Prenatal Sonography in Hydranencephaly

ydranencephaly is a severe, sporadic brain abnormality characterized by absence of the cerebral hemispheres, which are replaced by a large supratentorial fluid-filled saclike structure surrounding the brain stem.1,2 This condition is thought to be the result of extensive brain necrosis secondary to a vascular insult involving the internal carotid arteries, which occurs after the brain and ventricles have been fully formed.1,2 Prenatal diagnosis of hydranencephaly is usually made in the second or third trimester of pregnancy, at which time the most striking sonographic findings include the detection of a brain cavity filled with anechoic fluid and preservation of the brain stem and posterior fossa structures.3 Because of the rarity of this disorder, almost all descriptions of the prenatal diagnosis of this condition are based on single case reports in fetuses presenting remote from the episode of cerebral stroke. In a few cases, serial scans illustrating the prenatal evolution are available,4–6 all demonstrating different sonographic features at presentation, including the identification of an admixture of dense Waldo Sepulveda, MD, Hernan Cortes-Yepes, MD, Amy E. Wong, MD, Victor Dezerega, MD, Edgardo Corral, MD, Gustavo Malinger, MD