title: Fetal rhombencephalon: normal US findings.
abstract: Using ultrasound (US), the authors examined 25 embryos that were 8-10 menstrual weeks old for gestational age and the presence of a small cystic structure (3-4 mm) in the posterior aspect of the cranium. This structure was seen in all embryos. The US images of an in vitro embryo at 8 weeks menstrual age were also evaluated for anatomic correlation. Analysis of these US images determined that the cystic structure was the open rhombencephalon or hindbrain. Follow-up US studies or postpartum clinical examinations of the 25 in utero embryos demonstrated no abnormal posterior cranial cystic structures or neurologic deficits. This first-trimester structure should be considered a normal finding, since it develops into the normally proportioned fourth ventricle after the 11th menstrual week.
authors.affiliation: Department of Radiology, University of Washington, Seattle 98195.
authors.forename: D R
authors.initials: DR
authors.lastname: Cyr
authors.forename: L A
authors.initials: LA
authors.lastname: Mack
authors.forename: D A
authors.initials: DA
authors.lastname: Nyberg
authors.forename: T H
authors.initials: TH
authors.lastname: Shepard
authors.forename: W P
authors.initials: WP
authors.lastname: Shuman
mesh_terms: D005260:Female; D005333:Fetus / Q000033:anatomy & histology*; D006801:Humans; D011247:Pregnancy; D012249:Rhombencephalon / Q000033:anatomy & histology*; D014463:Ultrasonography