What Degree of Radiological Compression Predicts Cauda Equina Syndrome: A Retrospective Study at a National Tertiary Centre.

OBJECTIVE Cauda Equina Syndrome (CES) is diagnosed both clinically and radiologically. However, it's unclear if a specific degree of cauda equina compression (CEC) on imaging can confirm the diagnosis. This study aimed to identify an optimal percentage of prolapse to canal ratio (PCR) on MRI that correlates with CEC, facilitating reliable decision-making for CES symptoms. METHODS A single-center retrospective case series analysis was conducted from 2020 to 2021. Sixty-one patients who underwent emergency lumbar discectomy within 48 hours of presentation were included, divided into a CES group and a disc prolapse (DP) group. CES cases were identified using ICD-10 code G83.4. PCR was calculated by dividing the width of the disc herniation by the total width of the spinal canal at the level of the herniation on single mid-sagittal T2 MRI scans, using the IC Measure software on Windows. RESULTS CES most frequently occurred at the L4/5 level (37/61). The median PCR in CES cases was 76.19% (66.67 - 85.71), significantly higher than in DP cases, 48.08% (31.33 - 55.56) (p<0.001). A PCR threshold of 40% maximized sensitivity at 100% but had a specificity of 45%. Conversely, a threshold of 75% maximized specificity at 100% with a sensitivity of 50%. The optimal PCR, determined by the Youden index, was 66%, yielding a sensitivity of 75% and specificity of 97%, with an area under the curve (AUC) of 0.923. CONCLUSIONS Simple radiological measurements of PCR can potentially triage CES patients and guide their management. Future studies should correlate PCR with clinical signs and symptoms for a comprehensive assessment.