Diffusion-weighted MRI (DWI) "claw sign" is useful in differentiation of infectious from degenerative Modic I signal changes of the spine

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1 Diffusion-weighted MRI (DWI) "claw sign" is useful in differentiation of infectious from degenerative Modic I signal changes of the spine Poster No.: C-0894 Congress: ECR 2012 Type: Scientific Exhibit Authors: M. Poplawski, P. S. Pawha, B. N. Delman, T. Naidich, L. N. Tanenbaum; New York, NY/US Keywords: DOI: Comparative studies, MR-Diffusion/Perfusion, MR, Spine, Neuroradiology spine, Infection /ecr2012/C-0894 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 8

2 Purpose Modic signal changes, a common observation in MR imaging, are signal intensity findings in vertebral body marrow adjacent to the endplates of degenerative discs. Type II and III patterns are easy to recognize and indicative of chronic degenerative disease. Type I Modic change is more likely to be clinically symptomatic and is characterized by decreased signal on T1WI and increased signal on T2WI, that can be difficult to differentiate from and often suggestive of vertebral osteomyelitis and discitis. Of late, diffusion-weighted MR imaging (DWI) has been shown to be a useful tool in imaging of osseous and epidural spinal lesions, including spinal infection. In this retrospective observational study of patients who were referred for spinal MRI, we characterize and correlate the MRI appearance of spinal levels in patients with Modic I signal changes, and in patients with confirmed spinal infection, with particular attention to the presence or absence of the DWI "claw sign"- a well defined, typically paired linear foci of increased signal on diffusion weighted images at the advancing border of T1 and T2 signal changes with the adjacent normal appearing marrow. Methods and Materials Seventy three patients with Modic I type endplate abnormalities were selected and classified into three groups (Fig. 1 on page 2): clinically confirmed discitis/ osteomyelitis (n=20), degenerative Modic I change (n=33), and suggestive of infection but clinically disproved (n=20). Each abnormal spinal level was blindly evaluated in terms of MR endplate and disc signal changes, enhancement, and appearance on DWI (b value of 500s/mm2) independently by two neuroradiologists. The presence of diffusion "claw sign" was scored (Fig. 2 on page 3) on a scale of 1=definite, 2=probable, 3=questionable, 4=absent (diffuse DWI signal). Images for this section: Page 2 of 8

3 Fig. 1: Study groups and patient characteristics Page 3 of 8

4 Fig. 2: Grading the "claw sign" Page 4 of 8

5 Results Type I changes in the absence of infection invariably correlated with a characteristic DWI "claw sign" of high diffusion signal (Fig. 3 on page 5) at the boundary of the active marrow process and the normal marrow, while patients with type I Modic signal and confirmed spondylodiscitis exhibited significant absence of the "claw sign" (average "claw" scores by neuroradiologist #1 of 1.21±0.07 vs. 3.75±0.16, p<0.01; neuroradiologist #2: 1.58±0.14 vs. 3.50±0.17, p<0.01). Similarly, the group in which infection was initially suggested, but subsequently discounted, had an average score in independent reads of 1.45±0.13 and 1.70±0.18. Suggestion of infection in the original report seemed to be related to the presence of high T2 signal in the disc space, which in this study had a high sensitivity (85-95%), but low specificity (62-69%) and positive predicitive value (49-52%) for infection. Similarly, while high degree of disc enhancement had some specificity, it appeared to be a poor predictor of infection. On the other hand, absence of the "claw sign" (combined score 3 and 4) had a high sensitivity (85-95%), specificity (85-98%) and predictive values for infection (Fig. 4 on page 6: results). Images for this section: Page 5 of 8

6 Fig. 3: "Claw sign" in a case of Modic I change vs. discitis Page 6 of 8

7 Fig. 4: Results Page 7 of 8

8 Conclusion DWI offers powerful characterization information in patients with Type I Modic MR signal changes and assists in the differentiation of degenerative disease from spondylodiscitis of the spine. References 1. Dunbar JA, Sandoe JA, Rao AS, et al. The MRI appearances of early vertebral osteomyelitis and discitis. Clin Radiol Dec; 65(12): Epub 2010 Jul Eguchi Y, Ohtori S, Yamashita M, et al. Diffusion magnetic resonance imaging to differentiate degenerative from infectious endplate abnormalities in the lumbar spine. Spine (Phila Pa 1976) Feb 1;36(3):E Personal Information Page 8 of 8