Filling a Critical Gap in Metastatic Spine Care: A Novel Classification System for Neoplastic Cauda Equina Compression

Cross-sectional survey and retrospective cohort study (2010-2021). We sought to: (1) Create a novel epidural cauda-equina compression (ECEC) grading system; (2) Determine its inter/intrarater reliability; and (3) Report its ability to predict preoperative neurologic status. While metastatic epidural spinal-cord compression is well characterized, ECEC remains poorly understood. Patients undergoing ECEC surgery were included. Severity was graded on axial MRI using a novel four-point scale: grade 0 = bone only; grade 1 = thecal sac indented <50% effaced; grade 2 = &#x2265;50% thecal sac effaced; grade 3 = entire thecal sac effaced, no cerebrospinal fluid seen; +F modifier signified foraminal stenosis. Primary outcomes were inter/intrarater reliability and the score's ability to predict baseline neurologic deficits. Reliability was assessed among spine surgeons, trainees, and radiation oncologists using the intraclass correlation coefficient. The survey included nine spine attendings, seven trainees, and four radiation oncologists. Among 45 patients (mean age: 61.6&#xb1;10.6&#xa0;yr; 64.4% male), 15.5% each had grade 1/2 compression, while 68.9% had grade 3; foraminal stenosis was present in 82.2%. For grades 0 to 3, overall inter/intrarater reliability was good at 0.635 (95% CI: 0.412-0.776) and 0.676 (95% CI: 0.503-0.810), with similar performance among spine attendings (inter/intrarater: 0.611; 0.662), trainees (inter/intrarater: 0.685; 0.707), and radiation oncologists (inter/intrarater: 0.634; 0.679). Sensory deficits (28.6% vs. 28.6% vs. 16.1%, P =0.627), motor deficits (71.4% vs. 57.1% vs. 35.5%, P =0.171), and bowel/bladder disturbances (0% vs. 28.6% vs. 19.4%, P =0.346) were similar across grades. +F modifier: overall inter/intrarater reliability was poor at 0.350 (95% CI: 0.180-0.505) and 0.391 (95% CI: 0.219-0.555), with fair reliability for spine attendings (inter/intrarater: 0.421; 0.485), and trainees (inter/intrarater: 0.414; 0.443), and poor for radiation oncologists (inter/intrarater: 0.259; 0.299). Baseline neurological status showed no association with foraminal stenosis. The novel ECEC grading system provides a reliable framework for characterizing metastatic ECEC, demonstrating good reliability for grades 0 to 3 across spine surgeons, trainees, and radiation oncologists. Although compression grade was not associated with neurologic deficits, bowel/bladder deficit rates were nonsignificantly higher in grades 2/3. Conversely, the poor reliability of the foraminal modifier underscores the limitations of static MRI in assessing foraminal stenosis. Overall, the ECEC scale may enhance communication in describing neoplastic ECEC.