Evaluation of the Effect of Myelotomy on Experimental Acute Spinal Cord Injury with Spinal Evoked Potentials

ABSTRACT

Direct spinal epidural surface of spinal evoked potentials have been made in 16 adult cats with acute spinal cord injuries produced experimentally in which myelotomy was performed in 8 cats 1 hour after the injury. The remaining 8 animals served as control. The spinal cord injury with 20gm - 20 cm was inflicted over the entire dorsal surface of the spinal cord at L2-3 interspace by Allen's weight-drop method which was improved by placing a curved steel plate anterior to the spinal cord to provide a smooth, hard surface for the receipt of posterior cord impact. Under the operating microscope, a median posterior longitudinal myelotomy approximately 10mm to 15mm in length was made at the injury site 1 hour after the injury. Animals were evaluated electrophysiologically either from preinjury state to postinjury 4 hours(control group) or from preinjury state to post myelotomy 3 hours(myelotomy group). The component waves of the spinal somatosensory evoked potentials(SSEP) of control group disappeared sequentially after the injury in the following order N4, N3, N2, N1. In myelotomy group, N4 and N3 wave also disappeared, but N1 and N2 wave remained. The latencies of the component waves increased & its amplitudes decreased sequentially after the injury. In myelotomy group, as com-with the control group, post-traumatic latency rate increase as well as amplitude were both reduced.