The Sedimentation Sign for Differential Diagnosis of Lumbar Spinal Stenosis

Study Design. Cross-sectional cohort study. Objective. To evaluate the diagnostic value of the sedimentation sign further by assessing its performance on the differential diagnosis of patients with lumbar spinal stenosis (LSS) and other lumbar conditions with similar clinical presentations. Summary of Background Data. Recently, a new test using MR imaging, the sedimentation sign, was introduced to aid in the diagnosis of LSS. The initial testing demonstrated that the sign was positive in 100% of patients with LSS with decreased walking ability and dural sac cross-sectional areas (CSA) less than 80 mm(2), and negative in 94% of patients with nonspecific low back pain, no leg pain or claudication and dural sac CSA greater than 120 mm(2). Methods. Fifty patients with central or combined LSS, 22 with lateral stenosis only and 43 with posterolateral disc herniation with unilateral radiculopathy were included. Using axial MR images of the lumbar spine, the sedimentation sign was assessed by 2 observers independently, without knowledge of participant clinical history or diagnosis. Frequencies of a positive sign in each patient group were calculated. Results. The sedimentation sign was positive in 2% of patients with disc herniation, 23% with lateral stenosis, and 54% with central or combined stenosis. When the analysis included only patients with LSS with dural sac CSA less than 80 mm(2) and walking limitations similar to the original study introducing the sedimentation sign (n = 17), the proportion of patients presenting with a positive sign increased to 82%. Conclusion. The sedimentation sign is more prevalent in patients with the clinical diagnosis of central or combined LSS than in patients with lateral stenosis only or posterolateral disc herniation. Yet, whether it enhances current diagnostic practices remains undetermined.