The function of the blood-nerve barrier appears quite unique in the nerve root. Protein tracers that were injected into the subarachnoid space passed through the nerve root sheath and entered into the capillary lumen in the endoneurial space but tracers that were injected intravenously did not appear in the endoneurial space. Marked extravasation of 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 magnetic resonance imaging. In twenty-one of fifty patients with lumbar disc herniation, the affected nerve root was strongly enhanced by Gadolinium-diethylene-triaminepentaacetic acid, indicating that the blood-nerve barrier in the affected nerve root was broken and intraradicular edema was produced in these cases.
From the Department of Orthopaedic Surgery, Fujita Health University School of Medicine, Toyoake, Aichi, Japan.
Supported in part by a grant from the Japanese Ministry of Education, Science, and Culture, grant-in-aid for scientific research no. 63570712 and Grant of Japan Orthopaedics and Traumatology Foundation, Inc. No. 0054 (Zimmer-Japan).
The authors thank Ikuko Nagatu, MD, Masao Sakai, MD, and Ituko Nakano, Ms, for their dedicated assistance in this study.
Accepted for publication April 19, 1993.