An immunohistochemical study of innervation of lumbar spinal dura and longitudinal ligaments

Study Design. An immunocytochemical study of nerve fibers in lumbar spinal dura and longitudinal ligaments was conducted in New Zealand white rabbits. Objectives. To demonstrate the presence of nerve fibers and to establish the presence of nociceptive and sympathetic nerve fibers in lumbar dura and longitudinal ligaments. Summary of Background Data. The role of dura as a source of low back pain is still unclear, and the data present a somewhat conflicting picture of the nature of nociceptive innervation in this tissue. Methods. An immunocytochemical method was used to study dura and longitudinal ligaments from New Zealand White rabbits. Results. Numerous fine nerve fibers and some small bundles were demonstrated in both the dura and the longitudinal ligaments. In dorsal dura, the fibers were seen at lateral margins running toward midline. In ventral dura and longitudinal ligaments, the fibers were seen throughout the substance of these tissues. A population of substance P, calcitonin gene-related peptide, and tyrosine hydroxylase-reactive nerve fibers were observed in all the tissues. In addition, fibers exhibiting nicotinamide adenine dinucleotide phosphate diaphorase activity were also observed, indicating the presence of nitric oxide in dura. Conclusions. The results clearly demonstrate an extensive distribution of nerve fibers in dura and longitudinal ligaments. The presence of a significant number of putative nociceptive fibers supports a possible role far these structures as a source of low back pain and radicular pain.