Image courtesy of Natus Medical Incorporated

Auditory Brainstem Response (ABR)

A Diagnostic ABR is a computerized evaluation which is used to measure the brain wave activity your ear produces when it hears sounds. Sometimes an ABR is called BAER (brainstem auditory evoked response) and may be automated or diagnostic.

An ABR test is ordered when complete results cannot be obtained with a routine hearing test (audiogram), often with infants and young children. If there is a hearing loss, the ABR helps to determine the severity of the problem.  

An ABR is also often needed when a simple hearing test shows a certain type of hearing loss pattern. The test is extremely helpful in ruling out or confirming auditory nerve lesions such as acoustic neuroma. In addition, it is helpful in diagnosing demyelinating diseases such as multiple sclerosis.  

The test, whether diagnostic or threshold, usually takes one to two hours. It requires the patient to lie very still so the computer will not pick up any muscle movement. Flat electrodes (or wires) are taped to the forehead and ears. These electrodes will measure the response to sound from the ears and brain. Clicks are emitted through earplugs, and your brain's response to the sound will be recorded by a computer and analyzed by the audiologist. 

Image courtesy of Natus Medical Incorporated

Otoacoustic Emissions (OAEs)

An OAE is a computerized hearing test that evaluates the physical function of the ear. Sound at five different pitches is sent into the ear through a small eartip. Sound passes through the outer and middle ears into the inner ear, where small hair cells in the cochlea respond to sound. If the ear physically functions properly, these outer hair cells move in response and generate a sound of their own. This response is measured by a microphone in the eartip and analyzed by the computer.

The response, or emission, is identified by its presence in comparison to the surrounding noise as well as to normative data. For this reason, the testing requires the patient to be very quiet. Noise can keep the computer from measuring the response. This noise, in addition to middle ear fluid, an ear canal blocked with debris, or hearing loss are possible reasons a person does not pass this test.