Brainstem auditory evoked potentials in Japanese Black and Holstein cattle

This study was performed to examine normal brainstem auditory evoked potential (BAEP) data for adult Japanese Black cattle and to evaluate whether differences exist in the peak latencies, interpeak latencies (IPL) and waveforms of BAEP between Japanese Black and Holstein cattle. The peaks were detected as major waves I, II, III and V in each group. The threshold of the BAEP waves in the Holstein cattle was 65-75 dB nHL, but the threshold in the Japanese Black cattle was 75-85 dB nHL. The I-III and I-V IPLs were significantly shorter in the Japanese Black compared with the Holstein cattle at an intensity of 105 dB nHL. The present findings suggest that the IPL and wave threshold of BAEP are influenced by bovine breed.     

Use of BAER to identify loss of auditory function in older horses

Objective To use the brainstem auditory evoked response (BAER) to test the hypothesis that auditory function could be worse in older horses than in younger horses. Procedure BAER waveforms in response to click stimuli were measured in five younger horses (5–8 years) and four older horses (17–22 years). Results Compared with the younger horses, the older horses showed significantly (P < 0.02) worse BAER thresholds and significantly (P < 0.02) worse BAER wave V amplitudes to the 90 decibels above normal hearing level stimulus. These results were consistent with partial deafness in the older horse group. Conclusion BAER assessment can be used to identify partial deafness in older horses. Such horses should be managed appropriately, with particular care taken in noisy environments where hearing loss could put the horse and/or its owner at risk of harm.     

Reference values of the brainstem auditory evoked response of methoxyflurane anesthetized and unanesthetized dogs

The brainstem auditory evoked response (BAER) was recorded from 7 unanesthetized and 27 methoxyflurane anesthetized dogs. A 0.1 msec, 70 dB stimulus delivered at 10 Hz evoked the expected seven wave BAER. Mean peak wave latencies and standard deviations were calculated. Differences were not found between neither right and left ears, nor male and female dogs. The anesthetized dogs had a significantly longer latency for all waves, except wave I, than the unanesthetized dogs. Use of the BAER as a diagnostic technique for brainstem lesions is recommended.     

Brainstem Auditory Evoked Responses Elicited by Tone-Burst Stimuli in Clinically Normal Dogs

Brainstem auditory evoked responses (BAERs) to click and tone-burst stimuli (0.5, 1, 2, 4, and 8 kHz) were recorded from 32 ears in 16 adult Beagles. BAERs were used to establish a normative database and describe response thresholds and latencies (wave I-IV) for the different stimuli. The frequencies of sound used were 8, 4, 2, 1, and 0.5 kHz. Sound stimuli were delivered by a closed headphone and masking stimuli were not applied. The BAER waveforms obtained were similar to those reported previously, except for a frequency-following response evoked by 1-kHz tone-bursts. The threshold was lowest when clicks and 4-kHz tone-bursts were used. Significant differences were observed between the mean values of the peak latencies for clicks and 4-and 8-kHz tone-bursts. The tone-burst stimulation used in our experiment was shown to be an appropriate method for detecting the BAERs. Thus, for investigating the frequency-specificity of the auditory sense, BAER data obtained using tone-burst sound in dogs may be meaningful.     

Effects of heparin, citrate, and EDTA on plasma biochemistry of sheep: comparison with serum

This study was carried out to evaluate the features of neurological dysfunction in experimentally-induced bovine spongiform encephalopathy (BSE)-infected cattle using brainstem auditory evoked potentials (BAEP). The progressive prolongation of peak latency of waves III and V was observed right-and-left bilaterally at the onset of neurological symptoms. The peak latency of wave V and the I-V interpeak latency (IPL) in BSE cattle 22 and 24 months after intracerebral inoculation were significantly (P < 0.05) prolonged compared with the control cattle. In addition, the amplitude of the BAEP waves of the BSE cattle were low compared with the control cattle. Hearing loss occurred in the BSE cattle that showed advanced neurological symptoms such as tremor. It is thought that this BAEP data reflects a functional disorder in the central auditory nerve pathways characteristic of experimentally-induced BSE.     

Reference values of the brainstem auditory evoked response of methoxyflurane anesthetized and unanesthetized dogs

The brainstem auditory evoked response (BAER) was recorded from 7 unanesthetized and 27 methoxyflurane anesthetized dogs. A 0.1 msec, 70 dB stimulus delivered at 10 Hz evoked the expected seven wave BAER. Mean peak wave latencies and standard deviations were calculated. Differences were not found between neither right and left ears, nor male and female dogs. The anesthetized dogs had a significantly longer latency for all waves, except wave I, than the unanesthetized dogs. Use of the BAER as a diagnostic technique for brainstem lesions is recommended.Publication No. 1702, School of Veterinary Medicine, Auburn University, AL 36849, USA     

Brainstem auditory evoked potential wave V latency-intensity function in normal Dalmatian and Beagle puppies

This study investigated whether Dalmatian puppies with normal hearing bilaterally had the same click-evoked brainstem auditory potential characteristics as age-matched dogs of another breed. Short-latency brainstem auditory potentials evoked by condensation and rarefaction clicks were recorded in 23 1.5- to 2-month-old Dalmatian puppies with normal hearing bilaterally by a qualitative brainstem auditory evoked potential test and in 16 Beagle dogs of the same age. For each stimulus intensity, from 90 dB normal hearing level down to the wave V threshold, the sum of the potentials evoked by the 2 kinds of stimuli were added, giving an equivalent to the alternate click polarity stimulation. The slope of the L segment of the wave V latency-intensity curve was steeper in Dalmatian (-40 +/- 10 micros/dB) than in Beagles (-28 +/- 5 micros/dB, P < .001) puppies. The hearing threshold was lower in the Beagle puppies (P < .05). These results suggest that interbreed differences may exist at the level of cochlear function in this age class. The wave V latency and wave V-wave I latencies differences at high stimulus intensity were different between the groups of puppies (4.3 +/- 0.2 and 2.5 +/- 0.2 milliseconds, respectively, for Beagles; and 4.1 +/- 0.2 and 2.3 +/- 0.2 milliseconds for Dalmatians, P < .05). A different maturation speed of the neural pathways is one possible explanation of this observation.     

Abnormalities of the brainstem auditory response of the dog associated with equilibrium deficit and seizure

The brainstem auditory evoked response (BAER) was recorded from 20 dogs, 10 exhibiting vestibular deficit, and 10 presented with a history of seizures. Two dogs exhibited both types of signs. Abnormalities of the BAER, prolonged interwave latency, were seen in 8 of the 10 animals with vestibular problems, and in 7 of the 10 animals with seizure history. Several different diagnosis were associated with BAER abnormalities in both groups of animals. In 55.5% of the cases exhibiting abnormalities of the BAER, postmortem evidence of brainstem pathology was not detected. The electroencephalogram (EEG) was normal in three instances of abnormalities of the BAER. The BAER was normal in three dogs with abnormalities of the EEG. The BAER is presented as a useful diagnostic tool for brain lesions in animals with vestibular deficit and seizure history, but appears most useful when used in conjuction with the EEG. Correlations of abnormalities of the BAER and clinical course of disease are discussed.Publication No. 1707, School of Veterinary Medicine, Auburn University, AL 36849     

Effects of high dietary sulfur on brain functions using evoked potentials technique.

Brain stem auditory-evoked response (BAER) is a noninvasive technique used for detecting neurophysiological abnormalities of the brain stem along the auditory pathway. Brain stem auditory-evoked response recordings were obtained from subcutaneous skin electrodes from two control sheep and 22 other sheep fed high sulfur (S) diets with low or high concentration of thiamine (B1), copper (Cu), and molybdenum (Mo). At least four peaks (I,II,III,IV) of varied amplitude were observed in all animals. Neurophysiological abnormalities due to decreased conductivity and/or excitability of nerve fibers along the auditory pathway were found on the BAER recordings of sheep fed high S diet. Abnormalities of peaks and interpeak latencies within BAER recordings were related to histopathological observations of brain stem lesions. Lesions in the areas of the cochlear nuclei and lateral lemniscus were seen in conjunction with altered BAER components. However, abnormalities in BAER recordings and lesions in the brain stem also occurred in the absence of overt clinical signs. Analysis of interpeak latencies between peaks I and IV revealed significant differences among dietary groups. Sheep given diets low in Cu, Mo, and B1 were affected most. Factorial analysis indicated B1 and interactions among Cu, Mo, and B1 as significant factors influencing interpeak latencies.     

Brain stem auditory-evoked responses in the dog

Brain stem auditory-evoked responses (BAER) were recorded from 58 dogs that did not have a known history of hearing problems. The BAER wave forms had an overall mean amplitude approximately 3.0 microV and typically consisted of a series of 4 to 5 vertex-positive peaks (peaks I through V). When acoustic clicks having intensities of 60-dB hearing level (decibels relative to the subjective hearing threshold) were used as stimuli, peak I had a latency of 1.49 +/- 0.13 ms; peak II, 2.32 +/- 0.14 ms; peak III, 3.01 +/- 0.25 ms; peak IV, 4.22 +/- 0.27 ms; and peak V, 5.55 +/- 0.37 ms. Latency values were influenced by a number of nonpathologic factors, including stimulus intensity and the body temperature of the dog. As stimulus intensity was decreased, there was a lengthening of the latency of each peak coupled with a decrease in the overall amplitude of BAER. Decreases in rectal temperature caused a similar lengthening of peak latencies. Age may have an influence on BAER, but under the conditions of the present study, the effect was not significant.     

Brainstem auditory-evoked potential assessment of auditory function and congenital deafness in llamas (Lama glama) and alpacas (L. pacos)

Auditory function of llamas and alpacas was assessed objectively by means of brainstem auditory-evoked response audiometry (BAER) to establish the normal hearing range and to test the hypothesis of a correlation between blue eyes, white coat, and deafness. Sixty-three camelids were available for the study. Thirteen animals had blue irides; 1 animal had 1 blue and 1 pigmented iris. Wave latencies, amplitudes, and interpeak latencies were measured under general anesthetic. Click stimuli (dB [HL]) were delivered by an insert earphone. Four to five positive peaks could be detected; waves I, II, and V were reproducible; wave II appeared infrequently; and wave IV generally merged with wave V to form a complex. Peak latencies decreased and peak amplitudes increased as stimulus intensity increased. A hearing threshold level of 10-20 dB (HL) was proposed as the normal range in llamas and alpacas. None of the animals with pigmentation of coat and iris showed any degree of hearing impairment. Seven of the 10 blue-eyed, pure-white animals were bilaterally deaf and one of them was unilaterally deaf. However, 2 blue-eyed, white animals exhibited normal hearing ability. Three blue-eyed animals with pigmented coat did not show any hearing impairment. All white animals with normal iris pigmentation had normal auditory function; so did the 1 animal with 1 normal and 1 blue iris. The high frequency (78%) of bilaterally deaf animals with pure white coat and blue iris pigmentation supports the hypothesis of a correlation between pigmentation anomalies and congenital deafness in llamas and alpacas.     

Short latency auditory evoked potentials recorded from non-anaesthetized thoroughbred horses.

The Brainstem Auditory Evoked Potential (BAEP) is a recording of the electrical activity of the brainstem following an acoustic stimulation. Up to seven peaks may be identified within 10 ms, and are labelled I to VII. The first five of these peaks are of most clinical importance, and in normal horses, peaks I, III and V are always present at stimulus intensities of 70-100 dB. Repeated sampling of clinically normal subjects at different stimulus intensities has enabled mean latency values to be determined for the ipsilateral and contralateral peaks I, III and V, and also for the interpeak latencies (IPLs) at each intensity. The maximum, normal, absolute latency for ipsilateral peak I was 1.86 ms, for peak III, 3.53 ms and for peak V, 5.52 ms. The equivalent contralateral values were 2.50 ms, 4.44 ms and 5.59 ms. The maximum, normal, contralateral IPL for I-III was 1.78 ms, that for III-V was 2.26 ms and for I-V was 3.76 ms. The maximum, normal, contralateral IPLs were 2.17 ms for I-III, 1.41 ms for III-V and 3.32 ms for I-V. If a peak or peaks are absent or delayed, or the IPL is greater than expected, the patient can be determined to have abnormal brainstem or auditory nerve conduction. The amplitudes of peaks I and V were measured, and the ratio of amplitudes was determined, to find the normal V:I values. At a stimulus intensity of 100 dB, the ipsilateral ratio was 0.49 +/- 0.19, and the contralateral value 1.49 +/- 0.48. Dispersal values were also calculated, by dividing the height of the III-V complex by its duration. For a stimulus intensity of 100 dB, the ipsilateral dispersal value was 0.416 +/- 0.104 microV/ms, and the contralateral value of 0.473 +/- 0.074 microV/ms. A range of normal values for both V:I ratio and dispersal were calculated. Height, weight and inter-aural distance were measured, and the relationship of the various peaks and IPLs to these variables was ascertained by statistical analysis. For the ipsilateral values, the correlation between the latency of wave V, and III-V and I-V IPLs and weight were significant (P less than 0.01). Significant correlations were found between weight and the latency of contralateral waves III (P less than 0.05) and V (P less than 0.05) and the I-III (P less than 0.01) and I-V (P less than 0.001) IPLs.(ABSTRACT TRUNCATED AT 400 WORDS)     

Peaks of brainstem auditory evoked potentials in dogs

The effects of electrode configuration and click polarity on brainstem auditory evoked potentials (BAEP) in dogs were investigated to clarify the inconsistent nomenclature for each peak. Four positive peaks (waves 1, 2, 3 and 4) before a deep negative trough and a fifth positive peak (wave 5) following the trough were the basic components of BAEP in dogs, which were easily identified regardless of recording conditions such as electrode configuration and click polarity. Additional peaks tended to be present when a noncephalic reference electrode and/or single-polarity (rarefaction or condensation) click stimuli were used. The Roman nomenclature for the individual positive peaks of BAEP in dogs is confused owing to variations in the observed waveforms among researchers, but click polarity and/or reference electrode position can explain all the previously reported variations in BAEP waveforms in dogs. When the criteria concerning wave V in the guidelines of BAEP in human beings are applied to avoid further confusion of Roman nomenclature in dogs, it is recommended that the basic five positive peaks (waves 1, 2, 3, 4 and 5 as identified easily with Ai-Vertex configuration and alternating clicks) are designated as waves I, II, III, V and VI, respectively. Wave IV (wave 3b) occurs occasionally before wave V in dogs.Abbreviations BAEP brainstem auditory evoked potentials - dBHL dB hearing level - IPL interpeak latency - Ai the caudodorsal end of the zygomatic arch ipsilateral to the stimulated ear - Nape the neck over the spinous process of the fourth cervical vertebra     

Analysis of auditory and neurologic effects associated with ventral bulla osteotomy for removal of inflammatory polyps or nasopharyngeal masses in cats

OBJECTIVE: To determine whether cats undergoing ventral bulla osteotomy (VBO) for removal of inflammatory polyps or nasopharyngeal masses have altered ability to hear and whether polyp or mass removal affects auditory function as measured via air-conducted brainstem auditory evoked response (BAER). DESIGN: Prospective case series. ANIMALS: 21 cats. PROCEDURES: Cats were sedated and had otic-oral examinations to confirm presence of nasopharyngeal masses; BAER testing was done immediately prior to and following the completion of a VBO and polyp or mass removal. Recheck examination, including otic examination and BAER in sedated cats, was performed when possible. Results-17 cats met final inclusion criteria, and long-term follow-up was available for 15. Six of 17 had deafness as measured via air-conducted BAER prior to surgery. Mean followup time was 161 days, and there was no change from presurgical status in auditory ability in any cat. Eleven of 17 developed ipsilateral Horner syndrome in the immediate postoperative period, and 1 of 16 had polyp regrowth. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that in cats, VBO for removal of inflammatory polyps or masses is unlikely to affect hearing as measured via air-conducted BAER. Most cats developed short-term Horner syndrome. Cats with deafness prior to surgery did not regain auditory function. Ventral bulla osteotomy to remove nasopharyngeal polyps or masses provided no functional advantage with regard to restoration of hearing, compared with other surgical techniques. Polyp recurrence and long-term adverse effects were uncommon.     

Evaluation of auditory function in a population of clinically healthy cats using evoked otoacoustic emissions

Cats may demonstrate deafness due to a variety of aetiologies and the current preferred method for assessing auditory function is the brainstem auditory evoked response (BAER). The BAER has largely been replaced by otoacoustic emission (OAE) testing in human neonatal deafness screening as the equipment is more readily available, is cheaper and the test is less invasive and simpler. This is the first study to demonstrate that transient evoked OAEs (TEOAE) and distortion product OAEs (DPOAE) can be recorded in cats using commercially available equipment. Protocols for recording the emissions and analysing the results are given. DPOAE testing is suggested to be quicker in this population of healthy cats and shows promise in rapidly providing detailed information about auditory function at a variety of different frequencies.     

Origin of the equine middle latency auditory evoked potential

Recordings of the middle latency of the auditory evoked potential (MLAEP) were made in eight conscious ponies. These traces were compared to those made under halothane anaesthesia with and without paralysis of the skeletal muscles. Recordings were also made from percutaneous electrodes placed along the neck with the same stimulus used for the auditory evoked potentials. The results of these experiments were used to deduce the origin of latencies in the auditory evoked potential occurring between 10 and 25 ms after the stimulus. The MLAEP was found to contain two positive peaks between the latencies of 10 and 25 ms. The first of these two peaks was not abolished by halothane anaesthesia or muscle paralysis. The second of these two peaks was abolished by halothane anaesthesia in all but one animal. In this animal the second peak was abolished by muscle paralysis. No peaks of corresponding latency were recorded from the percutaneous electrodes except from one electrode position at the caudal neck in one pony. The first peak of the middle latency auditory evoked potential seen in conscious ponies appeared to be of central nervous orign. The second peak appeared to be of muscular origin, possibly from the external auditory muscles. The second peak may be analogous to the post-auricular waveform described in man.     

Brain Stem Auditory-Evoked Response Abnormalities in 14 Dogs With Confirmed Central Nervous System Lesions

Abnormal brain stem auditory-evoked responses (BAER) were recorded on 14 dogs with brain lesions confirmed by necropsy (n = 13) or magnetic resonance imaging and surgical biopsy (n = 1). Lesions included brain stem or cerebellar tumors (6 dogs), brain stem trauma (1 dog), forebrain tumors (3 dogs), hydrocephalus (2 dogs), granulomatous meningoencephalitis (1 dog), and meningoencephalitis (1 dog). Five affected dogs were comatose at the time of recording. BAER abnormalities could be classified as (1) absence of some or all of waves I to V, (2) increased latencies, with wave V being most frequently affected, or (3) a reduction in the amplitude ratio of waves V/1.     

Brainstem auditory-evoked responses in horses with temporohyoid osteoarthropathy

Background: Facial and vestibulocochlear nerve dysfunction occurs commonly in horses with temporohyoid osteoarthropathy (THO); however, auditory dysfunction has not been thoroughly assessed.
Objective: To determine if auditory abnormalities occur in horses with THO.
Animals: Eleven diseased and 8 control horses.
Methods: This is a prospective study in which brainstem auditory-evoked responses (BAER) were recorded in 11 horses diagnosed with THO through neurologic, endoscopic, radiographic, or computed tomographic examinations. BAER findings were compared with those recorded from 8 adult control horses.
Results: All horses with THO were found to have BAER abnormalities that included complete unilateral BAER loss (82%, n = 9/11), partial unilateral BAER loss (18%, n = 2/11) on the most affected side, and contralateral partial BAER loss (46%, n = 5/11). Nine horses had bilateral THO based on diagnostic imaging findings; of these, 5 (56%) horses also had bilateral BAER abnormalities. The complete absence of BAER in affected horses was most consistent with peripheral sensorineural hearing loss. There was a significant association between complete BAER loss and neurologic and diagnostic abnormalities.
Conclusions and Clinical Importance: Auditory abnormalities such as complete or partial BAER loss are common in horses with THO. The BAER test is an objective diagnostic tool that can aid along with other diagnostic modalities in the assessment, management, and follow-up of horses with THO. Furthermore, BAER studies may help to elucidate the pathophysiology of THO in horses.     

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.

     

Comparison of the brainstem auditory evoked responses during sevoflurane or alfaxalone anaesthesia in adult cats

Objective

To compare the effects of general anaesthesia using sevoflurane or alfaxalone on the brainstem auditory evoked response (BAER) test in adult healthy cats.