Auditory Brainstem Response
An Auditory Brainstem Response or ABR evaluation is actually not a hearing test as some people might think. It is a test of neural synchrony. The test usually uses a click sound that is presented to one or both ears of the listener. The click causes many neurons (nerve cells) in the cochleas (hearing portion of the inner ears) to fire at the same time. When they fire, they send an electrical signal up the hearing nerve and through the brainstem to the midbrain.
The response of the different areas of the brainstem is picked up by sensitive electrodes which have been placed on the skin by the ears (earlobes or on the mastoid bone) and on the forehead and top of the head (vertex). A brainwave response is sent to the examiner’s computer for evaluation and identification of waveforms.
The ABR is useful in collecting data about how fast sound information is travelling up the brainstem and is compared to normal data. Different volume levels are presented to determine the softest level where a response can be seen. The test is often used for testing infants or individuals where neural responses may be compromised due to some conditions (e.g. hearing loss, brain damage, neurodevelopmental impairment, auditory neuropathy, etc.). ABR testing is often used as part of a more comprehensive audiological test battery.