Dynamic changes in the dural sac of patients with lumbar canal stenosis evaluated by multidetector-row computed tomography after myelography

Abstract

Purpose Some reported studies have evaluated the dural sac in patients with lumbar spinal stenosis (LSS) by computed tomography (CT) after conventional myelography or magnetic resonance imaging (MRI). But they have been only able to evaluate static factors. No reports have described detailed dynamic changes in the dural sac during flexion and extension observed by multidetector-row computed tomography (MDCT). The aim of this study was to elucidate or demonstrate, in detail, the influence of dynamic factors on the severity of stenosis. Methods One hundred patients with LSS were enrolled in this study. All underwent MDCT in both flexion and extension positions after myelography, in addition to undergoing MRI. The anteroposterior diameter (AP-distance) and cross-sectional area of the dural sac (D-area) were measured at each disc level between L1-2 and L5-S1. The dynamic change in the D-area was defined as the absolute value of the difference between flexion and extension. The rate of dynamic change (dynamic change in D-area/D-area at flexion) in the dural sac at each disc level was also calculated. Results The average AP-distance in flexion/extension (mm) was 9.2/7.4 at L3-4 and 8.3/7.4 at L4-5. The average D-area in flexion/extension (mm 2 ) was 96.3/73.6 at L3-4 and 72.3/61.0 at L4-5. The values were significantly lower in extension than in flexion at all disc levels from L1-2 to L5-S1. AP-distance was narrowest and D-area smallest at L4-5 during extension. The rates of dynamic changes at L2-3 and L3-4 were higher than those at L4-5. Conclusions MDCT clearly elucidated the dynamic changes in the lumbar dural sac. Before surgery, MDCT after myelography should be used to evaluate the dynamic change during flexion and extension, especially at L2-3, L3-4, and L4-5.

Imaging of the spine: Where do we stand?

“…Thirdly, and to add complexity, spinal canal stenosis should be perceived as a dynamic phenomenon. A lot of spinal canal stenosis subjects report position-dependent symptoms due to postural changes in the dimensions of the spinal canal[12,37].…”

Intraoperative Myelography in Transpsoas Lateral Lumbar Interbody Fusion for Degenerative Lumbar Spinal Stenosis: A Preliminary Prospective Study

“…Specifically, forward flexion and relaxed supine position provide larger spinal canal volume, thus relieving neurological symptom. While extension position can decrease its volume and reduce dural sac cross-sectional area [ 21 – 24 ]. Preoperative images of CT or MRI are often acquired in relaxed supine position, so it may underestimate severity of lumbar canal stenosis to some extent.…”

Tumor Occupation in the Spinal Canal and Clinical Symptoms of Cauda Equina Schwannoma: An Analysis of 22 Cases

“…Some reports have described dynamic changes in the lumbar dural sac [2021222324]. Kanbara et al [21] reported that bulging of the ligamentum flavum had 50%–85% contribution to spinal canal narrowing.…”

“…Kanbara et al [21] reported that bulging of the ligamentum flavum had 50%–85% contribution to spinal canal narrowing. Thus, bulging of intervertebral discs is expected to contribute to spinal canal narrowing under loading conditions by approximately 15%–50%.…”