M. Vonunge et al., SHAPE AND DISPLACEMENT PATTERNS OF THE GERBIL TYMPANIC MEMBRANE IN EXPERIMENTAL OTITIS-MEDIA WITH EFFUSION, Hearing research, 82(2), 1995, pp. 184-196
This study assesses the visco-elastic properties of the tympanic membr
ane (TM) in isolated gerbilline temporal bones as a function of time a
fter inducing experimental otitis media with effusion (OME). To do thi
s we measured the TM displacements produced by application of sequence
s of static pressures across the TM, with a high resolution, real-time
, differential moire interferometer, and the results were compared wit
h measurements on healthy ears. Two methods of producing OME were used
: in one group tubal plugging was performed to produce mild OME (the '
TP group'); in the other group electro-cauterization of the nasopharyn
geal orifice of the Eustachian tube was used to cause a severe form of
OME (the 'EC group'). The measurements were performed from one day up
to ten weeks after surgery. In the TP group the displacement fringe p
atterns were normal, i.e. qualitatively they resembled the patterns of
the control group. Quantitatively there was a significant decrease of
displacement for a given pressure on the first day after surgery, fol
lowed by a trend of increase with time; after seven to ten days the di
splacement was larger than in the control group. In the EC group the d
isplacement was significantly reduced after half a week, followed by a
trend of increase with time, similar to what was found in the TP grou
p; at one week the displacement was larger than in the control group,
and at ten weeks the largest displacement was recorded. In the EC grou
p the displacement patterns were often irregular; in some cases with c
hanges suggesting the presence of weak spots in the TM where retractio
n pockets most likely could develop. OME seems to affect the stiffness
of the TM promptly so that it is a potential parameter for early diag
nosis. The stiffness changes may, if measurable in the clinical situat
ion, become prognostic parameters in the treatment of OME.