JBR-BTR : organe de la Société royale belge de radiologie (SRBR) = orgaan van de Koninklijke Belgische Vereniging voor Radiologie (KBVR)
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Though CT and MRI are presently the most frequently required noninvasive methods for the diagnosis of lumbar spinal stenosis (LSS), imaging of a supine patient may not demonstrate the maximal spinal stenosis shown by upright flexion-extension myelography (FEM). Our prospective study tries to assess the averaging discrepancies between the supine CT-myelograms and the upright FEM in 50 patients. Considering all L2-L3 to L4-L5 vertebral levels, a mean underestimation of 16% of the diameter of the dural sac is found when and CT-myelograms are compared with extension myelography. ⋯ Measuring the mean cross-sectional surface occupied by the neural elements in the dural sac on CT-myelograms (189 evaluations), our study also empirically confirms a 60 to 80 mm2 are++ being the landmark of absolute stenosis. Finally, measurements of the cross-sectional area of the dural sac-109 L2-L5 levels inferior to 8.5 mm on CT myelograms or CT studies--show a large dispersion of areas for diameters superior to 6.5 mm and confirm cross-sectional area of the dural sac to be a much reliable parameter of LSS than diameter of the dural sac. We conclude that upright FEM--while not a first-line imaging modality for LSS--should be performed to exclude functional or dynamic position-dependent LSS in the patients whose symptoms are not explained by routine cross-sectional imaging, as long as no other upright technology is available.