Longitudinal structural MRI study in process of mild cognitive impairment converting to AD dementia

Abstract

Objective To explore the longitudinally changed patterns in the structure of mild cognitive impairment (MCI) due to Alzheimer's disease (AD) during the process of converting to AD dementia and further investigate the structural features at the baseline of MCI converters with the purpose of finding the potential structure l biomarkers which may predict the conversion in a short term. Methods Twenty-seven patients with MCI, collected from September 2009 to March 2011, and 31 normal controls (NC) were enrolled in this study; neuropsychological assessment and structural magnetic resonance imaging (sMRI) data were acquired respectively at baseline and follow-up. Voxel-based morphometry (VBM) was used to calculate the whole brain gray matter volume. According to the follow up results, patients were divided into MCI converters group (MCI-c, n=16) and MCI non-converters group (MCI-nc, n=11); the trajectory of longitudinal sMRI among the three groups was compared and the correlation between sMRI and neuropsychological assessment was analyzed. Results As compared with MCI-nc group, there was obvious brain atrophy in the bilateral ventromedial prefrontal cortices, bilateral middle frontal gyri and bilateral superior temporal gyri in the MCI-c group. In the comparison of trajectory of sMRI longitudinal changes in the three groups, the degree of brain atrophy in NC group was much lower than the other two groups, and there was no significant difference between MCI-c and MCI-nc group. There were positive correlations between scores of mini-mental state examination and Montreal cognitive assessment and decreased volume of gray matter in the medial temporal lobe, hippocampus, parahippocampal gyrus, precuneus, inferior parietal lobule, lateral temporal lobe and dorsolateral frontal lobe. Conclusions No essential difference in the pattern of encephalatrophy is noted between MCI-c and MCI-nc groups. The decline of brain gray matter volume in medial temporal lobe, hippocampus, parahippocampal gyrus, precuneus and inferior parietal lobule may be one of the potential structural biomarkers which will predict the conversion of MCI to AD dementia. Key words: Alzheimer's disease; Mild cognitive impairment; Longitudinal study; Magnetic resonance imaging