Abstract
Objectives
The purpose of this study was to document the anatomic relationship of the postero-superior segment of the tympanic membrane and its clinical implications.
Methods
100 temporal bones from adults without history of otologic pathology were studied. The morphological and anatomical details of the tympanic membrane were observed in 70 bones, which implied the use of macroscopic sections of the bones. The histological results were documented in 30 serially sectioned bones, stained previously with hematoxylin-eosin.
Results
We established that the postero-superior quadrant was the largest in size, with a mean dimension of 21.05 mm2, which represents 28.7% of the total area of the tympanic membrane. This feature implies that this quadrant is more exposed to pressure changes. We also verified that the posterosuperior part of the tympanic sulcus, above the chorda tympanic nerve, lost its depth in an unexpected way (60%) or that it gradually diminished from 0.9 to 0.5 mm until it disappeared near the posterior tympanic spine. In association, we established that at this level there was a decrease in the annulus caliber. Additionally, in 25% of cases, given the absence of the circular fibers of lamina propria, the postero-superior quadrant had only the radial fiber layer.
Conclusions
Anatomic and morphologic details in the postero-superior quadrant were newly described and may explain the greater incidence of retraction pockets and marginal perforations that provide the origin of cholestheatoma.
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