Redundant Nerve Roots Of The Cauda Equina In Lumbar Spinal Canal Stenosis, An MR Study On 222 Cases

ObjectiveThe purpose of this study was to evaluate magnetic resonance (MR)-detected redundant nerve roots (RNRs) of the cauda equina in patients with lumbar spinal canal stenosis.MethodsA retrospective study was conducted of 222 lumbar spinal canal stenosis patients between January 2014 and March 2016. Patients were divided into two groups with and without RNRs. The dural sac cross-sectional area (CSA) and anteroposterior diameter were measured on T2w axial MRI. The inclusion criterion for the lumbar spinal canal stenosis was a dural sac CSA 100 mm2 or anteroposterior diameter 10mm in at least one measured level. The cross-sectional area (CSA) of the dural sac, the intra canal protuberances in the site of stenosis and the length of the RNRs relative to the height of the upper vertebral body of the level of the stenosis were measured.ResultsRNRs were detected in 26.1% of the patients. The mean age of the patients with RNRs was 67.3±9.8 years, and the patients without RNRs was 57.1±12.4 years(p<0.05). The patients with RNRs, the spinal canal stenosis was significantly more frequent at L2-4(p<0.05). The maximum stenosis of the patients with RNRs was 45.2±16.3 mm2, and without RNRs was 60.3±21.5(p<0.05). The presence of an intracanal protuberance with sharp margin in the site of the stenosis(OR=6.1) and the presence of the multilevel lumbar spinal stenosis (OR=1.9) were independent risk factors for the development of RNRs. The mean relative length of the RNRs was significantly higher in patients with multilevel lumbar spinal stenosis than those with single level lumbar spinal stenosis(p<0.05).ConclusionsWith an occurrence rate of 26.1%, RNRs of the cauda equina are not uncommon in cases with lumbar spinal canal stenosis. Advanced age, the degree of the maximum lumbar spinal canal stenosis, a canal stenosis at L2-4, the presence of a sharp intracanal protuberance in the site of the stenosis, and the presence of the multilevel lumbar spinal stenosis are the related risk factors.