for young children.
Once completed, the ABR results must be analyzed by the audiologist and a physician. Therefore, the test results are not available on the day of the test. After being analyzed, results will be reported back to the patient or family in a timely manner.
Last revised November 3, 2010