Resolving discogenic pain.

Recent basic science studies on discogenic low back pain have provided new knowledge about this condition. This paper reviews some of these results and presents an overview of the following findings. The rat lumbar intervertebral disk may be innervated non-segmentally through the paravertebral sympathetic nerve and segmentally through the sinuvertebral nerves, and also by dichotomizing sensory fibers. The exposure of the nucleus pulposus (NP) to the outer annulus fibrosus (AF) may induce nerve injury and ingrowth into the disk. Nerve growth factor (NGF)-sensitive neurons are predominant in the rat intervertebral disk, which indicates that hyperalgesic responses can be induced by inflammation. NGF in the NP may promote axonal growth. Lumbar fusion may inhibit nerve ingrowth into the degenerated disk and reduce the percentage of calcitonin gene related peptide (CGRP)-positive neurons.