Brain Structure And Resting-state F MRI Studies Of Type 2 Diabetes Mellitus Patients With Olfactory Dysfunction

Objective:To explore the changes of brain function and structure in the type 2 diabetes mellitus(T2DM) with olfactory dysfunction by using resting-state functional magnetic resonance imagingand voxel-based morphometry.To explore the relationship between the brain function and olfactory test score, to evaluate the diagnostic value of olfactory function in diabetic brain damage.Materials and Methods:Some subjects in this study were patients in the endocrine department of Zhongshan hospital affiliated to Da Lian university and the other were healthy normal person, finally13 diabetes mellitus patients with olfactory dysfunction(ODM), 19 diabetes mellitus patients without olfactory dysfunction(DM) and 20 cases of healthy controls(HC) were included in this study. All subjects underwent 3.0T axial T1, sagittal T2 FLAIR and Rest f MRI scans,the T2 FLAIR used to exclude base lesions(including severe demyelinating lesions, lacunar cerebral infarction,cerebral hemorrhage, brain tumors, et al). Images preprocessing were completed by SPM8 software based on Matlab platform, regional homogeneity(Re Ho) and amplitude of low frequency fluctuation(ALFF) were calculated with the software of REST, gray matter volume(GMV)imaging was got with the software of VBM. Using two independent samples t test to compare the differences between the every two groups of Re Ho、ALFF and GMV. Then we analysed the relationship between the result of ALFF and olfactory test score in ODM group.Results:1.The VBM results:compared to HC,GMV in DM group decreased in the cerebellum, bilateral anterior cingulate, the right precuneus, insula and Heschl’s gyrus;compared to DM,GMV in ODM group decreased in the right superior frontal gyrus andinferior occipital gyrus;compared to HC,GMV in ODM group decreased in the cerebellum, bilateral olfactory cortex, anterior cingulate, middle frontal gyrus, caudate head and rectus gyrus, increased in the bilateral cuneus; 2.The ALFF results:compared to HC,ALFF in DM group decreased in the bilateral precuneus and right lingual gyrus, increased in the left middle temporal gyrus;compared to DM,ALFF in ODM group decreased in the bilateral orbital of bilateral superior frontal gyrus and middle frontal gyrus, bilateral rectus gyrus, bilateral olfactory cortex and right amygdale, increased in the bilateral superior frontal gyrus and right middle frontal gyrus;compared to HC,ALFF in ODM group decreased in the right lingual gyrus, cuneus,left superior occipital gyrus and middle occipital gyrus, bilateral calcarine cortex, right caudate nucleus, olfactory cortex, rectus gyrus, middle frontal gyrus, bilateral cingulate gyrus and left posterior central gyrus, increased in the right inferior temporal gyrus; 3.The Re Ho results:comparedto HC, Re Ho in DM group decreased in the cerebellar, bilateral lingual gyrus, hippocampus, and left inferior temporal gyrus, increased in the left precuneus, middle temporal gyrus and inferior parietal lobule;compared to DM, Re Ho in ODM group increased in the supplementary motor area, bilateral superior frontal gyrus,right middle frontal gyrus and inferior frontal gyrus; compared to HC, Re Ho in ODM group decreased in the left lingual gyrus, left thalamus, left hippocampus, left fusiform gyrus,right cerebellum, bilateral olfactory cortex, right amygdala, right superior frontal gyrus, right caudate head,right rectus gyrus, left posterior central gyrus, left paracentral lobule and inferior parietal lobule, increased in the left middle frontal gyrus and inferior frontal gyrus; 4.The positive correlation between the olfactory test score and ALFF was found in the right precuneus,left middle occipital gyrus, left calcarine gyrus,bilateral middle temporal gyrus, orbital of left superior frontal, bilateral rectus gyrus and superior frontal gyrus; the negative correlation was found in bilateral posterior cerebellar lobe.Conclusions: 1.T2 DM patients had functional and morphological damage in some brain regionswith cognitive, visual and olfactory function,some brain regions showed increasing GMV、ALFF and Re Ho because of appropriate compensatory mechanisms; 2.The extent of olfactory dysfunction in T2 DMpatients with olfactory dysfunctions reflected the degree of impairment in cognitive brain regions. Effective monitoring of olfactory function will be reliable indicator to assess the degree of cognitive impairment in T2 DM.