Purpose: Sedimentation sign was reported to have high sensitivity and specificity for diagnosis of lumbar spinal stenosis (LSS). We aimed to determine cerebrospinal fluid signal loss (CSFSL) at the intervertebral disc levels in the sagittal plane using a numerical scoring system and to evaluate the diagnostic value of this method in differential diagnosis of LSS and non-specific low back pain (LBP) and compare it with SS.Materials and Methods: We included consecutive patients between 50 and 80 years old, with lumbar spinal MRI examination in our institution. These patients were divided into two groups as LSS and LBP, according to symptoms and radiological findings. CSFSL sign was evaluated for both groups by two radiologists independently, using MR images. Sensitivity and specificity of both signs were calculated.Results: A total of 406 patients (98 LSS and 308 non-specific LBP) were included. SS and CSFSL sign had a sensitivity of 90.8% and 82.7% and specificity of 75.4% and 84.1% in the whole cohort, respectively. When patients were grouped by dural sac cross-sectional areas (CSA), sensitivity and specificity of SS were 100% and 4.4%, 87.5% and 31.8%, and 41.7% and 76%, respectively, and sensitivity and specificity of CSFSL sign were 95.7% and 11.1%, 75% and 77.3%, and 16.7 and 92% for severe (CSA < 80 mm2), moderate (CSA: 80-100 mm2), mild (CSA: 100-120 mm2) radiologic stenosis, respectively. In moderate stenosis, accuracies of SS and CSFSL sign were 76.3% and 55.3%, respectively.Conclusion: CSFSL sign might be used to distinguish LSS from LBP and unlike SS it is successful in moderate stenosis. [ABSTRACT FROM AUTHOR]