MRI MEASUREMENTS IN CAUDA EQUINA SYNDROME: REPRODUCIBILITY AND PREDICTION OF CLINICAL OUTCOME

Abstract

Introduction: Current evidence suggests CES should be operated < 48 hours from onset. MRI scanning is often not available 24 hours a day.

Objectives: (1) Determine whether MRI findings correlate with clinical outcome. (2) Study the reproducibility of MRI measurements of large disc prolapses. (3) Estimate the ability to predict CES based on MRI alone.

Study Design: 31 CES patients were identified,contactedand invited to follow up. Clinical outcome consisted of history and examination, and validated questionnaire assessments. 19 patients who underwent discectomy were identified. T2 mid-sagittal and axial digital photographs of all 50 MRIs were obtained. Observers did not know the number of patients in each group (1 Consultant Radiologist, 2 Consultant Spinal Surgeons and 1 SHO). They estimated the percentage spinal canal compromise on each view (0–100%) and indicated whether they thought the scan findings could produce CES. Measurements were repeated after 2 weeks.

Results: 26 patients attended clinic (mean follow up 51 months). There were no significant correlations found between MRI canal compromise and clinical outcome. Kappa values for the measurements ranged 0.52–0.85 and 0.61–0.75 for intra- and inter-observer reproducibility. Based on MRI alone correct identification of CES has sensitivity 67%, specificity 81%, positive predictive value 85% and negative predictive value 60%.

Conclusions: Canal compromise on MRI does not predict the outcome of patients with CES. Reproducibility of MRI measurements of large disc protrusions has substantial agreement. MRI could be of help in equivocal cases if the scan shows a large disc.