Page 117 - August 2022

Hearing Tests
“We do hearing tests in horses
the same way we do in dogs and humans,” says Stewart. “We put a little headphone on the ear and do one ear at a time. We put tiny electrodes under the skin on the face, and these help
us determine which part of the ear is affected—whether it’s the external ear or down into the cochlea.”
Hearing tests can be performed at veterinary teaching hospitals or other specialist referral centers. Magdesian
says some large veterinary practices that have a neurologist on staff will also have the equipment. “It is fairly common to test puppies of certain breeds (such as Dalmations) for hearing. Any place that does this can use the same machine to test horses,” he says.
“This procedure does not require general anesthesia and is well tolerated by the horse, often with minimal restraint and no sedation,” says Stewart. Auditory response-testing records the horse’s brain waves and looks at wave patterns that change in response to noise.
“Headphones are held over the ears or placed in the ears, and equipment capable of making a series of click noises of various intensities stimulates the auditory (hearing) pathway from the ear to the brain. Several tiny electrode wires are inserted under the skin across the face to detect the brain’s response to the click noise. Placement of the electrodes and the presence of the electrode leads across the face may create a tickling sensation and the horse may shake his head and dislodge the leads,” says Stewart.
“An occasional horse objects to having the ears touched. Light sedation may be required. There are no risks to the horse; however, and the procedure usually takes about 15 minutes,” she says.
Top photo: “We put a little headphone on the ear and
do one ear at a time. We put tiny electrodes under the skin on the face, and these help us determine which part of the ear is affected—whether it’s the external ear or down into the cochlea.” - Allison Stewart
Bottom photo: Auditory response-testing records horse brain waves and looks at wave patterns that change in response to noise – no waves will be observed in a deaf horse.
SPEEDHORSE August 2022 115
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