Article
Redundant nerve roots in lumbar spinal stenosis – inter and intra-rater reliability of an MRI-based classification
Redundant nerve roots in der lumbalen Spinalkanalstenose – Validierung der Inter- und Intraobserver-Reliabilität einer MRT-basierten Klassifikation
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Published: | June 26, 2020 |
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Objective: Patients with central lumbar spinal stenosis (LSS) have a longer symptom history, more severe stenosis, and worse postoperative outcomes if redundant nerve roots (RNRs) are evident in the preoperative MRI. An RNR classification in the MRI report could provide clinicians with clinically relevant information. This is a retrospective validation study to test the inter- and intra-rater reliability of an MRI-based classification for RNR.
Methods: This retrospective reliability study retrieved data from a central database. A neuroradiologist, an orthopedic surgeon, and a neurosurgeon (senior raters) and three orthopeadic surgeons in training (junior raters) classified RNRs on 126 preoperative MRIs of patients with LSS admitted for microsurgical decompression. On sagittal and axial T2-weighted images, the following four categories were defined: Allocation (A) of the key stenotic level (KSL); Shape (S) of RNR (serpentines or loops); Extension (E) of RNR (less or more than one vertebral height); and Direction (D) of the RNR in reference to A (cranial, caudal, or cranio-caudal). A second read with cases ordered differently was performed four weeks later. Fleiss and Cohen’s kappa procedures were used to determine reliability.
Results: The ASED classification showed moderate to almost perfect inter-rater reliability, with kappa values of k= 0.86 (0.83, 0.90), k= 0.62 (0.57, 0.66), k= 0.56 (0.51, 0.60), and k= 0.66 (0.63, 0.70) for Allocation, Shape, Extension, and Direction, respectively. Intra-rater reliability was almost perfect, with k= 0.90 (0.88, 0.92), k= 0.86 (0.84, 0.88), and k= 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).
Conclusion: The MRI-based classification of RNRs showed moderate to almost perfect inter-rater and almost perfect intra-rater reliability. The classification is easy to learn and easy to document in the MRI report.
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