Dural Cross-sectional Area Research Articles

Comparison Accuracy in Determining the Degree of Lumbar Spinal Stenosis between Lumbar Spine MRI with Axial Loading and Routine Conventional MRI with Clinical Correlation

Objective: To evaluate the accuracy in determining the degree of lumbar spinal stenosis in patients utilizing lumbar spine magnetic resonance imaging (MRI) with axial loading as compared to conventional lumbar spine MRI with clinical correlation. To assess the difference in the dural cross sectional area (DCSA) between lumbar spine MRI with axial loading and conventional lumbar spine MRI. Materials and Methods: Thirteen patients with clinically diagnosed lumbar spinal stenosis, which comprised of three males and ten females, aged 20 to 80 years, and that had the severity of their stenosis clinically and radiologically graded by history taking, physical examination, and by performing both conventional and axial loaded MRI were included in this study. Results: The present study found a statistically significant difference (p<0.05) after applying load at all lumbar levels. The L4-L5 level showed the greatest reduction at 12.8%, followed by L3-L4 and L2-L3, in which the DCSA was reduced by 11.2% and 9.0%, respectively. Comparing the clinical severity and degree of each lumbar spinotic level and the maximum severity per person, the results showed that the most accuracy was at the L3-L4 level followed by L5-S1 and L2-L3 levels. No accuracy between clinical severity and the degree of lumbar spinal stenosis at L1-L2 and L4-L5 levels were shown, suggesting that more than the DCSA change influence the clinical severity. To gain further insights, following up patients and a study with more patients are needed. The maximum severity by DCSA measurement, both pre- and post-loading, of individual patients compared with clinical severity showed concordance for three patients. No significant difference in accuracy was found between pre- and post-loading. Conclusion: Changes in the DCSA of lumbar spinal stenosis after loading MRI was statistically significant especially at the moderate and severe stenotic levels particularly at the L3-4 level and L5-S1 level. Keywords: Lumbar spine MRI; Axial loading; Lumbar spinal stenosis

The prevalence of redundant nerve roots in standing positional MRI decreases by half in supine and almost to zero in flexed seated position: a retrospective cross-sectional cohort study

PurposeThis retrospective cross-sectional cohort study investigated the influence of posture on lordosis (LL), length of the spinal canal (LSC), anteroposterior diameter (APD L1-L5), dural cross-sectional area (DCSA) of the lumbar spinal canal, and the prevalence of redundant nerve roots (RNR) using positional magnetic resonance imaging (MRI) (0.6 T).MethodsSixty-eight patients with single-level degenerative central lumbar spinal stenosis (cLSS) presenting with RNR in the standing position (STA) were also investigated in supine (SUP) or neutral seated (SIT) and flexed seated (FLEX) positions. Additionally, 45 patients complaining of back pain and without MRI evidence of LSS were evaluated. Statistical significance was set at p < 0.05.ResultsControls (A) and patients with cLSS (B) were comparable in terms of mean age (p = 0.88) and sex (p = 0.22). The progressive transition from STA to FLEX led to a comparable decrease in LL (p = 0.97), an increase in LSC (p = 0.80), and an increase in APD L1-L5 (p = 0.78). The APD of the stenotic level increased disproportionally between the different postures, up to 67% in FLEX compared to 29% in adjacent non-stenotic levels (p < 0.001). Therefore, the prevalence of RNR decreased to 49, 26, and 4% in SUP, SIT, and FLEX, respectively.ConclusionThe prevalence of RNR in standing position was underestimated by half in supine position. Body postures modified LL, LSC, and APD similarly in patients and controls. Stenotic levels compensated for insufficient intraspinal volume with a disproportionate enlargement when switching from the STA to FLEX.

Quantification of Lumbar Spinal Canal Stenosis by Quantitative Fat-Suppressed Contrast-Enhanced Magnetic Resonance Imaging.

Fat-suppressed T1-weighted magnetic resonance images (MRIs) enhanced with gadolinium can evaluate the internal vertebral venous plexus and cauda equina. This study compared such findings with clinical situations and discusses whether these are helpful for symptomatic grading and selection at the surgical level in patients with lumbar central stenosis. A total of 263 patients (337 levels < 75 mm2 of dural cross sectional area (DCSA)) were included. The enhancement patterns of dorsal epidural vein (DVCE), periradicular vein (PVCE) and intraradicular vein (IRCE) were assessed qualitatively. The quantification of IRCE was acquired by the ratio (%) (enhancement parameters: MS/P1, MS/P2, WR/P1, WR/P2) of signal intensities between the cauda equina (MS-IRCE: maximal spot rootlet, WR-IRCE: whole rootlets) and psoas muscle (P1, P2). Receiver-operator characteristic curves were plotted to obtain imaginary cutoff values for the prediction of symptomatic appearance or operation decision. All levels were classified into seven groups on the basis of pain distribution and the presence of IRCE. PVCE was significantly related to high incidences of symptoms, unilaterality and operation. DVCE and IRCE were connected with high incidences of symptoms, bilaterality and operation. IRCE was also related to high visual analogue scale (VAS), small DCSA and high enhancement parameters. The order of the group was concordant with the degree of enhancement parameters (p = 0.000). Cutoff values of enhancement parameters for prediction were as follows: symptoms (147/123/140/121), bilaterality (165/139/157/137) and operation (164/139/159/138). Enhancement patterns and parameters could help in stratification, grading and decision-making at the surgical level.

How does preoperative opioid use impact postoperative health-related quality of life scores for patients undergoing lumbar microdiscectomy?

Background ContextNarcotic use amongst patients suffering from lumbar radiculopathy is common, but the clinical benefit of narcotics for lumbar radiculopathy is likely minimal. It is unknown what the impact of preoperative use of narcotics has on outcomes related to lumbar microdiscectomy. PurposeDetermine the impact that preoperative opioid use has on postoperative outcomes after lumbar microdisectomy. Study DesignRetrospective analysis of a prospectively collected database. Patient SampleOne hundred and twenty-six patients undergoing a microdiscectomy for a lumbar disc herniation. Outcome MeasuresPatient-reported outcomes measurement information system mental health scores (PROMIS MHS), patient-reported outcomes measurement information system physical health scores (PROMIS PHS) and oswestry disability index (ODI). MethodsWe analyzed a prospectively collected database of patients undergoing a lumbar microdiscectomy for preoperative opioid use. We measured the severity of lumbar pathology on MRI based on degree of facet/disc degeneration and cross-sectional area of the dural tube at the disc herniation. We tracked PROMIS MHS, PROMIS PHS and ODI for patients both preoperatively and postoperatively. A Mann-Whitney test was used to compare HRQOL scores and time to MCID for the opioid using cohort (OC) and the nonopioid using cohort (non-OC). We performed a linear regression analysis to determine correlation between preoperative opioid use and postoperative HRQOLs. ResultsThere were 44 of 126 microdiscectomy patients in the OC (32.5%). There was no difference in the dural cross-sectional area (p=.91), degree of facet degeneration (p=.38), or disc degeneration (p=.5) between OC and non-OC. There were no differences in PROMIS PHS, PROMIS MHS or ODI between the OC and non-OC at the preoperative visit and all postoperative time points. There were no differences in time to reach MCID between the OC and non-OC for ODI (p=.9), PROMIS PHS (p=.64) or PROMIS MHS (p=.90). At three months out from surgery there was a statistically significant correlation between pre-op opioid use and ODI (p=.02), PROMIS MHS (p=.02) and PROMIS PHS (p=.049). ConclusionsOur results demonstrate that patients that use opioids prior to lumbar microdiscectomy have equivalent postoperative outcomes as those that do not use opioids. Use of higher doses of opioids is associated with worse short-term outcomes.

The prevalence of redundant nerve roots in patients with lumbar spinal stenosis is body position dependent: a retrospective observational study with repeated measures design in an upright MRI scanner

PurposeRedundant nerve roots (RNRs) are a negative prognostic factor in patients with central lumbar spinal stenosis (LSS). Forty percent of candidates for surgical decompression show RNRs (RNR+) on preoperative conventional magnetic resonance imaging (MRI). We investigated the prevalence of RNRs in three functional postures (standing, neutral sitting and flexed sitting) with an upright MRI (upMRI).MethodsA retrospective observational study with a repeated measures design. Thirty surgical candidates underwent upMRI. Sagittal and axial T2-weighted images of the three functional postures were evaluated. The segmental length of the lumbar spine (sLLS), the lordotic angle (LA) and the dural cross-sectional area (DCSA) were measured in each body position. Generalized linear mixed models were carried out. The 0.05 level of probability was set as the criterion for statistical significance.ResultsThe prevalence of RNRs decreased from 80% during standing to 16.7% during flexed sitting (p < 0.001). The sLLS increased significantly from standing to neutral sitting in both RNR groups (p < 0.001). The increase from neutral sitting to flexed sitting was only significant (p < 0.001) for the group without RNRs (RNR−). The LA decreased significantly for both RNR groups from standing to flexed sitting (p < 0.001). The DSCA increased significantly in the RNR− group (p < 0.001) but not in the RNR+ group (p = 0.9).ConclusionThe prevalence of RNRs is body position dependent. Increases in DCSA play a determinant role in resolving RNRs.

P.132 Is a positive nerve root sedimentation sign associated with better outcomes after lumbar laminectomy?

Background: The nerve root sedimentation sign (SedSign) has been correlated with clinically significant lumbar spinal stenosis (LSS), and promoted as a possible prognostic indicator. However, diagnostic methods were not clearly defined in prior reports. In this study, the clinically validated Saskatchewan Spine Pathway enabled diagnosis of neurogenic claudication due to LSS. The objective was to compare the outcome of lumbar laminectomy for neurogenic claudication with respect to SedSign. Methods: This was a retrospective analysis of prospectively-collected data in patients with neurogenic claudication who underwent lumbar laminectomy. Outcome measures included Oswestry Disability Index, Visual Analogue Scale (VAS) for back and leg pain, and EuroQol 5-Dimension questionnaire. Results: Laminectomy was performed in 106 patients, and 60 were SedSign positive. Outcomes did not differ with respect to SedSign for all outcome measures, in non-instrumented and instrumented cohorts. Improvement in walking distance was associated with dural cross-sectional area of stenosis (p=0.02). VAS back and leg improvements were associated with back dominant (p=0.038) and leg dominant (p=0.0036) pain. Conclusions: This is the largest analysis of SedSign with respect to operative outcomes, and the only study with validated criteria for defining neurogenic claudication. Although other radiological and clinical factors are associated with improvements, SedSign did not correlate with laminectomy outcome.

Comparison of Surgeon Rating of Severity of Stenosis Using Magnetic Resonance Imaging, Dural Cross-Sectional Area, and Functional Outcome Scores

To determine the relationship between the severity of stenosis graded using both surgeons' visual assessment of spinal stenosis as well as measurement of dural cross-sectional area on magnetic resonance imaging (MRI), with the patient's disability. Seven fellowship-trained spine surgeons reviewed MRI studies retrospectively of 30 symptomatic consecutive patients with lumbar stenosis and graded stenosis in the central canal, the lateral recess, and the foramen at T12-L1 to L5-S1 as none, mild, moderate, or severe. Dural cross-sectional area was measured at each level from T12-L1 to L5-S1. All patients completed the questionnaires for Oswestry Disability Index (ODI), Short Form 36 (SF-36), and recorded Visual Analog Scale scores for leg and back pain, and symptom severity scale of the Zurich claudication questionnaire. There was positive correlation between the right leg pain Visual Analog Scale score and the mean surgeon grades for central and lateral recess stenosis at L4-L5 and lateral recess stenosis at L5-S1. Except for a positive correlation between role physical score and surgeon grade for lateral recess stenosis at L5-S1, we found no correlation between the surgeons' grading of stenosis at any level with the ODI or SF-36. We found no correlation between the dural cross-sectional area with the ODI or SF-36. We did not find any correlation between the Zurich symptom severity scale and surgeons' grading of stenosis at any level. Although surgeons rely on visual assessment of the severity of stenosis while making surgical decisions, we found that objective and subjective imaging parameters to grade severity of stenosis did not consistently indicate the patient's disability level.

Improved magnetic resonance myelography of the lumbar spine using image fusion and volumetry

The goal of this study was to investigate the usefulness and diagnostic potential of an improved MR myelography approach using a dedicated, heavily T2-weighted, 3D MRI sequence in combination with image fusion. A further aim was to compare dural areas and volumes of normal and pathological altered lumbar spine levels, and accuracy in the assessment of the stenoses, with those obtained by postmyelographic CT. Fifty patients underwent myelography, postmyelographic CT, and the improved MR myelography approach using a dedicated, heavily T2-weighted, 3D MRI sequence and image fusion. Dural cross-sectional areas and volumes for normal lumbar levels and levels with stenosis were calculated for postmyelographic CT and MR myelography data. The significant differences and Pearson correlations between dural cross-sectional areas and volumes from L1-2 to L5-S1 of postmyelographic CT and MR myelography were analyzed. The 99% CIs for normal and stenotic levels in patients with claudication distances less than 100 meters were calculated. For both dural areas and volumes in normal lumbar levels, the authors found no significant differences and strong correlations between postmyelographic CT and MR myelography. For the lower lumbar levels (L4-5 and L5-S1) they found significantly larger dural areas on MR myelography compared with postmyelographic CT, but not for the upper levels (L2-3 and L3-4). Dural volume analysis revealed significantly larger volumes for MR myelography at all 4 lumbar levels with stenoses in the cohort (L2-3 to L5-S1). Complete separation with no overlap was found between the 99% CIs for normal levels and stenotic levels. Differences in dural areas and volumes in this study may have been caused by the fact that in the case of a severely compressed thecal sac, the viscosity of the intrathecally applied contrast agent is too high in the framework of myelography. The gravitationally dependent component is thus too low to achieve sufficient fluid contrast. An optimized MR myelography approach-a dedicated 3D MR myelography sequence with high spatial resolution in combination with image fusion-is required to achieve a more reliable diagnosis of lumbar spine stenoses, especially with severe compression, compared with postmyelographic CT. This MR myelography approach may be helpful in preventing overestimation of lumbar spine stenoses. The upper limits of 99% CIs for stenotic levels can be interpreted as an indication for surgical treatment. However, further studies that include postoperative outcomes are required.

Pilot Study of the Dynamic Effects of Simulated Axial Loading Magnetic Resonance Imaging in Lumbar Disc Herniation

Study Design: A pilot study of lumbar disc herniation patients examined with magnetic resonance imaging in both psoas-relaxed position and axial compression in extension of the lumbar spine is described. Objective: To discuss the clinical value of axially loaded magnetic resonance imaging in patients with lumbar disc herniation and to evaluate the effect on the dural cross-sectional area. Summary of Background Data: Magnetic resonance imaging tests are performed in a supine relaxed position. It is well documented that a narrowing of the spinal canal is provoked by axial loading, especially when it is combined with spinal extension. Physiological or pathological changes due to loading effects might thus remain undetected by conventional imaging tests. This unloading effect could lead surgeons to a diagnosis that does not take into account these dynamic aspects. The present pilot study seeks to evaluate the effect of axial loading compression on the dural cross-sectional area in patients with lumbar disc herniation. The purpose of this study is to help surgeons in making treatment decisions or surgery indications. Methods: 15 patients underwent magnetic resonance imaging examinations in both psoas-relaxed position and axial compression in extension using a compression device (DynaWell ® ). An axial load corresponding to 50% of the body weight was applied. Changes in the dural cross-sectional area were registered. Results: A significant decrease in dural cross-sectional area was found in only 2 patients (13.3%). In 13 patients, no significant changes in dural cross-sectional area were found. Concerning the overall results, no significant differences were observed between both MRI. Conclusions: Using magnetic resonance imaging, no statistical significant decrease in dural cross-sectional area after axial loading was found. These findings do not support the recommendation of magnetic resonance imaging with axial compression in patients with sciatica secondary to lumbar disc herniation.

The increase in dural sac area is maintained at 2 years after X-stop implantation for the treatment of spinal stenosis with no significant alteration in lumbar spine range of movement

Background context The X-stop interspinous process decompression (IPD) device has been used effectively in the management of symptomatic spinal stenosis. This study examines the radiological outcomes at 2 years postoperatively after X-stop implantation. Purpose To measure the effect of X-stop IPD device on the dural sac and foraminal areas at 24 months postoperatively at instrumented level in symptomatic lumbar canal stenosis. We also aimed to assess its effect on change in lumbar spine movement. Study design Prospective observational study. Patient sample Forty-eight patients treated with X-stop had preoperative positional magnetic resonance imaging (MRI) scans, 40 of whom had 2 years postoperative positional MRI scans. Complete scans were available for 39 of these patients. Outcome measures Positional MRI scans were performed pre- and postoperatively. Measurements were done on these scans and are presented as the outcome measures. Methods All patients had a multipositional MRI scan preoperatively and at 6 and 24 months postoperatively. Foraminal area was measured in flexion and extension. Dural cross-sectional area was measured in standing erect and in sitting neutral, flexion, and extension (sitting) positions. The total range of movement (ROM) of the lumbar spine and individual segments was also measured. Results Complete scan data for 39 patients' scans were available. An increase in mean dural sac area was found in all positions. At 24 months after surgery, the mean dural sac area increased significantly in all four postures mentioned above. A small increase in mean foraminal area was noted, but this was not statistically significant. Mean anterior disc height reduced from 5.9 to 4.1 mm (p=.006) at 24 months at the instrumented level in single-level cases, from 7.7 to 6.1 mm (p=.032) in double-level cases caudally, and from 8.54 to 7.91 (p=.106) mm cranially. We hypothesize that the reduction in anterior disc heights could be a result of the natural progression of spinal stenosis with aging. There was no significant change in posterior disc heights at instrumented level or adjacent levels. The mean lumbar spine motion was 21.7° preoperatively and 23° at 24 months (p=.584) in single-level cases. This was 32.1° to 31.1° (p=.637) in double-level cases. There was no significant change in the individual segmental range of motion at instrumented and adjacent levels. Conclusion X-stop interspinous device remains effective in decompressing the stenosed spinal segment by increasing the anatomic dural cross-sectional area and foraminal area of spinal canal. It does not significantly alter the ROM of lumbar spine at instrumented and adjacent levels at 24 months postoperatively.

Unilateral Undercutting Laminoplasty in the Treatment of Lumbar Spinal Stenosis - Comparison with Conventional Bilateral Partial Laminectomy -

Study design: A retrospective study Objectives: Contralateral undercutting laminoplasty via a unilateral laminotomy has been performed instead of bilateral partial laminectomy in lumbar spinal stenosis. This study compared the radiographic and clinical results of undercutting laminoplasty with bilateral partial laminectomy. Summary of literature review: Less invasive surgery has become attractive for minimizing soft tissue injury and reducing the recovery time. Materials and Methods: Twenty five patients, who underwent decompressive surgery for lumbar spinal stenosis and were followed-up more than one year, were enrolled in this study. Unilateral undercutting laminoplasty and bilateral partial laminectomy was performed in 13 and 12 cases, respectively. The blood loss was compared and the presence of instability was observed. The increase in dural cross sectional area was measured in the preoperative and postoperative CT scans. In the clinical assessment, the Oswestry disability index (ODI) and visual analogue scale (VAS) to pain was used. Results: The average blood loss per segment was 273 ml and 436 ml in the laminoplasty and laminectomy group. There was no case of instability after surgery but there was a significant difference in the increase in dural cross sectional area between the two groups: 109.7 mm and 78.6 mm in the laminoplasty and laminectomy group, respectively. The preoperative and final change in the ODI and VAS scores was similar between the two groups. Conclusions: Unilateral undercutting laminoplasty is a minimally invasive procedure with less blood loss than the conventional technique and is equally effective.

Myelography Using Flat Panel Volumetric Computed Tomography

The technical feasibility of flat panel volumetric computed tomography (FPVCT) for lumbar myelographic imaging was evaluated in 20 patients and compared with multislice computed tomography (MSCT). The purpose of this study was to determine the feasibility and sensitivity of FPVCT for myelographic imaging in lumbar spinal stenosis. In the diagnosis of spinal stenosis, myelography and myelo-computed tomography (PCT) have been performed routinely for nearly 30 years. Rotational angiography is a new technique initially developed to visualize vessels but also allowing multiplanar reconstructed (MPR) CT images. The spatial resolution of FPCVT is even higher than in current MSCT. To date, this technique has not been evaluated for use in myelography. In 20 patients referred for CT for evaluation of low back pain, lumbar myelography was performed on a biplane angiography system equipped with flat panel detectors. FPVCT was provided from a volume data set out of a rotational acquisition and compared with MSCT performed on a 4-slice CT scanner. Hereby, for a total of 100 disc levels (range from L1-L2 to L5-S1), the narrowest dural cross-sectional diameter (D-CSD) and the dural cross-sectional area (D-CSA) referred to MSCT and FPVCT were calculated. Mean D-CSD and C-CSA for all disc levels as measured by MSCT was 9.26 +/- 3.0 mm and 63.2 +/- 10.8 mm, respectively. Compared with D-CSD and C-CSA measured by FPVCT, there was no statistically significant difference (9.48 +/- 2.9 mm and 64.7 +/- 11.2 mm, respectively; P > 0.89). The most pronounced lumbar spinal stenosis was seen on L4/5 level with D-CSD of 6.6 +/- 3.6 mm and 6.8 +/- 3.2 mm and D-CSA of 53.7 +/- 14.7 mm and 55.0 +/- 14.3 mm, respectively. In all patients, the diagnostic quality of the reconstructed FPVCT slice images is comparable to those acquired by MSCT. Using FPVCT, radiographic myelography and postmyelographic computed tomography can be performed with less radiation in a single session at the same imaging system.

Comparison of Radiologic Signs and Clinical Symptoms of Spinal Stenosis

Clinical findings of spinal stenosis were compared to graded radiologic findings of dural sac narrowing. To examine the changes of the dural sac area of the lumbar spine on computerized tomography (CT) performed without and with axial loading, and study the correlations between the radiologic findings and clinical symptoms suggestive of spinal stenosis. Although several studies have been performed regarding the advantage of an external compression device in lumbar CT, to our knowledge, none of these studies have correlated radiologic findings with clinical symptoms. The cross-sectional areas of the dural sac at the 3 lowest lumbar intravenous spaces, measured by CT both without and with external compression, were correlated to the clinical symptoms suggestive of spinal stenosis in 117 patients and 351 intervertebral levels. No statistically significant correlation between the severity of the clinical symptoms of spinal stenosis and dural cross-sectional areas was found. Neither did the use of an external compression device improve the correlation. Although an external compression simulates the dynamic condition in the back during standing position, it does not eliminate the need to compare the radiologic findings with the clinical symptoms of patients examined because of a suspected narrowing of the spinal canal.

Comparison of the Predictive Value of Myelography, Computed Tomography and MRI on the Treadmill Test in Lumbar Spinal Stenosis

To date, there have been no prospective, objective studies comparing the accuracy of the MRI, myelo-CT and myelography. The purpose of this study is to compare the diagnostic and predictive values of MRIs, myelo-CTs, and myelographies. Myelographies with dynamic motion views, myelo-CTs, MRIs and exercise treadmill tests were performed in 35 cases. The narrowest AP diameter of the dural sac was measured by myelography. At the pathologic level, dural cross-sectional area (D-CSA) was calculated in the MRI and Myelo-CT. The time to the first symptoms (TAF) and the total ambulation time (TAT) were measured during the exercise treadmill test and used as the standard in the comparison of correlation between radiographic parameters and walking capacity. The mean D-CSA by CT was 58.3 mm2 and 47.6 mm2 by MRI. All radiographic parameters such as AP diameters and D-CSA have no correlation to TAF or TAT (p>0.05). Our data showed no statistically significant differences in the correlation of the patients' walking capacity to the severity of stenosis as assessed by myelography, myelo-CT and MRI.

Axially loaded magnetic resonance image of the lumbar spine in asymptomatic individuals.

For this study, 43 asymptomatic individuals underwent magnetic resonance imaging of the lumbar spine in both supine psoas-relaxed position and supine axial compression in extension. The change in dural cross-sectional area between positions at each disc level was calculated. To evaluate the effect of axial loading on asymptomatic individuals, as compared with the effect on patients who have clinical signs of lumbar spinal canal stenosis, and to assess the effect that different magnitude and duration of the applied load have on the dural cross-sectional area. Degenerative changes in the spine are found in both symptomatic and asymptomatic individuals. A study of patients with suspected clinical lumbar spine encroachment examined in both psoas-relaxed position and axial compression in extension with computed tomographic myelography or magnetic resonance imaging of the lumbar spine is reported. A significant decrease in dural cross-sectional area was found, respectively, in 80% and 76% of the patients. The study subjects underwent magnetic resonance imaging examinations in both psoas-relaxed position and axial compression in extension. The examination of the subject under axial compression in extension was performed with the lumbar spine in a supine position using a compression device. Degenerative changes in and adjacent to the spinal canal were registered. The dural cross-sectional areas were determined for psoas-relaxed position and axial compression in extension, then compared. In seven reexamined individuals, the dural cross-sectional area was calculated after an axial load corresponding to 25% and 50% of their body weight and a loading time of 5 to 60 minutes. A significant decrease in dural cross-sectional area from psoas-relaxed position to axial compression in extension was found in 24 individuals (56%), most frequently at L4-L5, and increasingly with age. In four individuals (5 disc levels), a decrease in dural cross-sectional area to less than 100 mm2 from psoas-relaxed position to axial compression in extension was found. In seven reexamined individuals, a significant decrease in dural cross-sectional area was found: in five after 5 minutes load of 25% of their body weight, and in two with 50% of their body weight. Using magnetic resonance imaging, a significant decrease in dural cross-sectional area after axial loading was found less frequently in asymptomatic than in symptomatic subjects. The decrease was more frequent at L4-L5, and increasingly with age. The load should be 50% of the subject's body weight applied for at least 5 minutes.