title: Analysis of anatomical variations of bone and vascular structures around the posterior atlantal arch using three-dimensional computed tomography angiography.
abstract: OBJECTIVE
  The current study evaluates the incidence of anatomical variations of the V(3) segment of the vertebral artery (VA) and the posterior arch of the atlas (C-1). Failure to appreciate these types of anatomical variations can cause catastrophic injury to the VA during posterior approaches to the upper cervical spine.
  
  
  METHODS
  In the present study, the authors analyzed the records of 1013 Korean patients who underwent computed tomography (CT) angiography to evaluate the incidence of anomalous variations in the third segment of the VA and to determine the incidence and morphometric characteristics of any detected posterior ponticuli. The authors also hoped to determine any specific imaging features that might indicate a VA anomaly around the craniovertebral junction.
  
  
  RESULTS
  The mean age of the patients was approximately 55.7 years and the prevalence of a posterior ponticulus was 15.6%. The incidence rate of a posterior ponticulus in the male population was 19.3%, whereas in the female population it was 12.8%. The incomplete type of posterior ponticulus was more common than the complete type. The mean age of the patients with an incomplete posterior ponticulus (55.7 years) was significantly younger (p = 0.018) than the mean age of patients with a complete posterior ponticulus (57.6 years). The incidence rate of a persistent first inter-segmental artery was 4.7% and the incidence rate of a fenestrated VA was 0.6%. The area of the C-1 transverse foramen on the abnormal side was significantly smaller than that of the contralateral normal side.
  
  
  CONCLUSIONS
  The shape of the C-1 posterior arch and the third segment of the VA are heterogeneous. Therefore, preoperative radiological studies should be performed to identify any anatomical variations. Using preoperative 3D CT angiography, we can precisely identify an anomalous VA and significantly reduce the risk of VA injury.
authors.affiliation: Department of Neurosurgery, Catholic University of Korea, St. Vincent's Hospital, Suwon, Republic of Korea. jatagi@paran.com
authors.forename: Jae Taek
authors.initials: JT
authors.lastname: Hong
authors.forename: Sang Won
authors.initials: SW
authors.lastname: Lee
authors.forename: Byung Chul
authors.initials: BC
authors.lastname: Son
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Sung
authors.forename: Seung Ho
authors.initials: SH
authors.lastname: Yang
authors.forename: Il Sub
authors.initials: IS
authors.lastname: Kim
authors.forename: Chun Kun
authors.initials: CK
authors.lastname: Park
mesh_terms: D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000293:injuries / Q000601:surgery; D001863:Bone Screws; D002533:Cerebral Angiography; D001270:Cervical Atlas / Q000033:anatomy & histology* / Q000098:blood supply* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D016268:Internal Fixators; D007796:Laminectomy / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013124:Spinal Injuries / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D014711:Vertebral Artery / Q000033:anatomy & histology*