The clinical significance of redundant nerve roots of the cauda equina in lumbar spinal stenosis patients: A systematic literature review and meta-analysis

Abstract

Objectives: Decompression surgery for lumbar spinal stenosis (LSS) is the most performed spine surgery procedure in patients older than 65 years. Around 40% of LSS patients scheduled for decompression surgery have evidence of redundant nerve roots (RNR) of the cauda equina on their magnetic resonance images (MRI). Little is known about the clinical significance of RNR in LSS patients. The objective was to assess the effects of RNR on clinical scores and recovery in older adults diagnosed with LSS.

Patients and methods: A systematic literature search was performed in April 2018 on PubMed, Web of Science, MEDLINE and Cumulative Index to Nursing and Allied Health Literature (CINAHL). Prospective and retrospective cohort studies undertaken to assess differences in clinical outcomes in patients diagnosed with LSS with versus without evidence of RNR on their MRIs were selected. Two authors independently selected studies, abstracted data and assessed risk of bias. We calculated weighted mean differences (WMD) for continuous variables and odds ratio (OR) for variables reported in frequencies.

Results: Seven studies comprising a total of 1046 LSS patients were included in the meta-analysis. LSS patients with evidence of RNR (RNR+) were older, WMD 5.7 95% CI [2.2-9.2], p = 0.001, had smaller cross sectional area (CSA) of the stenotic level, WMD -12.2 95% CI [-17.7 to -6.7], p < 0.0001 and longer symptom onset duration, WMD 13.2 95% CI [-0.2-26.7], p = 0.05. The pooled preoperative clinical score in the RNR + group was worse but the difference was not statistically significant, WMD -3.8 95% CI [-7.9 to 0.2], p = 0.07. After decompression surgery RNR + patients had worse clinical scores, -4.7 95% CI [-7.3 to -2.1], p = 0.0004 and lower recovery rates, -9.8 95% CI [-14.8 to -4.7], p = 0.0001.

Conclusion: There is limited quality evidence that RNR + patients are older, have a longer symptom history and present higher degrees of lumbar stenosis as given by the narrow CSA in comparison to RNR- patients. After decompression surgery RNR + patients have worse clinical scores and lower recovery rates. In view of these results RNR can be seen as a negative prognostic factor in LSS patients.

Keywords: Clinical outcomes; Lumbar spinal stenosis; Meta-analysis; Redundant nerve roots.