INNERVATION OF PAINFUL LUMBAR DISCS

Study Design. The authors investigated the innervation of discographic ally confirmed degenerated and ''painful'' human intervertebral discs. Objective. To determine the type and distribution patterns of nerve f ibers present in degenerated human intervertebral discs. Summary of Ba ckground Data. The innervation of intervertebral discs has previously been extensively described in fetal and adult animals as well as human s. However, little is yet known about the innervation of severely dege nerated human lumbar discs. The question may be posed whether a disc t hat has been removed for low back pain possesses an increased innervat ion compared with normal discs. Methods. The presence of nerve fibers was investigated using acetylcholinesterase enzyme histochemistry, as well as neurofilament and substance P immunocytochemistry. From 10 deg enerated and 2 control discs, the anterior segments were excised and t heir nerve distribution studied by examining sequential sections. Resu lts. In all specimens, nerve fibers of different diameters were found in the anterior longitudinal ligament and in the outer region of the d isc. In 8 of 10 degenerated discs, fibers were also found in the inner parts of the disc. Substance P-immunoreactive nerve fibers were spora dically observed in the anterior longitudinal ligament and the outer z one of the anulus fibrosus. Conclusions. Findings indicate a more exte nsive disc innervation in the severely degenerated human lumbar disc c ompared with normal discs. The nociceptive properties of at least some of these nerves are highly suggested by their substance P immunoreact ivity, which provides further evidence for the existence of a morpholo gic substrate of discogenic pain.