ABSTRACT
Objective To evaluate the development of fetal cerebellar vermis using 3D transabdominal ultrasound,and provide evidence for prenatal screening fetal cerebellar vermis anomalies.Methods Totally 387 normal fetuses at 20～36 gestation weeks were examined by three-dimensional extended imaging(3DXI) to observe the fetal cerebellar vermis.The width,anteroposterior diameter,craniocaudal diameter of the cerebellar vermis,the angle between brain stem and vermis,a ratio between the area of anterior vermis and posterior vermis were measured,and the relationship between the gestational age and parameters mentioned above were analyzed.Results The multi slice view of 3DXI and 3D reconstructed sagittal section well evaluated the integrity of vermis morphous and vermis size,identified characteristic signs of vermis:the fourth ventricle apex and vermis crack.In normal fetus,brain stem and vermis were almost parallel,the angle between them was 3.97°±1.65°.There was no significant correlation between the angle and the gestational age.The area of the anterior vermis was smaller than that of posterior vermis,with a ratio of 0.76±0.06,which was also not related to gestational age.The width,anteroposte rior diameter and craniocaudal diameter of the cerebellar vermis were positively correlated with gestational age.Conclusions The multi slice view of 3DXI and 3D reconstructed sagittal section should help evaluate the development of the cerebellar vermis,accurately show the cerebellar vermis and its surrounding strutures,and provide a new way to evaluate the fetal cerebellar vermis.