title: Pars flaccida displacement pattern in purulent otitis media in the gerbil.
abstract: OBJECTIVE
  Our hypothesis is that purulent otitis media and otitis media with effusion cause stiffness loss of the tympanic membrane. This loss of stiffness may be persistent and precede the development of retraction pockets and cholesteatoma.
  
  
  BACKGROUND
  Postinflammatory changes such as retraction pockets and cholesteatoma develop in the pars flaccida and in the pars tensa of the tympanic membrane. In our previous experimental studies, stiffness changes were shown to develop early in the pars tensa in response to purulent otitis media and otitis media with effusion. These changes are suggested to be precursors to a later development of retraction pockets and cholesteatoma. In the clinical situation, retraction pockets are often found in the pars flaccida only. The aim of the current study was thus to investigate whether stiffness changes appear also in the pars flaccida during purulent otitis media.
  
  
  METHODS
  Streptococcus pneumoniae type 3 was injected into the middle ear to induce purulent otitis media. As a measure of pars flaccida stiffness, peak displacement versus middle ear pressure was used. The peak displacement measurements were obtained from full-field moiré; interferometry, which is a noncontacting optical technique for deformation measurements.
  
  
  RESULTS
  Ears with purulent otitis media showed increased peak displacement of the pars flaccida at a middle ear pressure of 200 daPa, compared with normal controls.
  
  
  CONCLUSIONS
  There was a decreased mechanical stiffness of the pars flaccida in acute purulent otitis media. This decreased stiffness may predispose for future retraction pocket formation and cholesteatoma development.
authors.affiliation: Department of Otorhinolaryngology, Karolinska Hospital and Karolinska Institute, Stockholm, Sweden. larson_christina@hotmail.com
authors.forename: Christina
authors.initials: C
authors.lastname: Larsson
authors.forename: Joris J J
authors.initials: JJ
authors.lastname: Dirckx
authors.forename: Willem F
authors.initials: WF
authors.lastname: Decraemer
authors.forename: Dan
authors.initials: D
authors.lastname: Bagger-Sjöbäck
authors.forename: Magnus
authors.initials: M
authors.lastname: von Unge
mesh_terms: D000818:Animals; D018424:Cholesteatoma, Middle Ear / Q000382:microbiology / Q000473:pathology; D015169:Colony Count, Microbial; D003470:Culture Media; D004195:Disease Models, Animal; D005849:Gerbillinae; D010035:Otitis Media, Suppurative / Q000382:microbiology / Q000473:pathology* / Q000503:physiopathology*; D038781:Otoscopy; D013290:Streptococcal Infections / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000254:growth & development; D014432:Tympanic Membrane / Q000382:microbiology / Q000473:pathology* / Q000503:physiopathology*
chemical_list: D003470:Culture Media