"Hearing loss occurs in foals, but it’s rarely reported—probably because people are rarely looking for it," said Monica Aleman, MVZ, PhD, Dipl. ACVIM. But in reality, many conditions common to foals can contribute to or cause auditory dysfunction.

Aleman, an associate professor of medicine and epidemiology at the University of California, Davis (UC Davis), School of Veterinary Medicine, reviewed hearing loss in foals at the 2014 American Association of Equine Practitioners Convention, held Dec. 6-10 in Salt Lake City, Utah.

Because foals’ auditory systems are fully functional at birth, veterinarians can utilize a brainstem auditory evoked response (BAER) test to evaluate hearing ability, she said. This hearing test uses small electrodes placed under the skin of the scalp to detect electrical activity from the inner ear all the way to the brain (auditory pathway) when the horse is exposed to a noise through head- or insert phones.

Additionally, she said, veterinarians can use a neurologic exam including a sound test, in which the horse hears a single or repetitive loud sound. If the horse reacts to the sound and is able to localize it, he likely has good auditory function. If he reacts to the sound, but can’t seem to determine where it’s coming from, he probably has partial hearing loss. And if the horse shows no reaction whatsoever, his hearing loss is likely complete. Aleman cautioned, however, that this test might not be useful when evaluating critically ill foals’ hearing abilities, as these foals tend to be unresponsive to most external stimuli.

To gain a better understanding of the causes o