The pain of discography.

Lumbar discography is a commonly employed diagnostic tool, but important questions about it remain unresolved. Why is an abnormal discogram painful in one patient and not in another? This study was performed to investigate the changes in Substance P (SP) and Vasoactive-Intestinal Peptide (VIP), found in the dorsal root ganglion, following discography in normal and abnormal canine lumber intervertebral discs. The data from this study suggest that dorsal root ganglion SP and VIP are indirectly affected by manipulations of the intervertebral disc. It may be that various neurochemical changes within the intervertebral disc are expressed by sensitized (injured) annular nociceptors, and in part modulated by the dorsal root ganglion. Therefore, the concomitant pain sometimes associated with an abnormal discogram image may in part be related to the chemical environment within the intervertebral disc and the sensitized state of its annular nociceptors.