Neurophysiological monitoring during acute and progressive experimentally induced compression injury of the spinal cord in pigs.

Abstract

To evaluate the degree of acute or progressive lateral compression needed to cause neurologic injury to the spinal cord assessed by electrophysiological monitoring. In five domestic pigs, the spinal cord was exposed and compressed between T8-T9 roots using a precise compression device. Two sticks placed on both sides of the spinal cord were sequentially brought together (0.5 mm every 2 min), causing progressive spinal cord compression. Acute compression was reproduced by a 2.5-mm displacement of the sticks. Cord-to-cord evoked potentials were obtained with two epidural catheters. Increasing latency and decreasing amplitude of the evoked potentials were observed after a mean progressive displacement of the sticks of 3.2 ± 0.9 mm, disappearing after a mean displacement of 4.6 ± 1.2 mm. The potential returned after compression removal (16.8 ± 3.2 min). The potentials disappeared immediately after an acute compression of 2.5 ± 0.3 mm, without any sign of recovering after 30 min. The experimental model replicates the mechanism of a spinal cord injury caused by medially displaced screws into the spinal canal. The spinal cord had more ability for adaptation to progressive and slow compression than to acute mechanisms.