DIFFERENTIAL VULNERABILITY OF SPINAL CORD STRUCTURES TO ANOXIA

Abstract

The differentially sensitivity of various spinal elements to lack of O2 was established by observing the responses recorded from the dorsum of the dog''s spinal cord, the ventral root and muscle reflex responses, during asphyxia of entire animal or ischemia of the cord. The motoneuron somata are about 1.5 times as sensitive as the interneurons. The latter are about 2.5 times as sensitive as the dorsal column fibers. All intramedullary primary afferent A fibers fail to conduct after about 20 minutes of asphyxia. Clamping of the aortic arch rendered the lumbosacral cord ischemic and permitted reversibility studies. Full recovery of any given cord structure may be expected if the duration of complete ischemia does not exceed about 4 times the functional survival time of that structure. The differential vulnerability is thus an expression of both sensitivity to and capacity for recovery from lack of O2.