title: Foramen magnum size and involvement of its intraoccipital synchondroses in Crouzon syndrome.
abstract: BACKGROUND
  Cranial sutures and synchondroses tend to close prematurely in patients with Crouzon syndrome. This influences their skull vault and skull base development and may involve in common disturbances such as increased intracranial pressure and cerebellar tonsillar herniation. The authors' hypothesis was that Crouzon patients patients have a smaller foramen magnum than controls because of premature fusion of the intraoccipital synchondroses, putting them at risk for cerebellar tonsillar herniation. Therefore, foramen magnum size and time of intraoccipital synchondroses closure were evaluated and were related to the presence and degree of cerebellar tonsillar herniation.
  
  
  METHODS
  The foramen magnum surface area and anteroposterior diameter were measured on three-dimensional computed tomographic scans of 27 Crouzon patients and 27 age-matched controls. Scans had a slice-thickness between 0.75 and 1.25 mm and were aligned in a three-dimensional reformatting platform. The t test was used to study size differences. Synchondroses were graded as described by Madeline and Elster and studied with ordinal logistic regression analysis.
  
  
  RESULTS
  Crouzon patients had a smaller foramen magnum surface area (602 mm versus 767 mm, p < 0.001) and anteroposterior diameter (31 mm versus 35 mm, p < 0.001) compared with controls. Differences stayed constant over time. Intraoccipital synchondroses closed 3 to 9 months earlier in Crouzon patients than in controls (p < 0.05).
  
  
  CONCLUSIONS
  Since intraoccipital synchondroses close earlier in Crouzon patients, from early life on their foramen magnum is smaller compared with controls. Within Crouzon patients, the presence of cerebellar tonsillar herniation could not be related to foramen magnum size.
  
  
  METHODS
  Risk, II.
authors.affiliation: Rotterdam, The Netherlands From the Departments of Plastic, Reconstructive and Hand Surgery, Paediatric Radiology, Biostatistics, and Paediatric Neurosurgery, Dutch Craniofacial Center, Erasmus Medical Center Sophia Children's Hospital.
authors.forename: Bianca F M
authors.initials: BFM
authors.lastname: Rijken
authors.forename: Maarten H
authors.initials: MH
authors.lastname: Lequin
authors.forename: Johan J
authors.initials: JJ
authors.lastname: de Rooi
authors.forename: Marie-Lise C
authors.initials: MC
authors.lastname: van Veelen
authors.forename: Irene M J
authors.initials: IMJ
authors.lastname: Mathijssen
mesh_terms: D002648:Child; D002675:Child, Preschool; D003393:Cranial Sutures / Q000000981:diagnostic imaging* / Q000254:growth & development; D003394:Craniofacial Dysostosis / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000601:surgery; D004677:Encephalocele / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000601:surgery; D005260:Female; D005539:Foramen Magnum / Q000000981:diagnostic imaging* / Q000254:growth & development; D006801:Humans; D021621:Imaging, Three-Dimensional; D007223:Infant; D007231:Infant, Newborn; D007427:Intracranial Pressure; D008297:Male; D012307:Risk Factors; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed