title: Prevalence and appearance of the posterior wall defects of the temporal bone caused by presumed arachnoid granulations and their clinical significance: CT findings.
abstract: OBJECTIVE
  Arachnoid granulations (AGs) of the posterior wall of the temporal bone are a rare cause of spontaneous CSF leakage. The purpose of this study was to investigate the prevalence and appearance of presumed AGs, evidenced by the posterior wall defects of the temporal bone with lobulated or scalloped margins on CT scans.
  
  
  METHODS
  We retrospectively reviewed CT scans of the temporal bone obtained in 1255 patients (573 men and 682 women; mean age, 42 years). We evaluated the prevalence, multiplicity, size, and location of presumed AGs in the posterior wall of the temporal bone. Preservation of the posterior wall of the mastoid air cells was also investigated and correlated with clinical features.
  
  
  RESULTS
  Thirty patients (2.4%), including 13 men and 17 women, aged 27-88 years (mean, 55 years), showed a total of 40 presumed AGs on CT scans. Their prevalence tended to increase with age. They were most commonly located at the lateral third of the temporal bone at a level of or above the common crus. Although 15 lesions in 11 patients also caused focal loss of the posterior wall of the mastoid air cells, symptomatic CSF leakage was found in only 2 patients, in both of whom the adjacent mastoid air cells were also opacified on CT scans.
  
  
  CONCLUSIONS
  Although rare, radiologists need to be familiar with the posterior wall defects of the temporal bone caused by presumed AGs on CT scans, because they might cause CSF leakage.
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: M H
authors.initials: MH
authors.lastname: Lee
authors.forename: H-J
authors.initials: HJ
authors.lastname: Kim
authors.forename: I H
authors.initials: IH
authors.lastname: Lee
authors.forename: S T
authors.initials: ST
authors.lastname: Kim
authors.forename: P
authors.initials: P
authors.lastname: Jeon
authors.forename: K H
authors.initials: KH
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001099:Arachnoid / Q000000981:diagnostic imaging*; D002558:Cerebrospinal Fluid Otorrhea / Q000000981:diagnostic imaging* / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D003392:Cranial Sinuses / Q000000981:diagnostic imaging; D003430:Cross-Sectional Studies; D004388:Dura Mater / Q000000981:diagnostic imaging; D005260:Female; D006547:Hernia / Q000000981:diagnostic imaging; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008416:Mastoid / Q000000981:diagnostic imaging; D016920:Meningitis, Bacterial / Q000000981:diagnostic imaging / Q000453:epidemiology; D008875:Middle Aged; D013701:Temporal Bone / Q000000981:diagnostic imaging*; D036542:Tomography, Spiral Computed; D055815:Young Adult