[Olfactory functional magnetic resonance imaging in patients with mild cognitive impairment]

Objective: To analyze the activation of brain regions associated with olfactory in patients with mild cognitive impairment (MCI) by olfactory functional magnetic resonance imaging (fMRI). Methods: Twenty six patients with MCI were compared with twenty six controls in the dementia center of Tianjin HuanHu hospital in terms of olfactory function T&T testing, the differences between the activation of the whole brain and region of interest associated with olfactory (bilateral primary olfactory cortex(POC), bilateral hippocampus, bilateral orbital frontal gyrus) by olfactory stimulator using event correlation design for olfactory fMRI scanning. To analyze the correlation between the number of activator in POC and the threshold of olfactory discriminate as well as the severity of cognitive impairment.SPSS 19.0 software was used for the statistical analysis. Results: T&T olfactory testing revealed that MCI patients had higher scores than controls (3.57±1.29 (x±s) vs 1.02±0.35, t=4.372, P<0.05). The activation range of whole brain in MCI patients was less than controls (pleasant odor (po) 147.36±21.45 vs 323.11±39.76, unpleasant odor (upo) 201.86±24.93 vs 447.73±57.22, t(po)=4.241, t(upo)=5.365, both P<0.05). The activation range of whole brain in inhaling unpleasant odor was more than pleasant odor in controls (447.73±57.22 vs 323.11±39.76, t=3.936, P<0.05). The number of activator in ROI(awo) in MCI patients was less than controls (pleasant odor (po) 51.0[8.0, 109.0](M[P(25), P(75)]) vs 135.0[21.0, 321.5], unpleasant odor (upo) 65.0[6.0, 158.0]vs 205.0[36.5, 491.0], Z(po)=-2.199, Z(upo)=-2.216, both P<0.05). The number of activator in POC in MCI patients was less than controls (pleasant odor (po) 19.0[4.0, 35.5]vs 46.0[9.0, 118.5], unpleasant odor (upo) 26.0[2.0, 51.0]vs 79.0[17.5, 189.0], Z(po)=-1.898, Z(upo)=-2.167, both P<0.05). The number of activator in POC was negatively correlated with olfactory discriminate threshold in MCI patients (r(po)=-0.415, r(upo)=-0.409, both P<0.05). The number of activator in POC was positively correlated with MoCA in MCI patients (r(po)=0.289, r(upo)=0.296, both P<0.05). Conclusion: Olfactory fMRI can objectively assess the olfactory function in MCI, it is a imaging indicator with neuropsychological tests for detection in MCI, the number of activator in POC can reflect the severity of MCI.