Redundant nerve roots in lumbar spinal stenosis: inter- and intra-rater reliability of an MRI-based classification

Relationship between lumbar spinal stenosis and cauda equina movement during the Valsalva maneuver

OBJECTIVE

To confirm the relationship between lumbar spinal stenosis (LSS) and cauda equina movement during the Valsalva maneuver.

MATERIALS AND METHODS

Two radiologists at our institution independently evaluated cauda equina movement on pelvic cine MRI, which was performed for urethrorrhea after prostatectomy or pelvic prolapse in 105 patients (99 males; mean age: 69.0 [range: 50-78] years), who also underwent abdominopelvic CT within 2 years before or after the MRI. The qualitative assessment of the cine MRI involved subjective determination of the cauda equina movement type (non-movement, flutter, and inchworm-manner). The severity of LSS on abdominopelvic CT was quantified using our LSS scoring system and performed between L1/2 and L5/S1. We calculated the average LSS scores of two analysts and extracted the worst scores among all levels.

RESULTS

Cauda equina movement was observed in 15 patients (14%), inchworm-manner in 10 patients, and flutter in five patients. Participants with cauda equina movement demonstrated significantly higher LSS scores than those without movement (P < 0.001, Wilcoxon's rank-sum test). A significant difference was observed in the worst LSS scores between participants without movement and those with inchworm-manner movement (P < 0.001, Bonferroni's corrected). There were no significant differences between participants without movement and those with flutter movement (P = 0.3156) and between participants with flutter movement and those with inchworm-manner movement (P = 0.4843).

CONCLUSION

Cauda equina movement in cine MRI during the Valsalva maneuver is occasionally observed in patients with severe LSS, and may be associated with pathogenesis of redundant nerve roots.

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

PURPOSE

This 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).

METHODS

Sixty-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.

RESULTS

Controls (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.

CONCLUSION

The 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.

Cauda equina movement during the Valsalva maneuver in two patients with Lumbar spinal canal stenosis

Lumbar spinal canal stenosis (LSS) is a common spinal disorder among older people. Some LSS patients say that their pain worsens when they lift heavy objects. The Valsalva maneuver is the optimal breathing pattern for producing maximal force. Herein, we present two cases of LSS where the movement of the cauda equina was observed during the Valsalva maneuver.

Clinical Significance of Redundant Nerve Roots in Patients with Lumbar Stenosis Undergoing Minimally Invasive Tubular Decompression

OBJECTIVE

Symptomatic lumbar spinal stenosis (LSS) is a common indication for surgery in the elderly. Preoperative radiographic evaluation of patients with LSS often reveals redundant nerve roots (RNRs). The clinical significance of RNRs is uncertain. RNRs have not been studied in the setting of minimally invasive surgery. This study investigates the relationship between RNRs and clinical outcomes after minimally invasive tubular decompression.

METHODS

Chart review was performed for patients with degenerative LSS who underwent minimally invasive decompression. Preoperative magnetic resonance imaging parameters were assessed, and patient-reported outcomes were analyzed.

RESULTS

Fifty-four patients underwent surgery performed at an average of 1.8 ± 0.8 spinal levels. Thirty-one patients (57%) had RNRs. Patients with RNRs were older (median = 72 years vs. 66 years, P = 0.050), had longer median symptom duration (32 months vs. 15 months, P < 0.01), and had more levels operated on (2.1 vs. 1.4; P < 0.01). The median follow-up after surgery was 2 months (range = 1.3-12 months). Preoperative and postoperative patient-reported outcomes were similar based on RNR presence. Patients without RNRs had larger lumbar cross-sectional areas (CSAs) (median = 121 mm² vs. 95 mm², P = 0.014) and the index-level CSA (52 mm² vs. 34 mm², P = 0.007). The CSA was not correlated with RNR morphology or location.

CONCLUSIONS

Preoperative RNRs are associated with increased age, symptom duration, and lumbar stenosis severity. Patients improved after minimally invasive decompression regardless of RNR presence. RNR presence had no effect on short-term clinical outcomes. Further study is required to assess their long-term significance.

Redundant Nerve Roots of the Cauda Equina, MRI Findings and Postoperative Clinical Outcome: Emphasizing an Overlooked Entity

STUDY DESIGN

Retrospective study.

OBJECTIVE

To describe the MRI findings of RNRs in patients with low back pain, and observe the imaging findings and the clinical outcome post decompression surgery.

METHODS

The lumbar spine MRI of 202 patients (122 females) with proven RNRs were retrospectively reviewed. The morphology and the location of the RNRs in relation to the level of stenosis were described. The level(s), grade and cause of lumbar canal stenosis were recorded. The persistence of symptoms and the imaging findings on follow up post decompression surgery were recorded. The imaging findings were correlated among each other and with patients' demographics.

RESULTS

Two distinctive morphological appearance of the RNRs were noted: loop (56.4%), and serpentine-shaped. In the majority of the cases the RNRs were located above the level of stenosis (79.7%). Eighteen patients underwent decompression surgery, only 4 patients remained symptomatic post decompression surgery. The RNRs changed in shape and location after decompression surgery. Age was a strong predictor value in the location of the RNRs. There was no correlation between the shape and location of the RNRs, or with the gender of the patients.

CONCLUSION

RNRs is not an uncommon finding on lumbar spine MRI with lumbar canal stenosis. Its importance remains a controversy. A common language between the radiologists and the clinicians is mandatory to aid in the management planning.

Reliability of preoperative MRI findings in patients with lumbar spinal stenosis

Background

Magnetic Resonance Imaging (MRI) is an important tool in preoperative evaluation of patients with lumbar spinal stenosis (LSS). Reported reliability of various MRI findings in LSS varies from fair to excellent. There are inconsistencies in the evaluated parameters and the methodology of the studies. The purpose of this study was to evaluate the reliability of the preoperative MRI findings in patients with LSS between musculoskeletal radiologists and orthopaedic spine surgeons, using established evaluation methods and imaging data from a prospective trial.

Methods

Consecutive lumbar MRI examinations of candidates for surgical treatment of LSS from the Norwegian Spinal Stenosis and Degenerative Spondylolisthesis (NORDSTEN) study were independently evaluated by two musculoskeletal radiologists and two orthopaedic spine surgeons. The observers had a range of experience between six and 13 years and rated five categorical parameters (foraminal and central canal stenosis, facet joint osteoarthritis, redundant nerve roots and intraspinal synovial cysts) and one continuous parameter (dural sac cross-sectional area). All parameters were re-rated after 6 weeks by all the observers. Inter- and intraobserver agreement was assessed by Gwet’s agreement coefficient (AC1) for categorical parameters and Intraclass Correlation Coefficient (ICC) for the dural sac cross-sectional area.

Results

MRI examinations of 102 patients (mean age 66 ± 8 years, 53 men) were evaluated. The overall interobserver agreement was substantial or almost perfect for all categorical parameters (AC1 range 0.67 to 0.98), except for facet joint osteoarthritis, where the agreement was moderate (AC1 0.39). For the dural sac cross-sectional area, the overall interobserver agreement was good or excellent (ICC range 0.86 to 0.96). The intraobserver agreement was substantial or almost perfect/ excellent for all parameters (AC1 range 0.63 to 1.0 and ICC range 0.93 to 1.0).

Conclusions

There is high inter- and intraobserver agreement between radiologists and spine surgeons for preoperative MRI findings of LSS. However, the interobserver agreement is not optimal for evaluation of facet joint osteoarthritis.

Trial registration

www.ClinicalTrials.gov identifier: NCT02007083, registered December 2013.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04949-4.

Introduction and reproducibility of an updated practical grading system for lumbar foraminal stenosis based on high-resolution MR imaging

In this paper we sought to develop and assess the reproducibility of an updated 6-point grading system for lumbar foraminal stenosis based on the widely used Lee classification that more accurately describes lumbar foraminal stenosis as seen on high-resolution MRI. Grade A indicates absence of foraminal stenosis. Grades B, C, D and E indicate presence of foraminal stenosis with contact of the nerve root with surrounding anatomical structures (on one, two, three or four sides for B, C, D and E respectively) yet without morphological change of the nerve root. To each grade, a number code indicating the location of contact between the nerve root and surrounding anatomical structure(s) is appended. 1, 2, 3 and 4 indicate contact of the nerve root at superior, posterior, inferior and anterior position of the borders of the lumbar foramen. Grade F indicates presence of foraminal stenosis with morphological change of the nerve root. Three readers graded the lumbar foramina of 101 consecutive patients using high-resolution T2w (and T1w) MR images with a spatial resolution of beyond 0.5 mm³. Interreader agreement was excellent (Cohen’s Kappa = 0.866–1). Importantly, 30.6%/31.6%/32.2% (reader 1/reader 2/ reader 3) of foramina were assigned grades that did not appear in the original Lee grading system (grades B and D). The readers found no foramen that could not be described accurately with the updated grading system. Thus, an updated 6-point grading system for lumbar foraminal stenosis is reproducible and comprehensively describes lumbar foraminal stenosis as seen on high-resolution MRI.

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

Purpose

Redundant 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).

Methods

A 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.

Results

The 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).

Conclusion

The prevalence of RNRs is body position dependent. Increases in DCSA play a determinant role in resolving RNRs.