Radiographic assessment of degenerative lumbar spinal stenosis: is MRI superior to CT?

OBJECTIVE: To determine the reliability and dependability of magnetic resonance imaging (MRI) and computerized tomography (CT) in the assessment of lumbar spinal stenosis and correlate the qualitative assessment to both a quantitative assessment and functional outcome measures. Multiple studies have addressed the issue of CT and MRI imaging in lumbar spinal stenosis. None showed superiority of one modality.

METHODS: We performed a standardized qualitative and quantitative review of CT and MRI scans of 54 patients. Intra-observer and inter-observer reliability was determined between three reviewer using Kappa coefficient. Agreement between the two modalities was analyzed. ODI and SF-36 outcomes were correlated with the imaging assessments.

RESULTS: Almost perfect intra-observer reliability for MRI was achieved by the two expert reviewers (κ = 0.91 for surgeon and κ = 0.92 for neuro-radiologist). For CT, substantial intra-observer agreement was found for the surgeon (κ = 0.77) while the neuro-radiologist was higher (κ = 0.96). For both CT and MRI the standardized qualitative assessment used by the two expert reviewers had a better inter-observer reliability than that between the expert reviewers and the general reporting radiologist, who did not utilize a standardized assessment system. When the qualitative assessment was compared directly, CT overestimated the degree of stenosis 20-35 % of the time (p < 0.05) while MRI overestimated the degree of stenosis 2-11 % of the time (p < 0.05). No correlation was found between qualitative and quantitative analysis with functional status.

CONCLUSIONS: This study directly demonstrates that MRI is a more reliable tool than CT, but neither correlates with functional status. Both experience of the reader and the standardization of a qualitative assessment are influential to the reliability.