Correlation between white matter damage and cognitive function in patients with Alzheimer's disease

Objective To investigate the nature of white matter damage and its correlation to the cognition function in patients with Alzheimer's disease(AD)by using the diffusion tensor imaging(DTI).Methods Diffusion tensor imaging,as well as T_1-fluid attenuated inversion recovery(FLAIR) and T_2-FLAIR,was performed in probable AD patients and sex and age matched healthy volunteers to measure the fractional anisotropy(FA) and mean diffusivity(MD) in the genu and splenium of the corpus callosum,anterior and posterior limbs of the internal capsule and the white matter of the frontal,temporal,parietal and occipital lobes.Correlation analysis was applied to reveal the relationship between the FA and MD values and the MMSE scores.Results In contrast to healthy controls,patients with AD have a lower FA in the splenium of corpus callosum(0.602±0.043),as well as in the white matter of the frontal(0.270±0.034),temporal(0.302±0.032),and parietal lobes(0.294±0.043).Besides,FA of AD patients was also strongly positive correlated with MMSE scores,but there was no difference in FA between AD patients and controls in the anterior and posterior limbs of internal capsule,occipital lobes white matter and the genu of corpus callosum.While in comparison with that of healthy controls,MD of AD patients was significantly higher in the splenium of corpus callosum((0.918±0.029)×10~(-9) m~2/s) and parietal lobes white matter((0.826±0.015)×10~(-9) m~2/s) and was strongly negative correlated with MMSE scores,but there was no difference in MD between AD patients and controls in the anterior and posterior limbs of internal capsule,as well as in frontal,temporal,occipital lobes white matter and the genu of corpus callosum.Conclusion The white matter of patients with AD should be selectively impaired and the extent of damage should have a strong correlation with the cognition function.The selective impairment might reflect the cortico-cortical and cortico-subcortical disconnections in the pathomechanism of AD.DTI technique might be used to monitor the disease progression and as a surrogate marker for evaluation of drug efficacy(in vivo).