Short latency auditory evoked potentials recorded from non-anaesthetized thoroughbred horses.
Abstract: 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)
Publication Date: 1992-07-01 PubMed ID: 1498644DOI: 10.1016/0007-1935(92)90084-EGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research investigates the Brainstem Auditory Evoked Potential (BAEP) in unanesthetized thoroughbreds and establishes normal values for both the V:I ratio and dispersal amplitude. Factors like height, weight, and inter-aural distance are examined for their relationship with various BAEP peaks and interpeak latencies (IPLs).
Concept of BAEP and its Importance
- The Brainstem Auditory Evoked Potential (BAEP) is an electrical activity recording from the brainstem following an acoustic stimulation.
- It is a crucial clinical diagnostic tool that can determine abnormal brainstem or auditory nerve conduction if specific BAEP peaks are absent, delayed, or the interpeak latencies (IPLs – the time difference between the peaks) are exceeding the expected range.
Finding Normal BAEP Peaks Values
- The researchers tested clinically normal horses with different stimulus intensities to determine average latency values for both ipsilateral (same side as the stimulus) and contralateral (opposite side to the stimulus) for BAEP peaks I, III, and V, the most clinically important peaks.
- The maximum normal absolute latency for ipsilateral peak I, III, and V were defined, and the equivalent contralateral values were also identified.
- The maximum normal contralateral IPLs were determined for peak pairs I-III, III-V, and I-V, giving a reference range for healthy horses.
Calculating Peak Amplitudes and Ratios
- The researchers have calculated the amplitude ratio for BAEP peaks I and V in both conditions (ipsilateral and contralateral).
- The dispersal values were also calculated, defined as the height of the III-V complex divided by its duration. A normal range for both the V:I ratio and dispersal values were identified.
Correlation with Physical Variables
- Physical variables like height, weight, and inter-aural distance were measured on each subject.
- Statistical analysis showed significant correlations between the ipsilateral latency of wave V, and IPLs III-V and I-V with the weight of the horse.
- Correlations were also found between weight and the latency of contralateral waves III and V and the IPLs I-III and I-V, suggesting the influence of these physical variables on BAEP characteristics.
This research is critical in establishing normal values for BAEP measures in thoroughbred horses, enabling better diagnosis and understanding of brainstem and auditory nerve conditions in these animals.
Cite This Article
APA
Mayhew IG, Washbourne JR.
(1992).
Short latency auditory evoked potentials recorded from non-anaesthetized thoroughbred horses.
Br Vet J, 148(4), 315-327.
https://doi.org/10.1016/0007-1935(92)90084-E Publication
Researcher Affiliations
- Animal Health Trust, Newmarket, Suffolk.
MeSH Terms
- Animals
- Evoked Potentials, Auditory, Brain Stem
- Horses / physiology
- Reference Values
Citations
This article has been cited 3 times.- Lecoq L, Gains M, Blond L, Parent J. Brainstem auditory evoked responses in foals: reference values, effect of age, rate of acoustic stimulation, and neurologic deficits. J Vet Intern Med 2015 Jan;29(1):362-7.
- Aleman M, Holliday TA, Nieto JE, Williams DC. Brainstem auditory evoked responses in an equine patient population: part I--adult horses. J Vet Intern Med 2014 Jul-Aug;28(4):1310-7.
- Harland MM, Stewart AJ, Marshall AE, Belknap EB. Diagnosis of deafness in a horse by brainstem auditory evoked potential. Can Vet J 2006 Feb;47(2):151-4.
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