title: Brainstem auditory evoked responses in an equine patient population: part I--adult horses.
abstract: BACKGROUND
  Brainstem auditory evoked response has been an underused diagnostic modality in horses as evidenced by few reports on the subject.
  
  
  OBJECTIVE
  To describe BAER findings, common clinical signs, and causes of hearing loss in adult horses.
  
  
  METHODS
  Study group, 76 horses; control group, 8 horses.
  
  
  METHODS
  Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Horses were grouped under disease categories. Descriptive statistics and a posthoc Bonferroni test were performed.
  
  
  RESULTS
  Fifty-seven of 76 horses had BAER deficits. There was no breed or sex predisposition, with the exception of American Paint horses diagnosed with congenital sensorineural deafness. Eighty-six percent (n = 49/57) of the horses were younger than 16 years of age. The most common causes of BAER abnormalities were temporohyoid osteoarthropathy (THO, n = 20/20; abnormalities/total), congenital sensorineural deafness in Paint horses (17/17), multifocal brain disease (13/16), and otitis media/interna (4/4). Auditory loss was bilateral and unilateral in 74% (n = 42/57) and 26% (n = 15/57) of the horses, respectively. The most common causes of bilateral auditory loss were sensorineural deafness, THO, and multifocal brain disease whereas THO and otitis were the most common causes of unilateral deficits.
  
  
  CONCLUSIONS
  Auditory deficits should be investigated in horses with altered behavior, THO, multifocal brain disease, otitis, and in horses with certain coat and eye color patterns. BAER testing is an objective and noninvasive diagnostic modality to assess auditory function in horses.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: M
authors.initials: M
authors.lastname: Aleman
authors.forename: T A
authors.initials: TA
authors.lastname: Holliday
authors.forename: J E
authors.initials: JE
authors.lastname: Nieto
authors.forename: D C
authors.initials: DC
authors.lastname: Williams
mesh_terms: D000818:Animals; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D034381:Hearing Loss / Q000503:physiopathology / Q000662:veterinary*; D006734:Horse Diseases / Q000503:physiopathology*; D006736:Horses / Q000502:physiology; D008297:Male; D012189:Retrospective Studies
keywords: Deafness; Electrophysiology; Equine; Hearing