title: An investigation into the relationship between the severity of obstructive sleep apnoea/hypopnoea syndrome and the vertical position of the hyoid bone.
abstract: OBJECTIVE
  This study aimed to identify a correlation of diagnostic clinical significance between the vertical position of the hyoid bone in relation to structures within the dentofacial skeleton and: (1) The severity of obstructive sleep apnoea hypopnoea syndrome, (OSAHS), (2) Decisions relating to the management of the condition.
  
  
  METHODS
  Randomised retrospective survey of cephalometric records of subjects having been diagnosed as suffering with OSAHS by in patient overnight polysomnographic testing at the Edinburgh Royal Infirmary Sleep Centre, 2001-2002.
  
  
  METHODS
  Pre-polysomnograph orthoposition lateral cephalograms of 94 subjects tested, during the period from April 1996 to September 1997, were randomly selected and traced following strict adherence to standard protocol. Edentulous arches (one or both) formed the only exclusion criterion owing to obvious effects upon vertical dimensions of the cervico-pharyngeal region. Measurement of the vertical position of the hyoid bone was made relative to a number of planes validated by numerous previous cephalometric investigations, and these were recorded along with the apnoea/hypopnoea index (AHI), and subsequent management (mandibular repositioning appliances (MRA) / continuous positive airway pressure (CPAP)). Correlations between measurements and AHI were investigated using Spearman's Correlation Coefficients, and analysis of the relationship between hyoid bone position and management groups was undertaken using Wilcoxon Ranked Sum Testing.
  
  
  RESULTS
  Statistically significant correlations were found between all linear measurements locating the hyoid bone in the vertical plane and subject AHI. The linear relationships were less reliable for subjects with AHI > 100, possibly due to a breakdown in the body's ability to respond posturally in order to maintain airway patency in more extreme cases. When the treatment groups (MRA/CPAP) were considered independently there was found to be a clear delineation between the two groups at a length of 120 mm between the sella (S- a point upon the anterior cranial base) and the hyoid (H). This, in turn, may suggest that cephalometric radiographs may be used as a reproduciable diagnostic tool.
authors.affiliation: Orthodontic Department, Victoria Hospital, Fife, UK.
authors.forename: J W
authors.initials: JW
authors.lastname: Young
authors.forename: J P
authors.initials: JP
authors.lastname: McDonald
mesh_terms: D002508:Cephalometry; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000033:anatomy & histology*; D008297:Male; D017286:Polysomnography; D011175:Positive-Pressure Respiration; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000175:diagnosis* / Q000628:therapy*; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000628:therapy; D016896:Treatment Outcome