title: The posterosuperior quadrant of the tympanic membrane.
abstract: OBJECTIVE
  To document the anatomic relationship of the posterosuperior segment of the tympanic membrane.
  
  
  METHODS
  Point-prevalence study of postmortem material.
  
  
  METHODS
  One hundred seventy temporal bones from adults without history of otologic pathology were studied. The anatomic details of the tympanic membrane were observed, histology was documented on 30 sectioned bones, and, with the use of the scanning electron microscope, lamina propria was studied in 40 bones.
  
  
  RESULTS
  We established that the posterosuperior quadrant was the largest, representing 28.7 percent of the total area of the eardrum. This feature implies that this quadrant is more likely than are the other quadrants to exhibit changes prompted by pressure challenges. We also verified that the posterosuperior part of tympanic sulcus, above the chorda tympanic nerve, lost its depth in an unexpected way in 60 percent of the cases. In association, we established that at this level there was a decrease in annulus caliber. In 25 percent of cases, by the absence of the circular fibers of lamina propria, the posterosuperior quadrant had only the radial fiber layer.
  
  
  CONCLUSIONS
  Anatomic and morphologic details in posterosuperior quadrant were newly described and may explain the greater incidence of retraction pockets and marginal perforations that provide origin for the cholesteatoma.
authors.affiliation: Hospital Cuf Infanto Santo, Lisbon, Lisbon, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Paço
authors.forename: Carla
authors.initials: C
authors.lastname: Branco
authors.forename: Hugo
authors.initials: H
authors.lastname: Estibeiro
authors.forename: Diogo
authors.initials: D
authors.lastname: Oliveira E Carmo
mesh_terms: D002102:Cadaver; D005260:Female; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D012016:Reference Values; D014432:Tympanic Membrane / Q000033:anatomy & histology* / Q000648:ultrastructure