Auditory Loss in Horses, Part II: Foals

Common neonatal diseases such as sepsis, ischemic hypoxia, neonatal isoerythrolysis, prematurity, and congenital anomalies can result or be associated with auditory loss in foals. Therefore, evaluation of hearing should be part of the physical and neurological examination in ill-neonatal foals. Authors’ address: The William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA 95616; e-mail: mraleman@ucdavis.edu.

1. Introduction

Auditory deficits occur in foals but are rarely recognized. In human medicine, several neonatal diseases are common causes of permanent hearing loss in infants. Descriptions of auditory loss in neonatal foals are limited to 3 foals with lethal white foal syndrome. The association of auditory loss with common neonatal diseases has not been studied. Therefore, the objective of the study was to investigate auditory deficits in ill-neonatal and nonneonatal foals.

2. Materials and Methods

Brainstem auditory evoked response (BAER; a study to investigate auditory function) records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Clinical data were extracted from the medical records. Descriptive statistics were performed.

3. Results

Ten of 15 neonatal foals had absent BAER and were associated with sepsis, neonatal encephalopathy, neonatal isoerythrolysis, and prematurity. Auditory deficits were also observed in foals with certain coat and eye color patterns such as completely or mostly white with blue irises and lavender with pale yellowish irises. One non-neonatal foal (n = 1⁄3) with an intracranial abscess had auditory loss. 

4. Discussion

Hearing deficits occur in foals and are associated with common neonatal diseases and certain coat and eye color patterns. Neurologic and intracranial disease can also result in auditory loss in foals of any age.

Acknowledgments

Conflict of Interest

The Authors declare no conflicts of interest.