We report on a neonatal patient case with a cerebral vascular dilation consistent with a vein of Galen malformation diagnosed on an antenatal doppler ultrasound examination. Antenatal diagnosis was confirmed by fetal MRI scan. After delivery, cerebral MRI scan found the same dilatation and showed no cerebral parenchymal damage. The infant's condition was stable and particularly there was no congestive cardiac failure. Before discharge at ten days of age, clinical examination and particularly cardiac examination was normal. At 14 days of age, symptoms in relation to a congestive cardiac failure appeared. Echocardiography showed a high output cardiac failure with no cardiac malformation. Infectious laboratory tests were normal. Evolution was initially favourable after digitalo-diuretic treatment. Unfortunately, death occurred at 36 days of age due to intractable cardiac failure. This case highlights that, unusually, heart failure can occur long after the first days of life in cases of Galen vein aneurysmal malformation. The optimal time for vascular embolization in neonatal cases of Galen vein aneurysmal malformation is discussed.