THE IMPORTANCE OF THE BRAINSTEM AUDITORY EVOKED RESPONSES IN THE DIAGNOSIS OF HEARING DEFICITS IN DOG

Brainstem auditory evoked potential study (BAERs) is the most used electrophysiological test in veterinary medicine to determine morphofunctional integrity of the auditory system. When performing the BAERs test, the clinician is able to distinguish between a conductive and a sensorineural hearing loss. The goal of this study is to describe BAERs findings recorded with surface electrodes, clinical signs and causes of hearing loss in dogs. BAERs tests were recorded in 14 dogs with hearing deficits, for monoauricular and binauricular stimulation in response to stimulus intensities of 90 dBSPL, in the auditory brainstem response program (ABR). Examination was made under general anesthesia with medetomidine hydrochloride (Domitor, Pfizer, Finland) 0.03 mg kg, inj. i.m. The latencies, amplitudes and the intervals of the waves were calculated. The results were statistical analyzed in SPSS 20 with Wilcoxon Signed Ranks Test. The most common causes of BAERs abnormalities were congenital sensorineural deafness (CSD) (9/14), brain disease (3/14), and otitis media/interna (2/14). The BAERs morphological changes of waves I, II, III and V included: absence of BAER peaks, absence of peaks following I or II, abnormal prolongation of interpeak intervals (I-III, III-V, and I-V) and decreased amplitudes of all waves. Thus, BAERs testing classified auditory deficiencies in bilateral (28.57 %), unilateral (35.71%) and conductive deafness (14.28%), and hearing loss (21.42%). In conclusion, auditory deficits should be regarded in conjunction with any altered behavior, brain disease, otitis, and certain coat and eye color patterns. When the patient is deaf, BAERs test is able to asses if the impairment of auditory system is uni- or bilateral.