Clinical Research On Fetal Cerebellar Vermis With Volume Contrast Imaging Plus C Plane By Transabdominal Three-dimentional Ultrasonography

ObjectiveTo establish local normal data of fetal cerebellar vermis (CV) by evaluating therelationship between CV observation parameters and gestational weeks with volumecontrast imaging plus C plane technology by transabdominal three-dimensionalultrasonography (3DVCI-C). And to evaluate the value in the diagnosis and differentialdiagnosis of fetal cerebellar vermis anomalies between normal and abnormal groupaccording to our local normal data.MethodsA total of335normally developed fetuses at18-34gestational weeks were examinedprospectively in Prenatal Ultrasound Center of Suzhou Municipal Hospital from July2013to July2014. Two-Dimensional Ultrasonography (2D) was used to observe the fetalstructure, measure the fetal growth and development indexes, focus on the shape ofcerebellum and cerebellar vermis, and measure the width of posterior fossa. Themid-sagittal section of fetal head was obtained by3DVCI-C. The shape and detailedstructures (primary fissure, secondary fissure and sublobes) of CV were observed carefully.The shape of the fourth ventricle and the relations between CV and surrounding structures(brainstem, tentorium) were observed. The CV observation parameters including cranio-caudal diameter, anterior-posterior diameter, perimeter, surface area, brainstem vermisangle (BV) and brainstem tentorium angle (BT) were measured and their correlations withthe gestational weeks were analyzed.27cases were selected for the diagnosis of Dandy-Walker complex (DWC) after2D ultrasound examination at the same time. Thestructures and parameters of CV were observed and measured in them. The results werecompared to normal group. Those27cases got fetal magnetic resonance imaging (MRI)scan. Among them,15fetuses had the abortion,2cases had autopsy after the abortion.Results1. In normal fetuses, the shape of CV was well-stacked on midsagittal section,brainstem and vermis was almost parallel, the fastigial recess of fourth ventricle wasacuminate. The fastigial of the fourth ventricle could be observed after18gestationalweeks, the primary fissure could be observed after22gestational weeks, the primaryfissure and secondary fissure could be observed clearly after25gestational weeks, thesublobes and fissures could reveal clearer after29gestational weeks.2. In normal fetuses, cranio-caudal diameter, anterior-posterior diameter, perimeter,and surface area of CV were positively correlated with gestational weeks and increasedwith gestational weeks. Correlation coefficient (r) was0.915,0.87,0.932, and0.926respectively.3. In normal fetuses, the mean angle of BV was3.3±1.7°. The BV angles were notcorrelated with gestational weeks and Correlation coefficient (r) was0.1, P=0.07(P>0.05). The mean angle of BT was31.5±6.9°，and the correlation with gestational weekswas small (r=0.4).4. Twenty-seven cases of abnormal CV included4cases of Dandy-WalkerMalformation (DWM),7Dandy-Walker variant (DWV),6Blake’s pouch cyst (BPC), and10isolated mega cisterna megna (MCM). In the midsagittal section, DWM showed:primary fissure and secondary fissure of fetal CV displayed unclearly; the vermis area wassmaller significantly than that of normal control; the marked cystic dilated fourth ventriclewas communicated with enlarged posterior fossa; BV angle increased significantly(88.9±18.1°); the cerebellar tentorium was superior displaced; BT angle increasedremarkably (89.0±12.8°). DWV showed: The shape of CV was not well-stacked andinferior vermis became smaller and sharp-pointed; primary fissure and secondary fissure of fetal CV could not displayed clearly; the vermis area was smaller than5thpercentile of thatof normal controls; the fastigial recess of the fourth ventricle was shallow and flat; thedilated fouth ventricle was communicated with normal posterior fossa; the CV was upwardrotated. BV angle increased (23.7±5.2°) and BT angle increased slightly (54.5±12.0°). BPCshowed: the CV was well stacked; cranio-caudal diameter, anterior-posterior diameter,perimeter and surface area were in the normal group corresponding measurements range.The dilated fouth ventricle was communicated with posterior fossa; the CV was upwardrotated. BV angle increased slightly (16.7±1.8°), BT angle was increased mildly（50.3±8.2°）. Isolated MCM showed: the diameter of posterior fossa≥10mm, the shapeof CV is well-stacked; the fastigial recess of fourth ventricle was acuminate; the CVobservation parameters were in the normal group corresponding measurement range.Conclusion1.3DVCI-C technology can accurately show the shape, detailed structures of CV andthe surrounding relations, which can be applied to evaluating the development of fetal CV.2. In normal fetus, the cranio-caudal diameter, anterior-posterior diameter, perimeter,surface area of CV increases with gestational weeks. The mean angle of BV is3.3±1.7°,the mean angle of BT is31.5±6.9°.3. It is helpful to make diagnosis and differential diagnosis of fetal cerebellar vermismalformations with careful observation of fetal cerebellar vermis and the adjacent tissuemorphology, identification of CV detailed structures, measurements of cerebellar vermisarea, BV and BT angle on the midsagittal section of fetal cerebellar vermis.