VASOGENIC EDEMA INDUCED BY COMPRESSION INJURY TO THE SPINAL NERVE ROOT - DISTRIBUTION OF INTRAVENOUSLY INJECTED PROTEIN TRACERS AND GADOLINIUM-ENHANCED MAGNETIC-RESONANCE-IMAGING

The function of the blood-nerve barrier appears quite unique in the ne rve root. Protein tracers that were injected into the subarachnoid spa ce passed through the nerve root sheath and entered into the capillary lumen in the endoneurial space but tracers that were injected intrave nously did not appear in the endoneurial space. Marked extravasation o f protein tracers in the nerve root was induced at the compressed part by strong compression (60 gram force, 30 gram force) and capillaries in the nerve root showed opening of the tight junction accompanied by an increase in vesicular transport under the electron microscope. This situation was reflected as high intensity on Gadolinium-enhanced magn etic resonance imaging. In twenty-one of fifty patients with lumbar di sc herniation, the affected nerve root was strongly enhanced by Gadoli nium-diethylene-triaminepentaacetic acid, indicating that the blood-ne rve barrier in the affected nerve root was broken and intraradicular e dema was produced in these cases.