Olfactory Function Detected By FMRI In The Alzheimer’s Disease And Vascular Dementia

Objective:To study the value of the fMRI in the detection of the olfactory relevant cortex function in patients with AD (Alzheimer’s disease, AD) and VaD (vascular dementia, VaD) and explore the value of olfactory fMRI in the early diagnosis, differential diagnosis of Alzheimer’s disease and vascular dementia value, and to provide evidence for the further explore in the the olfactory dysfunction in neurodegenerative diseases.Subjects and Methods:17cases of normal elderly (NC),18patients with MCI,17patients with AD and12patients with VaD we re recruited in this study collecting basic information and the related clinical history, excluding depression and anxiety and other neurological diseases that impacting olfactory function. All subjects were underwent MOCA, MMSE, CDR, HIS and HAMD neuropsychological scores. The data were scanned by the Siemens3.0T MR scanner with a32-channel head coil, in event-related fMRI design, and according the approach (from low to high according to the order of0.10%, respectively,0.33%,1.00%solvent vapors lavender olfactory stimuli) to make the olfactory fMRI scan. The data was processed by the Matlab7.11.0and SPM8software. Firstly, observe the number of olfactory activated voxels in the olfactory-related regions of the whole brain and made anatomical localization across the four groups, using one-sample t-test group analysis and one-way ANOVA analysis to analye the number of activated voxels in the olfactory-related whole brain; then designated the primary olfactory cortex (POC) as the ROI, calculated the number of activated voxels in the POC, using the SPSS19.0for statistical analysis:1) Compare the activated voxels in the POC of the four groups;2) Analyzing the trend of activated voxels induced by the three different concentrations in the POC of the four groups, then Observe the olfactory patterns of the four groups.Results:1) The activated voxels in the whole brain of the NC were significantly more than the other three groups;2) The number of activated voxels in POC of the NC group (mean±standard deviation):210.47±161.36; MCI group:101.44±131.94; AD group:38.56±57.92, VaD group:46.64±62.25; The difference of activated voxels in the POC between the NC and MCI, NC and AD, NC and VaD were statistically significant; but the difference MCI and AD, AD and VaD were not statistically significant.3) The activation pattern of POC induced different concentrations:NC group showed olfactory adaptation, MCI’s like NC, AD’s showed lacking of olfactory adaptation, VaD’s showed weakened olfactory adaptation.Conclusion:Comparing the olfactory fMRI activated voxels of the whole brain and POC between the AD, VaD, MCI patients and NC group. The activated voxels in the whole brain and POC of NC were significantly more than the other three groups, demonstrated that the patients with AD、MCI and VaD had olfactory deficit. Moreover, analyzing the olfactory pattern of the POC, only the AD patients showed special pattern-lacking olfactory habitation, that different from the NC、MCI and VaD groups. So not only to prove the olfactory fMRI can detect pathological changes of AD, but also can distinguish AD from VaD by the special activation patterns.Then it may can provide an objective imaging method in earier diagnosis of AD and its differential diagnosis with VaD. And following up the MCI patients with olfactory fMRI, AD patients can be found in the very early stage, given the intervention, then improve the prognosis of patients significantly.