Redundant nerve roots of the cauda equina in lumbar spinal canal stenosis, an MR study on 500 cases

Abstract

The 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. A total of 500 lumbar MR studies in patients with lumbar spinal canal stenosis were reviewed for the presence and characteristics of RNRs of the cauda equina. The length of the RNRs relative to the height of the upper vertebral body of the level of the stenosis was used as a prognostic indicator. RNRs were detected in 15 % of the patients, the majority above the level of the stenosis (85 %) and loop shaped (72 %). Advanced age (i.e., a parts per thousand yen56 years old, odds ratio = 1), a lumbar spinal canal stenosis at L2-4 (odds ratio = 2.5), and the presence of an intracanal protuberance with sharp margin in the site of the stenosis (odds ratio = 7.2) were independent risk factors for the development of RNRs. A direct, significant correlation was found between the relative length of the RNRs and patients' age (Pearson r = 0.36, p = 0.001). The mean relative length of the RNRs was significantly higher in patients with RNRs located above the level of the stenosis than those with RNRs located below the site of the block. The degree of stenosis was associated with neither the presence nor the relative length of the RNRs. With an occurrence rate of 15 %, RNRs of the cauda equina are not uncommon in cases with lumbar spinal canal stenosis. Advanced age, a canal stenosis at L2-4, and the presence of a sharp intracanal protuberance in the site of the stenosis are the related risk factors. Patients' age and the location of RNRs may be of prognostic value.