15. Discogenic Low Back Pain

Abstract

An estimated 40% of chronic lumbosacral spinal pain is attributed to the discus intervertebralis. Degenerative changes following loss of hydration of the nucleus pulposus lead to circumferential or radial tears within the annulus fibrosus. Annular tears within the outer annulus stimulate the ingrowth of blood vessels and accompanying nociceptors into the outer and occasionally inner annulus. Sensitization of these nociceptors by various inflammatory repair mechanisms may lead to chronic discogenic pain. The current criterion standard for diagnosing discogenic pain is pressure-controlled provocative discography using strict criteria and at least one negative control level. The strictness of criteria and the adherence to technical detail will allow an acceptable low false positive response rate. The most important determinants are the standardization of pressure stimulus by using a validated pressure monitoring device and avoiding overly high dynamic pressures by the slow injection rate of 0.05 mL/s. A positive discogram requires the reproduction of the patient's typical pain at an intensity of > 6/10 at a pressure of < 15 psi above opening pressure and at a volume less than 3.0 mL. Perhaps the most important and defendable response is the failure to confirm the discus is symptomatic by not meeting this strict criteria. Various interventional treatment strategies for chronic discogenic low back pain unresponsive to conservative care include reduction of inflammation, ablation of intradiscal nociceptors, lowering intranuclear pressure, removal of herniated nucleus, and radiofrequency ablation of the nociceptors. Unfortunately, most of these strategies do not meet the minimal criteria for a positive treatment advice. In particular, single-needle radiofrequency thermocoagulation of the discus is not recommended for patients with discogenic pain (2 B-). Interestingly, a little used procedure, radiofrequency ablation of the ramus communicans, does meet the (2 B+) level for endorsement. There is currently insufficient proof to recommend intradiscal electrothermal therapy (2 B±) and intradiscal biacuplasty (0). It is advised that ozone discolysis, nucleoplasty, and targeted disc decompression should only be performed as part of a study protocol. Future studies should include more strict inclusion criteria.

Nerve growth factor increases MMP9 activity in annulus fibrosus cells by upregulating lipocalin 2 expression

“…The pathogenesis of the chronic LBP associated with IVD degeneration is complex but changes in IVD innervation appear to be important [3]. In the normal IVD, nerve fibers, derived from branches of sympathetic trunk and sinuvertebral nerves, are present only in the outer annulus fibrosus (AF) and vertebral endplate [4]. During IVD degeneration, however, nerve fiber ingrowth into the nucleus pulposus (NP) is seen and is believed to possibly contribute to chronic LBP [5].…”

Discogenic pain: Who cares?

“…In fact, there is a high prevalence of degenerative disc disease findings in asymptomatic persons [54]. MR is the most appropriate modality for evaluation of degenerative disc disease [8,55]. It has a sensitivity ranging from 60% to 100% and specificity of 43% to 97% [55].…”

“…The diagnostic criteria for IVD disease established by the International Association for the Study of Pain (IASP) are occurrence of a concordant pain response during discography, internal annular disruption shown by CT after discography and at least one adjacent disc without concordant pain. Nevertheless, its predictive value has been repeatedly questioned, mainly as a result of reported false positive rates [8]. Physicians must be aware of exaggerated responses to disc stimulation due to other factors, as psychometric variables or high contrast infusion rates [58].…”

“…Sensory fibers are mostly nociceptive, located in the posterior outer layers of the AF and in the central portion of the vertebral endplates. Proprioceptive fibers can also be found in a lesser extent [8]. This innervation is accomplished by branches of the sinuvertebral nerve (capable of nociception) and branches of the paravertebral sympathetic trunks [5].…”

“…The IVD along with the facet joints provide support and stability by limiting the movement of the spine in all directions [8,9]. The IVD along with two adjacent vertebrae and all the ligaments between them constitute the spinal functional unit, defined as the smallest physiological motion unit of the spine to exhibit biomechanical characteristics similar to those of the entire spine.…”