Pars flaccida displacement pattern in otitis media with effusion in the gerbil.

Objective: Our hypothesis is that otitis media with effusion causes stiffness loss in the pars flaccida of the tympanic membrane. This loss of stiffness may be persistent and may trigger the development of retraction pockets and cholesteatoma.

Background: Otitis media with effusion is a very common disease in childhood. It can cause minor to moderate hearing loss and delayed speech development. Otitis media with effusion is a risk factor for retraction pocket formation.

Methods: Otitis media with effusion was induced unilaterally in 15 gerbils by obstructing the eustachian tube with glue. The contralateral ears served as normal controls. As a measure of mechanical stiffness, pars flaccida peak displacement versus pressure was used. The displacement measurements were made with moire interferometry. This is a noncontacting optical technique with which the displacement of an object can be measured in real time.

Results: The mean peak displacement of the pars flaccida in the group with otitis media with effusion was increased threefold as compared with normal controls. This difference was statistically significant.

Conclusions: There was a loss of mechanical stiffness in the pars flaccida caused by otitis media with effusion. This loss of stiffness may be persistent and may predispose for retraction pocket formation and cholesteatoma development.