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

Abstract

Purpose Patients with central lumbar spinal stenosis (LSS) have a longer symptom history, more severe stenosis, and worse postoperative outcomes, when redundant nerve roots (RNRs) are evident in the preoperative MRI. The objective was to test the inter-and intra-rater reliability of an MRI-based classification for RNR. Methods This is a retrospective reliability study. A neuroradiologist, an orthopedic surgeon, a neurosurgeon, and three orthopedic surgeons in-training classified RNR on 126 preoperative MRIs of patients with LSS admitted for microsurgical decompression. On sagittal and axial T2-weighted images, the following four categories were classified: allocation (A) of the key stenotic level, shape (S), extension (E), and direction (D) of the RNR. A second read with cases ordered differently was performed 4 weeks later. Fleiss and Cohen's kappa procedures were used to determine reliability. Results The allocation, shape, extension, and direction (ASED) classification showed moderate to almost perfect inter-rater reliability, with kappa values (95% CI) of 0.86 (0.83, 0.90), 0.62 (0.57, 0.66), 0.56 (0.51, 0.60), and 0.66 (0.63, 0.70) for allocation, shape, extension, and direction, respectively. Intra-rater reliability was almost perfect, with kappa values of 0.90 (0.88, 0.92), 0.86 (0.84, 0.88), and 0.84 (0.81, 0.87) for shape, extension, and direction, respectively. Intra-rater kappa values were similar for junior and senior raters. Kappa values for inter-rater reliability were similar between the first and second reads (p = 0.06) among junior raters and improved among senior raters (p = 0.008). Conclusions The MRI-based classification of RNR showed moderate-to-almost perfect inter-rater and almost perfect intra-rater reliability.

Reliability of preoperative MRI findings in patients with lumbar spinal stenosis

“…When mimicking symptoms of LSS by causing radiculopathy, intraspinal synovial cysts are treated surgically [ 7 ] and a preoperative MRI is necessary to evaluate the status of the adjacent facet joint and the nerve root. Our reliability estimates for presence of RNR were similar to those reported by Papavero et al [ 32 ] for their four-part classification of cauda equina redundancy. This finding is believed to associate with the level(s) of central canal stenosis [ 33 ].…”

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

“…We emphasize the importance of establishing a classification system for RNRs to facilitate communication between the radiologists and clinicians such as the ASED classification system proposed by Papavero et al describing the allocation, shape, extension, and direction of the RNRs. 27 The limitations of our study are the small number of patients who underwent decompression surgery and whose images were available for evaluation. Additionally, it was a retrospective study, and the pain scores of the patients evaluated before and after decompression surgery were not clinically recorded by the authors.…”

“…We emphasize the importance of establishing a classification system for RNRs to facilitate communication between the radiologists and clinicians such as the ASED classification system proposed by Papavero et al describing the allocation, shape, extension, and direction of the RNRs. 27…”

Introduction and reproducibility of an updated practical grading system for lumbar foraminal stenosis based on high-resolution MR imaging

“…Interreader agreement was quantified with Kappa statistics 3 , 9 . A kappa value of less than 0.20 was considered slight; 0.21–0.40, fair; 0.41–0.60, moderate; 0.61–0.80, substantial; and 0.81 or greater, nearly perfect agreement 3 , 10 .…”