title: Traumatic Atlanto-occipital Dislocation (AOD).
abstract: OBJECTIVE
  Traumatic atlanto-occipital dislocation (AOD) results from high energy trauma and is an uncommon and usually fatal injury due to an injury to the cervicomedullary junction. Recently, improved prehospital management, early diagnosis and effective treatment led to increasing reports of survival. This study of patients with AOD initial imaging modalities recognizes the clinical features and diagnostic considerations for a quick diagnosis.
  
  
  METHODS
  In this article, five survived adult patients with traumatic AOD are presented and retrospectively reviewed. Diagnosis was made by lateral cervical spine x-ray, cervical computed tomography (CT), or magnetic resonance imaging(MRI). Treatment consisted of early immobilization, respiratory support, and subsequent occipitocervical fusion.
  
  
  RESULTS
  Four patients were male and the other one was female. Three were diagnosed early and the others were delayed in confirmations. One was type I AOD and four were type II AOD. All patients were applied occipitocervical fusion. Two cases were worse; neurological states and the other three that showed no change. Lateral X-ray film of all patients in the prevertebral soft tissue swelling at the C2 level was noted. The mean thickness of prevertebral soft tissue C2 level was 17.88 mm(15.18 to 20.17mm). Two were in the normal range of dens-basion index(DBI), three showed abnormalities, and Power's ratio was abnormal in 3 patients.
  
  
  CONCLUSIONS
  As for damages caused by a strong external force in patients with severe prevertebral soft tissue swelling at C2 level abnormaly, the doctor determines whether more should be carefully AOD and considers 3D CT or MRI to confirm AOD in these patients.
authors.affiliation: Department of Neurosurgery, Gachon University Gil Hospital, Incheon, Korea.
authors.forename: Yeon-Joon
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, Gachon University Gil Hospital, Incheon, Korea.
authors.forename: Chan-Jong
authors.initials: CJ
authors.lastname: Yoo
authors.affiliation: Department of Neurosurgery, Gachon University Gil Hospital, Incheon, Korea.
authors.forename: Chan-Woo
authors.initials: CW
authors.lastname: Park
authors.affiliation: Department of Neurosurgery, Gachon University Gil Hospital, Incheon, Korea.
authors.forename: Sang-Gu
authors.initials: SG
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Gachon University Gil Hospital, Incheon, Korea.
authors.forename: Seong
authors.initials: S
authors.lastname: Son
authors.affiliation: Department of Neurosurgery, Gachon University Gil Hospital, Incheon, Korea.
authors.forename: Woo-Kyung
authors.initials: WK
authors.lastname: Kim
keywords: Atlanto-occipital dislocation; Atlanto-occipital joint; Craniovertebral junction; Occipital condyle; Occipito-cervical fixation