Doing More with Less: Diagnostic Accuracy of CT in Suspected Cauda Equina Syndrome.

CT 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.