Otomicroscopic and histologic findings of induced myringosclerosis in rats: a critical study of an experimental model

Abstract

Myringosclerosis is characterized by hyaline changes of the lamina propria of the tympanic membrane. Experimental studies have used otomicroscopy or histology to evaluate myringosclerosis in animals, but they do not correlate precisely these two methods.

Aim: The present study evaluates the accuracy of otomicroscopy in the diagnosis of myringosclerosis in rats.

Study design: Experimental.

Material and method: Myringosclerosis was induced by transtympanic inoculation of Streptococcus pneumoniae in 25 Wistar rats, which were examined weekly through otomicroscopy and sacrificed after eight weeks for histologic study of their tympanic membranes.

Results: From the comparison of the otomicroscopic data in relation to the histologic findings, we could observe sensibility of 80% and specificity of 75% for the otomicroscopy.

Conclusion: Considering the results in this study, otomicroscopy did not represent a good method to evaluate myringosclerosis in this experimental model.

Figure 1

Otomicroscopy showing marked opacification of the posterior portion of the tympanic membrane (*), showing the anterior half with normal transparency (arrow). m – malleus manubrium.

Figure 2

Otomicroscopy showing marked diffuse opacification of the tympanic membrane. m – malleus manubrium.

Figure 3

Axial section stained with HE, 10 X, of the tympanic membrane (MT) with tympanosclerosis phase 3. CAE – external auditory canal; OM – middle ear.

Figure 4

Detail of Figure 1: Note the sparse fibroblasts, involved by hyaline collagen (*). CAE – external auditory canal.

Figure 5

Axial section stained with HE, 10 X, of tympanic membrane (MT) with tympanosclerosis phase 4. CAE – external auditory canal.; OM – middle ear.

Figure 6

Detail of Figure 3. We can observe the typical aspect of bone metaplasia (*) on the medium layers of the tympanic membrane.