Abstract
The present experimental study explored pathomorphological changes and calcium depositions in the tympanic membrane during experimental acute otitis media caused by nontypeable Haemophilus influenzae in myringotomized and nonmyringotomized ears. A rat model of experimental acute otitis media caused by nontypeable Haemophilus influenzae was employed. Sixteen Sprague-Dawley rats were used. Four days following middle ear inoculation, a bilateral myringotomy was performed in six randomly selected animals. Another group of 10 animals was inoculated only. On days 4, 7, 14, and 28 after inoculation, two animals from each group were sacrificed. The temporal bones were removed and the tympanic membranes were dissected, followed by paraffin embedding. Adjacent sections were stained with PAS-alcian blue for basic histopathological observations and by von Kossa method for determination of calcium phosphate depositions. Particularly intense invasion of polymorphonuclear neutrophil leukocytes was seen on day 4 after inoculation. The highest infiltration of macrophages was observed on day 7. The peak number of lymphocytes was seen on day 14. No difference occurred in the number of polymorphonuclear leukocytes in myringotomized and nonmyringotomized tympanic membranes. The infiltration with lymphocytes and activated macrophages in all parts of the myringotomized tympanic membranes was statistically significantly higher than in the nonmyringotomized animals. The total amount of interstitial calcium phosphate depositions during days 7, 14, and 28 of study was statistically higher in the sections of pars tensa from myringotomized membranes compared to the nonmyringotomized membranes. Nontypeable Haemophilus influenzae-induced acute otitis media and myringotomy provoke more extensive inflammatory reaction with microcalcification in the tympanic membranes.
Highlights
Myringotomy is an incision of the tympanic membrane
On day 4 after inoculation, all ears infected with nontypeable Haemophilus influenzae (NTHi) had typical signs of acute otitis media (AOM)
Thickness of the tympanic membrane (TM) changed during AOM
Summary
Myringotomy is an incision of the tympanic membrane. Until the 18th century, myringotomy was used for the treatment of deafness [1]. Later myringotomy was applied in the treatment of acute otitis media (AOM) and secretory otitis media (SOM). Myringotomy is still recommended in case of complicated AOM. It has been shown in experimental myringotomy that early inflammatory reaction develops in the tympanic membrane (TM). Experimental myringotomy in rats has been shown to heal within 9–11 days. Myringotomy performed during Streptococcus pneumoniae-induced AOM was shown to yield a slower resolution of the AOM compared nonmyringotomized ears [5]. Another study on the rats concluded that myringotomy in AOM provoked a delayed recovery from the inflammatory process within the TM [6]
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