Patient demographics and MRI-based measurements predict redundant nerve roots in lumbar spinal stenosis: a retrospective database cohort comparison

Abstract

BackgroundUp to 40% of patients diagnosed with lumbar spinal stenosis (LSS) show evidence of redundant nerve roots (RNR) of the cauda equina on their magnetic resonance images (MRI). The etiology of RNR is still unclear. Preoperative evidence of RNR is associated with a worse postsurgical outcome. Consequently, potential predictors of RNR could have a prognostic value. The aim was to test whether patient demographics and MRI-based measurements can predict RNR in LSS patients.MethodsIn a retrospective database-based cohort study the preoperative data of 300 patients, 150 with (RNR+) and 150 without (RNR-) evidence of RNR on their MRI were analyzed. Three independent researchers performed the MRI reads. Potential predictors were age, gender, body height (BH), length of lumbar spine (LLS), segmental length of lumbar spine (SLLS), lumbar spine alignment deviation (LSAD), relative LLS (rLLS), relative SLLS (rSLLS), number of stenotic levels (LSS-level), and grade of LSS severity (LLS-grade, increasing from A to D). Binomial logistic regression models were performed.ResultsRNR+ patients were 2.6 years older (p = 0.01). Weak RNR+ predictors were a two-years age increase (OR 1.06; p = 0.02), 3 cm BH decrease (OR 1.09; p = 0.01) and a 5 mm SLLS decrease (OR 1.34; p < 0.001). Strong RNR+ predictors were a 1% rLLS decrease (OR 2.17; p < 0.001), LSS-level ≥ 2 (OR 2.59; p = 0.001), LLS-grade C (OR 5.86; p = 0.02) and LLS-grade D (OR 18.4; p < 0.001). The mean rSLLS of RNR+ patients was 0.6% shorter (p < 0.001; 95% C.I. 0.4 to 0.8) indicating a disproportionate shorter lumbar spine.ConclusionsWe identified LSS severity grade and LSS levels as the strongest predictors of RNR. In addition to previous studies, we conclude that a shortened lumbar spine by degeneration is involved in the development of RNR.

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

“…In patients with multilevel canal stenosis, the redundancy was noted to be above the most cranial stenotic level, this might be explained by the fact that the nerve roots are fixed between 2 points: the conus medullaris and intraforaminal ganglia and by the stensois caudally causing them to move within a tight container and thus causing them to become redundant. In our study, there was no significant statistical correlation between the multiplicity and degree of stenosis and the occurrence of RNRs opposed to the study conducted by Papavero et al 19 In our study, the presence of degenerative changes was attributed as being the cause of LCS; these changes were observed to be mainly DDB with LFH in 94% of our patients while 41.1% of them suffered from an additional change, FJH, and 6.4% had associated spondylolisthesis. Our findings support the proposition of Hur et al that suggests that LFH rather than isolated intervertebral disc bulges is the major contributing factor to spinal canal stenosis that causes mechanical stress on the nerve roots, eventually leading to their redundancy.…”

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

“…Moreover, after decompression surgery, patients with RNRs showed worse clinical scores and lower recovery rates than those without RNRs [9]. A study on potential RNR predictors demonstrated that patients with LSS with evidence of RNRs on the preoperative MRI were older had a shorter lumbar spine canal, displayed stenosis at more levels, and had more severe stenosis, compared to patients without RNRs [10]. Yokoyama et al studied patients with LSS and found that most RNRs resolved postoperatively, but some did not.…”

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

“…The prevalence of RNRs dropped from 80% during standing to 16.7% during flexed sitting. The role of DCSA as the strongest predictor of RNRs [12] was confirmed.…”

“…In a study on potential predictors of RNRs in patients with LSS, several factors were identified as significant predictors [12]. The strongest predictors were LSS grade D and C according to Schizas [13], the number of stenotic levels involved and a decrease in the relative length of the lumbar spine.…”