Previous experimental studies have shown the effects of acute compression of the spinal cord and peripheral nerve roots. However, few animal model of chronic compression of the cauda equina has been described. The purpose of this study was to
develop a
reproducible animal model of lumbar spinal stenosis in order to detect early indices of the long-term histological and electrophysiological changes of chronic compression of the cauda equina. An animal model of lumbar spinal stenosis, in which
the
pathophysiology of this condition could be examined, was retrieved according to Delamarter's method.
Four experimental groups, each containing six dogs, were studied. One group had a laminectomy of the sixth and sevental lumbar vertebrae only ; these animals served as controls. In the three other groups a laminectomy was performed and the cauda
equina
was constricted by 25, 50 or 75 percent to produce chronic compression. Weekly neurological examination were carried out, and the neurological deficits were graded using the Tarlov system. Sensory evoked potentials, motor evoked potentials were
recorded
preoperatively, immediately after constriction, and at two weeks, one, two and three months postoperatively. After three months of constriction, the cauda equina of six dogs in each group was examined histologically.
Sensory and motor evoked potentials revealed neurological abnormalities before the appearance of neurological signs and symptoms. Constriction of more than 50 per cent was the critical point that resulted in complete loss or reduction of evoked
potentials and in neurological deficits and histological abnormalities. In cases recovered from motor and sensory evoked potentials, neurological symptom and sign have also gradually been recovered.
In conclusion, for the accurate forecasting of prognosis of chronic cauda equina compression, the combined diagnostic study of sensory and motor evoked potential is recommanded.
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