title: Linear fractures occult on skull radiographs: a pitfall at radiological screening for mild head injury.
abstract: BACKGROUND
  Skull radiography is widely used to screen for fractures in patients with mild head injury. However, the clear depiction of a fracture requires a gap in the skull separated by the fracture that is wide enough to allow the passage of x-rays. We studied atypical linear fractures that were not visualized clearly, because a specific anatomical configuration hampered the passage of x-rays.
  
  
  METHODS
  We retrospectively evaluated 278 patients with mild head injuries who had undergone routine skull radiography (anteroposterior and lateral views) and head computed tomography (CT). We found that some patients negative for linear fracture on skull radiographs were positive on bone window CT scans.
  
  
  RESULTS
  Of the 278 patients aged between 2 months and 66 years, 8 (2.9%) manifested a linear fracture on CT scans that presented as a cross section of the fracture oblique to the direction of the x-rays. Four of the 8 developed acute epidural hematoma; 2 of these patients underwent craniotomy.
  
  
  CONCLUSIONS
  Radiographic study returned false-negative results, because x-rays were absorbed by the double-layered skull along fractures whose cross section was oblique to the direction of the x-rays. The evaluation of head injury by radiography only may miss these fractures and their undetected presence may result in sequelae such as intracranial hematoma.
authors.affiliation: Department of Neurosurgery, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan. nakahara19@hotmail.com
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Nakahara
authors.forename: Satoru
authors.initials: S
authors.lastname: Shimizu
authors.forename: Satoshi
authors.initials: S
authors.lastname: Utsuki
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Oka
authors.forename: Takao
authors.initials: T
authors.lastname: Kitahara
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kan
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Fujii
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging*; D003951:Diagnostic Errors / Q000517:prevention & control; D005260:Female; D005596:Fractures, Closed / Q000000981:diagnostic imaging*; D005624:Frontal Bone / Q000000981:diagnostic imaging / Q000293:injuries; D015600:Glasgow Coma Scale; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000000981:diagnostic imaging / Q000293:injuries; D010294:Parietal Bone / Q000000981:diagnostic imaging / Q000293:injuries; D012189:Retrospective Studies; D012886:Skull / Q000000981:diagnostic imaging; D012887:Skull Fractures / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed; D055815:Young Adult