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MR Spectroscopy In Non-Herniated Painful, Herniated Painful, And Non-Painful Lumbar Discs 2013

Category General Spine Lawrence N. Tanenbaum, MD, FACR
James C. Peacock III.
Matthew F. Gornet, M.D.
Jeffrey Lotz, Ph.D.
David Bradford, M.D.
John Claude, M.S.
Paul Kane, M.S.
Francine W. Schranck, B.S.N.
Dawn Stewart, RT
Purpose A prior reported study demonstrated that in vivo single voxel MR spectroscopy (SVS; 3T GE scanner, per custom acquisition and post-processing protocols) can non-invasively measure 'intradiscal' pain biomarkers, including proteoglycan (PG) and lactic acid (LA), that strongly correlate to non-herniated painful (NHP) and non-painful (NP) lumbar discs.[1]The purpose of this study was to further develop the disc SVS technique on a 3T Siemens scanner, and evaluate SVS correlations for NHP versus NP discs, and versus herniated painful (HP) discs which irritate ‘extradiscal’ nerves as a different suspect pain mechanism in LBP patients with significant radiculopathy. Materials & Methods Non-invasive in vivo SVS exams were conducted at a single center via commercial Siemens 3T Verio scanner (investigational acquisition/post-processing protocols developed in study) on disc nuclei of 133 discs from 39 subjects, including PD patients with chronic, severe LBP and asymptomatic control volunteers (ASY).  Eleven of 14 PD patients had leg pain >4 and >50% of backpain (VAS); 10 also had 11 protrusion or extrusion-type HP discs.  Ninety-three disc spectra acquired during this technique development study had sufficient quality for quantitative pain correlation, with most spectral loss due to earlier acquisition issues that were later mitigated with protocol refinements.  Positive Controls (PC) = 8 PD positive (PD+) discs: 7 HP discs, 6 with leg pain; 1 NHP disc with leg pain; 2 spondylolisthesis and scoliosis, respectively. Negative Controls = 85 NP discs: 14 PD negative (PD-) discs plus 71 ASY discs. PD was performed in the PC group by a single discographer, generally per ISIS guidelines.  PG and LA spectral regions were evaluated to correlate with disc types. P401 Nocigram (all discs) spectra only 121210.pdf Results PG/LA ratios were: <1 for only the NHP disc of the PC group; but were >1 for all other 7 HP discs in the PC group and all 85 NP discs of the NC group, and did not differ significantly between the HP and NP disc types.  Prior 3T in vivo (and 11T ex vivo) studies also demonstrated SVS biomarkers for PG and LA differed significantly between NHP versus NP discs. [1,2]  Nociceptor in-growth into disc nuclei has been observed in NHP discs, but not typically in NP discs - potentially related to inflammation and PG reduction.[3,4]  Increased intradiscal lactic acid has also been suggested to irritate intradiscal nociceptors to cause discogenic pain.  However, annulus fibrosus disruptions of HP discs can irritate external nerves instead, and may allow extradiscal fluid interaction to neutralize intradiscal acidity. NM002 PG_LA Peak (Disc Groups) XYplot 120914jp.pdf Conclusion Our data suggest PG and LA-related biomarkers via SVS on a commercial Siemens 3T Verio scanner may differentiate NHP from HP and NP discs. Chemical differentiation between these different disc types and pain profiles may help guide clinical management of LBP patients in the future. Further study is warranted to confirm these encouraging findings. References 1.   Hu, S., et al., Modified Magnetic Resonance Spectroscopy Diagnosis of Painful and Non-Painful Lumbar Intervertebral Discs, Annual Meeting of the Orthopaedic Research Society,  2010. 2.   Keshari, K.R., et al., Lactic acid and proteoglycans as metabolic markers for discogenic back pain. Spine (Phila Pa 1976), 2008. 33(3): p. 312-7. 3.   Freemont, A.J., et al., Nerve ingrowth into diseased intervertebral disc in chronic back pain. Lancet, 1997. 350(9072): p. 178-81. 4.   Johnson, W.E., et al., Human intervertebral disc aggrecan inhibits nerve growth in vitro. Arthritis Rheum, 2002. 46(10): p. 2658-64.