MRI Study of Lumbar Canal Stenosis by Morphological Grading and Thecal Sac Measurement- A Cross-sectional Study

Introduction: Lumbar Spinal Stenosis (LSS) is a condition in which the spinal canal narrows to the point at which it can exert pressure on the nerves that travel through the spine. Aetiology is categorised into congenital, developmental and acquired (degenerative) causes. Magnetic Resonance Imaging (MRI) is an investigation of choice in the evaluation of patients with symptoms related to lumbar central canal stenosis.

Aim: To assess the morphologically grade of thecal sac in lumbar central canal stenosis on MRI.

Materials and Methods: This cross-sectional observational study was conducted from November 2017 to October 2019 at Department of Radiology of Pinnamaneni Siddhartha Institute of Medical Sciences and Research Foundation, Gannavaram, Andhra Pradesh, India. Study included 100 patients who were referred with symptoms of lumbar stenosis and outcome was to determine the correlation between the morphological grade and thecal sac axial anteroposterior diameter grade. Correlation was assessed by Fisher’s-exact test and Spearman’s rank correlation coefficient test. A p-value <0.0001 was considered highly significant.

Results: Morphological Grade II corresponded to maximum number of cases, amounting to 46% with mean anteroposterior thecal sac diameter of 6.21 mm, followed by 36% of Grade III with mean thecal sac diameter of 4.57 mm. Grade I corresponded to 14% of cases mean thecal sac diameter of 8.35 mm and Grade IV corresponded to 4% of cases with mean thecal sac diameter of 1.1 mm. A significant correlation was obtained (r=0.78) in this study between the morphological grade and thecal sac measurement.

Conclusion: Morphological grade of the thecal sac has significant correlation with the canal measurements and it helps in quick assessment of the severity of the lumbar canal stenosis.