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Tympanic membrane changes in experimental cholesteatoma in the gerbil
C Larsson1, M von Unge, D Bagger-Sjöbäck
1Department of Otorhinolaryngology, Karolinska Hospital and Karolinska Institute, Stockholm, Sweden.
The American Journal of Otology
|May 25, 1999
Summary
Early cholesteatoma significantly increases tympanic membrane (TM) stiffness and thickness. These acoustic and morphologic changes in the TM are comparable to those seen in other middle ear diseases.
Area of Science:
- Otolaryngology
- Biophysics
- Pathology
Background:
- The exact cause of cholesteatoma development is unknown.
- Changes in the tympanic membrane's (TM) physical characteristics may be crucial.
- TM atrophic regions and retraction pockets in chronic middle ear disease might predispose to cholesteatoma.
Purpose of the Study:
- To investigate acoustic stiffness and morphologic changes in the TM during early cholesteatoma development.
- To compare these findings with previous studies on otitis media with effusion and purulent otitis media.
Main Methods:
- Early-stage cholesteatoma was induced in Mongolian gerbils by occluding the external ear canal.
- Acoustic admittance measurements were taken at 1, 2, and 3 months post-surgery.
- Tympanic membranes were morphologically analyzed after acoustic measurements.
Main Results:
- Acoustic stiffness of the TM was significantly elevated in cholesteatoma ears compared to controls.
- Early cholesteatoma featured pronounced TM thickening and proliferative activity.
- Increased keratin production and a thickened fibrous layer with more collagen were observed.
Conclusions:
- The fibrous layer of the TM nearly doubled in thickness due to increased collagen.
- Significantly increased acoustic stiffness was a consistent finding in cholesteatoma ears.
- Acoustic admittance results align with findings from studies on purulent and effusive otitis media.