title: When is the vestibular aqueduct enlarged? A statistical analysis of the normative distribution of vestibular aqueduct size.
abstract: OBJECTIVE
  The size of vestibular aqueducts (VAs) seen on CT studies varies. The current practice of calling a VA enlarged when it exceeds a certain threshold (eg, 1.5 mm at the midpoint) is arbitrary. Our hypothesis was that statistical analysis of the range of VA widths in a normal-hearing population would lead to a mathematic definition of the upper-limit-of-normal VA width.
  
  
  METHODS
  The VA midpoint and opercular widths were measured in 73 children with normal hearing. Statistical analysis yielded values of the 99 th, 97.5th, 95th, 90th, 75th, and 50th percentiles for this normal distribution.
  
  
  RESULTS
  The upper-limit-of-normal (95th percentile) values for the VA midpoint and opercular widths were 0.9 and 1.9 mm, respectively. The VAs with greater widths may reasonably be considered enlarged.
  
  
  CONCLUSIONS
  The VAs with midpoint or opercular widths of 1.0 and 2.0 mm or greater, respectively, are enlarged.
authors.affiliation: Department of Otolaryngology, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, Ohio 45229-3039, USA.
authors.forename: S
authors.initials: S
authors.lastname: Vijayasekaran
authors.forename: M J
authors.initials: MJ
authors.lastname: Halsted
authors.forename: M
authors.initials: M
authors.lastname: Boston
authors.forename: J
authors.initials: J
authors.lastname: Meinzen-Derr
authors.forename: D M E
authors.initials: DM
authors.lastname: Bardo
authors.forename: J
authors.initials: J
authors.lastname: Greinwald
authors.forename: C
authors.initials: C
authors.lastname: Benton
mesh_terms: D000886:Anthropometry / Q000379:methods*; D002648:Child; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D008959:Models, Neurological; D015233:Models, Statistical; D016011:Normal Distribution; D009929:Organ Size / Q000502:physiology*; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014723:Vestibular Aqueduct / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*