Study to compare owners’ perceptions of their dogs’ hearing and brainstem auditory-evoked response findings in 45 dogs (C.L. Ball)
Carly Ball (UK) used a questionnaire to assess whether owners were able to determine the degree of hearing impairment of their pet dog with otitis and whether the questionnaire could be used to determine hearing deficits of dogs with otitis when compared to the results of subsequent BAER testing.
A questionnaire with eight questions was sent by postal mail to 45 owners prior to their referral consultation. The first question ascertained whether the dog could hear well and seven additional questions targeted the ability of the dog to hear common noises. When two or more abnormalities were consistently identified by an owner in the questionnaire, hearing deficits were subsequently detected.
A minimal hearing threshold (MHT) was measured for each ear; each ear was assigned a grade and an overall grade was given. The grading system from the World Health Organization for humans was utilized, because there is currently no grading system available for veterinary patients: grade 0: no impairment, MHT ≤25 dB; grade 1: slight impairment, MHT 26–40 dB; grade 2: moderate impairment, MHT 41–60 dB; grade 3: severe impairment, MHT 61–80 dB; grade 4: profound impairment, MHT ≥81 dB).
With regard to dogs with no measurable hearing loss in both ears detectable by BAER (grade 0), all owners correctly determined absence of hearing impairment in grade 0 cases. Unilateral hearing loss (slight, moderate and severe) was observed in 31.1% of the dogs, and this hearing loss level couldn’t be detected by the owners. Bilateral hearing loss was observed in 40% of the tested dogs; grades 2, 3 and 4 of those could be detected by 100% of the owners, whereas only 33% of the owners could detect grade 1 bilateral hearing loss.
In summary, owners were not able to accurately detect unilateral hearing loss in their dogs, and dogs with mild to severe unilateral hearing loss appear to adapt well in their home environment. Owners were able to consistently detect bilateral hearing deficits of grade 2 and higher, consistent with moderate or severe bilateral hearing loss. The questionnaire predicted the detection of bilateral grade 2 and higher hearing deficits, but not unilateral or mild hearing deficits. A larger study is required with more patients in each group to evaluate the sensitivity and specificity of the questionnaire. It is projected that the questionnaire can be adapted to a clinical setting to assist practitioners in the assessment of hearing loss in dogs where practitioners have limited or no access to BAER testing.
Amanda Burrows asked what sort of questions clinicians should be asking owners of dogs with potential unilateral hearing loss to assist in clarifying whether this may be a problem.
Carly Ball responded that her study had not specifically examined that issue, but having owned a dog with unilateral hearing loss, she had observed that by approaching the dog in the home environment from behind and making a loud noise, that the dog would move the head from side-to-side in an attempt to determine the source and the direction of the sound. She stressed that the dog needed to be in a quiet environment, out of sight of the owner, and that a noise stimulus needed to be made from both directions to evaluate whether the dog reacted in a different manner.
Amanda Burrows commented that it seemed as if dogs with unilateral hearing loss lose the ability to locate the direction of the sound, and Paul Coward (UK) agreed with this, commenting that owners of dogs with unilateral hearing loss mention that when calling their dog while exercising off-lead, the dog has to look around to locate them.
Carly Ball agreed with the comments from Amanda Burrows and Paul Coward.
Myringotomy: when and how to perform; indications and complications (L. Cole)