9–12 September 2012, Copenhagen, Denmark Poster abstracts ultrasound showed the cystic structure to be a vascular anomaly 20 × 16 mm in size. The lesion demonstrated high blood flow and the presumed diagnosis was that of Vein of Galen aneurysm. No other intracranial anomalies were found (with special attention to possible altered brain structure, edema or ventriculomegaly). The only associated finding was slight cardiomegaly, but there were no apparent signs of cardiac overload (normal ventricular function, no A-V regurgitation, and no pericardial effusion). Dopplers were normal. A fetal MRI was performed to confirm the character of the lesion, as well as the otherwise normal brain structure. The findings were consulted with the department of neurosurgery and radiology to plan appropriate management, and the high-risk character of the lesion and uncertain prognosis were explained to the parents. The patient was followed weekly to assess the growth of the lesion, cardiac function, and possible signs of worsening. An elective cesarean section was performed eight weeks after the diagnosis, leading to the delivery of a male infant, 2770 g, showing no signs of cardiopulmonary compromise immediately after birth. The infant soon underwent endovascular embolization with an uncomplicated postoperative course. P17.12 Prenatal diagnosis of hydranencephaly V. Donadono 1 , G. Esposito 1 , R. Napolitano 2 , M. Di Cresce 1 , M. Volo 1 , R. Saviano 1 , A. Sirico 1 , A. Capone 1 , L. Mazzarelli 1 , M. Sansone 1 , P. Martinelli 1 1 High Risk Pregnancy-Department of Obstetrics and Gynecology, University of Naples Federico II, Naples, Italy; 2 Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford, United Kingdom Hydranencephaly is a fatal central nervous system disorder that often occurs without other associated malformations. It involves approximately 1 in 5000 pregnancies and almost always are sporadic cases. The neurological disorder is characterized by marked reduction of the total brain cortex which is replaced by cerebrospinal fluid within a relatively normal cranium. In this report we present the case of sonographic findings of a fetus with hydranencephaly followed by ultrasound from 13 weeks gestation. The patient was a primigravidae 25-year-old African pregnant woman, she was HIV- infected not in therapy with antiretrovirals. There were no known teratogenic exposures and risk factors reported. At 13 weeks of amenorrhea echography revealed a usual fetal development with a NT thickness of 1.4 mm and a normal cross-sectional view of the fetal brain, including the visualization of both choroid plexuses and a regular midline. Follow-up ultrasound examination was repeated directly at 25 weeks gestation, because the patient did not perform second-trimester ultrasound screening. It showed a cranial circumference two weeks smaller than gestational age; the brain was malformed with a large anechogenic area, revealing absence of the bilateral cerebral hemispheres which were replaced by fluid. Only the cerebellum and the thalamus were preserved. No craniofacial dysmorphism or deformities of the extremities were noted. The intracranial dysgenesis detected by ultrasonography and its evolution during the first-second trimester suggested the diagnosis of hydranencephaly. After counseling the parents opted for termination of pregnancy. According to our experience it is important a carefully monitoring of cerebral anatomy during all pregnancy considering the possibility of the evolution of the abnormalities. P17.13 Prenatal diagnosis of a cerebellar tumor: a case report D. V. Deva , G. Nicolae, A. Poteca, M. Comanescu Fetal Medicine, ALCO-SAN, Bucharest, Romania Fetal malignancies are rare complications during pregnancies. We present a case of prenataly diagnose cerebellar atypical teratoid tumor. A 26 years old primigravida was refered to our fetal medicine unit at 22 weeks of gestation for a rutin scan. Her history was unremarcable. There was no history of teratogen exposure, infections, miscarriages, mental retardation or other inherited conditions. Amniotic fluid was normal. Scanning the CNS, we found in the posterior fossa a solid tumor that replace the left cerebellar lobe and modifies the shape of right lobe which is moved laterally. The cerebral emispheres were asymmetrical, we found borderline ventriculomegaly and agenesis of the corpum callosum. The pacient choose to finish the pregnancy and the pathologically examination established the diagnosys: atypical teratoid tumor. Supporting information can be found in the online version of this abstract. P17.14 Postnatal ultrasound visualization of the optic chiasm C. Martinez-Payo Obstetricia y Ginecologia, Hospital Universitario Puerta de Hierro Majadahonda, Majadahonda, Spain Check the possibility to see the optic chiasm by 3D ultrasound postnatally. We captured a volume, with a 3D probe, of the CNS of a newborn through the major fontanelle. The ultrasound probe was put over the major fontanelle, widening the area of capture to the base of the skull. In a off-line mode, the volume was turned 180 degrees to place the chiasmatic region immediately below the line of sight and the area of interest was closed enough to display the optical chiasma neatly. Following the steps above, the optic chiasm was clearly visible. Is possible displaying postnatally the optic chiasm by 3D capture made through the major fontanelle. This can be useful in the diagnosis of diseases in which this organ may be affected, as in cases of septo optic dysplasia. Supporting information can be found in the online version of this abstract. P17.15 A case of Meckel-Gruber syndrome: the evolution of the sonographic features from 8 th to 13 th gestational weeks H. Bakry, Z. Leibovitz , S. Degani, I. Shapiro, G. Ohel Ob/Gyn, Bnai Zion Medical Center, Haifa, Israel Meckel-Gruber syndrome (MGS) is a rare and lethal autosomal recessive disorder with phenotypic variability. The classical triad is: polycystic kidneys, occipital encephalocele and postaxial polydactyly. Other manifestations may include: liver fibrosis, sloping forehead, bowing of long bones, Dandy-Walker malformation and Arnold-Chiari malformation. We report a case of MGS that was suspected at 8 week of gestation. The evolution of the sonographic features was followed until termination of pregnancy at 12.4 weeks. The patient was first examined at 8 week of gestation. She had history of 3 early spontaneous abortions and one pregnancy termination at 13 weeks because of fetal encephalocele. Her sister had a pregnancy with fetal Dandy-Walker malformation and her sister-in-law had pregnancy with fetal MGS. At 8 weeks of gestation the TVS revealed prominent fetal brain telencephalic and rhombencephalic vesicles. On 3D-MPR imaging we revealed a fluid filled protrusion in the posterior cephalic aspect. At 9 weeks these features were more prominent. The sonographic scan at 11 weeks demonstrated an occipital encephalocele containing brain tissue, a postaxial polydaclyly at one hand, echogenic kidneys. Thus, the diagnosis of MGS was made. At 12.4 weeks we clearly observed postaxial feet polydactyly, enlarged echogenic kidneys with tiny multiple cysts, and short and deformated tibial bones. The amniotic Ultrasound in Obstetrics & Gynecology 2012; 40 (Suppl. 1): 171–310 239