Myringotomy: A Prerequisite for the Development of Myringosclerosis?

Streptococcus pneumoniae was inoculated into the left middle-ear cavity in two groups of rats, resulting in purulent otitis media. After 3 days, one group of infected animals and a third group of noninfected animals were subjected to left-sided myringotomy. The tympanic membranes were examined both otomicroscopically and histologically 1 and 3 months later. On otomicroscopic examination the noninfected myringotomized animals had developed extensive myringosclerotic lesions, whereas only minimal sclerotic deposits were noted in the myringotomized animals with acute otitis media (AOM). On histologic examination both the noninfected myringotomized animals and the myringotomized animals with AOM were similar in the frequency and extension of sclerotic lesions in the tympanic membrane. The nonmyringotomized rats with AOM were free of sclerotic lesions, except for minor changes found in one animal.     

The inhibitory effect of topical N-acetylcysteine application on myringosclerosis in perforated rat tympanic membrane

OBJECTIVE: Myringosclerosis often occurs in patients in whom ventilation tube insertion and tympanoplasty procedures are performed. Recent studies have revealed a relationship between the development of myringosclerosis and oxygen-derived free radicals, and some investigations have demonstrated that free radical scavengers prevent the development of myringosclerosis. N-acetylcysteine is a well-known anti-oxidant and anti-inflammatory agent. In this study, we aimed to investigate the preventive effect of N-acetylcysteine on myringosclerosis in myringotomized rat tympanic membranes. METHODS: Twenty Sprague-Dawley rats were bilaterally myringotomized and divided into four groups. Group 1 received no treatment, group 2 was treated with topical saline solution in Spongostan, group 3 received topical 0.6 mg N-acetylcysteine in Spongostan and group 4 received 1.2 mg N-acetylcysteine in Spongostan daily for 12 days. Tympanic membranes were examined by otomicroscopy on day 12. Then, the membranes were harvested and evaluated histologically by light microscopy. RESULTS: The tympanic membranes of groups 1 and 2 (saline and non-treated) showed extensive occurrence of myringosclerosis, whereas groups 3 and 4 (treated with N-acetylcysteine) showed lesser occurrence of myringosclerosis in otomicroscopic evaluation (P<0.01). Under light microscopic examination, lamina propria of pars tensa was found thicker in groups 3 and 4 when compared with groups 1 and 2. There was no significant difference between groups 3 and 4 (P: 0.30). CONCLUSIONS: Topically applied N-acetylcysteine was found to be effective in the prevention of sclerotic lesions in myringotomized rat tympanic membranes.     

Treatment with dexamethasone arrests the development of myringosclerosis after myringotomy

HYPOTHESIS: To attempt to inhibit the development of myringosclerosis by intraperitoneal injection of dexamethasone. BACKGROUND: The authors' earlier report showed that the development of myringosclerosis after myringotomy was associated with an inflammatory reaction. The present study was performed to secure evidence for this hypothesis. METHODS: Three groups of bilaterally myringotomized rats were treated at 12-hour intervals with intraperitoneal injection of dexamethasone, RU486 (a glucocorticoid receptor antagonist), and saline, respectively. At 6, 12, 24, and 48 hours after the myringotomy, 2 animals were anesthetized on each occasion and examined otomicroscopically. The animals were then killed, and the tympanic membranes were excised and prepared for light microscopic studies. RESULTS: Dexamethasone treatment retarded and diminished the development of sclerotic lesions markedly. Moreover, no inflammatory signs were seen in the flaccida specimens. When the RU486-treated animals were compared with the animals in the control group, there were no evident differences concerning the development of myringosclerosis or the extent of the inflammatory reaction. CONCLUSION: These findings confirm the earlier hypothesis that an inflammatory reaction in collagen tissue is involved in the mechanism that causes the development of myringosclerosis.     

The effect of caffeic acid phenethyl ester on the prevention of experimentally induced myringosclerosis

OBJECTIVES: Myringosclerosis is a common sequela of ventilation tube insertion for the treatment of the otitis media with effusion. Several antioxidants have been identified to prevent myringosclerosis. The objective of this study was to investigate the effect of caffeic acid phenethyl ester (CAPE) on the prevention of experimentally induced myringosclerosis. METHODS: Thirty-five Sprague-Dawley rats were unilaterally myringotomized. The rats were divided into four groups randomly: group 1 received no treatment, group 2 received intraperitoneally administered saline and group 3 received intraperitoneally administered CAPE. The tympanic membranes were examined by otomicroscopy on the 15th day after treatment. The membranes were then harvested and evaluated histologically by light microscopy. RESULTS: The tympanic membranes from group 1 showed extensive myringosclerosis; those from group 2 showed a similar occurrence of myringosclerosis. However, group 3 had a reduced occurrence of myringosclerosis by otomicroscopic evaluation. Under light microscopic examination, the lamina propria of the pars tensa was found to be thicker and more sclerotic in groups 1 and 2 when compared with group 3. CONCLUSIONS: Systemic treatment with CAPE was found to be effective in the prevention of sclerotic lesions in myringotomized rat tympanic membranes.     

The anti-oxidant and anti-apoptotic activities of selenium in the prevention of myringosclerosis in rats

The possible effect of selenium on the prevention or reduction in occurrence of myringosclerosis was investigated. Fifteen rats were myringotomized bilaterally and separated into two groups. Nine rats were treated with selenium in the study group. Six rats were administered physiological serum and formed the control group. The occurrence of myringosclerotic lesions and anti-apoptotic activity in the tympanic membranes of the two groups were compared otomicroscopically and histopathologically. The sclerosis was occasional in three, moderate in five and severe in three tympanic membranes in the control group. On the other hand sclerosis was observed in only two of 18 specimens in the study group and sclerosis was seen only occasionally in these two sections. Although Bcl-2 staining, which indicates apoptosis, was not statistically different between the groups, it was observed that apoptosis was slightly more apparent in the study group (eight of 18 tympanic membranes versus two of 12 tympanic membranes in the control group). In conclusion, the formation of myringosclerosis following myringtomoy in rats can be reduced by intraperitoneal selenium administration.     

Tympanometric changes in an experimental myringosclerosis model after myringotomy.

HYPOTHESIS: The goal of this experimental study was to investigate the specific effect of myringosclerosis on tympanograms in the tympanic membranes of myringotomized rats by using otomicroscopy, tympanometry, and histopathology. BACKGROUND: Myringosclerosis is a common sequela of ventilation tube treatment of otitis media with effusion. The condition involves the hyalinization and calcification of the collagen layer in certain areas of the tympanic membrane. Previous animal experiments suggest an intimate relationship between the formation of myringosclerosis and an increased oxygen concentration in the environment of the wound after myringotomy. The result of a myringotomy therefore is an increased production of free oxygen radicals, initiating irreversible tissue damage involving fibrosis, hyalin degeneration, and finally apoptosis as observed in myringosclerosis. We propose an experimental model specific for creating sclerotic plaques solely on the tympanic membrane and for performing tympanometric measurements on this pure myringosclerosis model without creating any abnormality in the middle ear to test in what proportion myringosclerosis contributes to decrease of amplitude in tympanograms. METHODS: To assess the normal tympanometric values of Wistar albino rats, the pressure and peak admittance of the left middle ears were measured using a semiquantitative computerized clinical admittance meter using a sound frequency of 226 Hz. Twelve animals were randomly selected for the myringotomy group and perforations in the left ears were created. All tympanic membrane perforations in this group had healed and closed prior to the otomicroscopic examination and no pathologic reaction was observed in the external ear canals of rats. Otomicroscopic and tympanometric measurements were carried out on Day 15 and the degree of myringosclerosis was noted before the animals were killed. Twelve specimens in the myringotomy group were histopathologically examined for the presence of myringosclerotic plaques. RESULTS: Under light microscopy, extensive sclerotic lesions were found in the tympanic membranes of the myringotomy group, and these sclerotic deposits were located in the lamina propria. The myringosclerosis occurred predominantly adjacent to the handle of the malleus, but also near the annular region. In all ears with myringosclerosis, the magnitude of the maximum admittance reduced to approximately 50% of the Day-0 values, and this reduction was statistically significant (Z=-3.061, p=0.002). CONCLUSION: The present findings in this study are consistent with the fact that the movement of the tympanic membrane is hampered by lesions of sclerotic material, resulting in a decrease of amplitude in tympanograms (such as Type As) without any effusion or inflammation in the middle ear.     

Topical ascorbic acid reduces myringosclerosis in perforated tympanic membranes. A study in the rat.

Myringosclerosis, a common finding after myringotomy, has been recently associated with an increased production of oxygen free radicals. Ascorbic acid's proposed actions include collagen synthesis, antioxidation, and free radical scavenging. The effects of topical ascorbic acid on healing tympanic membranes were studied. Particular attention was given to detecting the presence of myringosclerosis. Twelve Sprague-Dawley rats were bilaterally myringotomized. Their ears were randomized into group A, which received topical ascorbic acid in Gelfoam, group B, which received topical saline solution in Gelfoam, and group C, which received no treatment. The tympanic membranes were harvested on day 13, after routine otomicroscopy. Under light microscopy, the connective tissue layer of the untouched side of the pars tensa was distinctly thicker in group A than in group B or group C. At this level, the extent of sclerotic lesions was significantly less in the ascorbic acid-treated group. It is inferred that topical ascorbic acid reduces the occurrence of myringosclerosis following tympanic membrane perforations in the rat.     

The effect of topical doxycycline in the prevention of experimental tympanosclerosis

Objectives: The aim of this study is to determine the effectiveness of topical doxycycline used in the process of experimental myringosclerosis and tympanosclerosis. Study Design: A prospective experimental animal study. Methods: Experimental tympanosclerosis was accomplished in 25 healthy adult guinea pigs by inoculation with 2.5 × 10⁷ colony‐forming units of type‐3 Streptococcus pneumoniae microorganisms followed by bilateral myringotomy. While the animals' right ears received a topical doxycycline treatment daily, their left ears were left untreated and used as controls. Otomicroscopic examination was carried out weekly and healing tympanic membranes were remyringotomized. After a 6‐week follow‐up, the temporal bones of 24 of 25 animals were removed and light‐microscopy examination was done regarding tympanic membrane myringosclerosis and middle ear mucosal sclerosis. Results: Myringosclerosis was noticed to a lesser extent in the doxycycline‐treated group when compared to the untreated control group. Light microscopy evaluation revealed a difference in the area and thickness of the sclerotic plaques of myringosclerosis of the tympanic membranes in the doxycycline‐treated group and the control group, being significantly smaller and thinner in the treated group (P < .001, P < .04, respectively). Similarly, the area and thickness of the sclerotic plaques in the middle ear mucosa were significantly smaller and thinner in the doxycycline treated group (P < .001, P < .03). Conclusion: This study demonstrated that the potent matrix metallo‐proteinase inhibitor doxycycline plays a preventive role in the development of experimentally induced tympanosclerosis.     

The preventive effect of N-nitro L-arginine methyl ester in experimentally induced myringosclerosis

Objective

The purpose of this study was to investigate the antiinflammatory and antifibrotic effects of N-nitro l-arginine methyl ester (l-NAME) in experimentally induced myringosclerosis.

Methods

Twenty Wistar albino rats were bilaterally myringotomized and divided randomly into four groups, each including five rats. Group I received no treatment, Group II was treated with topical saline solution, Group III received topical l-NAME and Group IV received intraperitoneally administered l-NAME. After 2 weeks, the tympanic membranes were examined and scored by otomicroscopy regarding the extent of the myringosclerosis. Then the tympanic membranes were harvested and evaluated histopathologically by light microscopy. The intensity of inflammation and degree of myringosclerosis were evaluated, the mean thickness of tympanic membranes were also measured.

Results

The tympanic membranes of Groups I and II showed extensive myringosclerosis in contrast to those of Groups III and IV which had significantly less or no changes (p < 0.05). The inflammation and fibroblastic activity of the lamina propria in the tympanic membranes of Groups III and IV were found to be significantly less pronounced (p < 0.05). The tympanic membranes were found to be significantly thicker in Groups I and II when compared with Groups III and IV (p < 0.05).

Conclusion

Our results showed that both topical and intraperitoneal applications of l-NAME supressed inflammation, reduced fibroblastic proliferation and decreased the formation of myringosclerosis in myringotomized rat tympanic membranes.     

Is there any effect of coenzyme Q10 on prevention of myringosclerosis? Experimental study with rats

Recent studies have shown that the formation of myringosclerosis could be reduced by the application of antioxidant enzymes and elements.ObjectiveThe aim of this study was to investigate the effectiveness of coenzyme Q10 on the prevention of experimentally induced myringosclerosis.MethodForty-eight healthy female wistar albino rats were bilaterally myringotomized and divided into four groups randomly. Group A received no treatment, group B was administered oral coenzyme Q10. Group C was treated with topical saline solution, group D received topically coenzyme Q10. On the 15^th day of treatment, tympanic membranes were examined by otomicroscopy. Myringosclerotic lesions were documented semiquantitatively by using 4-point scale. After harvesting tympanic membranes were evaluated histopathologically.ResultsIn group D (topical coenzyme Q10), we observed otitis within the first four days of the study and this group was excluded from the study. Regarding otomicroscopic examinations, there were no significant differences among groups in myringosclerosis formation (p = 0.241). When group A (non treatment) compared to groups B and C regarding histopathologic examination, the results demonstrated statistical significant differences (p = 0.004; p < 0.001), respectively. There was no statisticaly significant difference between groups B and C (p = 0.160).ConclusionOral administration of coenzyme Q10 did not reduce myringosclerosis formation in myringotomized rats.     

Topical application of calcium channel blockers to reduce the progression of experimentally induced myringosclerosis and tympanosclerosis

OBJECTIVES: This study aimed to evaluate the ability of topically applied calcium channel blockers (diltiazem) to reduce the progression of experimentally induced myringosclerosis and tympanosclerosis. STUDY DESIGN: Animal model. Experimental prospective study. METHODS: The study included 25 adult albino guinea pigs that were bilaterally myringotomized and inoculated with a suspension of Streptococcus pneumonia type 3. The right ears were treated with topical application of diltiazem, and the untreated left ears served as the control group. Otomicroscopy and remyringotomy were conducted every week. One animal was sacrificed after 1 week and the remaining at the end of 6 weeks. Temporal bones were dissected, and tympanic bullae were analyzed with light microscopy. RESULTS: The untreated control ears showed evidence of extensive myringosclerosis on otomicroscopy, and the ears treated with calcium channel blockers did as well although to a lesser degree. Under light microscopy, the lamina propria of both tympanic membranes and middle ear mucosae of the control group exhibited thicker (P < .1 and P < .05, respectively) and larger (P < .01 and P < .01, respectively) sclerotic tissue in comparison with the treatment group. CONCLUSION: The results suggest that calcium channel blockers had an influence in the prevention of tympanosclerosis.     

Myringotomized tympanic membranes cultured in vitro do not develop myringosclerosis

The aim of this study was to evaluate the development of myringosclerosis in in vitro-cultured tympanic membranes. Sprague-Dawley rats were myringotomized bilaterally and the tympanic membranes were excised after sacrifice. The explants were placed in inserts in wells filled with a nutrient medium. Every second day the tympanic membranes were photodocumented and after 9 days the explants were prepared for histology. On the 4th day the explants had attached to the bottom of the inserts and the specimens had thickened. From the perforation borders and the dissection edges a thin outgrowth was extending across the surface. By Day 9 the perforation had clearly diminished in size when examined in a stereomicroscope. In a light microscope the keratin layer was seen to protrude towards the centre of the perforation and, at the borders, epithelial cells were bridging the gap. Neither the pars tensa nor the pars flaccida showed any sclerotic lesions. The pars flaccida had thickened and the basal cells of the outer keratinized epithelium had invaded the connective tissue. Inflammatory cells were sparse in both the pars tensa and pars flaccida. The in vitro-cultured myringotomized tympanic membrane therefore shows a similar healing pattern to that in vivo. However, inflammatory reactions are sparse and there is no development of myringosclerosis.     

The anti-oxidant effect of alpha-tocopherol in the prevention of experimentally induced myringosclerosis.

HYPOTHESIS: The objective of this study was to investigate the possible effect of alpha-tocopherol on the prevention of experimentally induced myringosclerosis. BACKGROUND: Myringosclerosis is a common sequela of ventilation tube treatment of otitis media with effusion. The relationship between oxygen-derived free radicals and occurrence of myringosclerosis has been proven in experimental models, and it was also shown that the formation of myringosclerosis after experimental myringotomy could be reduced by application of various free radical scavengers. METHODS: Eighteen Wistar albino rats were myringotomized on the left side and randomly separated into two groups: group A consisted of rats which received intramuscular alpha-tocopherol injections 100 mg/kg daily and group B which were injected with physiological serum only. The occurrence of myringosclerotic plaques in the tympanic membranes of the two groups was compared by otomicroscopy, histopathology, and tympanometry, which is a novel method of quantification. Blood samples were collected for biochemical evaluation, and the tympanic membranes were harvested on the 15th day of the experiment. RESULTS: In otomicroscopic evaluation, tympanic membranes in group B revealed varying degrees of myringosclerotic plaques; on the other hand, tympanic membranes in group A showed faint or no existence of myringosclerosis. The mean malondialdehyde levels were 1.33 +/- 0.11 micromol/L in group A and 7.49 +/- 1.37 micromol/L in group B (Z = -1.906, p = 0.057). In all ears from group B, the magnitude of the maximum admittance measured by tympanometry reduced to approximately 40% of the values obtained from group A (Z = -2,160, p = 0.031). The mean magnitude of the maximum admittance from group A was very close to the standardization values of Wistar albino rats, which predicts a functional outcome. CONCLUSION: The formation of myringosclerosis after experimental myringotomy can be diminished by intramuscular alpha-tocopherol injections.     

The effect of L-carnitine on the prevention of experimentally induced myringosclerosis in rats

The objective of this study was to investigate the possible effect of L-carnitine on the prevention of experimentally induced myringosclerosis. Twenty Sprague-Dawley rats were bilaterally myringotomized. The rats were divided into two groups randomly: group 1 which were intraperitoneally administered saline and group 2 which were intraperitoneally administered L-carnitine. Blood samples were collected for biochemical evaluation and the tympanic membranes were harvested after 28 days. Histopathological and immunohistochemical evaluation were done under light microscopy. The mean malondialdehyde levels were 3.9+/-0.9 in group 2, and 7.9+/-1.1 in group 1 (P<0.001), nitric oxide levels were 25.6+/-6.4 in group 2 and 30.8+/-8.2 in group 1 (P=0.14) and acetylcholinesterase was 1035+/-60 in group 2 and 678+/-35 in group 1 (P=0.001). Myringosclerosis was more frequent and severe in group 1 than group 2 (P<0.007). Immunoreactivity was seen in 16 of 20 tympanic membranes in group 2 and six of 20 tympanic membranes in group 1 (P=0.005). We conclude that L-carnitine diminishes the occurrence of myringosclerosis in rats after myringotomy possibly by antioxidant activity and decreasing the formation of reactive oxygen species.     

The effect of Nigella sativa oil on prevention of myringosclerosis in a Guinea pig model

ObjectivesIn this study, our aim was to identify the possible effects of Nigella sativa L. (NS) [blackcumin] seed oil on the prevention of experimentally induced myringosclerosis (MS).Materials and methodsFourteen Guinea pigs were used and they were divided into three groups. Tympanic membranes (TM) of all animals were perforated and then group I was treated with saline soaked gel foams as a control group, group II was treated with 0.5 ml NS oil soaked gel foams at 0, 24 and 48 h and group III was treated with 5 ml NS oil orally at 0, 24, 48, 72 and 120 h. After 15 days, all animals were euthanized. Tympanic membranes were evaluated macroscopically and histopathologically.ResultsGroups I showed extensive myringosclerosis in contrast to those of Groups II and III which had significantly less changes (p < 0.05). The fibrosis and inflammation in the lamina propria of the tympanic membranes of Groups I was found to be significantly more pronounced (p < 0.05). The tympanic membranes were found to be significantly thinner in Groups II and III when compared with Groups I (p < 0.05).ConclusionsThe results of this study suggested that topical or oral administration of NS oil supressed the inflammation and fibroblastic activity in the lamina propria of the myringotomized TMs of the Guinea pigs. For providing further evidence to use plant extracts as antioxidant and antiinflammatory therapy after myringotomy or ventilation tube insertion, further clinical studies with larger population will be essential.     

Inhibition of the development of myringosclerosis by local administration of fenspiride, an anti-inflammatory drug

Earlier studies have revealed a relationship between the development of myringosclerosis and oxygen-derived free radicals. The latter can be blocked by the anti-inflammatory drug fenspiride. The present study was undertaken to test the ability of fenspiride to prevent myringosclerosis from developing during healing of the tympanic membrane. Myringotomized rats were treated with either topical applications or intraperitoneal injections of fenspiride for 12 days, after which the tympanic membranes were examined by otomicroscopy and studied histologically by light microscopy. Topically applied fenspiride was found to inhibit the development of sclerotic lesions, whereas intraperitoneal injections were ineffective.     

Calcium deposition and expression of bone modelling markers in the tympanic membrane following acute otitis media

BACKGROUND AND OBJECTIVES: In accordance with clinical findings, myringosclerosis develops after otitis media (OM) and paracentesis in an experimental setting. The pathogenesis of this phenomenon of calcification is poorly understood. As the calcification process and the sclerotic plaques of the drum mimics features of bone tissue, this study explores tympanic membrane calcium deposition in association with the expression of three bone modelling markers: osteopontin (OPN), osteoprotegerin (OPG) and osteonectin (ON). OPN is secreted by osteoblasts and is found at calcification sites, e.g. during pathological calcification in chronic OM. The cytokine OPG is an inhibitor of bone resorption and consequently bone remodelling. ON is a calcium binding glycoprotein necessary for the maintenance of bone mass and remodelling. It is found in bone matrix and synthesized by osteoblasts. METHOD: A rat model of acute otitis media (AOM) caused by non-typeable Haemophilus influenzae was used. Four days following middle ear inoculation, a myringotomy was performed in six animals. Another group of ten animals was inoculated only. The drum was dissected in two animals from each group on day 4, 7, 14 and 28 post-inoculation, and the expression of OPN, OPG and ON was determined by immunohistochemistry. von Kossa staining determined the deposition of calcium and immune staining for CD68 identified macrophages. RESULTS: Calcium depositions were initially accumulated in the cytoplasm of macrophages and dispersed in the connective tissue layers of the pars flaccida and tensa. Late accumulation occurred in the lamina propria of pars tensa, more extensively in myringotomized ears. OPN expression was found early in inflammatory cells including especially macrophages and late in pars tensa fibrocytes. OPG expression was initially located to inflammatory cells and late to pars tensa fibrocytes and the inner basal membrane of pars flaccida. Some ears displayed a marked pars flaccida expression of ON in the connective tissue matrix on early days and at the inner basal membrane on later days. The latter cases were from myringotomized ears. Otherwise, no apparent differences of marker expression occurred between myringotomized and non-myringotomized animals. CONCLUSION: We conclude that osteopontin, osteoprotegerin and osteonectin are expressed by different cell types in the tympanic membrane during calcification in association with AOM, with or without myringotomy. These molecules may accordingly play a role in the pathogenesis of myringosclerosis, in which macrophages and fibrocytes appear as potential major players.     

Vitamin e-coated tympanostomy tube insertion decreases the quantity of free radicals in tympanic membrane

OBJECTIVE: Tympanosclerosis is a common sequela of ventilation tube treatment of otitis media with effusion causing hearing disability. It is associated with an increased production of free radicals (also known as reactive oxygen species) after myringotomy. Vitamin E is a scavenger of different free radicals by working as an antioxidant. The aim of the present study was to evaluate the effect of vitamin E-coated tympanostomy tube insertion at quantity of free radicals in rat tympanic membrane. METHODS: This prospective, controlled animal study consisted of male Sprague-Dawley rats divided into two groups of 10 animals each. Ordinary silcone tubes were applied to the right ears of the first group and vitamin E-coated silcone tubes were applied to the right ears of the second group. The left ears were used as controls. Then, the animals were killed and chemiluminescence measurements were made for tympanic membranes. RESULTS: Reactive oxygen species levels (ROS) were significantly increased in right ears of the first group when compared with the control ears (P < .0001), and the levels were statistically significant decreased in right ears of the second group as compared with the operated ears of the first group (P < .0001). The free radical levels of right and left ears in the second group were similar. CONCLUSIONS: Our results indicate that vitamin E-coated tube insertion decreases the quantity of reactive oxygen species in tympanic membrane after myringotomy and tympanostomy tube insertion.     

Ginkgo biloba,a free oxygen radical scavenger,affects inflammatory mediators to diminish the occurrence of experimental myringosclerosis

Conclusion: Systemic Ginkgo biloba extract treatment reduces the levels of nitrite/nitrate, malondialdehyde, and superoxide dismutase and increases the levels of glutathione peroxidase. By scavenging free oxygen radicals, ginkgo extract prevents the formation of myringosclerosis. Objective: Our objective was to evaluate inflammatory mediators to determine the antioxidant and anti-inflammatory effect of Ginkgo biloba extract to diminish myringosclerosis. Materials and methods: Thirty Wistar Albino rats, weighing 320–400 g were used. The upper posterior quadrants of both tympanic membranes were myringotomized and divided into four groups. Ginkgo biloba extract was given orally to groups 1 and 2 comprising eight rats with doses of 100 mg/kg/day and 200 mg/kg/day, respectively. Seven rats in group 3 received 1.5 ml/day saline and seven rats were left untreated. After 10 days of treatment, otomicroscopic evaluation of tympanic membranes and measurement of anti-inflammatory mediators such as superoxide dismutase, nitrite/nitrate, glutathione peroxidase and malondialdehyde were performed. Results: Myringosclerosis was significantly more severe in control and saline groups than in Ginkgo biloba groups. The levels of nitrite in ginkgo-treated groups were significantly lower than in untreated and saline-treated groups, while glutathione peroxidase levels were significantly higher. The levels of malondialdehyde and superoxide dismutase were lower in ginkgo groups but not significantly.     

Myringotomized Mice Develop Myringosclerosis in the Pars Flaccida and Not in the Pars Tensa

The development of myringosclerosis has been correlated with increased production of oxygen-derived free radicals. For the present study, we used a null mutant mouse lacking extracellular superoxide dismutase to test the hypothesis that increased production of free radicals can cause the development of myringosclerosis. Null mutant mice and wild-type, control mice were myringotomized and kept in ambient air for 3 weeks. Both groups developed myringosclerosis in the pars flaccida, but not in the pars tensa. The sclerotic lesions were visible in both the light and the electron microscope but not in the otomicroscope. In particular, the localization of the sclerotic deposits was found beneath both the inner and outer epidermal epithelium. No difference concerning the extent or number of sclerotic lesions between the null mutant and the wildtype mice could be distinguished.