title: Fenestration of vertebral artery at the craniovertebral junction in Down syndrome: a case report.
abstract: METHODS
  Case report of a Down syndrome patient with right vertebral artery fenestration and abnormalities of the craniovertebral junction.
  
  
  OBJECTIVE
  Describe the utility of 3-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery.
  
  
  BACKGROUND
  Previous reviews evaluating catheter angiograms identified various anomalies of vertebral artery at the craniovertebral junction. The frequency of vertebral artery anomalies is increased in patients having osseous anomalies at the craniovertebral junction. Down syndrome is associated with a high incidence of bone abnormalities at the craniovertebral junction, but there have been no published reports of vertebral artery anomalies per se at the craniovertebral junction.
  
  
  METHODS
  A 16-year-old woman with trisomy 21 presented with gait abnormalities and myelopathy in association with bone abnormalities at the craniovertebral junction, including hypoplastic odontoid and ossiculum terminale. Computed tomography angiography showed that right vertebral artery bifurcated after exiting the C2 transverse foramen with one branch passing through the C1 transverse foramen, whereas the other turned posteromedially and entered the spinal canal between C1 and C2.
  
  
  RESULTS
  Occipito-C2 posterior fusion was performed with a rod and screw system. Intraoperatively, the course of the anomalous right vertebral artery was identified by Doppler angiography, and the surgical approach was modified to allow safe pedicle screw insertion while avoiding vertebral artery injury. After surgery, myelopathy resolved within 3 months.
  
  
  CONCLUSIONS
  Before corrective surgery of craniovertebral junction anomalies in patients with Down syndrome, the possibility of vertebral artery anomalies associated with abnormal craniovertebral junction anatomy should be considered. With preoperative 3-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and modify the surgical approach to reduce the possible risk of intraoperative vertebral artery injury in advance.
authors.affiliation: Department of Orthopaedic Surgery, Chiba University Graduate School of Medicine, Chuo-ku, Chiba, Japan. masashiy@ho.chiba-u.ac.jp
authors.forename: Masashi
authors.initials: M
authors.lastname: Yamazaki
authors.forename: Akihiko
authors.initials: A
authors.lastname: Okawa
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: Masao
authors.initials: M
authors.lastname: Koda
mesh_terms: D000293:Adolescent; D001269:Atlanto-Occipital Joint / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000601:surgery*; D001863:Bone Screws; D004314:Down Syndrome / Q000150:complications / Q000601:surgery*; D005260:Female; D020234:Gait Ataxia / Q000209:etiology / Q000601:surgery; D006801:Humans; D016268:Internal Fixators; D007796:Laminectomy; D013117:Spinal Cord Compression / Q000209:etiology / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods; D014057:Tomography, X-Ray Computed; D014711:Vertebral Artery / Q000002:abnormalities / Q000601:surgery*