Auditory Brainstem Response
Auditory Brainstem Response (ABR) is one of the objective hearing tests, in which responses to sound stimuli are collected by a measuring device. This test records the electrical activity that propagates along the auditory pathways, from the auditory nerve to the auditory areas of the brain, in response to auditory stimuli. These signals are collected using electrodes placed on the forehead and mastoids, and sometimes on the scalp.
In clinical practice, Auditory Brainstem Response, which explore the auditory nerve and auditory pathways of the brainstem are useful for :
- Screening for deafness in infants and children.
- In the search for retrocochlear auditory damage (auditory nerve neuroma).
- Screening for Auditory Neuropathy Spectrum Disorders in children and adults, when subjective hearing tests show a discrepancy between tonal audiometry and speech audiometry, which measures intelligibility. ABR is then combined with acoustic Otoacoustic Emission.
The different types of Auditory Evoked Potentials
In practice, short-latency evoked potentials (ABR) are used to measure thresholds, wave amplitudes and differences between different waves.
ASSRs (Auditory Steady-State Response) deserve special mention because they allow the objective assessment of auditory thresholds over a wide frequency range to the nearest 10-15 dB HL.
Medium- and long-frequency auditory evoked potentials are mainly used to assess higher cognitive processes, such as music perception, auditory memory and emotion recognition. They are not commonly used.
Like all investigations aimed at assessing a patient’s hearing, this test is only of value if it is part of a comprehensive assessment of the auditory system, which includes a thorough anamnesis, microscopic otoscopy and subjective hearing tests (tonal and vocal audiometry).
Your questions about the auditory brainstem response (ABR):
What is the ABR (auditory brainstem response) used for?
ABR testing (auditory evoked potentials) helps to:
- screen for hearing loss in newborns and infants;
- look for retrocochlear damage (e.g. acoustic neuroma/vestibular schwannoma);
- investigate auditory neuropathies and situations where pure-tone and speech audiometry results do not match (ABR is then combined with otoacoustic emissions).
What does the ABR measure?
Using electrodes placed on the forehead, the mastoids (behind the ears) and sometimes the scalp, the test records the small waves generated by the auditory system after a brief sound (clicks or tone bursts) delivered to the ear through headphones or a foam insert.
In routine practice, early auditory evoked potentials (ABR) are mainly used, focusing on the responses of the auditory nerve and the brainstem.
What happens during an ABR test?
The patient is made comfortable, the skin is lightly cleaned and self-adhesive electrodes are applied. After that, you have nothing to do: the device sends sounds and records the responses.
Is the auditory brainstem response test painful?
The ABR test is quiet and painless. It does not send any electrical current into the body; it simply records electrical activity.
How long does an ABR test take?
An ABR test usually takes 30 to 60 minutes, depending on age, cooperation and the number of conditions tested (one or both ears, intensities, repetitions, etc.).
What is the ABR used for in adults?
- To estimate hearing objectively when behavioural responses are uncertain (ABR with response threshold measurement).
- To look for signs of retrocochlear damage (delays or abnormalities in certain waves).
- To confirm auditory neuropathy when subjective tests (pure-tone/speech) and objective tests do not match (for example, normal OAEs but abnormal ABR).
