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MRI Correlation of Painful Discs with Low Pressures at Discography 2008

Interventional Spine

Avanti Ambekar, M.D.
Cynthia Chin, M.D., ASSR Member

Scientific Paper

Purpose

Lumbar discography is widely used to evaluate discogenic low back pain. Pressure-controlled manometric discography is valuable in diagnosis of painful discs. Many theories of intradiscal pain generation exist, including mechanical and chemical irritation of specific receptors. The morphology of discs on MR imaging has been shown to correlate poorly with painful levels. The purpose of this study is to examine the MR appearance of discs with the combination of high pain response and low intradiscal pressures at provocative discography.

Methods & Materials

We retrospectively reviewed 86 patients with discogenic back pain (32 men, 54 women) who underwent provocative discography. A total of 242 disc levels were assessed for pain level and concordance, intradiscal pressure, and injected volume. Patterns of intradiscal contrast distribution on CT were analyzed. Lumbar spine MR imaging before and after discography was evaluated for intradiscal T2 signal, annular tear, disc height loss, and endplate signal change.

Results

116 of 242 interrogated disc levels demonstrated low pressure, defined as less than 20 psi. 87 of these 116 low pressure disc levels (75%) correlated with pain intensity levels of 8/10 or greater on a standard pain scale. 49 (56%) of these disc levels demonstrated disc desiccation and height loss on MR. 24 (28%) of discs showed posterior annular tears on MR while 32 (37%) showed annular tears and contrast leakage on post-discogram CT.

Conclusion

Pressure-controlled discography can identify painful discs and correlate with morphologic abnormalities on MRI. In the setting of low intradiscal pressures in painful discs, two distinct pathologies are identified, either frank annular tears or severe disc degeneration. Pain generation in these groups is likely due to stimulation of chemosensitive receptors or mechanical nociceptors respectively. Future non-surgical, minimally invasive therapies for discogenic pain may be guided by differentiating these pain generators with a combination of MRI and discographic pressure measurements.