Ozawa T, et al. The Degenerated Lumbar Intervertebral Disc is Innervated Primarily by Peptide-Containing Sensory Nerve Fibers in Humans. Spine 1 October 2006; 31(21):2418-2422.
ABSTRACT: Study Design: Immunohistochemical study of the sensory innervation of the human lumbar intervertebral disc. Objective: To determine the type of sensory fibers innervating human degenerated lumbar intervertebral discs. Summary of Background Data: Sensory neurons involved in pain perception related to inflammation in rats are typically small, peptide-containing neurons immunoreactive for calcitonin gene-related peptide (CGRP). Small non-peptide-containing neurons binding to isolectin B4 (IB4) may also be involved in pain states, such as nerve injury pain. The character of such sensory neurons in humans has not been clarified. Methods: A degenerated, painful lumbar intervertebral disc was harvested from each of 8 patients during surgery. Sections were immunostained for protein gene product 9.5 (PGP 9.5, a general neuronal marker), CGRP, and IB4. The numbers of PGP 9.5- and CGRP-immunoreactive, and IB4-finding nerve fibers in the disc were counted. Results: PGP 9.5-immunoreactive fibers were observed in all discs. Nerve fibers immunoreactive for CGRP were also observed in 6 of 8 cases. IB4-binding nerve fibers were not found in any case. Conclusions: Almost all of the nociceptive nerve fibers in the human intervertebral disc are peptide-containing nerve fibers, similar to the rat disc, suggesting that nerve fibers related to inflammation may transmit pain originating from human degenerated discs.
COMMENTS: Nerve fibers have been found in the outermost layers of the intact anulus fibrosis. Researchers have found nerve fibers extending into the inner anulus and even into the nucleus pulposus of damaged discs. These nerve fibers found in damaged discs have been found to accompany blood vessels. The function of these nerve fibers had not been determined. Some opined that some of these fibers may transmit nociceptive impulses and be a cause of discogenic back pain.