Diagnostic Values of Magnetic Resonance Imaging in the Diagnosis of Lumbar Foraminal Stenosis Compared with Surgical Findings

Abstract

Objective: To measure the diagnostic values of preoperative Magnetic Resonance Imaging (MRI) for diagnosis of lumbar foraminal stenosis in the symptomatic lumbar spinal stenosis patients who need surgery. Materials and Methods: Thirty-two lumbar spinal stenosis patients with indication for surgical treatment were included. Two radiologists independently interpreted foraminal narrowing on sagittal T2W image by means of quantitative measurements including posterior disc height, foraminal height, cross-sectional area and qualitative MRI grading system. Using surgical findings as standard reference that was performed by routinely intraoperative probing. Results: The sensitivity, specificity, PPV and NPV of critical posterior disc height of 4 mm or less for diagnosis of foraminal stenosis were 40.5%, 96.8%, 93.8% and 57.7%, respectively, and using critical foraminal height of 15 mm or less were 97.3%, 72.6%, 80.9% and 95.7%, respectively. The corresponding values for MRI grading system were 83.8%, 90.3%, 91.2% and 82.4%, respectively. Conclusion: Both of quantitative measurements and qualitative MRI grading system assessing on sagittal MR image are helpful for preoperative diagnosis of foraminal stenosis and have correlated well with the surgical findings. Among of these variables, critical posterior disc height demonstrated highest specificity and PPV. In addition, MRI grade 2 and 3 might be clinically significance and be the indicator for judgment of additional foraminotomy in lumbar spinal stenosis patients.