Hearing (BAER) testing

The brainstem auditory evoked response (BAER) is an electrodiagnostic test that can be broadly classified as an evoked potential.

Evoked potentials are electrical potentials that are recorded from a patient after a specified stimulus has been applied. In the instance of the BAER, the stimulus is in the form of sound (clicks) or bone conduction stimuli (applying vibrations to the mastoid region of the skull) being delivered to the ear.

Several hundred discrete stimuli are delivered and the computer software averages the electrical responses (brain waves) measured (signal averaging).

The end result of this process is a tracing called the BAER. The BAER consists of 4–6 characteristic waveforms.

Download more information on BAER waveforms (pdf format).

In a clinically normal patient, the BAER recorded from each ear is symmetrical.

Under what circumstances are BAER examinations performed?

Most commonly, the BAER test is used for assisting in diagnosing various forms of deafness.

Deafness is categorized as congenital or acquired, and sensorineural or conductive.

Congenital forms of hearing loss include conditions where the patient is born deaf or is born with a condition resulting in deafness at maturity such as inherited coat colour-related deafness.

Acquired forms of deafness occur after normal hearing has developed such as exposure of the inner ear to an ototoxic drug. Sensorineural deafness is a form of deafness resulting from disease processes affecting the neural structures of the hearing pathway.

Conduction deafness is deafness that results from failure of conduction of the sound waves to the inner ear such as severe otitis externa/media.

It is important to consider referring patients with suspected hearing impairment, or conditions associated with hearing loss, for BAER evaluation.

How to organise a BAER test

The dermatology clinic has recently acquired a BAER machine and will be able to perform hearing tests for puppies.

All puppy testing will be conducted from Tuesday to Friday inclusive by veterinary Skin, Allergy and Ear Clinic staff.

Pet owners wishing to make an appointment can call Murdoch University Veterinary Hospital on 1300 652 494 or the Skin, Allergy and Ear Clinic on 9360 7387 (Tuesday to Friday inclusive) or email ear@murdoch.edu.au.

All BAER testing of adult dogs with deafness or dogs with chronic ear infection will be conducted through the Skin, Allergy and Ear Clinic.