title: First stage in predicative measure for transnasal transsphenoidal approach to petrous apex cholesterol granuloma.
abstract: OBJECTIVE
  This study evaluates the feasibility of the transsphenoidal approach to petrous apex cholesterol granuloma based on the petrous angle. This is the angle centered at the vomer, extending between the medial aspect of the C3 segment of the internal carotid artery and the occipital protuberance. The aim of this study is to determine the average petrous angle in a population of normal computed tomography scans.
  
  
  METHODS
  Retrospective review at the University of Cincinnati Medical Center.
  
  
  METHODS
  Two of the authors independently reviewed 400 consecutive normal temporal bone computed tomography scans obtained between September and December of 2009. All scans had slice thickness of 1.25 mm at 0.6-mm intervals. Axial images parallel to the orbitomeatal plane were analyzed, and the petrous angle was measured bilaterally. Interrater reliability was tested on 50 of the computed tomography scans.
  
  
  RESULTS
  A total of 400 temporal bones were reviewed. The mean and median petrous angle was 17.7 and 16.5 degrees, respectively. Eleven (2.8%) had an angle ≤ 10.0, 331 (82.8%) between 10.1 to 20.0, and 58 (14.5%) ≥ 20.1. The interrater variability was highly correlated (r = 0.912, P < .005).
  
  
  CONCLUSIONS
  Normative data on consistent petrous apex radiographic landmarks are important for assessing the feasibility of the transphenoidal approach to the petrous apex for cholesterol granuloma drainage. Based on a large population of normal computed tomography scans, the majority of temporal bones (82.8%) have a petrous angle ranging between 10.0 and 20.0 degrees.
authors: Department of Otolaryngology Head and Neck Surgery, University of Cincinnati Academic Health Center, Cincinnati, Ohio 45267-0528, USA.
authors: Neal
authors: N
authors: Shoman
authors: Angela M
authors: AM
authors: Donaldson
authors: Jeffrey
authors: J
authors: Ksiazek
authors: Myles L
authors: ML
authors: Pensak
authors: Lee A
authors: LA
authors: Zimmer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002784:Cholesterol; D005260:Female; D015745:Granuloma, Foreign-Body / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013517:Otorhinolaryngologic Surgical Procedures / Q000379:methods*; D010579:Petrous Bone; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D002784:Cholesterol