The Brainstem Auditory Evoked Response (BAER) is an objective measure of the electrical activity of the auditory nerve pathway from the inner ear to the brainstem. In this test, a clicking sound is presented to one ear at a time. The electrical activity of this signal is recorded by electrodes and averaged for more than 2,000 signals.
The averaged response is displayed as a waveform that contains peaks, which correspond to various points along the nerve pathway. The time between these peaks is measured and compared to those obtained from studies of normal individual. A delay in a response can indicate a growth on the hearing nerve.
The BAER is also helpful in the diagnosis of demyelinating diseases (multiple sclerosis) of the brain, tumors of the hearing and balance nerve (acoustic neuroma), and brain stem strokes. Threshold testing can be done to determine if hearing is present in a person unable to perform a conventional hearing test. It can also give information on auditory function in infants that are at high-risk for having hearing disorders.