title: The occipitum-dens line: the purpose of a new ultrasonographic landmark in the evaluation of the relationship between the foetal posterior fossa structures and foramen magnum.
abstract: OBJECTIVE
  The aims of this study were to describe a new ultrasonographic technique to assess the normal level of the cerebellum and the brainstem in the posterior fossa in normal foetuses and to compare in pathologic cases.
  
  
  METHODS
  We propose a new line cross between the dens cervical and the inferior portion of occipitum (occipitum-dens line-ODL). In a cross-sectional study, a single observer with experience in foetal neurosonography evaluated 54 foetuses (40 normal and 14 with open neural tube defect) between 20 and 28 weeks of gestation. The reference points for the ODL are principally the lower portion of the occipital bone (occipitum) and odontoid process of the second cervical vertebra (dens). The line was considered the level zero (near level of foramen magnum). Structures above it had a positive measurement and below it had a negative measurement.
  
  
  RESULTS
  Moreover, in most foetuses with open neural tube defect (93 %), the end portion of cerebellum was below the ODL associated with different degrees of ventriculomegaly.
  
  
  CONCLUSIONS
  The proposed innovation aims to bring to the ultrasound the most likely anatomical parameters of evaluation in normal foetuses and in foetuses with spinal dysraphism.
authors.affiliation: Fetal Neurology Division, Department of Obstetrics, Paulista School of Medicine-Federal University of São Paulo (EPM-UNIFESP), Rua Carlos Weber, 956, apto. 113 Visage, São Paulo, SP, Brazil.
authors.forename: Enoch Quinderé
authors.initials: EQ
authors.lastname: de Sá Barreto
authors.forename: Antonio Fernandes
authors.initials: AF
authors.lastname: Moron
authors.forename: Hérbene José Figuinha
authors.initials: HJ
authors.lastname: Milani
authors.forename: Wagner Jou
authors.initials: WJ
authors.lastname: Hisaba
authors.forename: Luciano Marcondes Machado
authors.initials: LM
authors.lastname: Nardozza
authors.forename: Edward
authors.initials: E
authors.lastname: Araujo Júnior
authors.forename: Sérgio
authors.initials: S
authors.lastname: Cavalheiro
mesh_terms: D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005539:Foramen Magnum / Q000000981:diagnostic imaging*; D006801:Humans; D009436:Neural Tube Defects / Q000000981:diagnostic imaging*; D016216:Ultrasonography, Prenatal