• J G Peacock and V M Timpone.
• From the Department of Radiology, San Antonio Military Medical Center, San Antonio, Texas.
• AJNR Am J Neuroradiol. 2017 Feb 1; 38 (2): 391-397.

Background And PurposeCauda equina syndrome typically requires emergent MR imaging to detect compressive lesions on the cauda equina, which may require surgical decompression. While CT is sometimes performed as a complementary imaging technique to evaluate osseous integrity in patients with cauda equina syndrome, the accuracy of CT in detecting significant spinal stenosis and cauda equina impingement is not well-defined in the literature. We hypothesized that percentage thecal sac effacement on CT of the lumbar spine would have high sensitivity and high negative predictive value in evaluating significant spinal stenosis and cauda equina impingement.Materials And MethodsWe analyzed imaging studies for 151 consecutive patients with clinically suspected cauda equina syndrome. The percentage thecal sac effacement (<50%, ≥50%) was determined on CT and MR imaging. The presence or absence of cauda equina impingement was determined on MR imaging. Using MR imaging as the reference standard, we performed statistical analysis to determine the accuracy of CT in predicting significant spinal stenosis (percentage thecal sac effacement, ≥50%) and cauda equina impingement.ResultsForty of 151 patients had a percentage thecal sac effacement of ≥50% on MR imaging. Nineteen of 40 had cauda equina impingement. Readers determined that there was a CT percentage thecal sac effacement of <50% in 97/151 cases, and CT percentage thecal sac effacement of ≥50% in 54/151 cases. Reader sensitivity for the detection of significant spinal stenosis (MR percentage thecal sac effacement of ≥50%) was 0.98; specificity, 0.86; positive predictive value, 0.72; and negative predictive value, 0.99. No cases read as CT percentage thecal sac effacement of <50% were found to have cauda equina impingement.ConclusionsCT percentage thecal sac effacement of ≥50% predicts significant spinal stenosis on MR imaging in patients with clinically suspected cauda equina syndrome. CT percentage thecal sac effacement of <50% appears to reliably rule out cauda equina impingement. This imaging marker may serve as an additional tool for the clinician in deciding whether MR imaging can be deferred.© 2017 by American Journal of Neuroradiology.

22 keywords...

hide…