Auditory Loss in Horses, Part I: Adult Horses

Evaluation of hearing should be part of the physical and neurological examination since hearing loss occurs in horses and could result in altered behavior and performance. If hearing deficits are suspected, a brainstem auditory evoked response test should be performed. Authors’ address: The William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA 95616; e-mail: mraleman@ucdavis.edu.

1. Introduction

Hearing loss in horses has been seldom investigated and can be a cause of difficulty in training, decreased performance, and behavior alterations. Brainstem auditory evoked response (BAER) testing is a noninvasive, objective, and easy to perform diagnostic modality that evaluates the integrity of the auditory pathway. The objective of the study was to describe BAER findings, common signs, and causes of hearing loss in adult horses.

2. Materials and Methods

BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Medical records were reviewed, and horses were grouped under disease categories. Descriptive statistics included mean, standard deviation, and range.

3. Results

Fifty-seven of 76 horses that had a BAER had auditory deficits. There was no breed, gender, or age predisposition with the exception of American Paint horses diagnosed with congenital sensorineural deafness. Auditory loss was bilateral in 74% and unilateral in 26% of the horses. The most common causes of auditory loss included temporohyoid osteoarthropathy (35%), congenital sensorineural deafness (30%) associated to certain coat and eye color patterns, multifocal brain disease (23%), and otitis media/interna (7%). 

4. Discussion

Temporohyoid osteoarthropathy, multifocal brain disease, and otitis are common causes of hearing loss. Hearing should be investigated in horses with extensive white color markings.

Acknowledgments

Conflict of Interest

The Authors declare no conflicts of interest.