Objective: To investigate the extent and the nature of white matter tissue damage of patients with Alzheimer's disease using diffusion tensor magnetic resonance imaging (DT-MRI). Background: Although Alzheimer's disease pathology mainly affects cortical grey matter, previous pathological and MRI studies showed that also the brain white matter of patients is damaged. However, the nature of Alzheimer's disease associated white matter damage is still unclear. Methods: Conventional and DT-MRI scans were obtained from16 patients with Alzheimer's disease and 10 sex and age matched healthy volunteers. The mean diffusivity (D), fractional anisotropy (FA), and inter-voxel coherence (C) of several white matter regions were measured. Results: D was higher and FA lower in the corpus callosum, as well as in the white matter of the frontal, temporal, and parietal lobes from patients with Alzheimer's disease than in the corresponding regions from healthy controls. D and FA of the white matter of the occipital lobe and internal capsule were not different between patients and controls. C values were also not different between patients and controls for any of the regions studied. Strong correlations were found between the mini mental state examination score and the average overall white matter D (r=0.92, p<0.001) and FA (r=0.78; p<0.001). Conclusions: White matter changes in patients with Alzheimer's disease are likely to be secondary to wallerian degeneration of fibre tracts due to neuronal loss in cortical associative areas.

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Background and Purpose-In migraine patients, functional imaging studies have shown changes in several brain gray matter (GM) regions. However, 1.5-T MRI has failed to detect any structural abnormality of these regions. We used a 3-T MRI scanner and voxel-based morphometry (VBM) to assess whether GM density abnormalities can be seen in patients with migraine with T2-visible abnormalities and to grade their extent. Methods-In 16 migraine patients with T2-visible abnormalities and 15 matched controls, we acquired a T2-weighted and a high-resolution T1-weighted sequence. Lesion loads were measured on T2-weighted images. An optimized version of VBM analysis was used to assess regional differences in GM densities on T1-weighted scans of patients versus controls. Statistical parametric maps were thresholded at PϽ0.001, uncorrected for multiple comparisons. Results-Compared with controls, migraine patients had areas of reduced GM density, mainly located in the frontal and temporal lobes. Conversely, patients showed increased periacqueductal GM (PAG) density. Compared with patients without aura, migraine patients with aura had increased density of the PAG and of the dorsolateral pons. In migraine patients, reduced GM density was strongly related to age, disease duration, and T2-visible lesion load (r ranging from Ϫ0.84 to Ϫ0.73). Conclusions-Structural GM abnormalities can be detected in migraine patients with brain T2-visible lesions using VBM and a high-field MRI scanner. Such GM changes comprise areas with reduced and increased density and are likely related to the pathological substrates associated with this disease. (Stroke. 2006;37:1765-1770.)