title: Occipitoatlantal and occipitoaxial hypermobility in Down syndrome.
abstract: METHODS
  In this study, the authors evaluated upper cervical spine in 75 children and adolescents with Down syndrome on the basis of lateral flexion-extension radiographs.
  
  
  OBJECTIVE
  To assess occipitoatlantal motion and occipitoaxial motion in children and adolescents with Down syndrome compared with age-matched control subjects.
  
  
  BACKGROUND
  Although previous studies have described a high prevalence of occipitoatlantal hypermobility in Down syndrome, there have been no comparisons with age-matched control subjects. Only a few reports have mentioned the physiologic relation between the occiput and axis other than basilar impression. Moreover, there have been no reports examining anteroposterior mobility in abnormal conditions.
  
  
  METHODS
  Seventy-five children and adolescents with Down syndrome and 30 age-matched control subjects were examined. Lateral radiographs of the upper cervical spine in flexion and extension were taken, and anteroposterior translation of the occiput in relation to the atlas and axis was measured.
  
  
  RESULTS
  Anteroposterior occipitoatlantal hypermobility was found to be present in children and adolescents with Down syndrome even when compared with age-matched control subjects. Occipitoaxial hypermobility was observed only when atlantoaxial instability was present.
  
  
  CONCLUSIONS
  In evaluating the upper cervical spine in Down syndrome, it is necessary to pay attention to the relation between the occiput, atlas, and axis.
authors.affiliation: Department of Orthopaedic Surgery, Hyogo Nojigiku Hospital for Disabled Children, Kobe, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Uno
authors.forename: O
authors.initials: O
authors.lastname: Kataoka
authors.forename: R
authors.initials: R
authors.lastname: Shiba
mesh_terms: D000293:Adolescent; D000328:Adult; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001269:Atlanto-Occipital Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology