Characterization of White Matter Damage in Ischemic Leukoaraiosis with Diffusion Tensor MRI

Abstract

Background and Purpose-Information on the neuropathological changes underlying ischemic leukoaraiosis is only available postmortem, and there are limited data on histological appearances early in the disease. Diffusion tensor imaging allows determination of the directionality of diffusion, which is greater in the direction of white matter bundles. Therefore, the technique might be expected to show loss of anisotropy (directional diffusion) in leukoaraiosis. Methods-Nine patients with ischemic leukoaraiosis (radiological leukoaraiosis and clinical lacunar stroke) and 10 age-matched controls were studied. Diffusion tensor imaging was performed, and maps of diffusion trace and fractional anisotropy were constructed. Mean values of trace and fractional anisotropy were determined in standard regions of the anterior and posterior white matter in both hemispheres. Results-In all patients with ischemic leukoaraiosis, a characteristic abnormal pattern was found, with loss of anisotropy and increased trace in the white matter. For example, in the right anterior white matter mean (SD) trace/3 was 1.12 (0.33) ϫ10 Ϫ3 mm 2 s Ϫ1 in patients and 0.75 (0.11) in controls (Pϭ0.001). In the same region, fractional anisotropy was 0.53 (0.11) in patients and 0.78 (0.09) in controls (PϽ0.001). Within the white matter regions, there was a strong negative correlation between mean diffusivity and anisotropy (rϭϪ0.92, PϽ0.0001). Conclusions-The characteristic pattern found on diffusion tensor imaging in this patient group is consistent with axonal loss and gliosis leading to impairment to and loss of directional diffusion. The "in vivo histological" information obtained may be useful in monitoring disease progression and in investigating the pathogenesis of the cognitive impairment that may be present. (Stroke. 1999;30:393-397.)

Applications of diffusion‐weighted and diffusion tensor MRI to white matter diseases – a review

“…The mean volume ratio, 25 which characterizes anisotropy, was higher both in regions of T 2 -weighted hyperintensity (0.92 AE 0.04) and in NAWM (0.87 AE 0.07) compared with normal white matter in controls (0.68 AE 0.04). In common with the findings of Jones et al 19 in ischaemic leukoaraiosis, there was a strong correlation (r = 0.81; p = 0.0002) between mean diffusivity and anisotropy in regions of T 2 -weighted hyperintensity. In explaining the moderate increase in diffusion in NAWM and severe (60%) increase in white matter exhibiting T 2 -weighted hyperintensities, Chabriat et al suggested that the marked increase in diffusivity in regions of T 2 -weighted hyperintensity was due to neuronal loss, while the mild increase in the NAWM was due to myelin loss.…”

“…Jones et al 19 applied DT-MRI to a study of nine patients with ischaemic leukoaraiosis and 10 agematched controls. They defined ischaemic leukoraraiosis as the radiological appearance of diffuse periventricular white matter changes on conventional MR imaging in patients with a history of lacunar stroke and/or a subcortical dementia believed to be of vascular origin.…”

“…20,21 The mean diffusivity observed in leukoaraiosis is significantly lower than that observed in necrotic tissue such as found in a lacunar infarct. Jones et al 19 attributed this to proliferation of glial tissue (observed in post-mortem histological examinations), which serves to hinder the diffusion of water molecules.…”

Diffusion-weighted imaging of the spine using radialk-space trajectories

“…Other clinical applications include characterization of tumors [6,7] or multiple sclerosis lesions [8][9][10] and white-matter fiber-tract imaging by determining diffusion anisotropy [11][12][13][14].…”

Small Vessel Disease and the Resting Functional Architecture of the Brain

“…2,3 In vivo knowledge of SVD has developed largely as a result of progress in neuroimaging, which has allowed a detailed characterization and classification of anatomical and physiological changes associated with this condition. 4 As an example, recent studies using diffusion tensor imaging show an association between SVD and microstructural changes within selected white matter tracts, 5,6 changes which have been linked to gait disturbances, 7 decreased performance on cognitive testing, 8 and may precede the development of white matter lesions detected using conventional sequences such as T2 or FLAIR. 9 Despite such advances, a systems-level understanding of how SVD contributes to cognitive dysfunction is missing.…”