Diffusion imaging in multiple sclerosis: research and clinical implications

Abstract

Multiple sclerosis (MS) is an inflammatory-demyelinating and neurodegenerative disease of the central nervous system (CNS) and the most frequent cause of non-traumatic disability in young and middle-age adults. Although conventional MRI (including T2-weighted, pre- and post-contrast T1-weighted scans) has had a huge impact on MS by enabling an earlier diagnosis, and by providing surrogate markers for monitoring treatment response, it is limited by the low pathological specificity and the low sensitivity to diffuse damage in normal-appearing white matter and gray matter. Diffusion weighted MRI is a quantitative technique able to overcome these limitations by providing markers more specific to the underlying pathologic substrates and more sensitive to the full extent of 'occult' brain tissue damage. This review describes diffusion studies in MS, discusses their pathophysiological implications and emphasizes their clinical relevance.

Figure 1

Selected axial and sagittal diffusion tensor maps from a patient with multiple sclerosis. Mean diffusivity (A, B), fractional anisotropy (C, D) and color primary eigenvector map (E, F) illustrating different directions of the primary eigenvector: Red is left-right; green is cranio-caudal and blue is in-out of the page. Note that MS lesions (arrows) show higher mean diffusivity (bright), lower fractional anisotropy (dark) and disruption of the primary fiber direction (dark).

Figure 2

Selected axial T2-weighted image (A) of the cervical spinal cord of a MS patient acquired at C3 level (the arrow indicates a hyperintense lesion). MD (B) and FA (C) maps corresponding to the level of the T2 weighted image.

Figure 3

3D DTI-tractography of the corpus callosum (CC) (A) in a healthy control. CC (B) and antero-thalamic (AT) (C) tract probability maps in MNI space and in the corresponding single subject space (D) after transformation.

Figure 4

Selected T2-weighted image of a MS patient (A) showing multiple periventricular hyperintense lesions (arrows). Corresponding MD (B), FA (C) and MK (D) maps.