title: Chiari type I malformations in adults: a morphometric analysis of the posterior cranial fossa.
abstract: OBJECTIVE
  Chiari type I malformation (CMI) is a congenital disorder characterized by caudal displacement of the cerebellar tonsils through the foramen magnum into the spinal canal. Recent studies suggest that overcrowding in the posterior cranial fossa (PCF) because of underdeveloped bony structures in the intrauterine life is the main cause of this malformation. For this reason, the authors want to contribute to the current literature, which focuses on bone abnormalities in the PCF in patients with CMIs.
  
  
  METHODS
  We examined a retrospective cohort of 60 adult patients with CMIs, and multiple measurements were made on magnetic resonance imaging. The results were compared to 30 healthy adult control subjects. Mann-Whitney U test was used as a statistical method.
  
  
  RESULTS
  All measurements except mean anteroposterior diameter of the foramen magnum were reduced in patients compared to control. An increase in the anteroposterior mid-sagittal distance of the foramen magnum in patients reached statistically significant difference compared to control. All patients had tonsillar herniation at least 5 mm below the plane of the foramen magnum. Chiari type I malformation in this study was associated with syringomyelia in 46 patients.
  
  
  CONCLUSIONS
  This study with a limited number of patients suggests that the bony components of the PCF are not developed fully, supporting the current concept that CMI is a disorder of the para-axial mesoderm.
authors.affiliation: Department of Neurosurgery, Cerrahpasa Medical Faculty, Istanbul University, Istanbul 34301, Turkey.
authors.forename: Sabri
authors.initials: S
authors.lastname: Aydin
authors.forename: Hakan
authors.initials: H
authors.lastname: Hanimoglu
authors.forename: Taner
authors.initials: T
authors.lastname: Tanriverdi
authors.forename: Ercument
authors.initials: E
authors.lastname: Yentur
authors.forename: Mehmet Yasar
authors.initials: MY
authors.lastname: Kaynar
mesh_terms: D000328:Adult; D000368:Aged; D001139:Arnold-Chiari Malformation / Q000209:etiology / Q000473:pathology*; D016022:Case-Control Studies; D002508:Cephalometry; D015331:Cohort Studies; D003388:Cranial Fossa, Posterior / Q000196:embryology / Q000473:pathology*; D005260:Female; D005539:Foramen Magnum / Q000196:embryology / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies