title: The petromastoid canal in the young child: appearance on computed tomography.
abstract: OBJECTIVE
  The adult petromastoid canal (PMC) is a thin anatomical structure, but in young children, it can be wide on high resolution CT (HRCT) scans. We performed this study to evaluate the year-by-year change in width and shape of the PMC in the young child.
  
  
  METHODS
  We retrospectively reviewed temporal bone HRCT scans, performed between 2007 and 2012. Eighty children were included (age range: 0.3-6.9 years; median age: 3.1 years; 56% male). All scans had a slice thickness of ≤ 1 mm.
  
  
  RESULTS
  The average width of the PMC was 1.95 mm in children < 2 years, compared to 0.83 mm in children ≥ 2 (p < 0.001). We categorized the PMC into 4 subtypes. A bulky (type III) PMC was predominant < 2 years. A thin curvilinear (type I) PMC was more prevalent in the older children. Type II and IV PMC were found infrequently. The PMC width correlated inversely with the degree of pericapsular ossification (p<0.001), and mastoid pneumatisation (p < 0.001).
  
  
  CONCLUSIONS
  A wide PMC (≥ 1 mm) is a common finding in children < 2 years. As children grow older, the PMC progressively narrows. This correlates to increased temporal bone pneumatisation and ossification of the otic capsule.
authors.affiliation: Department of Radiology, Antwerp University Hospital & University of Antwerp, Wilrijkstraat 10, 2650 Edegem, Antwerp, Belgium. christophkenis@hotmail.com
authors.forename: Christoph
authors.initials: C
authors.lastname: Kenis
authors.forename: Michael
authors.initials: M
authors.lastname: Ditchfield
authors.forename: Eldho
authors.initials: E
authors.lastname: Paul
authors.forename: Paul M
authors.initials: PM
authors.lastname: Parizel
authors.forename: Stephen
authors.initials: S
authors.lastname: Stuckey
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008416:Mastoid / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D013701:Temporal Bone / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*