22nd World Congress on Ultrasound in Obstetrics and Gynecology Short oral presentation abstracts

magna were assessed. The diagnostic value and image quality wasevaluated. In all cases brain anatomy was verified by postnatalneurosonography, fetal/postnatal MRI or by autopsy.Results: Abnormal appearance of the posterior fossa was consistentwith complete absence of the cerebellar vermis (Dandy-Walkermalformation) in 8 fetuses, vermian hypoplasia in 3 fetuses andBlake’s pouch cyst (BPC) in 5 fetuses. Axial transcerebellar viewin all fetuses with posterior brain anomalies at 11+0–13+6 weeks’showed non-specific enlargement of the posterior fossa. Mid-sagittalview in fetuses with Dandy-Walker malformation demonstratedthe absence of border between 4th ventricle and cisterna magna.In contrast in fetuses with BPC normal size of cisterna magna,enlargement of the 4th ventricle with an intact border between thesetwo structures was noted in mid-sagittal view.Conclusions: Assessment of the fetal posterior fossa is possible in1st trimester of pregnancy by 3-D sonography. A mid-sagittal viewretrieved from 3D volume data set of the fetal head demonstratesa good display of the diagnostic landmarks of fetal posterior fossawith appropriate quality of images. By standardizing the approachto image acquisition and display 3D-sonography may potentiallyimprove our understanding of normal fetal brain developmentand help to increase the detection rate of fetal posterior brainabnormalities in early pregnancy.

OP14.06Comparing 4D Ultrasound with magnetic resonance inposterior fosa anomalies

N. Lenis Cordoba1,2, J. Bello-Munoz1,2, P. Oliveros1,2,E. Vazquez Mendez1,2, E. Carreras1,2, L. Cabero1,2

1Medicina Materno Fetal, Hospital Universitario Valld’Hebron, Barcelona, Spain; 2Facultad de Medicina,Universidad Autonoma de Barcelona, Barcelona, Spain

Objectives: To calculate based on a mathematically modelleddecision tree, the effectiveness of the RM and the 4D Ultrasound(4DUS) as an intervention for improving fetal medicine specialist’sdecisions in posterior fosa anomalies.Methods: All cases of fCNS were prospectively followed up untileither, termination of pregnany (TOP) or postnatal follow up (PF).All of them underwent dedicated ultrasonographic (US) assessmentand MR, at least once during prenatal evaluation. Neurologicalpostnatal outcome and anatomo-pathology records were registeredas gold standards. Positive and negative likelihood ratios (LR) werecalculated for specific findings. Altered posterior fosa (megacisternamagna, cerebellar anomalies, 4th ventricle enlargement andstructural misalignment were considered). Sensitivity, false positiverate, positive and negative likelihood ratios and McNemar test werecalculated.Results: 106 cases of fCNS anomalies were detected during thestudy period, 27 (25%) of them were posterior fosa anomalies. RMshowed a high diagnostic accuracy, with a 97% of sensitivity, buta 66% of specificity, which renders a LR of 2.86. 4DUS instead,showed a sensitivity of 98% and a 74% of specificity, leading toa LR of 4.75. McNemar test showed no significant difference inaccuracy. The decision tree slightly trended towards 4D US, mainlybecause of poor rendering of MR at early gestational ages.Conclusions: Albeit these techniques should be considered assupplementary tests, effectiveness decision tree slightly suggestsusing 4DUS; particularly in countries with legal issues regarding thegestational age for a definitive decision on pregnancy interruption.

OP14.07Assessment of fetal cerebellar vermis development andmalformations with transabdominal three-dimensionalultrasonography

G. Lv, J. Liu, J. Xie, Z. Wang

Department of Ultrasound, The Second Affiliated Hospital ofFujian Medical University, Quanzhou, China

Objectives: To obtain structural details and quantitative biometricdata of the fetal cerebellar vermis (CV) on the mid-sagittal plane byusing transabdominal three-dimensional ultrasonography (3D US)and evaluate the value of it in CV development and malformationsdifferentiation.Methods: The mid-sagittal view of 3D US was performed in 438normal fetuses and 28 fetuses with CV malformations at a gestionalage (GA) between 16 and 41 weeks. Structural details of the CV(lobules, fissures and the fourth ventricle) and biometric sizes(antero-posterior length; cranio-caudal length; circumference andsurface area) of all fetuses were measured, the correlation betweenthese data and GA was analyzed and the stage-specific norms wereestablished.Results: In normal fetuses, the fissures between the lobules werehyper-echoic and intra-lobule areas hypo-echoic. The CV contoursand the fastigial recess of the fourth ventricle were visible aroundpregnancy week 19. The main lobules and fissures were apparentaround pregnancy week 22, and all nine lobules, fissures and thefourth ventricle were clearly displayed until pregnancy week 28.CV biometric sizes grew in a linear fashion along with pregnancyweeks. In fetuses with CV malformations, CV structures were notrecognizable and boundaries of lobules were blurred in the Dandy-Walker malformation (DWM) group. Arborization of the lobuleswas reduced completely and the fastigial recess of the fourth ventriclewas relatively flat in the Dandy-Walker variant (DWV) group. Thevermis area of DWM and DWV were smaller significantly thanhealthy controls and isolated CM (P all < 0.05), and there were nodifference of CV area between isolated CM and healthy controls(P = 0.743).Conclusions: Structural details obtained by 3D US were clinicallyuseful in prenatal diagnosis for quantitative evaluation of the CVdevelopment and CV malformations, especially differentiation ofDWM from DWV.

OP14.08Prenatal diagnosis of Dandy-Walker malformation andBlake’s pouch cyst at 15–18 weeks

E. Contro1, F. De Musso1, G. Campobasso2,G. Rembouskos2, N. Rizzo1, P. Volpe2, G. Pilu1

1Fetal Medicine Unit, Dept Obstetrics and Gynaecology, St.Orsola Malpighi Hospital, Bologna, Italy; 2Fetal MedicineUnit, Di Venere and Sarcone Hospital, Bari, Italy

Objectives: To evaluate the role of the brainstem-vermis angle (BVangle) at 15–18 weeks in the early diagnosis of fetal posterior fossaabnormalities.Methods: A prospective multicenter observational study. Three-dimensional ultrasound volumes of the head were acquired in normalfetuses and in fetuses with Blake’s pouch cyst (BPC) and DandyWalker malformation (DWM) at 15–18 weeks. Three experiencedoperators measured the BV angle in the sagittal plane as previouslydescribed 1 (figure 1).Results: Between November 2009 and March 2011, 150 volumeswere acquired at 16 wks mean gestational age. Due to low-qualityimages, 49 cases were excluded, leading to a study population of101 cases. Of these, 6 were diagnosed with DWM and 2 with BPCin later gestation, the remaining were normal. Postnatal follow-upconfirmed the diagnosis in all cases. In all fetuses with posteriorfossa anomalies, the BV angle was significantly increased comparedto controls (57.3 ± 23.0◦ vs. 9.4 ± 7.7◦, U-Mann Whitney testP < 0.000005). In particular, all fetuses with DWM demonstrateda BV angle ≥ 45◦, whereas in the cases with BPC this was < 30◦(respectively 67.9 ± 13.9◦ vs. 25.2 ± 2.4◦, U-Mann Whitney testP < 0.05).Conclusions: Thus far, the diagnosis of cystic posterior fossaanomalies has been considered difficult or impossible prior to20 wks owing to the late development of the cerebellar vermis. Ourexperience suggest that measurement of the BV angle allows preciseidentification of this conditions at 15–18 wks. 1. The BV and BT

98 Ultrasound in Obstetrics & Gynecology 2012; 40 (Suppl. 1): 55–170