Purpose: To examine histopathologically the endothelium of contrast-enhancing spinal nerve roots.
Methods: In five adult baboons, chronic compression of the left S-1 spinal nerve root sufficient to produce a change in the evoked potential was produced by means of a suture tied around the nerve. The animals were studied with MR at 8 and 16 days after nerve compression and then killed for histopathologic and electron microscopic studies. Histopathologic changes in the nerve roots demonstrating contrast enhancement were described.
Results: In all compressed spinal nerves, contrast enhancement was observed. Histopathologically, wallerian degeneration of the root and inflammation and disruption of the endothelium of capillaries in the spinal nerve were evident.
Conclusions: Degenerative changes in the nerve root and the capillary endothelium of a lumbar spinal nerve are associated with contrast enhancement.