Galen vein aneurism (GVA) corresponds to a vascular dilation of the sinus venous in central nervous system (CNS). GVA is a rare category of congenital anomalies with a high mortality in neonatal and pediatric life. Regular diagnostic methods consist of 2D ultrasound and transvaginal neurosonogram when possible. Arteriovenous malformation are a heterogeneous group of dilated deep vein anomalies of Galen system with abnormal communications of the mid line. It is presented in 1 : 250000 deliveries. Main complications include heart failure in the neonatal period, hydrocephalus, brain calcifications, encephalomalacia, cerebral atrophy, bleeding and neurological progressive compromise. We describe a case of GVA diagnosed at 38 wo. Fetal evaluation was performed using Accuvix V10 ultrasonographic equipment (Medison. Seoul-Korea). Cerebral images were obtained using Virtual Organ Computer-aided AnaLysis (VOCAL™, 3DXI, Medison Sonoview Pro, Seoul, Korea) with 30 degrees swept. The obtained volumes were analyzed in the post-processor software 3DXI viewer and clinically correlated. It is a 19 yo, gravida 1, Para 0. She was evaluated in regular sonogram. The CNS evaluation reveled hypoecogenic mass in the mid brain, between the brain peduncles, behind the talami and under the corpus callosum. Transvaginal neurosonogram was performed with same findings, power angio Doppler revealed a vascular composition of the image with venous flow pattern at Pulsed Doppler Evaluation. A GVA was suspected. Patient underwent Cesarean section for obstetrical reasons and a 3410 grams female infant was delivery with APGAR 8 and 9. No hemodynamic decompensation was observed. MRI and CT scan confirmed diagnosis. Baby was discharged 3 days later. Although GVA is an uncommon life threatening condition, arteriovenous malformations are the most frequent vascular congenital anomalies in central nervous system. 3D ultrasound and post process software allow improving the accuracy of the 2D ultrasound when making central nervous system evaluation.