title: Evaluation of platybasia with MR imaging.
abstract: OBJECTIVE
  Platybasia, or abnormal obtuseness of the basal angle, was first measured on plain skull images. At present, evaluation of the brain and skull more commonly involves CT and MR imaging. We evaluated a new MR imaging method of evaluating platybasia.
  
  
  METHODS
  We retrospectively evaluated midline sagittal MR images in 200 adults and 50 children. The basal angle of the skull base was measured by using two methods: The standard MR imaging technique measured the angle formed by two lines-one joining the nasion and the center of the pituitary fossa connected by a line joining the anterior border of the foramen magnum and center of the pituitary fossa. The modified technique measured the angle formed by a line across the anterior cranial fossa and dorsum sellae connecting a line along the clivus.
  
  
  RESULTS
  With the standard MR imaging technique, we obtained mean angles of 129 degrees +/- 6 degrees for adults and 127 degrees +/- 5 degrees for children, compared with 135.3 degrees (composite mean) in previous series. The modified technique produced values of 117 degrees +/- 6 degrees for adults and 114 degrees +/- 5 degrees for children, which were significantly lower that those of standard MR imaging and traditional radiography (P <.05).
  
  
  CONCLUSIONS
  Both the standard and modified MR imaging techniques produced basal angles lower than those previously reported with standard radiography. The modified technique uses clearly featured landmarks that can be reproduced consistently on midline sagittal T1 images. This technique and its corresponding values can be used as the new standard for evaluating the basal angle.
authors.affiliation: Department of Radiologic Sciences, Drexel University College of Medicine, Philadelphia, PA 19102-1192, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Koenigsberg
authors.forename: Nakul
authors.initials: N
authors.lastname: Vakil
authors.forename: Tom A
authors.initials: TA
authors.lastname: Hong
authors.forename: Tun
authors.initials: T
authors.lastname: Htaik
authors.forename: Eric
authors.initials: E
authors.lastname: Faerber
authors.forename: Tina
authors.initials: T
authors.lastname: Maiorano
authors.forename: Monica
authors.initials: M
authors.lastname: Dua
authors.forename: Scott
authors.initials: S
authors.lastname: Faro
authors.forename: Carlos
authors.initials: C
authors.lastname: Gonzales
mesh_terms: D000328:Adult; D002508:Cephalometry / Q000379:methods; D002648:Child; D003388:Cranial Fossa, Posterior / Q000473:pathology; D005539:Foramen Magnum / Q000473:pathology; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D010985:Platybasia / Q000175:diagnosis*; D012189:Retrospective Studies; D012658:Sella Turcica / Q000473:pathology; D012680:Sensitivity and Specificity; D019291:Skull Base / Q000473:pathology