title: Petrous apex cephaloceles.
abstract: OBJECTIVE
  Petrous apex cephaloceles (PACs) are uncommon lesions that are usually incidental but may be symptomatic. We reviewed MR and CT studies in 10 patients with PACs to identify characteristic imaging features that facilitate their diagnosis.
  
  
  METHODS
  MR and CT studies from 10 patients with PACs were reviewed retrospectively. In each case the PAC was characterized by lesion center, signal intensity or attenuation, adjacent petrous apex pneumatization, and its relationship to Meckel's cave. Intraoperative findings were reviewed in the three cases in which surgery was performed.
  
  
  RESULTS
  All 10 patients had lobulated expansile cystic petrous apex lesions centered along the posterolateral margin of Meckel's cave. All cysts were contiguous with Meckel's cave. Three patients had bilateral PACs. Four patients had symptoms that could potentially be explained by the PAC, while findings in the other six were incidental observations. Three patients underwent surgery, during which two lesions were diagnosed as meningoceles while the third was diagnosed as an arachnoid cyst protruding through a dural defect.
  
  
  CONCLUSIONS
  PACs represent a protrusion of meninges and CSF from the posterolateral portion of Meckel's cave into the petrous apex, which is their characteristic imaging appearance. PACs are usually incidental but may be symptomatic. Surgical intervention should be approached cautiously and undertaken only when symptoms are clearly linked to the presence of this lesion.
authors.affiliation: Department of Radiology, University of Utah School of Medicine, Salt Lake City 84132, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Moore
authors.forename: N J
authors.initials: NJ
authors.lastname: Fischbein
authors.forename: H R
authors.initials: HR
authors.lastname: Harnsberger
authors.forename: C
authors.initials: C
authors.lastname: Shelton
authors.forename: C M
authors.initials: CM
authors.lastname: Glastonbury
authors.forename: D K
authors.initials: DK
authors.lastname: White
authors.forename: W P
authors.initials: WP
authors.lastname: Dillon
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D003937:Diagnosis, Differential; D004677:Encephalocele / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000601:surgery; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010579:Petrous Bone / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed