MRI Quantitative Evaluation Of Fetal Posterior Fossa Structure And Related Factors In Twin Pregnancy

Objective:The aim is to obtain the median sagittal plane passing through the fetal cerebellar vermis by 1.5T MRI.We measure the upper and lower diameters,anteroposterior diameters,area,BV angle and BT angle of the fetal cerebellar vermis by observing the structure of the fetal posterior cranial fossa to explore the law of change with the process of a period of gestation.The difference between the above-mentioned measured values of the remaining twin of abnormal pregnancy and the normal twin was analyzed to explore the clinical application value of measured values of fetal brain MRI median sagittal plane posterior cranial fossa in the progress of twin cerebellar vermis and to analyze the relationship of clinical factors that may cause the difference.Methods:A total of 39 normally developed and mild ventriculomegaly fetuses at 25-31 gestational weeks were examined by fetal brain MRI and US from February 2011 to October 2018 in Shengjing Hospital affiliated to China Medical University.No abnormalities of the central nervous system were found,and no double abnormalities were found in the mid-late pregnancy without any abnormalities after birth.The adjacent relationship between the cerebellar vermis and its adjacent structures was observed by the fetal brain MRI.On the median sagittal plane passing through the cerebellar vermis,the upper and lower diameters,anteroposterior diameters,area,BV angle and BT angle of the fetal cerebellar vermis were mapped manually.39 fetuses of middle and late pregnancy were diagnosed as abnormal twin by prenatal ultrasound and MRI at the same stage.And they were considered as the disease group.The posterior cranial fossa structure of the other remaining infants was observed with the same method.Every observation indexes was measured.The measured values of posterior cranial fossa were respectively compared and analyzed with measured values of the control group.Independent sample T test was used.Amniotic fluid increase,pregnancy-induced hypertension,gestational diabetes mellitus,increased fibrin degradation products and selective fetal growth restriction were adopted as the relevant clinical factors to conduct the regression analysis.Results:1.The measured values of different observation indexes(upper and lower diameter,anteroposterior diameter and area of vermis)of upper posterior cranial fossaon MRI median sagittal plane in thirty-nine normal twin fetuses were positively correlated with a period of pregnancy.2.At 25 to 30 weeks of pregnancy,the upper and lower diameters of vermis in the disease group were lower than those in the control group.And the difference between them gradually decreased with the increase of gestational weeks.There was a statistical significance(P<0.05).At 25 to 29 weeks of pregnancy,the vermis area in the disease group was lower than that in the control group.And the difference between them was statistically significant(P<0.05).At 26 to 29 weeks of pregnancy,the BV angle of the disease group was lower than that of the control group.And the difference between them was statistically significant(P<0.05).In the gestational weeks selected by the study,the difference of BT angle between the disease group and the control group had the significance of statistics(P > 0.05).3.Logistic regression analysis has showed that some factors,such as amniotic fluid increase,pregnancy-induced hypertension and gestational diabetes mellitus were connected with cerebellar vermis dysplasia in the case group.Conclusions:Fetal brain MRI is applied to get the median sagittal plane,which has crucial advantages in showing the morphology of cerebellar vermis,fourth ventricle and posterior fossa cistern and the adjacent relationship brainstem,cerebellar tentorium and cerebellar vermis.There is statistical significance about differences in vermis upper and lower diameter,anteroposterior diameter,area and BV angle of the control group and the disease group.Amniotic fluid increase,pregnancy-induced hypertension and gestational diabetes mellitus may have a influence on the cerebellum development of the rest of the twins with poor pregnancy.