The MR Study Between Hippocampus Abnormal Structure Connectivity,Functional Connectivity And Hippocampus Volume Of Alzheimer

Objective: Useing a variety of magnetic resonance imaging(MRI) technique, to study the hippocampus which is the earliest affected areas of Alzheimer’s disease(AD), in the AD development, the hippocampus related structure connectivity and functional connectivity are abnormal, and the relation between this abnormal connectivity with hippocampus volume. To clarify the above indicators(structure connectivity, functional connectivity and volume) in AD patients the brain changes law with clinical course, find the sensitive imaging index to early diagnosis of AD, and provide scientific basis and research strategy for early diagnosis, early treatment of AD.Subjects and Methods: The subjects were divided into normal control(NC)group,mild cognitive impairment group(MCI) and Alzheimer’s disease(AD) group. The number of three groups is 20, 20 and 25 respectively. Acquire basic clinical information of three groups, all the subjects in clinical routine screening of cognitive scale. Using Siemens 3.0 T scanner, 32 channel head coil. Combine Simultaneous Multi- Slice(SMS) technology with diffusion tensor imaging sequences or resting state functional magnetic resonance imaging sequences to get diffusion MRI and functional data. Using Diffusion toolkit, Track Vis, Matlab7.2, REST and SPM8.0 software for structure data and functional data processing, to obtain three groups of subjects 1) bilateral hippocampus, cingulum and posterior cingulum cortex factional anisotropy(FA) and mean diffusivity(MD) values, and the fiber number of bilateral hippocampus; 2) the functional connective map between hippocampus with other brain cortex(including hippocampus with posterior cingulum cortex); 3) bilateral hippocampus volume. The above three parameters(diffusion parameters, functional connection and volume) of the three groups underwent the group level analysis respectively(including analysis of variance, two sample t test and paired sample t test) and three kinds of parameter correlation analysis(linear regression).Results: The hippocampus, cingulum microstructure of MCI and AD was damaged, showed that the FA decrease and MD increase. The two parts MD difference of NC/MCI and NC/AD group had statistically significant(p < 0.05), while the difference of FA only in NC/AD group had statistically significant(p < 0.05).Function connection of hippocampus with multiple cerebral cortex, posterior cingulum cortex and medial prefrontal cortex reduce as AD development, the difference of NC/MCI and NC/AD group has statistical significance(p < 0.05).The difference of hippocampus and right posterior cingulum cortex functional connectivity has statistically significant in NC/AD and MCI/AD, but the left hippocampus with left posterior cingulum cortex functional connectivity did not have a difference in three groups. From NC, MCI to AD, bilaterally hippocampus volume was showed a trend of gradual decline, the difference of NC/AD and MCI/AD has statistically significant(p < 0.05).And the same time, bilateral hippocampus fiber quantity analysis has similar result as hippocampus volume, from NC, MCI to AD showed decline trend. The correlation analysis of three kinds of parameter showed that in MCI and AD stage, there has correlation between three kinds of abnormal parameter and has right lateral dominance, the structural connective and functional connective abnormal are sooner than hippocampus volume.Conclusion: From normal aging control, mild cognitive impairment to Alzheimer’s disease, in patients with the three stages of development:1) The hippocampus and cingulum of FA and MD value able to distinguish between three groups, and the sensitivity of the MD is higher than FA; 2) In the period of MCI and AD, hippocampus with multiple brain cortex functional connection are reduction(including right side of the hippocampus- posterior cingulum cortex) and able to distinguish from NC groups; 3) Bilateral hippocampus volume are shrinking, AD stage was especially significant; 4) In MCI and AD phase, the correlation of three parameters are better, it pointed out that three parameters change exists the close relation; 5) the diffusion tensor imaging and hippocampus- posterior cingulum cortex function connection abnormalities are occur earlier than volume contraction. Cingulum microstructure and hippocampus- posterior cingulum cortex functional connectivity abnormal can help early detection MCI and AD, and the sensitivity is higher than hippocampus volume decrease.