title: The formation of the foramen magnum and its role in developing ventriculomegaly and Chiari I malformation in children with craniosynostosis syndromes.
abstract: OBJECTIVE
  Craniosynostosis syndromes are characterized by prematurely fused skull sutures, however, less is known about skull base synchondroses. This study evaluates how foramen magnum (FM) size, and closure of its intra-occipital synchondroses (IOS) differ between patients with different craniosynostosis syndromes and control subjects; and whether this correlates to ventriculomegaly and/or Chiari malformation type I (CMI), intracranial disturbances often described in these patients.
  
  
  METHODS
  Surface area and anterior-posterior (A-P) diameter were measured in 175 3D-CT scans of 113 craniosynostosis patients, and in 53 controls (0-10 years old). Scans were aligned in a 3D multiplane-platform. The frontal and occipital horn ratio was used as an indicator of ventricular volume, and the occurrence of CMI was recorded. Synchondroses were studied in scans with a slice thickness ≤1.25 mm. A generalized linear mixed model and a repeated measures ordinal logistic regression model were used to study differences.
  
  
  RESULTS
  At birth, patients with craniosynostosis syndromes have a smaller FM than controls (p < 0.05). This is not related to the presence of CMI (p = 0.36). In Crouzon-Pfeiffer patients the anterior and posterior IOS fused prematurely (p < 0.01), and in Apert patients only the posterior IOS fused prematurely (p = 0.028).
  
  
  CONCLUSIONS
  The FM is smaller in patients with craniosynostosis syndromes than in controls, and is already smaller at birth. In addition to the timing of IOS closure, other factors may influence FM size.
authors.affiliation: Department of Plastic and Reconstructive Surgery, Dutch Craniofacial Center, Erasmus University Medical Center/Sophia Children's Hospital, Rotterdam, The Netherlands. Electronic address: b.rijken@erasmusmc.nl.
authors.forename: Bianca F M
authors.initials: BF
authors.lastname: Rijken
authors.affiliation: Department of Paediatric Radiology, Erasmus University Medical Center/Sophia Children's Hospital, Rotterdam, The Netherlands.
authors.forename: Maarten H
authors.initials: MH
authors.lastname: Lequin
authors.affiliation: Department of Paediatric Neurosurgery, Erasmus University Medical Center/Sophia Children's Hospital, Rotterdam, The Netherlands.
authors.forename: Marie-Lise C
authors.initials: ML
authors.lastname: Van Veelen
authors.affiliation: Department of Biostatistics, Erasmus University Medical Center, Rotterdam, The Netherlands.
authors.forename: Johan
authors.initials: J
authors.lastname: de Rooi
authors.affiliation: Department of Plastic and Reconstructive Surgery, Dutch Craniofacial Center, Erasmus University Medical Center/Sophia Children's Hospital, Rotterdam, The Netherlands.
authors.forename: Irene M J
authors.initials: IM
authors.lastname: Mathijssen
mesh_terms: D000168:Acrocephalosyndactylia / Q000150:complications; D001139:Arnold-Chiari Malformation / Q000150:complications* / Q000000981:diagnostic imaging; D001846:Bone Development / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003393:Cranial Sutures / Q000002:abnormalities; D003394:Craniofacial Dysostosis / Q000150:complications; D003398:Craniosynostoses / Q000150:complications* / Q000000981:diagnostic imaging; D004677:Encephalocele / Q000150:complications / Q000000981:diagnostic imaging; D005539:Foramen Magnum / Q000000981:diagnostic imaging / Q000254:growth & development*; D005625:Frontal Lobe / Q000000981:diagnostic imaging; D006801:Humans; D006849:Hydrocephalus / Q000150:complications* / Q000000981:diagnostic imaging; D021621:Imaging, Three-Dimensional / Q000379:methods; D007223:Infant; D007231:Infant, Newborn; D009777:Occipital Bone / Q000002:abnormalities; D009778:Occipital Lobe / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods
keywords: Chiari I malformation; Craniosynostosis syndromes; Foramen magnum; Ventriculomegaly