White matter hyperintensities and changes in white matter integrity in patients with Alzheimer's disease - PubMed (original) (raw)

Comparative Study

White matter hyperintensities and changes in white matter integrity in patients with Alzheimer's disease

Liya Wang et al. Neuroradiology. 2011 May.

Abstract

Introduction: White matter hyperintensities (WMHs) are a risk factor for Alzheimer's disease (AD). This study investigated the relationship between WMHs and white matter changes in AD using diffusion tensor imaging (DTI) and the sensitivity of each DTI index in distinguishing AD with WMHs.

Methods: Forty-four subjects with WMHs were included. Subjects were classified into three groups based on the Scheltens rating scale: 15 AD patients with mild WMHs, 12 AD patients with severe WMHs, and 17 controls with mild WMHs. Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (D(R)), and axial diffusivity (D(A)) were analyzed using the region of interest and tract-based spatial statistics methods. Sensitivity and specificity of DTI indices in distinguishing AD groups from the controls were evaluated.

Results: AD patients with mild WMHs exhibited differences from control subjects in most DTI indices in the medial temporal and frontal areas; however, differences in DTI indices from AD patients with mild WMHs and AD patients with severe WMHs were found in the parietal and occipital areas. FA and D(R) were more sensitive measurements than MD and D(A) in differentiating AD patients from controls, while MD was a more sensitive measurement in distinguishing AD patients with severe WMHs from those with mild WMHs.

Conclusions: WMHs may contribute to the white matter changes in AD brains, specifically in temporal and frontal areas. Changes in parietal and occipital lobes may be related to the severity of WMHs. D(R) may serve as an imaging marker of myelin deficits associated with AD.

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Conflict of interest statement

The authors declare that we have no conflict of interest.

Figures

Figure 1

Examples of WMHs observed in T2 weighted MRI and in different white matter regions and WMH scores based on the Sheltens rating scale. Cross section images (A and B) from a subject with mild WMHs show a hyperintensity lesion in the left occipital periventricular region (size < 5 mm, arrow indicated) with a score of 1 (A) and a hyperintensity lesion (size < 3 mm) in the left parietal region with a score of 1 (B). A total score up to 5 can be given to a subject in the mild WMHs category. For the severe WMHs category, WMHs can be also scored for a total of 20. For example, images from a subject in the severe WMHs group shows hyperintensity lesions in the both frontal periventricular regions (5mm < size < 10 mm) that have scores of 4; in the both occipital periventricular regions (size < 5mm) with 2 scores; in the both lateral periventricular regions (size < 5 mm) with 2 scores (C). Confluent hyperintensity lesions in the both of parietal regions shown in (D) are counted for 12 scores.

Figure 2

The ROIs were superimposed on the white matter skeleton (green) and anatomical (gray) images of selected regions: (A) frontal, anterior and posterior internal capsule, and occipital areas, (B) superior and middle temporal areas, and (C) parietal lobes.

Figure 3

Comparisons of averaged FA and/or MD values (A) and DR and/or DA (B) of different groups in the plot allow for showing white matter changes in specific white matter structures. * indicates the DTI measurement reached statistical significant differences (P<0.05) when comparing AD patients with mild WMHs (Group I) to control subjects with mild WMHs Group III).

Figure 4

The differences in white matter changes between AD with mild WMHs (Group I) and controls with mild WMHs Group III) appear to be lateralized in the left cerebral hemisphere. The contrast maps between DTI indices of Group I and Group III are superimposed on the white matter skeleton (green) from TBSS to demonstrate the alterations (red) of FA (right panel) and DR (left panel).

Figure 5

The pie plots demonstrate the power of each DTI measurement in distinguishing AD patients with mild WMHs (Group I) from controls with mild WMHs (Group III) (A), and differentiating AD patients with mild WMHs (Group I) from AD patients with severe WMHs (Group II) (B). The chart is normalized from the sum of all ROIs exhibiting statistically significant differences in at least one of the DTI indices, i.e. FA, DR, MD and DA. With higher percentages of effective ROIs compared to the others, FA and DR were more sensitive measurements for distinguishing AD patients from controls, and MD was more effective for differentiating the severity of WMHs.

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White matter hyperintensities and changes in white matter integrity in patients with Alzheimer's disease - PubMed (original) (raw)