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

Purpose: To evaluate the degree of acute or progressive lateral compression needed to cause neurologic injury to the spinal cord assessed by electrophysiological monitoring.

Methods: 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.

Results: 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.

Conclusions: 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.