title: Advances in the imaging of the embryonic brain.
abstract: OBJECTIVE
  Description of the development of the human embryonic brain visualized by transvaginal ultrasound. Methods. In two studies, healthy pregnant women without any pregnancy complications and normal outcomes were examined by transvaginal ultrasound in the early pregnancy between seven and twelve weeks of gestation. The hypoechogenic brain cavities were described and measured.
  
  
  RESULTS
  Initially, the rhombencephalic cavity was the largest brain cavity. It did not increase its size significantly during the first trimester. The mesencephalic cavity was rather large throughout the first trimester. The dimension of the future third ventricle decreased gradually. The hemispheres were the smallest cavities at the beginning of week seven. They grew fast and dominated the appearance of the embryonic brain from the week nine onwards.
  
  
  CONCLUSIONS
  Size and shape of the brain structures showed fast changes during the observation period. The ultrasound description of the brain development corresponded to that of classical embryology.
authors.affiliation: National Center for Fetal Medicine, Department of Obstetrics and Gynecology, University Hospital of Trondheim, Trondheim, N-7006, Norway.
authors.forename: H G
authors.initials: HG
authors.lastname: Blaas
authors.forename: S H
authors.initials: SH
authors.lastname: Eik-Nes
mesh_terms: D001921:Brain / Q000196:embryology*; D004453:Echoencephalography; D005260:Female; D005865:Gestational Age; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012016:Reference Values; D016216:Ultrasonography, Prenatal