Effects of otitis on hearing in dogs characterised by brainstem auditory evoked response testing

Hearing function was measured in normal dogs and in dogs with otitis using brainstem auditory evoked response testing. Data were obtained from 86 normal ears and from 105 ears with otitis, cntegorised into four degrees of severity. The data were analysed to illustrate the differences between the hearing function in the normal and abnormal ears and to estimate the degree of impairment associated with differing degrees of pathology. While severe hearing loss seemed to be present in the dogs with more severe otitis, only two individuals were identified as being totally deaf in the affected ears and no dogs were identified in which the cleaning and examination processes had caused damage to hearing function. Cleaning the ear canal produced measurable improvements in hearing in several dogs, indicating the profound effect of physical obstruction of the external ear canal by debris. It is concluded that most dogs with chronic otitis externa are not totally deaf and that the hearing impairment that does occur has the characteristics of conductive hearing loss.     

Use of brain stem auditory-evoked response to evaluate deafness in a group of Dalmatian dogs

A group of 18 adult and 28 six-week-old purebred Dalmatian dogs was tested for hearing by brain stem auditory-evoked responses. Each ear was tested independently. Absence of a response was considered evidence of deafness in that ear. Responses from bilaterally hearing adults and pups and unilaterally hearing dogs were compared with each other and with responses from normally hearing, adult, mixed-breed dogs. Of the 18 adults tested, 5 had normal responses from both ears, 6 were deaf in both ears, and 7 had a response from only one side. Of 28 pups tested, 14 had normal responses from both ears, 9 had a response from only one ear, and 5 were bilaterally deaf. Wave peak latencies from all ears that responded were within normal limits, except that the 5th and 6th waves from unilaterally hearing adults had significantly longer latencies. There were no differences between males and females.     

Investigation of hearing impairment in Cavalier King Charles spaniels using auditory brainstem response audiometry

Auditory brainstem response audiometry was used to investigate nine Cavalier King Charles spaniels with a history of hearing impairment. Successful recordings were made in all cases. In eight of the dogs, the hearing impairment was between 40 and 85 decibels re normal hearing level. In addition to confirming the degree of impairment in each ear, information was obtained concerning the site of the lesion. The auditory brainstem technique may have an important role to play in assessing treatment outcome. Other applications include screening animals used in breeding programmes as well as working dogs requiring good binaural hearing.     

A comparison of the brainstem auditory evoked response in healthy ears of unilaterally deaf dogs and bilaterally hearing dogs

Aims

Auditory plasticity in response to unilateral deafness has been reported in various animal species. Subcortical changes occurring in unilaterally deaf young dogs using the brainstem auditory evoked response have not been evaluated yet. The aim of this study was to assess the brainstem auditory evoked response findings in dogs with unilateral hearing loss, and compare them with recordings obtained from healthy dogs.

Methods

Brainstem auditory evoked responses (amplitudes and latencies of waves I, II, III, V, the V/I wave amplitude ratio, wave I-V, I-III and III-V interpeak intervals) were studied retrospectively in forty-six privately owned dogs, which were either unilaterally deaf or had bilateral hearing. The data obtained from the hearing ears in unilaterally deaf dogs were compared to values obtained from their healthy littermates.

Results

Statistically significant differences in the amplitude of wave III and the V/I wave amplitude ratio at 75 dB nHL were found between the group of unilaterally deaf puppies and the control group. The recordings of dogs with single-sided deafness were compared, and the results showed no statistically significant differences in the latencies and amplitudes of the waves between left- (AL) and right-sided (AR) deafness.

Conclusions

The recordings of the brainstem auditory evoked response in canines with unilateral inborn deafness in this study varied compared to recordings from healthy dogs. Future studies looking into electrophysiological assessment of hearing in conjunction with imaging modalities to determine subcortical auditory plasticity and auditory lateralization in unilaterally deaf dogs are warranted.

     

Frequency-specific electric response audiometry (ERA) and its clinical application in the diagnosis of hearing defects in the dog

Reference values were established for frequency-specific electric response audiometry (ERA) in dogs on the basis of the results of ERA examinations of 200 animals with normal hearing. Air-conducting acoustic tubes with foam stoppers were used in the determination of the following: the latencies of waves I, III and V; interpeak latencies (IPL) I-III, III-V and I-V; amplitudes I and V; and the amplitude difference I-V. A frequency-specific stimulus (tone pip) was used for frequency-specific examination (1 to 4 kHz) over the entire frequency range indicated. These reference values were then used for the clinical examination of 50 dogs with hearing defects. A frequency-specific ERA was conducted and the results evaluated. These findings made it possible to draw objective conclusions about the degree, type and site of the hearing defects. Frequency-specific electric response audiometry was shown to be an important diagnostic tool for the detection of partial high- and low-frequency hearing loss and for the characterisation of hearing defects of otological, otoneurological and neurological origin.     

Complex segregation analysis of deafness in Dalmatians

OBJECTIVE: To use pedigree analysis to evaluate the feasibility of a major locus model for deafness in Dalmatians. ANIMALS: 605 purebred Dalmatians from 42 families. PROCEDURE: Hearing loss was evaluated through the brainstem auditory-evoked response. Dogs were classified into mutually exclusive categories: normal hearing, unilaterally deaf, or bilaterally deaf. Information was collected on sex, coat color, presence or absence of a color patch at birth, and eye color. Statistical analyses were performed by use of regressive logistic models designed for complex segregation analysis. Genetic correlations among eye color, deafness, and color patch were estimated. RESULTS: Prevalence of hearing loss was 11% for dogs classified as unilaterally deaf and 5% for dogs that were bilaterally deaf. Complex segregation analysis detected statistical evidence of a single allele with an expected frequency of 0.21 that had an effect on the prevalence of deafness. Results of analyses suggested that this locus cannot completely explain the inheritance and incidence of deafness in Dalmatians. Genetic correlation estimates among deafness, eye color, and color patch revealed strong interrelationships among these characteristics. CONCLUSIONS AND CLINICAL RELEVANCE: To reduce the incidence of hearing loss in Dalmatians, unilaterally deaf, blue-eyed dogs should not be considered as potential parents.     

Treatment of Age‐Related Hearing Loss in Dogs with the Vibrant Soundbridge Middle Ear Implant: Short‐Term Results in 3 Dogs

Background: Age‐related hearing loss (ARHL), or presbycusis, is the most common form of acquired hearing loss in dogs. Middle ear implants have been used successfully in people with ARHL who cannot benefit from conventional hearing aids. Hypothesis: Audibility improves in dogs with ARHL after implantation of the Vibrant Soundbridge (VSB) middle ear implant. Animals: Three Beagle dogs with ARHL, mean age 11.1 years. Methods: The dogs were assessed pre‐ and postoperatively by brainstem‐evoked response audiometry (BERA), otoscopy, and computed tomography scans of the ears. A VSB middle ear implant was implanted unilaterally. Three months later the functionality of the implants was assessed by auditory steady‐state responses (ASSRs), after which the dogs were euthanized for histopathological examination. Results: The VSB was implanted successfully in all dogs. Recovery from surgery was uneventful, except for transient facial nerve paralysis in 2 dogs. ASSRs showed that hearing improved after activation of the implants with a mean of 20.7, 13, and 16.3 dB at 1, 2, and 4 kHz, respectively. The implantation procedure did not affect residual hearing (with inactive implants) as measured by BERA. Conclusions and Clinical Importance: Implantation of the VSB resulted in lower ASSR thresholds, but only at the higher gain settings of the audioprocessor. As in humans, a more powerful audioprocessor is required to treat sensorineural hearing loss exceeding 20 dB in dogs. A substantial improvement in patient‐owner communication will have to be demonstrated in future studies before the procedure can be recommended in clinical practice.     

Clinical evaluation of cochlear hearing status in dogs using evoked otoacoustic emissions

Objectives : Evoked otoacoustic emission testing is the preferred test in human patients for sensorineural deafness screening in neonates and cochlear outer hair cell function monitoring in adults. This study evaluated evoked otoacoustic emission testing for cochlear function assessment in dogs within a clinical setting. Methods : Two populations of anaesthetised dogs were included. In group 1 the evoked otoacoustic emission response was compared to the brainstem auditory evoked response in 10 dogs having hearing assessment. Group 2 comprised 43 presumed normal dogs, in which the suitability of two types of evoked otoacoustic emissions, transient‐evoked and distortion product otoacoustic emissions, were evaluated (brainstem auditory evoked response was not performed in this group). Results : Valid transient‐evoked otoacoustic emission and distortion‐product otoacoustic emission responses were successfully recorded within the clinical setting and correctly identified deaf and hearing ears. Within presumed healthy dogs, normal otoacoustic emission response was demonstrated in more than 80% of dogs using a single, short distortion‐product otoacoustic emission run and in 78% of dogs with valid transient‐evoked otoacoustic emission responses using a series of three repeated transient‐evoked otoacoustic emission short runs. Clinical Significance : Transient‐evoked otoacoustic emission and distortion‐product otoacoustic emission testing provided a rapid, non‐invasive frequency‐specific assessment of cochlear function. Transient‐evoked otoacoustic emission and distortion product otoacoustic emission testing is suitable as a screening procedure to detect loss of cochlear function in dogs, although further investigation is needed.     

Soft palate hypoplasia and concurrent middle ear pathology in six dogs

This retrospective clinical study describes six consecutive cases of bilateral hypoplasia/malformation of the soft palate in dogs in which associated middle ear disease was investigated and the palatine defects were surgical repaired. Radiographic abnormalities of the tympanic bullae were seen in both ears of all six dogs (12 of 12). Negative tympanocentesis findings were recorded in 11 of 12 ears. A purulent otitis media was confirmed in one ear of one dog, and loss of hearing was also demonstrated in this ear on brainstem auditory evoked response hearing assessment. There was no evidence of hearing loss on brainstem auditory evoked response in any of the remaining ears. Surgical repair of the soft palate defect was undertaken in all six dogs. Long-term assessment of the clinical outcome was considered excellent in five dogs and reasonable in one dog (mean 18 months, range seven to 27 months). It would appear that surgical intervention for the treatment of bilateral palatine malformation/hypoplasia may be associated with a better prognosis than reported previously. The lack of middle ear effusion and associated hearing impairment suggests that the underlying aetiology of middle ear pathology in dogs suffering from congenital palatine defects may be different from that observed in human beings. The true nature of the radiographic bullae changes seen in dogs with soft palate defects remains unclear.     

Normative auditory brainstem response data for bone conduction in the dog

Auditory brainstem response (ABR) is a valuable tool for the diagnosis of hearing disorders in dogs, but is hampered by the lack of published normative data. The aim of the present study was to obtain normative data for bone conduction, without masking, under clearly defined conditions. Subjects comprised 20 Dalmatians and 20 Jack Russell terriers. Two methods were investigated: holding the bone vibrator against the head by hand or by applying a 500 g weight. The results revealed no difference in hearing threshold between the two breeds or for the two methods of applying the bone vibrator to the head. The mean hearing threshold was close to 0 decibels re normal hearing level (dB nHL), which is the biological norm for humans. Hence, bone conduction thresholds can be used for confirmation of conductive hearing impairment in the dog, in the same way as in humans.     

Treatment of canine lymphoma with COPLA/LVP

Seventy-five dogs with cytopathologically or histopathologically confirmed lymphoma received L-asparaginase, vincristine, cyclophosphamide, prednisone, and doxorubicin (COPLA) induction followed by chlorambucil, vincristine, and prednisone (LVP) maintenance between January 1994 and June 1997. Toxicity was evaluated using the National Cancer Institute (NCI) toxicity criteria. Age, weight, sex, and response were evaluated for prognostic significance against first remission duration. A complete response (CR) was obtained in 61 (80%) dogs, a partial response (PR) was obtained in nine (12%) dogs, and no response (NR) was obtained in five (8%) dogs. The median first remission duration was 25 weeks, with 17% and 5% of the dogs in remission at one and two years, respectively. Observed toxicity was low, with 84% of dogs given an NCI score of 1 or 2. Median survival time for dogs achieving CR was 36 weeks versus four weeks for those achieving PR or NR.     

Prevalence of Deafness in Dogs Heterozygous or Homozygous for the Merle Allele

Background: Deafness in dogs is frequently associated with the pigment genes piebald and merle. Little is known about the prevalence of deafness in dogs carrying the merle allele.
Objective: To determine the prevalence of deafness in dogs heterozygous and homozygous for the merle allele of the mouse Silver pigment locus homolog (SILV) gene.
Animals: One hundred and fifty-three privately owned merle dogs of different breeds and both sexes.
Methods: Hearing was tested by brainstem auditory-evoked response and classified as bilaterally hearing, unilaterally deaf, or bilaterally deaf. DNA from buccal cells was genotyped as either heterozygous or homozygous for the merle allele. Deafness association tests among merle genotype, eye color, and sex were performed by the χ² test.
Results: Deafness prevalence in merles overall was 4.6% unilaterally deaf and 4.6% bilaterally deaf. There was a significant association between hearing status and heterozygous versus homozygous merle genotype. For single merles ( Mm ), 2.7% were unilaterally deaf and 0.9% were bilaterally deaf. For double merles ( MM ), 10% were unilaterally deaf and 15% were bilaterally deaf. There was no significant association with eye color or sex.
Conclusions: Deafness prevalence in merle dogs was greater than that in some dog breeds homozygous for the piebald gene, such as the English Cocker Spaniel, but comparable to, or lower than, that in the Dalmatian and white Bull Terrier. Dogs homozygous for the merle allele were significantly more likely to be deaf than heterozygotes.     

Otoacoustic emission in a dog

A 7-month-old female Poodle was evaluated for a sound continuously emanating from its left ear. The frequency and intensity of the tone was matched by use of a multifrequency audiometer. The frequency and intensity of the sound were 9,594 Hz and 45.5 decibels sound pressure level, respectively. On the bases of normal brain stem auditory-evoked responses and behavioral response to sound, the dog was believed to have normal hearing in both ears. Emission of sound from an ear, referred to as an otoacoustic emission, is a condition that has been reported in human beings and small animals. Successful treatment in human patients with drugs and masking sounds is difficult, and treatment has not been reported in animals. This condition in dogs is not considered life-threatening.     

Behavior of hearing or vision impaired and normal hearing and vision dogs (Canis lupis familiaris): Not the same,but not that different

The article compared behavioral characteristics of dogs (Canis lupis familiaris) labeled as hearing and/or vision impaired by their owners with cohort dogs labeled as having normal hearing and vision (NHV) by their owners. The Canine Behavioral Assessment and Research Questionnaire, developed by Hsu and Serpell (2003), was used to survey owners. Four hundred sixty-one dog owners completed the online survey, with 183 of these being owners of hearing and/or vision impaired (HVI) dogs. Data analysis revealed that HVI dogs were reported by owners to show less aggression, less excitement, and were less likely to engage in behaviors, such as chasing of rabbits and rolling in feces than their normally hearing/seeing (NHV) cohorts. HVI dogs, however, were reported to be more likely to chew inappropriate objects, consume feces, bark excessively, and engage in greater licking behavior. When owners were surveyed about the type of training method used, owners of HVI dogs were found to be more likely to use hand signs, physical prompts, or combination of these training methods. Owners of NHV dogs reported being more likely than owners of HVI dogs to use gestures or report no formal training with their dogs. The data provide evidence that HVI dogs are as trainable as NHV dogs, can make excellent pets, and show behavior that is well within the parameters of NHV dog behavior. Still, because of their sensory limitations, specialized training methods and adaptations should be implemented with these dogs. This may limit HVI dogs to owners who are motivated, understand the sensory deficits, and are willing to engage in the modified training.     

The use of contralateral masking noise in the detection of unilateral deafness in Dalmatian puppies

BACKGROUND: The brainstem auditory-evoked response (BAER) is currently the standard evaluation method of hearing in dogs. In asymmetrical hearing loss in human patients, simultaneous presentation of masking noise to the nontest ear is routinely performed during BAER to eliminate the crossover effect. HYPOTHESIS: The crossover effect occurs during canine BAER, and masking noise of 20 decibels (dB) below click stimulus intensity is sufficient to abolish this effect. ANIMALS: Fifty-six Dalmatian puppies with confirmed unilateral deafness. METHODS: The BAER was elicited with 80 and 100 dB normalized hearing level (dBnHL) stimulus intensity in the deaf ear. The 100 dBnHL stimulus was repeated while simultaneously applying 80 dBnHL white masking noise to the nontest ear. RESULTS: Ten dogs were excluded because of BAER trace baseline fluctuation. In the remaining 46 dogs, 8 dogs had no waveforms, but 38 dogs had an identifiable wave-V in the deaf ear BAER at 80 dBnHL intensity stimulus. At 100 dBnHL intensity stimulus, all but 1 dog had a discernible wave-V in the deaf ear BAER. The deaf ear BAER waveforms were abolished by white masking noise at 80 dBnHL in the nontest ear in all dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Abolition of BAER wave-V in the deaf ear by white masking noise in the nontest ear suggests that this wave is caused by the crossover effect. beta distribution indicates 95% confidence that white masking noise, at 20 dB below click stimulus intensity, would abolish this crossover effect in over 90% of the dogs. This supports using masking noise in the nontest ear during canine BAER.     

Clinical assessment of a chemosensitivity assay as a treatment planning tool for dogs with cancer

This study evaluated the clinical utility of a commercially available chemosensitivity assay. In the first part of the study, tumor tissues from dogs with various malignancies were tested, and the dogs were treated with a mitoxantrone/cyclophosphamide combination protocol. Tumor response was evaluated and compared to the predicted response. Assay results were not a significant predictor of clinical response to chemotherapy or of survival time. In the second part of the study, assay results were used to direct therapy in dogs with refractory lymphoma. There was no significant correlation (p equals 0.323) between predicted response and case outcome.     

Post‐anesthesia deafness in dogs and cats following dental and ear cleaning procedures

Objective The present study was performed to document hearing loss in dogs and cats following procedures performed under anesthesia. Most cases of reported hearing loss were subsequent to dental and ear cleaning procedures. Study design Prospective and retrospective case survey. Animals Subjects were dogs and cats with deafness, personally communicated to one author, cases discussed on a veterinary information web site, and cases communicated through a survey of general practice and dental specialist veterinarians. Methods Reported deafness cases were characterized by species (dog, cat), breed, gender, age, and dog breed size. Results Sixty‐two cases of hearing loss following anesthesia were reported between the years 2002 and 2009. Five additional cases were reported by survey respondents. Forty‐three cases occurred following dental procedures. Sixteen cases occurred following ear cleaning. No relationship was observed between deafness and dog or cat breed, gender, anesthetic drug used, or dog size. Geriatric animals appeared more susceptible to post‐anesthetic, post‐procedural hearing loss. Conclusions Deafness may occur in dogs and cats following anesthesia for dental and ear cleaning procedures, but the prevalence is low. The hearing loss appears to be permanent. Clinical relevance Deafness can be a consequence following anesthesia for dental or ear cleaning procedures. Older animals may have greater susceptibility.     

Wound Healing and Brain Stem Auditory Evoked Potentials After Experimental Ventral Tympanic Bulla Osteotomy in Dogs

Ventral tympanic bulla osteotomy was performed in 13 normal dogs to evaluate healing and retention of brain stem auditory evoked potentials (BSAEP). Healing was evaluated by gross and microscopic examination of the middle ears after 1 (n = 2), 4 (n = 8), 5 (n = 1), and 6 (n = 1) weeks. One dog was eliminated from the study. Brain stem auditory evoked potentials were measured using an air-conducted sound stimulus before and after surgery and before killing. Nine of 12 dogs re-formed the tympanic bulla by formation of fibrous connective tissue lined with cuboidal epithelium in the osteotomy site. Four of the nine dogs had a reduced tympanic bulla volume (estimated 20% to 40% volume reduction) caused by soft tissue ingrowth through the osteotomy. Nine of 12 dogs had proliferation of subperiosteal new bone from the inner surface of the tympanic bulla that varied in severity. Three of these nine dogs had nearly complete obliteration of the tympanic cavity by proliferating subperiosteal new bone. Eight dogs had nodules of granulation tissue containing new bone and mineralization diffusely distributed on the surfaces of the middle ear. The measured BSAEP sensitivity before killing was equivalent to preoperative levels in 11 dogs. The remaining dog had no change in auditory sensitivity after surgery but had a markedly reduced BSAEP detection threshold before killing. This appeared to be attributable to mechanical impingement on the ossicles and tympanic membrane by proliferating bone within the tympanic cavity. This study showed that after ventral tympanic bulla osteotomy the tympanic bulla rapidly re-forms with no deleterious effect on hearing in most dogs treated. However, the internal surfaces of the middle ear appear to be sensitive to surgical trauma, and extensive new bone proliferation is easily induced. This response may be extreme, resulting in middle ear obliteration and reduced auditory sensitivity.     

Safety and tolerability of 0.1% tacrolimus solution applied to the external ear canals of atopic beagle dogs without otitis

Tacrolimus is a nonsteroidal alternative to treat noninfectious otitis externa (OE) in people. This 21‐day study investigated whether twice daily application (0.2 mL/dose) of sterile olive oil based 0.1% tacrolimus suspension in ears of atopic beagle dogs without OE was associated with adverse local reactions, development of OE, change in otic cytology, vestibular dysfunction, or hearing loss detected by brainstem auditory evoked response (BAER). The study was randomized, double‐blinded, and placebo‐controlled. Twenty‐two dogs matched for age and sex were randomized to tacrolimus or vehicle control treatment groups. Two investigators independently evaluated dogs for signs of adverse effects including OE the first 4 days of treatment, then every 3 days. A logistic regression model was fit for each investigator’s clinical scores (SAS, 9.2, 2008). Time (P = 0.0032) and group (P = 0.0167) were always significant for OE. Inter‐observer reliability of clinical scores was strong, measured using Kappa coefficients and proportion of agreement. All nine exclusions (7/10 control‐ and 2/12 tacrolimus‐treated dogs) were excluded for yeast OE. Inter‐observer agreement to exclude was 100%. All dogs not excluded had normal BAER assessments before treatment, weekly during treatment, and after 21 days of treatment. None showed vestibular abnormalities at these times. Tacrolimus blood concentrations (Abbott IMx Tacrolimus II) were below detection limits (3 ng/mL) at baseline and after 21 days of treatment. Results suggest otic application of olive oil based tacrolimus suspension to canine ears with intact tympanic membranes is unlikely to result in hearing loss or vestibular dysfunction but yeast OE is a possible risk.     

Effects of aging on brainstem responses to toneburst auditory stimuli: a cross-sectional and longitudinal study in dogs

BACKGROUND: It is assumed that the hearing of dogs becomes impaired with advancing age, but little is known about the prevalence and electrophysiologic characteristics of presbycusis in this species. HYPOTHESIS: As in humans, hearing in dogs becomes impaired with aging across the entire frequency range, but primarily in the high-frequency area. This change can be assessed quantitatively by brainstem-evoked response audiometry (BERA). ANIMALS: Three groups of 10 mixed-breed dogs with similar body weights but different mean ages were used. At the start of the study, the mean age was 1.9 years (range, 0.9-3.4) in group I, 5.7 years (3.5-7) in group II, and 12.7 years (11-14) in group III. METHODS: In a cross-sectional study, the BERA audiograms obtained with toneburst stimuli were compared among the 3 groups. In a longitudinal study, changes in auditory thresholds of group II dogs were followed for 7 years. RESULTS: Thresholds were significantly higher in group III than in groups I and II at all frequencies tested, and higher in group II than in group I at 4 kHz. The audiograms in group II indicated a progressive increase in thresholds associated with aging starting around 8-10 years of age and most pronounced in the middle- to high-frequency region (8-32 kHz). CONCLUSIONS AND CLINICAL IMPORTANCE: Age-related hearing loss in these dogs started around 8-10 years of age and encompassed the entire frequency range, but started and progressed most rapidly in the middle- to high-frequency area. Its progression can be followed by BERA with frequency-specific stimulation.