title: Normal variation of vertebral artery on CT angiography and its implications for diagnosis of acquired pathology.
abstract: OBJECTIVE
  CT angiography (CTA) is rapidly becoming a popular tool for the evaluation of cerebrovascular diseases. Noninvasive diagnosis of vertebral artery pathology using CTA relies in part on diminished vertebral artery size or eccentric position relative to the transverse foramen. However, normal variation of the vertebral artery on CT has not been systematically described.
  
  
  METHODS
  Patients younger than 40 years who underwent CTA for reasons other than evaluation of vertebral artery disease were studied. Area measurements of the vertebral artery and the transverse foramen were performed by three radiologists. Variance component analysis was performed.
  
  
  RESULTS
  There is marked variation in the size of the vertebral artery relative to the transverse foramen, with the vertebral artery occupying 8-85% of the foramen. In many patients, marked asymmetry in relative vertebral artery size and position was observed. This asymmetry would often vary markedly from level to level within the same patient.
  
  
  CONCLUSIONS
  Vertebral artery size and position in the transverse foramina vary markedly in normal young subjects. These normal variations must be considered when evaluating vertebral artery pathology on CT angiograms.
authors.affiliation: Department of Radiology, Massachusetts General Hospital, Boston, USA. sanellip@hotmail.com
authors.forename: Pina C
authors.initials: PC
authors.lastname: Sanelli
authors.forename: Samuel
authors.initials: S
authors.lastname: Tong
authors.forename: R Gilberto
authors.initials: RG
authors.lastname: Gonzalez
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Eskey
mesh_terms: D000328:Adult; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D015588:Observer Variation; D012016:Reference Values; D014057:Tomography, X-Ray Computed; D014711:Vertebral Artery / Q000000981:diagnostic imaging*; D020217:Vertebral Artery Dissection / Q000000981:diagnostic imaging; D014715:Vertebrobasilar Insufficiency / Q000000981:diagnostic imaging