Electrodiagnostic and histologic changes of graded caudal compression on cauda equina in dog.

Abstract

An animal model of lumbar spinal stenosis, in which the pathophysiology of this condition could be examined, was retrieved according to Delamarter's method. The purpose of this study was to develop a reproducible animal model of lumbar spinal stenosis to further understanding of the long-term electrophysiologic changes, and to detect prognostic indices of the long-term anatomic and physiologic status of chronic compression of the cauda equina. Somatosensory-evoked potentials and bulbocavernosus reflexes revealed abnormalities before neurologic signs and symptoms appeared. If delayed somatosensory-evoked potentials and bulbocavernosus reflexes were recovered with the lapse of time, neurologic findings showed gradual recovery. The loss of somatosensory-evoked potentials, bulbocavernosus reflexes, and neurologic, histological abnormalities occurred at 50% constriction of the cauda equina; at the same time, that was the critical point of possible recovery. Four experimental groups, each containing six dogs, were studied. One group had a laminectomy of the sixth and seventh 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% to produce chronic compression according to Delamarter's method. Somatosensory-evoked potentials and bulbocavernosus reflexes revealed neurologic abnormalities before the appearance of neurological signs and symptoms. Constriction of more than 50% was the critical point; it resulted in loss of evoked potentials, reflexes, neurologic deficits, and histological abnormalities. To accurately forecast prognosis of chronic cauda equina compression, the combined diagnostic study of somatosensory-evoked potential with bulbocavernosus reflex is recommended.