Diagnostic Value of Stress Magnetic Resonance Imaging in Lumbar Canal Stenosis in Patients with Clinico-radiological Mismatch

Abstract Background: Lumbar spinal stenosis (LSS) is a dynamic condition whose severity can be underestimated on conventional supine magnetic resonance imaging (cMRI), especially in patients with a clinico-radiological mismatch between symptoms and imaging findings. Axial loaded MRI (al-MRI) has been proposed to simulate the spine conditions under physiological load, potentially improving the diagnostic accuracy. Materials and Methods: In this retrospective observational study, patients with clinically suspected LSS, whose cMRI findings did not fully explain their symptoms, underwent additional al-MRI between L3 and S1. Disk levels were assessed for changes in the grade of central canal stenosis, lateral recess stenosis, foraminal stenosis, and dural sac cross-sectional area (DSA). Results: Out of 237 patients (711-disk levels), significant changes were observed on al-MRI compared to cMRI. Central canal stenosis grade increased from A/B to C/D in 87-disk levels in 73 patients (30.8%). Lateral recess stenosis changed in 33 patients (13.9%) with clear nerve root compression on al-MRI. DSA decreased from >75 mm² to