Lumbar spinal canal stenosis examined electrophysiologically in a rat model of chronic cauda equina compression

Study Design. A model of chronic cauda equina compression with conductive stress was studied electrophysiologically. Objective. To analyze the pathophysiology arising from chronic compression electrophysiologically. Summary of Background Data. This rat model of cauda equina compression that is chronic, not acute, has been reported elsewhere. Methods. A stainless steel wire and plate were fastened to the spine at L5 of 8 rats 3 weeks old. One year later, the ascending and descending nerve action potentials were recorded and the conduction velocities (CVs) were measured. Electrophysiologic changes after high-frequency stimulation (HFS) were observed. Results. The waveform of the ascending cauda equina action potential at the cauda equina had three peaks, and that at the conus medullaris had a peak followed by a broad wave. The waveform of the descending nerve action potential had two peaks. The mean ascending and descending CVs of the treated rats were slower (P < 0.001) than those of the control rats. In the control rats, the mean CV and mean amplitude after HFS decreased slightly and returned to normal within 30 seconds, and the waveform was unchanged. In treated rats, the mean CV decreased after HFS but returned to normal within 10 minutes. The mean amplitude decreased after HFS and did not return to normal within 10 minutes. The waveform was unchanged. Conclusions. Because the differences between treated and control rats in amplitude (and CVs) were greater before HFS than after HFS, we concluded that treated rats had disturbance of the blood flow in vessels around the nerves of the cauda equina with histologic damage. In human patients, such disturbance may be one cause of intermittent claudication.