Structural and resting-state functional MRI characteristics of patients at high risk for Alzheimer’s disease

Objective To investigate the imaging characteristics of amnestic mild cognitive impairment (aMCI) patients using structural MRI (sMRI) and resting-state functional MRI (rs-fMRI), particularly structural and functional differences between the aMCI patients who progressed to probable Alzheimer’s disease (aMCI-P) within a relatively short period and others who remained stable (aMCI-S). Methods Thirty-two aMCI patients and 28 age-matched normal control (NC) underwent baseline and 1—5 years follow up sMRI scans. Thirteen of the 32 aMCI patients were in the aMCI-P group and others in aMCI-S group. The baseline sMRI and rs-fMRI data of NC and aMCI patients together with data of 22 Alzheimer’s disease (AD) patients were used, and image preprocessings were carried out using SPM 8, voxel-based morphometry and data parocessing assistant for rs-fMRI. Analysis of variance was performed to analyze the neuropsychological tests scores, gray matter (GM) volume and posterior cingulate cortex (PCC) resting-state functional connectivity (RSFC) changes among the three groups. Two-sample t test was processed to compare the neuropsychological tests scores, GM volume and PCC RSFC differences between the aMCI-P and aMCI-S groups. Results The value of GM volume loss in aMCI patients was between NC and AD patients, and the main regions were in the bilateral hippocampi and parahippocampal gyri, bilateral thalami, cingulate cortices and precuneus. Compared with AD patients, aMCI group showed less GM volume loss in bilateral parahippocampal gyri, heads of caudate nucleus, right insula and angular gyrus. While compared with aMCI-S group, aMCI-P patients performed severer GM atrophy in the bilateral temporal lobes. The aMCI patients showed a greater PCC RSFC decline than NC but less than AD, and the main regions were in the right angular gyrus and precuneus. Compared with aMCI-S group, aMCI-P patients showed decreased RSFC in the right angular gyrus. Conclusion These preliminary findings may provide structural and resting-state imaging-based biomarkers for the early diagnosis and prediction of the aMCI patients. Key words: Alzheimer disease; Mild cognitive impairment; Magnetic resonance imaging