Directional diffusion in relapsing‐remitting multiple sclerosis: A possible in vivo signature of Wallerian degeneration

Abstract

Purpose:To examine the role of directional dependence of the apparent diffusion coefficients in the evaluation of normal-appearing brain regions of patients with relapsingremitting multiple sclerosis. Materials and Methods:The role of diffusion tensor eigenvalues was investigated in the normal-appearing brain regions for 18 patients with relapsing-remitting multiple sclerosis and 15 age-matched normal controls. Results:The isotropic apparent diffusion was increased in all regions. However, reduced anisotropy was significant only in regions with high anisotropy, including the corpus callosum and the internal capsule, and was due to increased diffusion tensor eigenvalues corresponding to diffusion transverse to the fibers without significant increase along the fibers. This characteristic pattern of changes in diffusion tensor eigenvalues has been observed previously in cases of Wallerian degeneration. Low-anisotropy regions corresponded to gray matter and gray/white interface regions. Since fiber tract orientations are not determined for regions of low anisotropy, this characteristic pattern of diffusion change is not detectable in these regions. Conclusion:Examination of diffusion tensor eigenvectors may provide insight into the changes observed in diffusion and a signature of Wallerian degeneration in the normal-appearing white matter of relapsing-remitting multiple sclerosis patients.

Assessment of White Matter Tract Damage in Patients with Amyotrophic Lateral Sclerosis: A Diffusion Tensor MR Imaging Tractography Study: Fig 1.

“…However, the fasciculi that we investigated are major WM tracts associated with high anisotropy; therefore, the effect of crossing fibers should not have affected our results a great deal, especially in the case of CST. 58 Despite such limitations, this study highlights the potential of DTI of the brain to provide in vivo markers of cerebral involvement in ALS. 7 …”

“…2 Finally, some methodologic issues related to DTI should be addressed. Regions of crossing fibers are characterized by low anisotropy and, thus, the determination of fiber orientation may be difficult in these voxels, 58 leading to unreliable tensor estimates. However, the fasciculi that we investigated are major WM tracts associated with high anisotropy; therefore, the effect of crossing fibers should not have affected our results a great deal, especially in the case of CST.…”

Diffusion Tensor MR Imaging Tractography of the Pyramidal Tracts Correlates with Clinical Motor Function in Children with Congenital Hemiparesis

“…The increased transverse diffusivity and unchanged parallel diffusivity have been previously associated with wallerian degeneration in arterial infarcts 16,18 and is thought to reflect pathologic changes that involve loss of myelin, axonal loss, myelin debris, and inflammatory edema. 19 However, our patient population includes patients without arterial infarcts. Thus, other mechanisms must also result in the observed diffusion pattern.…”

Imaging of multiple sclerosis: Role in neurotherapeutics

“…20 The specialized anatomy of the brain results in alterations at a distance related to disruption along connected pathways that traverse focal lesions, and Wallerian degeneration along highly organized pathways may be reflected in altered diffusion tensor eigen values. 21 These distributed effects may help to explain some of the quantitative change that is rather consistently found in conventional MRI-defined NAWM.…”

“…11). 21,223,224,228 Clinical correlation. There is growing interest in studying the relationship between DWI-related data and clinical manifestations of MS such as physical disability, disease course and cognitive impairment.…”