Brainstem auditory evoked responses and bone conduction assessment in alpacas

M Aleman; C Crowe; J Dechant; R R Bellone; F Avila

doi:10.1016/j.rvsc.2021.02.024

Brainstem auditory evoked responses and bone conduction assessment in alpacas

Res Vet Sci. 2021 May:136:297-302. doi: 10.1016/j.rvsc.2021.02.024. Epub 2021 Mar 5.

Authors

M Aleman¹, C Crowe², J Dechant³, R R Bellone⁴, F Avila⁵

Affiliations

¹ Department of Medicine and Epidemiology, University of California, Davis, USA; School of Veterinary Medicine, University of California, Davis, USA. Electronic address: mraleman@ucdavis.edu.
² The William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, USA; School of Veterinary Medicine, University of California, Davis, USA.
³ Department of Surgical and Radiological Sciences, University of California, Davis, USA; School of Veterinary Medicine, University of California, Davis, USA.
⁴ Veterinary Genetics Laboratory, University of California, Davis, USA; Department of Population Health and Reproduction, University of California, Davis, USA; School of Veterinary Medicine, University of California, Davis, USA.
⁵ Veterinary Genetics Laboratory, University of California, Davis, USA; School of Veterinary Medicine, University of California, Davis, USA.

PMID: 33740564
DOI: 10.1016/j.rvsc.2021.02.024

Abstract

Auditory loss has been reported in camelids using brainstem auditory evoked responses (BAER). Differentiation between conductive versus sensorineural dysfunction has not been investigated. Therefore, the objective of the study was to investigate auditory function using BAER and bone conduction (BC). Twenty-four alpacas: 15 females, 9 intact males (2-16 years of age) were included in a randomized clinical trial. BAER and BC were recorded using two derivations (vertex to mastoid and vertex to cranial aspect of second cervical vertebra). All alpacas underwent complete physical examinations and were sedated with xylazine hydrochloride at 0.6 mg/kg IM. Peaks, when present, were identified and latencies, amplitudes, and amplitude ratios were determined. Eleven alpacas had normal responses and 13 had auditory loss based on BAER. The latter consisted of complete absence of peaks bilaterally (n = 3), absence of peaks unilaterally (n = 1), delayed latencies bilaterally (n = 4), and delayed latencies unilaterally (n = 5). Distinct peaks on BC supported conductive auditory loss in 6 alpacas, difficult to interpret due to stimulus artifact and additional undefined peaks in 4, and absent peaks in 3 alpacas. The cause of auditory loss was presumed to be due to otitis in 6, aging in 4 (10-16 years old), and congenital sensorineural (absent peaks on BAER and BC) in 3 alpacas with unpigmented fiber and irises. BAER and BC are useful and non-invasive to perform techniques for the investigation of auditory loss in alpacas, and further characterization as conductive or sensorineural.

Keywords: BAEP; Bone; Camelids; Deafness; Hearing.

Publication types

Randomized Controlled Trial, Veterinary

MeSH terms

Animals
Bone Conduction / physiology*
Camelids, New World / physiology*
Evoked Potentials, Auditory, Brain Stem / physiology*
Female
Male