| Background and PurposeCerebral infarction is a serious manifestation of ischemic cerebrovascular disease, which is one of the most common diseases of the central nervous system. With the accelerated speed of population aging of society, its incidence is gradual increase, accounting for about80%of all cerebral vascular diseases. Its high mortality, high morbidity and easy to recurrent severely impacts on human’s health and quality of life, brings great spiritual and economic burden to the society and the family. Recent studies have found that supratentorial focal brain damage can cause functional changes in distant areas (cerebellum), could be showed as the changes of apparent diffusion coefficient and fractional anisotropy on MRI. Most scholars believe that the mechanism may be related to the theory of crossed cerebellar diaschisis.Crossed cerebellar diaschisis refers to that supratentorial cerebral infarction causes contralateral cerebellar hemisphere blood flow reduced, thereby causing the phenomenon of contralateral cerebellar hemisphere neuron activity decreased and metabolic disorders. Most scholars believe that this phenomenon is related to the damage of the cortical-pons-cerebellum pathway. Other scholars believe that this phenomenon is related to the changes of cerebellar hemodynamics and late-onset death of cerebellar neurons. Magnetic resonance diffusion tensor imaging (DTI) is based on the echo-planar imaging (EPI) technology,on the basis of diffusion-weighted MR imaging(DWI),it is a new and noninvasive magnetic resonance imaging technology,visual observation of water molecules in vivo microscopic diffusion motion.By measuring the degree and direction of water diffusion,the changes of apparent diffusion coefficient and fractional anisotropy after the cerebral infarction could be shown.It can provide important reference value for the early diagnosis and treatment of cerebral infarction.The improved approach Longa suture method is used in this study, in which we should establish the cerebral ischemic models of middle cerebral artery occlusion (MCAO) with high reproducibility and greater stability with similar characteristic of hunman cerebral vessel. Apparent diffusion coefficient and fractional anisotropy in different parts of the rat brain tissues after MCAO can be detected by diffusion tensor magnetic resonance imaging technology at different time (1h,3h,6h,9h,12h,24h and72h),and using immunohistochemistry to detect RGMa protein expression with the same time and potision of MRI. In order to explore:1.The application value of DTI parameter in remote regions of MCAO models at different times,and then to provide experimental and theoretical foundation of DTI technology for evaluating diaschisis in cerebral infarction..2.The pathological changes of cerebellar in rats after cerebral infarction,and the relationship with magnetic resonance signal changes.3.The relevant mechanism of remote regions diaschisis in cerebral infarction.Materials and Methods1.70healthy SD rats of clean grade enrolled in the study,weight260-300g, average (286.2±8.9) g.The rats were randomly divided into two groups,the experimental group with56rats with the left MCAO models and the control group of14rats only exposing the left middle cerebral artery and no electric coagulating.2.The control group and the experimental group rats were examined axial T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI), sagital T2-weighted imaging, DWI and DTI,using3.0T high-field superconducting magnetic resonance scanner of GE in U.S and multichannel rat coil of chenguang in shanghai. Two rats in each group were selected and were cut into slice every3mm according to the level of axial T2WI.Using immunohistochemical to detect the RGMa protein expression in the center and remote areas cerebellum of cerebral ischemia in cerebral infarction.3.We observe and record the condition in the DWI of brain tissue in the left cerebral infarction core (basal ganglia) and bilateral cerebellar hemispheres by time,record the cerebral diffusion parameter including apparent diffusion coefficient (ADC) and fractional anisotropy (FA) at different times.Comparing the experimental group with normal group of the left basal ganglia and cerebellum hemispheres including the1h,3h,6h,9h,12h,24h and72h, if there are differences in ADC value and FA value and depicting their time curve. Exploring the relationship between FA value and the RGMa change at different times in the contralateral cerebellar hemisphere.4.All data are analysed by SPSS17.0package in statistics,and the quantitative data was expressed by X±SD.We use two random samples t-test to compare the quantitative data of the normal control group and MCAO group,and Spearman correlation test to analysis the correlation between the indicator of imaging and pathology.P<0.05as statistically significant difference.Results1.One hour after MCAO producer, the ADC value and FA value of the left basal ganglia began to decrease,12h achieved to the minimize,then rose slightly, but still lower than the control group. There was significant difference compared with the normal control group in the left basal ganglia of ADC value and FA value(P<0.05). The trend of ADC value and FA value in the bilateral cerebellar hemispheres was corresponding with infarction core area. The ADC value and FA value of the contralateral cerebellar hemisphere compared to the ipsilateral cerebellar hemiphere was larger degree of decline.2. After cerebral ischemia there was increase of RGMa protein expression at different times in the left basal ganglia,brown RGMa staining could be seen.One hour after focal cerebral ischemia,RGMa-positive cells in the lesion area continued to gather,24h reached the peak, the number of RGMa increased most obviously, fell slightly in the following72h.But compared with the control group,it still sustained high expression. The RGMa protein expression of cerebellum was corresponding with the infarct core area. The RGMa protein average gray value of the contralateral cerebellar hemiphere was higher than the ipsilateral cerebellar hemisphere. The RGMa protein expression could be seen in the control group choroid plexus, perivascular, cerebellar Purkinje cells and brainstem neurons.3. The RGMa upregulation were negatively correlated with the decreased FA value in remote regions (P<0.05,r=-0.341).Conclusion1.The phenomenon of diaschisis in remote regions can be found in supratentorial infarction.2.The diffusion parameter changes in remote regions following the supratentorial infarction core, which can illustrate that it exsit relationship between diaschisis and nerve conduction.3. After cerebral ischemia, the axon guidance molecule RGMa expression upregulation,illustrating that it participates in the process of axonal regeneration and repairment.4. The RGMa protein and the magnetic resonance parameters changes of bilateral cerebellum,demonstrates the existence of crossed cerebellar diaschisis. |
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