White matter changes in patients with amnestic mild cognitive impairment detected by diffusion tensor imaging.

Karl Herholz,Jianghong Liu,Longfei Jia,Shugao Xia,Yanqin Guo,Zhilian Zhao,Xiaobo Li,Jianping Jia,Ying Han,Changhao Yin

doi:10.1371/journal.pone.0059440

Abstract

Compared to normal aging adults, individuals with amnestic mild cognitive impairment (aMCI) have significantly increased risk for progressing into Alzheimer’s disease (AD). Autopsy studies found that most of the brains of aMCI cases showed anatomical features associated with AD pathology. The recent development of non-invasive neuroimaging technique, such as diffusion tensor imaging (DTI), makes it possible to investigate the microstructures of the cerebral white matter in vivo. We hypothesized that disrupted white matter (WM) integrity existed in aMCI. So we used DTI technique, by measuring fractional anisotropy (FA) and mean diffusivity (MD), to test the brain structures involved in patients with aMCI. DTI scans were collected from 40 patients with aMCI, and 28 normal controls (NC). Tract-based spatial statistics (TBSS) analyses of whole-brain FA and MD images in each individual and group comparisons were carried out. Compared to NC, aMCI patients showed significant FA reduction bilaterally, in the association and projection fibers of frontal, parietal, and temporal lobes, corpus callosum, bilateral corona radiation, right posterior thalamic radiation and right sagittal stratum. aMCI patients also showed significantly increased MD widespreadly in the association and projection fibers of frontal, parietal and temporal lobes, and corpus callosum. Assessment of the WM integrity of the frontal, parietal, temporal lobes, and corpus callosum by using DTI measures may aid early diagnosis of aMCI.

Highlights

Mild cognitive impairment (MCI) is a descriptive category that identifies patients with memory impairment beyond that expected for age and education, who do not qualify for a diagnosis of dementia [1]
Reduction of fractional anisotropy (FA) in Amnestic MCI (aMCI) Patients Between-group comparisons of the voxel-wise FA values showed that patients with aMCI exhibited significantly reduced FA values (TFCE-corrected p,0.05) in white matter (WM) clusters over large areas bilaterally, mainly in the frontal, parietal, and temporal lobes, the whole corpus callosum, and its association fibers including the superior longitudinal fasciculus, external capsule, cingulum bundle, sagittal stratum and fornix, projection fibers including internal capsule, corona radiation, and thalamic radiation (Figure 1)
Increase of mean diffusivity (MD) in aMCI Patients Between-group comparisons of the voxel-wise MD values showed that patients with aMCI exhibited significantly increased MD values (TFCE-corrected p,0.05) in WM clusters bilaterally, especially in the frontal, parietal, and temporal lobes, corpus callosum, association fibers, projection fibers

Summary

Introduction

Mild cognitive impairment (MCI) is a descriptive category that identifies patients with memory impairment beyond that expected for age and education, who do not qualify for a diagnosis of dementia [1]. The term MCI has become widely used, with the suggestion that it is a prodromal state of Alzheimer’s disease (AD) and possibly other dementias [2,3]. MCI has been classified broadly into amnestic and nonamnestic subtypes. Amnestic MCI (aMCI) presents clinically with memory disturbance as the main feature, other cognitive domains may be affected as well. AMCI is thought to progress into AD, whereas nonamnestic MCI may progress to the other types of dementia [4]. Recent autopsy studies indicate that AD pathology associated anatomical features were found in most of the brains from aMCI patients [6,7]. A meta-analysis reported the annual conversion rate from aMCI to AD at 5%–10% [8]

Methods

Results

Conclusion