Experimental Studies on the Spinal Cord Evoked Potentials in Compression Injury of the Cervical Spinal Cord

Summary

The waveform changes and their recovery processes were analyzed by recording the spinal cord evoked potential (SEP) before, during the after graded cervical ventral compression of the cat spinal cord. The SEP was recorded at three levels: compression site, and rostral and caudal sites, in response to single electric shocks at the level of the 8th thoracic vertebra. In the series of graded compression, the most significant changes were observed in the first negative component (Ncl) of the SEP. The magnitude of injury was classified into three groups according to the amplitude decrement of Nc1 component. After release of compression, the SEP showed no recovery in the group whose amplitude decrement was more than 50%.

The radial nerve evoked potential (radial NEP) was also induced by single electric shocks to the Cl-2 spinal cord level during graded compression. A significant correlation was observed between amplitude decrements of SEP (Ncl component) and the radial NEP when compression was applied to the spinal cord at the level of the C5 vertebra. For spinal surgery the most reliable monitoring technique is to record the SEP at the injury site; the distal peripheral nerve evoked potential is also useful when an appropriate nerve is selected for recording.