Agreement Between Computed Tomography and Magnetic Resonance Imaging in Grading Lumbar Spinal Stenosis

Abstract

BACKGROUND: Lumbar spinal stenosis is an important pathologic entity to recognize in patients with radicular symptoms as it can have a negative impact on quality of life. Although MRI is considered an appropriate tool for studying spinal stenosis. CT can be performed rapidly and allows precise evaluation of spinal canal and has a superior ability to discriminate cortical bone from soft tissue such as ligamentum flavum.

OBJECTIVE: To determine agreement between CT and MRI in grading Lumbar Spinal Stenosis.

STUDY DESIGN: Descriptive cross sectional study.

DURATION AND SETTING: The study was conducted at Radiology Department, PNS Shifa Hospital Karachi from 01st Feb 2015 to 31st Jul 2015. 

SUBJECTS AND METHODS: 100 patients with chronic backache referred to radiology department for MRI or CT scan of lumbar spine between 18 to 70 years of age were included on the basis of consecutive non probability sampling. The MRI and CT scan were performed on every patient which included axial images at mid inter vertebral disc level L4-5. Total of 100 pairs of MRI and CT axial images were created and Dural sac cross-sectional area (DSCA) were calculated using image analysis software. Lumbar spinal canal stenosis was graded as Grade 1 (No stenosis) with DSCA > 100 mm², Grade 2 (Moderate stenosis) with DSCA 75-100 mm² or Grade 3 (Severe stenosis) with DSCA < 75 mm².

RESULTS: There was agreement between CT and MRI in the grades of lumbar spinal stenosis in 73 cases (73%). The degree of agreement in grading lumbar spinal stenosis was calculated and kappa value was observed as 0.527 (p-value = 0.000) which signifies good (but not excellent, kappa > 0.75) agreement between CT and MRI for grading lumbar spinal stenosis.

CONCLUSION: It was concluded that the agreement between CT (without myelography) and MRI in grading Lumbar Spinal Stenosis is good although not excellent. So in cases where MRI is either not available or is contraindicated CT can be of diagnostic use.