Variety of the Wave Change in Compound Muscle Action Potential in an Animal Model

Study design: Animal study.

Purpose: To review the present warning point criteria of the compound muscle action potential (CMAP) and investigate new criteria for spinal surgery safety using an animal model.

Overview of literature: Little is known about correlation palesis and amplitude of spinal cord monitoring.

Methods: After laminectomy of the tenth thoracic spinal lamina, 2-140 g force was delivered to the spinal cord with a tension gage to create a bilateral contusion injury. The study morphology change of the CMAP wave and locomotor scale were evaluated for one month.

Results: Four different types of wave morphology changes were observed: no change, amplitude decrease only, morphology change only, and amplitude and morphology change. Amplitude and morphology changed simultaneously and significantly as the injury force increased (p<0.05) Locomotor scale in the amplitude and morphology group worsened more than the other groups.

Conclusions: Amplitude and morphology change of the CMAP wave exists and could be the key of the alarm point in CMAP.