The microvasculature in transitory traumatic paraplegia.  An electron microscopic study in the monkey. 
Fine structural alterations in the microvasculature, primarily of the gray matter, occur as one aspect of experimental spinal cord contusion.  A force of 300 gm-cm, shown by the authors to produce a transitory paraplegia, was applied to the T-10 level of exposed primate spinal cord.  At 5 min post-contusion, the muscular venules of the central gray matter were distended with erythrocytes.  Erythrocytes were seen within the perivascular spaces of the post-capillary venules and muscular venules at 15 and 30 min post-contusion, and there was hemorrhage into the gray matter at 1 hour post-contusion.  The appearance of erythrocytes within the perivenular spaces was apparently due to small ruptures in the walls of the muscular venules, which were first demonstrated by electron microscopy 15 min after contusion.  Alterations in capillary and post-capillary venule endothelium of both gray and white matter were present at 4 hours post-contusion and consisted of vacuolation and endothelial swelling.  In conclusion, following experimental contusion of the spinal cord sufficient to cause a transitory paraplegia, the principal changes were early perivascular and parenchymal hemorrhages followed by later evidence of ischemic endothelial injury in the microvasculature.