The neuropathology of intervertebral discs removed for low-back pain.

Thirty lower lumbar intervertebral discs (IVDs) removed for low-back pain were examined. There is a profuse non-myelinated axonal network and abundant free nerve terminals in the outer (lateral) half of the annulus fibrosus. The inner annulus and the nucleus pulposus did not contain nerve terminals. No significant changes in the nerve networks could be demonstrated in degenerate IVDs: in particular, ingrowth of nerve terminals into foci of granulomatous tissue was not seen. Early foci of degeneration are clearly shown by Marshall's silver method for metalophil cells. Mucinous filaments are argyrophilic and can be mistaken for axonal structures in the nucleus pulposus.