title: Anomalous vertebral artery at the extraosseous and intraosseous regions of the craniovertebral junction: analysis by three-dimensional computed tomography angiography.
abstract: METHODS
  This study examined the extraosseous and intraosseous anomalies of vertebral arteries in patients who underwent surgery of the craniovertebral junction.
  
  
  OBJECTIVE
  To describe the usefulness of three-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery.
  
  
  BACKGROUND
  Previous studies using catheter angiograms have identified anomalous courses of the vertebral artery at the craniovertebral junction. Studies using computed tomography reconstruction also showed deviation of the vertebral artery groove at the C2 isthmus, demonstrating a risk of vertebral artery injury for C1-C2 transarticular screw placement. These analyses provided us with useful information for identifying anomalies of the vertebral artery, but they could not visualize the artery and its circumferential osseous tissue simultaneously, nor could they analyze the reciprocal anatomy of both tissues.
  
  
  METHODS
  Thirty-one consecutive patients who submitted to surgery at the craniovertebral junction were evaluated before surgery by three-dimensional computed tomography angiography. Eleven of the patients had congenital osseous anomalies at the craniovertebral junction including os odontoideum and ossiculum terminale. Anomalous vertebral arteries at the extraosseous region were visualized by three-dimensional reconstruction images, and the intraosseous deviation of the vertebral artery at the C2 isthmus was evaluated by multiplanar reconstruction images.
  
  
  RESULTS
  Extraosseous and/or intraosseous vertebral artery anomalies were detected in 9 cases. Eight of the 9 cases had osseous anomalies at the craniovertebral junction. Abnormal courses of the vertebral artery at the extraosseous region were detected in 4 cases: 2 had fenestration and 2 had persistent first intersegmental artery. Asymmetry of bilateral vertebral arteries was found in 5 cases: the right was dominant in 3 cases and the left in 2 cases. A high-riding vertebral artery at the C2 isthmus was detected in 5 cases. Based on these findings, we modified our surgical approach and the screw placement; consequently, no vertebral artery injury occurred.
  
  
  CONCLUSIONS
  In patients having osseous anomalies at the craniovertebral junction, the frequency of vertebral artery anomalies at the extraosseous and intraosseous regions is increased. With preoperative three-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and reduce the risk of intraoperative injury to the vertebral artery, in advance.
authors.affiliation: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, Chiba, Japan. masashiy@faculty.chiba-u.jp
authors.forename: Masashi
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Masao
authors.initials: M
authors.lastname: Koda
authors.forename: Masa-aki
authors.initials: MA
authors.lastname: Aramomi
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Masaki
authors.forename: Akihiko
authors.initials: A
authors.lastname: Okawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D001269:Atlanto-Occipital Joint / Q000002:abnormalities* / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007796:Laminectomy / Q000379:methods; D008297:Male; D008875:Middle Aged; D013123:Spinal Fusion / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014711:Vertebral Artery / Q000002:abnormalities* / Q000000981:diagnostic imaging