Studies On The Development Of Fetal Cerebellar Vermis By Three-dimensional Sonography Extended Imaging

ObjectiveImaging of the posterior fossa has become an integral part of screening for fetal anomalies, and the sonographic evaluation of the cerebellum, vermis and cisterna magna has proven to be of value in the detection of several malformations. The key characteristic of these malformations is vermis agenesis,such as Dandy-Walker Complex and Joubert Syndrome. At present, there is no precise diagnostic criteria about fetal cerebellar vermis agenesis. Prenatal diagnosis of cerebellar vermis agenesis by conventional two-dimensional ultrasound are often inconsistent with the autopsy results. How to clear diagnosis cerebellar vermis agenesis has increasingly become a major concerns of clinical and ultrasound doctors. We observed the development of fetal cerebellar vermis by three-dimensional extended imaging technique (3DXI), and detect the following parameters, which represent key features of abnormalities of the vermis and posterior fossa: the size of cerebellar vermis;the angle between brain stem and vermis ;a ratio between anterior vermis and posterior vermis ,and their relationship with the gestational age were analyzed ,to provide important theoretical basis for prenatal screening fetal anomalies of cerebellar vermis .MethodsA total of 387 normally developed fetuses at 20-36 weeks' gestation and 12 fetus who were suspected agenesis of the vermis on axial plane imaging by two-dimensional ,were examined prospectively in the Shengjing Hospital of China Medical University from January 2007 to January 2008. Observing the development of fetal cerebellar vermis by three-dimensional extended imaging technique (3DXI). The width,anteroposterior diameter,craniocaudal diameter of the cerebellar vermis,the angle between brain stem and vermis ,a ratio between anterior vermis and posterior vermis were measured ,and their relationship with the gestational age were analyzed. And the normal range of vermis parameters which were measured, were established on different gestational age in the region. The 12 fetus suspected vermis agenesis were conducted a comprehensive evaluation with MRJ, chromosome examination and autopsy.ResultsThe reconstructed sagittal section by 3DXI technique of three-dimensional transabdominal sonography can evaluate the integrity of vermis shape and size, identify vermis characteristic signs: the fourth ventricle apex and vermis crack. The width , anteroposterior diameter, craniocaudal diameter of the cerebellar vermis are positively correlated with gestational age.Normal fetal, brain stem and vermis almost parallel, the mean of the angle between them is 3.97°, and a standard deviation is 1.65°,r=0.085,P=0.269>0.05,the angle greater than 7.3°defined as rotation. Vermis area of the anterior vermis is smaller than posterior vermis,with a ratio of 0.70, and a standard deviation is 0.12. r=0.013,P=0.887>0.05.The anterior vermis is greater than posterior vermis defined as agenesis of the posterior vermis .The vermis size within normal limits for gestational age with posterosuperior rotation in 3 cases; agenesis of the vermis were found in 5 cases; enlarged cisterna magna were found in 4 cases.Conclusion1. The 3DXI technology and three-dimensional reconstructed sagittal section will help determine the development of the cerebellar vermis, can accurately show cerebellar vermis and the surrounding relations, provide a new way of thinking for the evaluation of fetal development cerebellar vermis.2. The width , anteroposterior diameter, craniocaudal diameter of the cerebellar vermis are positively correlated with gestational age. No significant change in the angle between brain stem and vermis and the ratio of the anterior vermis and posterior vermis.The normal range of vermis parameters were established on different gestational age in the region. The parameters provide important theoretical basis for prenatal screening fetal anomalies of cerebellar vermis .3. Application of three-dimensional prenatal ultrasound can detect and quantify the vermis malformations characteristic:the angle between brain stem and vermis greater than 7.3°defined as rotation;the value of vermis diameter measurement less than the normal range of vermis parameters corresponding gestational age defined agenesis vermis ; the anterior vermis is greater than posterior vermis defined as agenesis of the posterior vermis ,provides a simple and effective method of ultrasonic examination for the prenatal diagnosis of fetal cerebellar vermis agenesis.