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  • Author or Editor: L. Poncelet x
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Abstract

Objective

To add objective measurements of the characteristics of evoked injury potentials (EIP) and their relations to clinical severity in dogs with thoracolumbar spinal cord damage.

Animals

25 dogs with naturally acquired spinal cord compression attributable to disk extrusion or vertebral fracture at the level of the thoracolumbar junction and with various degrees of paresis/paralysis.

Procedure

Spinal cord potentials evoked by tibial nerve stimulation were recorded every 5 to 10 mm at the lamina level in the vicinity of the cord compression. This allowed an EIP to be recorded even in the least handicapped dogs. A computer model yielded information about the waveform changes of the EIP in the vicinity of conduction blocks.

Results

The EIP waveform changed from biphasic to monophasic a short distance caudad to the location of spinal cord compression. Location of a maximal conduction block was measured in relation to position of the electrodes recording this waveform change. The distance between the assumed conduction block and the actual spinal cord compression was larger in the most affected dogs. The amplitude of the EIP was not related to severity of the clinical picture; however, the proximity of the recording electrode to the spine influenced the amplitude and the waveform of the EIP.

Conclusion and Clinical Relevance

Change in the EIP waveform from biphasic to monophasic makes it possible to estimate the conduction block location along the spinal cord. A large distance between the assumed conduction block and site of actual cord compression could be an objective argument to confirm severity of a lesion. (Am J Vet Res 1998;59:300–306)

Free access
in American Journal of Veterinary Research

Summary

We compared the effects of bilateral vs unilateral tibial nerve stimulation of percutaneously recorded spinal evoked potentials (sep) in the lumbar and caudal thoracic area in dogs. The overall amplitude of the sep is increased by this means. Use of this method could improve legibility of the recordings. Amplitudes of root and interneuronal components of the sep are doubled as are cranially transmitted depolarizations. However, the amplitude of the sep component arising from the primary afferents’ depolarization was less than doubled. Latencies of the components were unaffected by bilateral stimulation. Careful observation of the latencies disclosed a 0.9-ms delay in transmission of the fastest component in the midlumbar area. This delay was consistant with results of previous cordotomy experiments, and could influence precision of conduction velocity measurement.

Free access
in American Journal of Veterinary Research