527 - Non-invasive In-vivo MR Spectroscopy of Non-herniated versus Herniated...

#527 Non-invasive In-vivo MR Spectroscopy of Non-herniated versus Herniated Painful Lumbar Discs

General Session: Best Papers Session

Presented by: M. Gornet

Author(s):

J. Lotz (1), (2)
J. Peacock (1)
D. Bradford (1), (2)
M. Gornet (3)
J. Claude (1)
P. Kane (1)
D. Stewart (3)
F. Schranck (3)

(1) Nocimed, LLC, Redwood City, CA, USA
(2) University of California, San Francisco, CA, USA
(3) The Orthopedic Center of St. Louis, Saint Louis, MO, USA

Abstract

Introduction/Purpose: We previously reported in vivo investigational study results from 79 discs in 42 subjects, including discography patients with axial low backpain (LBP) and asymptomatic volunteers, that demonstrated single voxel MR spectroscopy (SVS) can non-invasively measure 'intradiscal' pain biomarkers that strongly correlate to non-herniated painful and non-painful lumbar discs (3T GE scanner; custom acquisition and post-processing protocols). However, disc herniations are often present in LBP patients with significant radicular leg pain, implicating affects of herniated disc material on surrounding 'extradiscal' nerves. We hypothesize this represents a different pain mechanism than in patients with contained, non-herniated discs with predominantly axial LBP caused by intradiscal pain generators. This study was intended to develop the investigational disc SVS approach for cross-platform MR system compatibility (3T Siemens), and to evaluate correlations of intradiscal SVS signatures of non-herniated painful discs and non-herniated non-painful discs (as previously reported), and herniated painful discs in LBP patients with significant leg pain.

Methods: Non-invasive SVS exams were conducted at a single center on 131 discs from 33 subjects under IRB-approved protocol to refine the investigational SVS acquisition/processing technique and evaluate diagnostic correlations: 47 discs from 14 provocative discography patients with chronic, severe LBP (PD); and 84 discs from 19 asymptomatic volunteers (ASY). Eleven PD patients had leg pain >4 and >50% of backpain (VAS); 10 also had 11 herniated discs (protrosion or extrusion/Grade 5 annular tear). Spectra acquired from 93 discs during technique development had sufficient quality for quantitative pain correlation. Positive Controls (PC) = 8 discography positive (PD+) discs: 7 herniated, 6 with leg pain; 1 non-herniated, with leg pain; 2 spondylolisthesis and scoliosis, respectively. Negative Controls = 85 non-painful discs: 14 discography negative (PD-) discs plus 71 ASY discs.

PD was performed in the PD group by a single discographer, generally per ISIS guidelines. SVS was performed on disc nuclei (3T Siemens, per investigational acquisition/post-processing protocols developed during the study). Proteoglycan, lactate, and alanine-related spectral regions were evaluated for correlative signatures.

Results/Discussion: SVS measures of intradiscal chemistry did not differentiate the 7 herniated PD+ discs from the 85 negative control discs (PD-,ASY). However, the one remaining non-herniated PD+ disc was the only disc having a proteoglycan/lactate ratio < 1. All other PC discs, and all NC discs, had a proteoglycan/lactate ratio >1.

Because disc nuclei are avascular, increased lactic acid production and accumulation can irritate intradiscal nociceptors to cause pain. However, disc herniations involving disruption of the annulus fibrosus can stimulate surrounding nerves as a different pain mechanism, and may also enable extradiscal fluid interaction to neutralize intradiscal acidity.

Conclusions: Our data demonstrate non-herniated painful discs have unique chemical signatures on SVS than herniated painful discs and non-herniated non-painful discs. These chemical differences can be measured non-invasively via the SVS approach. Differentiation between non-herniated painful, herniated painful, and non-painful degenerative lumbar discs may be important in the future for helping to guide clinical management of patients with lumbar degenerative disc disease. Further evaluation in more subjects, and in prospective studies, is warranted to confirm these encouraging findings.