Standing MRI exaggerated degree of lumbar foraminal stenosis but not improved correlation with patient symptoms Lau YYO 1, Lee KL 3, Chan LY 2, Griffiths JF 3, Law SW 2, Kwok KO 2 1 Department of Orthopaedics & Traumatology, Tseung Kwan O Hospital, Hong Kong 2 Department of Orthopaedics & Traumatology, Prince of Wales Hospital, The Chinese University of Hong Kong 3 Department of Imaging & Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong COI disclosure: No funds or benefits were received in support of this work
Introduction MRI lumbar spine in supine, non-weight bearing position may underestimate degree of neural foraminal stenosis 1,3,5,8 This study aims to evaluate dynamic change of neural foramens on standing MRI and its clinical correlation
Method & materials (1) Figure 1. G-Scan, Esaote. Low field open magnet with patient platform & hydraulic tilt mechanism allows imaging in horizontal & vertical positions Prospective, cross-sectional study performed Feb 2012- Dec 2013 100 patients with spinal stenosis symptoms (sciatica/ radiculopathy) recruited Clinical data questionnaires: duration symptom, walking distance, VAS leg pain, Chinese-ODI, SF-12 0.25-T MRI examination in Supine & Standing positions
Method & materials (2) Figure 2.Qualitative assessment of neural foramen stenosis by the 4-point grading scale (Wildermuth) 1 Grade 0 Grade 1 MRI measurement for neural foramen stenosis Widermuth 1 4-point grades (0-3) L3/4, L4/5 & L5/S1 levels Supine & standing positions Twice by 2 observers blinded to data Grade 2 Grade 3 Intra- /inter-observer reliabilities Good to Excellent Intra-obs. κ: 0.86 (95% CI: 0.74-0.92) Inter-obs. κ: 0.72 (95% CI: 0.60-0.86) G0: normal, oval or inverted pear; G1: slightly deformed epidural fat; G2: marked stenosis, fat partially surrounds nerve root; G3: obliterated
Results (1) Among 594 neural foramens, 10.8% Occult Stenosis, visualized exclusively on standing MRI, 7 detected 39.1% showed one grade increase of stenosis on standing compared with supine position
Results (2) Standing MRI demonstrated significant higher proportion of severe stenosis (grade 3) (21.5% vs 7.1%, p<0.001) than supine MRI But smaller % of normal foramen without stenosis (23.4% vs 33.6%, p<0.001)
Results (3) There was overall poor clinical correlation with foraminal stenosis Only leg pain VAS worsens in patients with marked foraminal stenosis on standing MRI Older patients got more severe foraminal stenosis
Discussion & Conclusion 1 2 3 Dimension of neural foramen was positional dependent. 2,4,6 Standing MRI under physiologic load is more capable to detect foraminal stenosis than supine. Our study detected 10.8% occult stenosis ; this result is comparable other studies. 3,5,7 This is the first standing MRI study analyzed clinical correlation with severity of foraminal stenosis. Dynamic change of foramens did not show relationship with most symptoms, except leg pain VAS, which is also true in sitting MRI. 3 Standing MRI, though not essential for screening, is useful for diagnosis in selected symptomatic cases with normal supine MRI findings. Future studies by quantitative measurement foramen size or adopting added weight in extension can be considered. 8 Radiology Clinical
References 1. Widermuth S, et al. Quantitative and qualitative assessment of positional (upright, flexion, extension) MRI and myelography. Radiology 1998;207:391-8. 2. Schmid MR, et al. Changes in cross-sectional measurements spinal canal & intervertebral foramina as a function of body position. AJR 1999;172:1095-102. 3. Weishaupt D, et al. Positional MRI of lumbar spine: does it demonstrate nerve root compromise not visible on conventional MR? Radiology 2000;215:247-53. 4. Fredericson M, et al. Changes in disc bulging and intervertebral foraminal size associated with flexion-extension movement. Spine J 2001;1:10-7. 5. McGregor AH, et al. Assessment of spinal kinematics using open interventional MRI. CORR 2001; 392:341-8. 6. Mauch F, et al. Changes in the lumbar spine of athletes from supine to the true standing position in MRI. Spine 2010; 35:1002-7. 7. Splendiani A, et al. Occult neural foraminal stenosis caused by association between disc degeneration & facet osteoarthirits. Radiol Med 2014;119:164-74. 8. Singh V, et al. Factors affecting dynamic foraminal stenosis in the lumbar spine. Spine J 2013;13(9):1080-7.
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