The Study Of Normal Fetal Lumbosacral Enlargment With Postmortem And Intrauterine MRI

Objective: To analyses the position of the end of the conus medullaris, left-right and anteroposterior diameter of lumbosacral enlargment and the changes of left-right and anteroposterior diameter of corresponding level spinal canal along with the gestational weeks with postmortem and intrauterine fetal MRI. Besides, we also need to discuss the differences and relations between the two kinds of images. By observing the development of lumbosacral enlargement and movement of spinal cord of different gestational age fetus, we can make corresponding growth curve and get reference values. According to the results, we can provide reliable and visualized imaging datas and pictures which can assess fetal development and help find congenital deformities of the spine and intraspinal lesions early.Methods:Postmortem MR imaging was performed on29fetuses ranging from17to39gestational weeks. Intrauterine MR imaging was performed on142fetuses randomly chosen from500normal fetuses ranging from20to38gestational weeks. T2-weighted MR imaging of the lumbar spine was performed in the coronal, sagittal and axial plane. The following parameters were measured:the position of the end of the conus medullaris, the position, area, left-right and anteroposterior diameter of lumbosacral enlargment,area of corresponding level spinal canal and the ratio of lumbosacral enlargment to the overall size of the vertebral canal.Results:①anteroposterior and left-right diameter and area of the lumbosacral enlargment increased linearly with gestational age (P<0.01).②the end of the conus medullaris continuously rise to L2～L3until midtrimester, but there’re obvious individual differences.③postmortem fetuses show that the end of the conus medullaris locate beneath L3between15th and21th week. From22th to30th week, it may locate between L1and L4. In the next ten weeks, it may locate between L1and L2. As a result, we can consider it abnormal low when the conus medullaris still stays beneath L2.④Intrauterine fetuses show that the conus medullaris has already reached L2level.⑤MR images of two kinds of samples are in accord with showing the development of spinal cord, but Postmortem MR imaging can provide clearer,more abundant and more correct messages.Conclusions:The study of normal fetal lumbosacral enlargment with postmortem and intrauterine MRI can provide correct reference values of the development of fetal spinal cord. According to this, we can describe its growth curve.Then we can provide reliable and visualized imaging datas and pictures which can assess fetal development and help diagnose diseases.