title: Vertebral artery anomalies at the craniovertebral junction in the US population.
abstract: METHODS
  Retrospective review.
  
  
  OBJECTIVE
  To evaluate the prevalence of anatomical variations of the vertebral artery at the craniovertebral junction and the posterior arch of the atlas in the US population.
  
  
  BACKGROUND
  Recent studies from Asia have reported a 5% to 10% prevalence of a persistent first intersegmental vertebral artery and 1% to 2% prevalence of a fenestrated artery. These anomalous vertebral artery courses lie directly over the starting point for atlas lateral mass screw insertion. The relatively high reported prevalence of these anomalies suggests that routine preoperative computed tomographic angiogram be considered prior to upper cervical fixation. We have not observed this anomaly as commonly as reported.
  
  
  METHODS
  The authors analyzed the records of 975 patients from a level I trauma center and adjacent university hospital who underwent computed tomographic angiography to evaluate the incidence of anomalous variations in the third segment of the vertebral artery. These results were compared with similar studies performed in Korea and Japan.
  
  
  RESULTS
  The mean age of the patients was 52.9 years. The ethnic distribution of the patients was as follows: 69.3% of the patients were Caucasian, 11% Asian, 10.8% African American, and 6% Hispanic. The prevalence of a persistent intersegmental artery was 0.01% (1/975); a fenestrated vertebral artery was 0.01% (1/975); and origin of a posterior inferior cerebellar artery was 0.4% (4/975). The incidence of these anomalies was significantly lower than those previously published from Korea and Japan.
  
  
  CONCLUSIONS
  Vertebral artery course anomalies in the upper cervical spine were rare (0.42%) in our patient population. This finding contrasts with recent published reports from Asia, citing as high as a 10% rate of vertebral artery presence over the starting point for C1 lateral mass screw insertion. On the basis of the infrequent occurrence of this anomaly, we do not recommend routine computed tomographic angiography when planning upper cervical instrumentation.
  
  
  METHODS
  N/A
authors: *Department of Sports and Orthopaedic Surgery, University of Washington, Seattle; and †Department of Sports and Orthopaedic Surgery, University of Wisconsin, Madison.
authors: Courtney M
authors: CM
authors: OʼDonnell
authors: Zachary A
authors: ZA
authors: Child
authors: Quynh
authors: Q
authors: Nguyen
authors: Paul A
authors: PA
authors: Anderson
authors: Michael J
authors: MJ
authors: Lee
mesh_terms: D000792:Angiography; D001270:Cervical Atlas / Q000098:blood supply*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D012886:Skull / Q000098:blood supply*; D014057:Tomography, X-Ray Computed; D014481:United States / Q000453:epidemiology; D054079:Vascular Malformations / Q000453:epidemiology / Q000473:pathology*; D014711:Vertebral Artery / Q000002:abnormalities* / Q000000981:diagnostic imaging