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Paraspinal soft tissue edema ratio: An accurate marker for early lumbar spine spondylodiscitis on an unenhanced MRI
Pritesh Mehta1, Roshni Patel2, Rafeeque Bhadelia1
1Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215, United States of America.
Purpose:
MRI is currently the gold standard imaging modality in the diagnosis of lumbar spine discitis/osteomyelitis. However, even with supportive clinical and laboratory data, the accuracy of MRI remains limited by several degenerative and inflammatory mimics, such that it continues to represent a challenge for radiologists. This study reports a new quantitative imaging marker of lumbar paraspinal soft tissue edema which shows significant accuracy for spondylodiscitis.
Methods:
Thirty-five patients with equivocal MRI findings of lumbar discitis/osteomyelitis vs endplate degenerative changes were reviewed over a 24-month period. Patients with a history of surgery, fractures/recent trauma, signs of advanced infection such as abscesses, phlegmon or severe osseous destruction were excluded. Two ABR board certified neuroradiologists who were blinded to the final diagnosis evaluated a new marker; the superior-inferior paraspinal edema ratio (SI-PER). The SI-PER was obtained by measuring the superior-inferior extent of increased signal/edema in the paraspinal soft tissues on the paraspinal inversion recovery images divided by the vertebral body height measured at midpoint. Cases positive for spondylodiscitis were those confirmed by biopsy, aspiration/drainage, surgery, or clinical improvement following antibiotic treatment. The diagnostic sensitivity and specificity of SI-PER were determined by Receiver operating characteristic (ROC) analysis.
Results:
In 23/35 (66%) patients, the diagnosis of discitis/osteomyelitis was confirmed. The SI-PER showed a significant association with a positive MRI diagnosis (p = 0.001). Inter-observer correlation for SI-PER was 0.92. ROC analysis showed an area under the curve of 0.84. A SI-PER of 2.5 was 96% sensitive and 75% specific for the diagnosis of discitis/osteomyelitis, with a PPV of 88% and a NPV of 90%.
Conclusion:
In this study, the superior inferior paraspinal edema ratio (SI-PER), a newly defined MRI marker, was found to have high sensitivity for differentiating spondylodiscitis from endplate degenerative changes on lumbar spine MRI.
Insights
A new MRI marker, the superior-inferior paraspinal edema ratio (SI-PER), accurately identifies lumbar spondylodiscitis. This quantitative imaging marker shows high sensitivity in differentiating infection from degenerative changes.
Area of Science:
- Radiology
- Medical Imaging
- Spine Surgery
Background:
- Magnetic Resonance Imaging (MRI) is the standard for diagnosing lumbar spine discitis/osteomyelitis.
- Diagnostic accuracy is limited by degenerative and inflammatory mimics, posing challenges for radiologists.
- A novel quantitative imaging marker is needed to improve diagnostic precision.
Purpose of the Study:
- To introduce and evaluate the superior-inferior paraspinal edema ratio (SI-PER) as a new quantitative MRI marker.
- To assess the accuracy of SI-PER in differentiating lumbar spondylodiscitis from degenerative endplate changes.
- To determine the diagnostic sensitivity and specificity of SI-PER.
Main Methods:
- Retrospective review of 35 patients with equivocal MRI findings.
- Exclusion of patients with surgery, trauma, abscesses, or severe osseous destruction.
- Two neuroradiologists blinded to diagnosis calculated SI-PER using paraspinal inversion recovery images and vertebral body height.
Main Results:
- The SI-PER demonstrated a significant association with confirmed spondylodiscitis (p=0.001).
- Inter-observer correlation for SI-PER was high (0.92).
- Receiver operating characteristic (ROC) analysis yielded an area under the curve of 0.84, with a SI-PER cutoff of 2.5 showing 96% sensitivity and 75% specificity.
Conclusions:
- The SI-PER is a novel MRI marker with high sensitivity for diagnosing lumbar spondylodiscitis.
- This quantitative marker effectively differentiates spondylodiscitis from degenerative endplate changes.
- SI-PER offers improved diagnostic accuracy in challenging lumbar spine MRI cases.
