Spinal cord quantitative MRI discriminates between disability levels in multiple sclerosis

Objective: The clinicoradiologic paradox, or disconnect between clinical and radiologic findings, is frequently encountered in multiple sclerosis (MS), particularly in the spinal cord (SC), where lesions are expected to cause clinical impairment. We aimed to assess whether quantitative diffusion tensor and magnetization transfer imaging measures in the SC can distinguish MS cases of comparable lesion burdens with high and low disability. Methods: One hundred twenty-four patients with MS underwent 3-T cervical SC MRI and were categorized into 4 subgroups according to SC lesion count and disability level. Regions of interest circumscribed the SC cross-section axially between C3 and C4. Cross-sectional area, fractional anisotropy (FA), mean diffusivity (MD), perpendicular diffusivity (λt), parallel diffusivity (λk), and magnetization transfer ratio (MTR) were calculated. Differences between patient subgroups were assessed using t tests and linear regression. Results: FA,MD, λt, λk,MTR, and SC cross-sectional area were more abnormal in the high-vs lowdisability subgroup of patients with low lesion counts (p < 0.05). MRI measures (except lk and MTR) were more abnormal in the high-vs low-disability subgroup of patients with high lesion counts (p < 0.05). In age-and sex-adjusted comparisons of high-vs low-disability subgroups, all MRI measures retained differences in the low-lesion subgroup, except λk, whereas only FA, MD, and lt retained differences in the high-lesion subgroup. Conclusions: In this cross-sectional study of patients with MS, quantitative MRI reflects clinically relevant differences beyond what can be detected by conventional MRI. Our findings support the utility of quantitative MRI in clinical settings, where accurate measurement of disease burden is becoming increasingly critical for assessing treatment efficacy.