Study of spinal cord evoked injury potential by use of computer modeling and in dogs with naturally acquired thoracolumbar spinal cord compression.
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.


METHODS
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.


METHODS
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.


CONCLUSIONS
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.
Poncelet
L
L
Department of Small Animal Surgery, Faculty of Veterinary Medicine, University of Liège, Belgium.
Michaux
C
C
Balligand
M
M
D000818:Animals; D003198:Computer Simulation; D004283:Dog Diseases; D004285:Dogs; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials; D005260:Female; D008297:Male; D008959:Models, Neurological; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D011930:Reaction Time; D013116:Spinal Cord / Q000503:physiopathology*; D013117:Spinal Cord Compression / Q000503:physiopathology / Q000662:veterinary*; D013904:Thoracic Vertebrae