Diffusional Kurtosis Imaging of the Corticospinal Tract in Multiple Sclerosis: Association with Neurologic Disability.

BACKGROUND AND PURPOSE: Multiple sclerosis is an autoimmune disorder resulting in progressive neurologic disability. Our aim was to evaluate the associations between diffusional kurtosis imaging-derived metrics for the corticospinal tract and disability in multiple sclerosis. MATERIALS AND METHODS: Forty patients with MS underwent brain MR imaging including diffusional kurtosis imaging. After we masked out T2 hyperintense lesions, the fractional anisotropy, mean diffusivity, radial diffusivity, axial diffusivity, mean kurtosis, radial kurtosis, and axial kurtosis were estimated for the corticospinal tract. Disability was quantified by using the Expanded Disability Status Scale at the time of MR imaging and 12 months post-MR imaging. The Pearson correlation coefficient and linear regression analyses were conducted to evaluate the associations between diffusion metrics and disability. RESULTS: Significant correlations were found between the Expanded Disability Status Scale scores during the baseline visit and age (r = 0.47), T2 lesion volume (r = 0.38), corticospinal tract mean diffusivity (r = 0.41), radial diffusivity (r = 0.41), axial diffusivity (r = 0.34), fractional anisotropy (r = -0.36), and radial kurtosis (r = -0.42). Significant correlations were also found between the Expanded Disability Status Scale scores at 12-month follow-up and age (r = 0.38), mean diffusivity (r = 0.45), radial diffusivity (r = 0.41), axial diffusivity (r = 0.45), mean kurtosis (r = -0.42), radial kurtosis (r = -0.56), and axial kurtosis (r = -0.36). Linear regression analyses demonstrated significant associations among radial kurtosis, age, and Expanded Disability Status Scale score during the baseline visit, while radial kurtosis was the only variable associated with Expanded Disability Status Scale score for the 12-month follow-up. CONCLUSIONS: Radial kurtosis of the corticospinal tract may have an association with neurologic disability in MS.