Magnetic resonance imaging findings of redundant nerve roots of the cauda equina

Redundant nerve roots on magnetic resonance imaging can predict ongoing denervation in patients with lumbar spinal stenosis

INTRODUCTION/AIMS

Redundant nerve roots (RNRs) are abnormally elongated and tortuous nerve roots that develop secondary to degenerative spinal stenosis. RNRs have been associated with poorer clinical outcomes after decompression surgery; however, studies on their clinical characteristics are limited. This study aimed to investigate the association between RNRs and denervation potentials, that is, abnormal spontaneous activity (ASA), on electromyography.

METHODS

We retrospectively reviewed data of patients who underwent an electrodiagnostic study of the lower extremities between January 2020 and March 2023. Of these, patients with lumbar central spinal stenosis, as seen on magnetic resonance imaging, were included. We analyzed clinical and imaging data, including presence of ASA, and compared them according to the presence of RNRs. Multivariable logistic regression analysis was employed to identify factors associated with development of ASA.

RESULTS

Among the 2003 patients screened, 193 were included in the study. RNRs were associated with advanced age (p < .001), longer symptom duration (p = .009), smaller cross-sectional area of the dural sac at the stenotic level (p < .001), and higher frequency of ASA (p < .001). Higher probability of ASA was correlated with greater RNR severity (p < .001). In the multivariable logistic regression analysis, ASA occurrence was associated with smaller cross-sectional area, multiple stenotic sites, and severe-grade RNRs.

DISCUSSION

The presence of RNRs, particularly severe-grade RNRs, was identified as a significant risk factor for the development of ASA on electromyography. This finding may aid physicians in estimating the prognosis of patients with central spinal stenosis.

MRI parameters predict central lumbar spinal stenosis combined with redundant nerve roots: a prospective MRI study

Background

To observe changes in the cauda equina nerve on lumbar MRI in patients with central lumbar spinal stenosis (LSS).

Methods

878 patients diagnosed with LSS by clinical and MRI were divided into the redundant group (204 patients) and the nonredundant group (674 patients) according to the presence or absence of redundant nerve roots (RNRs). The anteroposterior diameter of the spinal canal (APDS) and the presence of multiple level stenosis, disc herniation, thickening of ligamentum flavum (LF) and increased epidural fat were assessed on MRI. Univariate and multivariate logistic regression analyses were performed to explore the predictors of LSS combined with RNRs.

Results

Patients with LSS combined with RNRs had thicker epidural fat, smaller APDS and more combined multifaceted stenosis. Female patients and older LSS patients were more likely to develop RNRs; there was no difference between two groups in terms of disc herniation (p > 0. 05). Age, APDS, multiple level stenosis, and increased epidural fat were significantly correlated with the formation of LSS combined with RNRs (p < 0.05).

Conclusion

A smaller APDS and the presence of multiple level stenosis, thickening of LF, and increased epidural fat may be manifestations of anatomical differences in patients with LSS combined with RNRs. Age, APDS, multiple level stenosis, and increased epidural fat play important roles. The lumbar spine was measured and its anatomy was observed using multiple methods, and cauda equina changes were assessed to identify the best anatomical predictors and provide new therapeutic strategies for the management of LSS combined with RNRs.

Redundant nerve roots indicate higher degree of stenosis in lumbar spine stenotic patients

OBJECTIVES

Redundant Nerve Root (RNR) is a tortuous and elongated radiological appearance of cauda equina on Magnetic Resonance Imaging (MRI) in Lumbar Spinal Canal Stenosis (LSCS) patients. This study evaluated preoperative spinal morphometry associated with the development of RNR.

METHODS

The retrospective cohort was conducted at The Aga Khan University Hospital, and included patients undergoing decompressive spinal surgery secondary to degenerative LSCS in 2015. The patients were divided into two groups with respect to the presence of preoperative RNR. Spinal morphometry was defined by several radiological parameters, including areas of dural sac (DSA), spinal canal, spinal foramen, facets, and spinal joints, and bilateral angles based on vertebral anatomy.

RESULTS

A total of 55 patients were enrolled with a mean age of 57.1 years, in which 22 (40%) expressed RNR in their MRI. The RNR group had significantly lower mean DSA (59.64 vs 84.01 mm2; p = 0.028), bilateral posterior facet angle (Right: 33.84 vs 46.21, p = 0.004; Left: 36.43 vs 43.80, p = 0.039) and higher bilateral anterior facet angles (Right: 54.85 vs 44.57, p = 0.026; Left: 55.27 vs 46.36, p = 0.050) compared to the non-RNR group. The other bidimensional and angular parameters did not observe any statistical difference between the two groups.

CONCLUSION

RNR was associated with a higher degree of stenosis in patients with LSCS. Bilateral anterior and posterior facets angles contribute to its development, indicating particular spinal morphology to be vulnerable to the stenotic disease.

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.

Clinical Features and Efficacy Analysis of Redundant Nerve Roots

Introduction: Redundant nerve roots (RNRs) are common finding in lumbar spinal stenosis patients. Up to now, many relevant studies were carried out on the mechanism, pathogenic factors, and clinical features of redundant nerve roots. However, there are few studies on the surgical methods. In this study, posterior lumbar interbody fusion and internal fixations were used in 30 patients with RNRs in our hospital. Moreover, we also proposed new ideas about different types and subtypes of RNRs using patterns and their corresponding MRI images. Methods: Thirty patients with lumbar spinal stenosis and RNRs were enrolled in this study and underwent surgery between January 2009 and December 2014. Redundant nerve roots are identified as elongated, tortuous, or serpiginous nerve roots present in the subarachnoid space on sagittal T2-weighted magnetic resonance imaging (MRI) studies. Patients were treated with posterior decompression, intervertebral disc resection, and instrumented interbody fusion. The age, sex, disease course, operative time, intraoperative blood loss, operative segments were recorded. Outcome measures recorded to identify symptom improvement included pre-operative and post-operative visual analog scale (VAS), pre-operative and post-operative Oswestry Disability Index (ODI) and pre-operative and post-operative Japanese Orthopedic Association (JOA) scores. Results: VAS back pain, VAS leg pain VAS, ODI, and JOA with standard deviations were 6.4 ± 0.9, 7.1 ± 0.8, 43.0 ± 2.2, and 10.3 ± 2.6, respectively. At 3 months post-operatively, VAS back pain, VAS leg pain VAS, ODI, and JOA with standard deviations were 1.4 ± 0.5, 1.6 ± 0.6, 13.0 ± 1.6, and 25.0 ± 1.8, respectively. Nerve redundancy resolved in all cases on post-operative MRI. Conclusion: Posterior lumbar laminectomy and instrumented interbody fusion relieves low back and leg pain in patients with lumbar spinal stenosis and RNRs and can alleviate the tortuous appearance of the cauda equina in the decompressed segment.