Behavioral and morphologic studies of the chronically compressed cauda equina - Experimental model of lumbar spinal stenosis in the rat

Study Design. An experimental model in rats of chronically compressed cauda equina was produced, and behavioral and morphologic changes were examined. Objectives. To provide a useful model for analyzing the pathophysiologic ch anges of the cauda equina by chronic compression and to examine behavioral and morphologic changes in this model. Summary of Background Data. Several animal models have been reported in whi ch various materials were used to compress the cauda equina, However, the p athophysiology of the cauda equina by chronic compression is not yet well u nderstood. Studies in which rats were used are scarce. Methods. A silicone sheet was applied to the spinal canal at L4 in the rat. Walking durations on treadmill tests and paw-withdrawal latencies to therm al stimuli were measured before and after the operation for 24 weeks. Histo logic changes also were examined. Results. Walking durations decreased after chronic compression. However, pa w-withdrawal latencies were not significantly changed. Histologically, the number of large-diameter myelinated axons decreased after compression, wher eas the number of small-diameter myelinated axons increased. Electron micro scopic observation indicated that the continuous degeneration and regenerat ion of axons occurred throughout the chronic compression experiment. Conclusions. The current model and behavioral assessments may be useful in analyzing the pathophysiology of chronically compressed cauda equina.