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  • Author or Editor: Bruce L. Tedford x
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SUMMARY

Recordings of visual-evoked potentials that were induced by flashes of white light were obtained from 13 Beagle pups to document the development of the response from age 7 to 100 days. Responses were recorded between needle electrodes placed on the nuchal crest and the interorbital line, with ground at the vertex. Five alternating positive (P) and negative (N) peaks were observed in most visual-evoked potentials: P1, P2, N2, and P3. Responses were recorded from 2 pups prior to opening of the eyelids. Recordings were performed without sedation or dark adaptation. Peak latencies were essentially mature (equal to those of adult dogs) by day 11 for P1, and by day 38 for N1 and P2. The latencies to N2 and P3 did not reach adult values by day 100, but did reach plateau values by day 43. The P1-N1 amplitude measurements reached mature levels by day 14, whereas N1-P2 amplitudes were mature by day 32. The P2-N2 and N2-P3 amplitudes reached plateaus that greatly exceeded adult amplitudes by days 50 and 58, respectively. Maturation of visual-evoked potential responses paralleled reported morphologic development of the visual cortex. All of the measured latency and amplitude values had significant (P ≤ 0.004) linear regression lines of latency vs age or amplitude vs age.

Free access
in American Journal of Veterinary Research

SUMMARY

Recordings of averaged brain stem auditory-evoked potentials were obtained from 13 Beagle pups of both genders to document the postnatal development of the response from age 1 to 76 days. Responses were recorded between needle electrodes placed on the vertex and the ipsilateral ear, with ground at the interorbital line. Recordings were performed without sedation. Low-amplitude responses to high-intensity stimuli could be recorded from animals prior to opening of the ear canals. Peak latencies did not change after day 20 for peak I, day 30 for peaks II and III, and day 40 for peak V. As a result, the interpeak latencies between peaks I and III did not change after day 30, but continued to decrease until day 40 for peaks III-V and IV. Peak amplitudes reached plateau values by day 20 (peak I) or day 30 (peaks II, III, and V). All of the measured latency and amplitude values had significant (P < 0.001) linear regression lines of latency vs age and amplitude vs age. The brain stem auditory-evoked potential thresholds were mature by day 20.

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

-To document normal values for air- and bone-conducted brainstem auditory evoked potentials (BAEP) and for flash visual evoked potentials (VEP) in cats.

Animals

10 mixed-breed cats (5 males) with normal physical, neurologic, otoscopic, and funduscopic examination results.

Procedure

BAEP in response to air- and bone-conducted click stimuli and VEP in response to flash stimuli were recorded to document species normative data. Mean and SD values were calculated for amplitudes and latencies of 4 peaks in the BAEP in response to air- and bone-conducted stimuli, and for latencies to 5 peaks and the 4 associated peak-to-peak amplitudes in the VEP.

Results

BAEP peak latencies increased and peak amplitudes decreased with decreasing stimulus intensity. Latencies were shorter for bone-conducted stimuli owing to the shorter transit time to the cochlea through bone, compared with air, but there were no differences for interpeak latencies. The BAEP and VEP recordings were similar to those reported for cats in other reports and were similar to those seen in other species.

Clinical Relevance

Normative data will permit performance of noninvasive electrodiagnostic evaluation of feline auditory and visual systems. (Am J Vet Res 1998;59:135–137)

Free access
in American Journal of Veterinary Research

Abstract

Vestibulotoxic and ototoxic effects often are seen after long-term, high-dose systemic treatment with gentamicin, but toxic effects after topical use have not been reported in animals, to the authors’ knowledge. Vestibular and auditory effects of twice daily otic gentamicin treatment for 21 days were evaluated in 10 dogs with intact tympanic membranes and in the same 10 dogs after experimental bilateral myringotomy. Each dog served as its own control; 7 drops of gentamicin sulfate (3 mg/ml in a buffered aqueous vehicle) were placed in 1 ear, and 7 drops of vehicle were placed in the opposite ear. Treatment and control ears were reversed after myringotomy. Vestibular function was evaluated daily by neurologic examination and behavioral assessment. Auditory function was evaluated twice weekly by determination of brain stem auditory evoked potentials. Gentamicin sulfate placed in the ear of clinically normal dogs with intact or ruptured tympanic membranes, in the quantities used in this study, did not induce detectable alteration of cochlear or vestibular function. Serum gentamicin concentration after 21 days of treatment was detectable in only 2 dogs and was an order of magnitude below documented toxic concentrations.

Free access
in American Journal of Veterinary Research

Summary

Brain stem auditory evoked potential (baep) testing with air-conducted click stimuli can be used to diagnose sensorineural deafness in dogs if conductive deafness can be ruled out. Detection of conductive deafness can be performed by recording baep elicited by a vibratory stimulus transducer placed against the skull. Air- and bone-conducted baep were compared in dogs, varying bone stimulator placement, click polarity, and stimulus intensity. Optimal bone stimulator placement was determined to be over the mastoid process, followed by the mandible and the zygomatic arch. Condensation polarity clicks gave responses preferable to those elicited by rarefaction or alternating polarity. Bone-conducted baep peak latencies were significantly longer than air-conducted latencies after correction of the latencies for the air conduction time accompanying air-conducted stimuli. Significant differences between stimulus modalities were not seen for baep peak amplitudes or interpeak latencies. Latency-intensity and amplitude-intensity regressions had similar effects for both modalities: latencies decreased and amplitudes increased as stimulus intensity increased.

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To document that free skin grafts treated with hyperbaric oxygen (HBO) are at greater risk for reperfusion injury, resulting in lipid peroxidation, than are free skin grafts without HBO treatment.

Animals

40 Sprague-Dawley rats.

Procedure

Free skin grafting was performed bilaterally on each rat. The HBO-treated rats received HBO twice daily for 90 minutes at 2 ATA. Biopsy specimens were taken from each rat at the time of grafting and on days 2, 4, 7, 10, 14, 21, and 28, then were processed for tissue concentration of total glutathione (GSHt), glutathione peroxidase activity (GPx), and presence of thiobarbituric acid-reactive substances (TBARS).

Results

Both groups had a similar pattern of change in TBARS and GPx values—initial increase, returning to preoperative values at days 21 (control) and 28 (HBO). The GPx activity peaked later than did TBARS concentration (day 7 vs day 4). The pattern was significantly more pronounced in HBO-treated than in control rats. Both groups had a similar pattern of change in GSHt values—significant decrease from preoperative concentration at day 2, return to preoperative concentration by days 4 (HBO) and 7 (control), increase above preoperative concentration by day 21, and return to preoperative concentration by day 28. Obvious visual or histologic differences in the grafts were not detected between groups.

Conclusions

Cellular effects of oxidative stress were apparent in both groups of rats; however, the degree of these effects was exacerbated by HBO. In the face of enhanced cellular lipid peroxidation, use of HBO for the treatment of free skin grafts must be questioned. (Am J Vet Res 1998;59:913–917)

Free access
in American Journal of Veterinary Research

SUMMARY

A method was developed to record cortical somatosensory evoked potentials (sep) from thoracic and pelvic limb stimulation in cows. Recordings were similar in latency and amplitude to those reported for horses. Correction for conduction pathway length did not alter the average latency values because the cows of the study were uniform in size; however, the data provided will enable use of this normative data with smaller or larger individual animals.

Although latency variability for the sep peaks was low, variability of the amplitude measurements was high. This observed variability was similar to that seen in other species. Validity of the recorded responses was indicated by lack of a tibial nerve sep in 1 cow that had been given a tibial nerve conduction block, using lidocaine, and by repeatability of the response in 2 recordings taken 1 year apart in the same cow.

Free access
in American Journal of Veterinary Research