Auditory Brainstem Response (ABR)
Auditory brainstem response (ABR) is an objective electrophysiological test that measures the electrical activity generated by the auditory nerve and brainstem in response to sound. The test does not require a behavioral response from the person being assessed, which makes it particularly useful for evaluating newborns, young infants, and anyone who cannot participate reliably in standard behavioral hearing tests.
During ABR testing, electrodes are placed on the scalp and behind the ears. Clicks or tone-burst sounds are presented through earphones, and the resulting neural responses are recorded as a series of waveforms. Each waveform peak corresponds to a specific level of the auditory pathway, from the cochlear nerve through to the midbrain. Audiologists analyze the presence, latency, and amplitude of these peaks to estimate hearing thresholds and detect abnormalities along the auditory pathway.
ABR is used for several clinical purposes: threshold estimation in infants and difficult-to-test populations, screening for retrocochlear disorders such as vestibular schwannoma, diagnosing auditory neuropathy spectrum disorder (where OAEs may be present but ABR is absent or severely abnormal), and monitoring hearing function during certain surgeries. In Ontario, ABR is a standard component of the diagnostic pathway when newborn hearing screening results require follow-up.
