Safety and efficacy of topical mitomycin C in myringotomy patency

Histologic Evaluation of Healing Lip Defects Treated With Injected Onabotulinum Toxin A and Topical Mitomycin C

OBJECTIVE

Using an experimental rat model, the efficacy of injected Onabotulinum Toxin A (BoNT-A) versus topical Mitomycin C in surgical wound healing of rat lip defects was evaluated.

METHODS AND MATERIALS

Sixty-seven male Wister rats received a triangular cut (7 × 7 × 4 mm) on their upper lip. Then they were divided randomly into 4 equal groups: group A (topical Mitomycin C plus injected BoNT-A); group B (topical Mitomycin C); group C or control group (saline solution) and group D (injected (BoNT-A). After 3 months, the animals were euthanized and scars were evaluated using hematoxylin and eosin and Masson's trichrome.For qualitative analysis, inflammatory cell density, new capillary formation, fibroblast proliferation, and collagen deposition were reported using relative ranks from 0 to 3 (absence, mild, moderate, marked). Data were analyzed by post hoc and Kruskal-Wallis tests. The significance level was P < 0.05.

RESULT

Mean collagen deposition values and fibroblast proliferation in the 4 groups showed statistically significant differences with each other (P value < 0.001). A significant difference between group A and controls existed for fibroblast proliferation (median 1 versus 2, P value < 0.001); also, collagen deposition (median 1 versus 2, P value < 0.001). A significant difference existed between the control and group D (median 2 versus 1, P value = 0.004); also, group A and B (median 1 versus 2, P value = 0.002) for collagen deposition. However, no significant differences existed between the 4 groups regarding inflammatory cells and angiogenesis (P value > 0.05).

CONCLUSION

Local injection of BoNT-A plus Mitomycin C followed by BoNT-A alone provided less collagen formation and fibroblastic proliferation in the healing lip defect in a rat model.

Chronic model of tympanic perforation in rats with mitomycin C and dexamethasone

A rat model of chronic tympanic membrane perforation was developed to be used in the search of new materials for the sealing of these perforations. A longitudinal study was carried out in rats subjected to incisional myringotomy followed by the application of mitomycin C alone or with dexamethasone. Rats were checked at days 3, 7, 10, 14 and weekly thereafter until perforation closure, for up to 6 months. The addition of dexamethasone is a key component in order to obtain a chronic opening. Myringotomies treated with saline had a mean healing time of 8.5 days. At 8 weeks, between 62.5% and 77.7% of tympanic membranes treated with mitomycin C and dexamethasone remained perforated and at 6 months this number fell to 21.4%. This technique is able to maintain most tympanic membrane perforations patent for at least 8 weeks. This rat model is adequate for its use in preclinical or translational research.

A Preliminary Report on the Effects of Paclitaxel-Impregnated Stents on Sheep Nasal Mucosa

Introduction

Traditional frontal sinus stents serve only as mechanical devices. It has been proposed that stents also may serve as drug-delivery systems for the topical application of drugs that minimize postoperative scarring. Paclitaxel (Taxol), which has recognized antiscarring effects, may be incorporated via a polymeric formulation into standard rubber stents. The impact of topically applied paclitaxel on the morphology of the nasal mucosa is unknown.

Methods

An adult sheep model was used for this study. A modified rubber T-tube stent (incorporating paclitaxel at varying dosages) was secured to each side of the septum in four animals (eight sides). An unmodified T-tube was placed on each side of one animal, a T-tube with the drug carrier (but no paclitaxel) was placed on each side of the second animal, and T-tubes with varying paclitaxel were placed on each side of the final two animals. After 4 weeks, animals were killed and the nasal mucosa was harvested. The nasal mucosa was sectioned and stained with hematoxylin and eosin. A pathologist then assessed the nasal mucosa for vascular congestion, glandular atrophy, chronic inflammation, mucosal metaplasia, and mucosal ulceration.

Results

No consistent histopathological differences were noted in the specimens. All specimens showed varying degrees of vascular congestion, glandular atrophy, chronic inflammation, and mucosal metaplasia; the paclitaxel-impregnated stents were not consistently associated with more severe mucosal injury. Finally, mucosal ulceration was noted to be very rare in all specimens.

Conclusion

This preliminary report describes the impact of paclitaxel-impregnated stents on sheep nasal mucosa, which tolerated these stents very well. Because paclitaxel minimizes scarring reactions at very low concentrations, paclitaxel-impregnated stents may prove useful in clinical situations in which frontal sinus stenting is deemed necessary. Additional investigations with animal models, as well as clinical trials, may be warranted.

Contact Diode Laser Myringotomy and Mitomycin C in Children

OBJECTIVE: To investigate the use of contact diode laser myringotomy (C-LAM), combined with topical mitomycin C, as an alternative method for prolonged middle ear ventilation in children with otitis media with effusion.

STUDY DESIGN AND SETTING: Prospective study at a tertiary care pediatric institution.

METHODS: Fifteen children enrolled in the study. Mitomycin C was applied to the intact tympanic membrane in the right ears, whereas saline on the left side was used for controls. C-LAM was then performed in all ears. Outcome measures included healing rate and scarring, ear infection, and long-term audiometric follow-up.

RESULTS: There was no significant difference in median healing rate. In each group, the median was between the third and fourth month. Normal hearing thresholds were obtained in all children at 2-year follow-up.

CONCLUSION: C-LAM proved to be an effective method for medium-term ventilation, but topical mitomycin C before C-LAM did not prolong patency rate in our patients. No significant complication was encountered at 2-year follow-up. (Otolaryngol Head Neck Surg 2004;130:742-6.)

Safety and efficacy of Intraurethral Mitomycin C Hydrogel for prevention of post-traumatic anterior urethral stricture recurrence after internal urethrotomy

BACKGROUND

Evaluation of the safety and efficacy of intraurethral Mitomycin C (MMC) hydrogel for prevention of post-traumatic anterior urethral stricture recurrence after internal urethrotomy.

METHODS

A thermoresponsive hydrogel base consisting of 0.8 mg MMC with 1cc water and propylene glycol to PF-127 poloxamer was used in theater. 40 male patients with short, non-obliterated, urethral stricture were randomized into 2 groups: control and MMC. After internal urethrotomy, the MMC group patients received the MMC-Hydrogel while the others were just catheterized. Both groups had their catheters for at least 1 week. After surgery, they were followed up by means of medical history and physical examination, monitoring voiding patterns and retrograde urethrogram at 1 month, 6 months and 1 year after surgery.

RESULTS

40 male patients between 14 to 89 years old (Mean = 54.15) underwent internal urethrotomy. The average age for the control and MMC group was 54.55±21.25 and 53.75±24.75 respectively. In a comparison of age between the two groups, they were matched (P=0.574). Stricture length was 10.7±5.9 and 9.55±4.15 mm for the control and MMC group respectively. There were no statistically meaningful differences between the two groups (P=0.485). Fifteen patients had a history of one previous internal urethrotomy which in a comparison between the two groups meant there was no meaningful difference (P=0.327). During postoperative follow up, total urethral stricture recurrence happened in 12 patients: 10 patients (50%) in control group and 2 patients (10%) in MMC group. The difference was statistically significant (P=0.001). There were no significant complications associated with the MMC injection in our patients.

CONCLUSIONS

Based on our results, MMC Hydrogel may have an anti-fibrotic action preventing post-traumatic anterior urethral stricture recurrence with no side effects on pre-urethral tissue. Due to our study limitations, our follow up time and the small number of patients, our results were not conclusive and further studies will be needed with a longer follow up time.

Mitomycin C Effect on Fibrous Adhesions of Rabbit Temporomandibular Joint

OBJECTIVE: To evaluate influence of mitomycin C on fibrosis in temporomandibular joints of rabbits with mandibular traction.

STUDY DESIGN: Twenty rabbits (8 control, 12 mitomycin C group) were included. Titanium screws were placed in the anterior edge of the right masseter tuberosity and the posterior part of the right zygoma. Elastic bands were placed between 2 screws to initiate posterio-superior displacement of the mandible to the right. Animals in the control group (CG) received intraarticular NaCl (0.9%) on the nondrawing (left) side, and animals in the study group (SG) received mitomycin C weekly (0.4 mg/mL) for 6 weeks. Rabbits were decapitated, temporomandibular joints were removed, and histopathological investigation was performed.

RESULTS: Microscopically, 4 of 6 rabbits in the CG had fibrosis in the temporomandibular joint, whereas only 1 of 11 rabbits in the SG had fibrosis ( P < 0.05).

CONCLUSION: Application of mitomycin C to the temporomandibular joint of rabbits significantly reduces formation of intraarticular fibrous adhesions.

SIGNIFICANCE: This is the first study in the literature investigating the use of mitomycin C in the joints.

The Effects of Intradermal and Topical Mitomycin C on Wound Healing

OBJECTIVE: To determine the effect of intradermal and topical mitomycin C (MMC) on skin wound healing.

STUDY DESIGN/SETTING: A prospective, controlled study in a rat wound model performed in an academic medical center.

RESULTS: Intradermal and topical MMC application decreased wound integrity when compared with saline-treated animals at 1 week, 2 weeks, 1 month, and 6 months. Skin necrosis occurred in animals that received intradermal MMC. Hemotoxylin and eosin and immunohistochemical staining showed no consistent difference between treatment arms. Fibrosis and collagen deposition were reduced in MMC-treated wounds on trichrome staining.

CONCLUSIONS: MMC-treated wounds showed decreased wound strength compared with controls. Intradermal MMC can cause skin necrosis. Histologic findings did not always correspond with clinical data.

SIGNIFICANCE: The data suggest cautious use of MMC in clinical situations when wound breaking strength is critical.

Quantifying the Ototoxicity of Mitomycin: Before versus after Myringotomy

OBJECTIVES

Recent research has focused on mitomycin C (MMC) application as a means to circumvent complications that arise when using ventilation tubes during myringotomy. This study has two aims: (1) to synergize the current literature to create a standardized clinical approach for using MMC, and (2) to determine at which point during the myringotomy the application of MMC proves the safest (i.e., before or after incision).

METHODS

We measured the auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) in 9 female chinchillas to determine whether applying MMC before or after incision was also the safest. The tests were then repeated on days 3, 10 and 17.

RESULTS

The change in the ABR thresholds from baseline was greater in the experimental than in the control group; however, after stratification, the 'after' group experienced a statistically significant change (19.38 ± 8.26) on day 17, whereas the 'before' group did not (2.00 ± 3.26; p = 0.003). No such changes were seen with DPOAE testing.

CONCLUSIONS

Mitomycin is less ototoxic to the middle ear when applied before myringotomy is done. We recommend future studies to apply the clinical approach we have designed to standardize its use in selected cases.

Efficiency of cryotherapy in avoiding myringotomy closure in rats

Myringotomy and ventilation tube placement is an office-based procedure and represents the treatment of choice for middle ear effusions and for transtympanic drug administration. The aim of our study was to study the efficiency of low-pressure spray cryotherapy on protraction of patency time of myringotomies in rats. Bilateral myringotomies were performed with cold instruments. Afterward, one ear in each rat was randomly assigned for liquid nitrogen treatment of the perforated eardrum. Myringotomy patency was recorded daily and histological analysis of the eardrums was performed. In the myringotomy group patency time was 4.75 ± 2.93 days, while in the cryotherapy group was 11.01 ± 4.87 days. The difference is statistically significant: Student t test, p < 0.00001, 95 % CI (-8.82; -3.67). Moreover, according to Kaplan-Meier method, myringotomy survival is significantly longer in the cryotherapy group. The healing processes of the cryotreated eardrums last longer and the patency of myringotomy was longer as compared to untreated myringotomies.

Myringotomy in the Junbo mouse model of chronic otitis media alleviates inflammation and cellular hypoxia

OBJECTIVES/HYPOTHESIS

Ventilation of the chronically inflamed middle ear is a key outcome in functional middle ear surgery. Grommets eliminate middle ear effusion, but there is also evidence that they downregulate inflammation. The reason for this is not understood, but there is little to suggest alteration in eustachian tube ventilatory capacity. Previous work has shown that the Junbo mouse model of chronic otitis media has hypoxic middle ear mucosa and bulla fluid leucocytes. Here we explore whether surgical ventilation may alleviate chronic otitis media through downregulation of hypoxia.

STUDY DESIGN

Surgical intervention on a mouse model of disease.

METHODS

We established patency of myringotomy incision as 5 days in wild-type mice. We performed unilateral myringotomy on three cohorts of mice: 10 wild-type controls, 12 Junbo mice, and 15 Junbo mice with additional removal of middle ear effusion. A small cohort of these mice were labeled in vivo by intraperitoneal injection of pimonidazole to identify tissue hypoxia. Tissues were assessed for mucoperiosteal thickening and pimonidazole labeling, comparing operated to nonoperated ears.

RESULTS

Ventilation of the inflamed Junbo middle ear revealed significant reduction in inflammatory thickening associated with loss of pimonidazole labeling, suggesting resolution of cellular hypoxia.

CONCLUSIONS

Surgical ventilation may achieve therapeutic effect through alleviation of cellular hypoxia in the chronically inflamed middle ear. Targeted molecular therapy of hypoxia signaling may offer future alternative therapy for chronic otitis media.

The effect of mitomycin-C in reducing pericardial adhesion after cardiac surgery in rabbits

BACKGROUND

Mitomycin-C has been in clinical use primarily as a chemotherapeutic agent and is well known for antifibrotic properties. It has been widely used to prevent postoperative fibroblast proliferation and reduce scar adhesion in ophthalmologic and otolaryngologic operations. We investigated the efficacy of mitomycin-C in reducing postoperative pericardial adhesions in a rabbit model.

METHODS

New Zealand white rabbits were used and categorized into 2 groups, study (use of mitomycin-C) and control. Group 1 (n = 8) was treated with a sponge impregnated with mitomycin-C solution that was applied over the abraded epicardium. In group 2 (control group), the sponge was impregnated with 0.9% isotonic NaCl solution and was applied with the same protocol as the mitomycin-C-impregnated sponge in group 1 (n = 8). Rabbits were humanely killed at a mean of 2 weeks. The scores of adhesion were graded by macroscopic examination, and the pericardial tissues were analyzed microscopically in terms of inflammation and fibrosis.

RESULTS

In group 1, the adhesion scores were significantly lower than the control group's. No significant difference was found between the groups in terms of the severity of inflammation. There was a difference between groups in terms of the degree of fibrosis.

CONCLUSIONS

The use of mitomycin-C to prevent postoperative pericardial adhesions reduced adhesion and fibrosis scores in an experimental rabbit model. However, efficacy in reducing inflammation was not demonstrated.

Microscopic comparison of topical use of Mitomycin C and Fluorouracil on cold knife myringotomy

Objective/hypothesis A comparison of the histopathological effect of topical use of Mitomycin C and 5-Fluorouracil in preventing myringotomy closure in rats.

STUDY DESIGN

clinical trial. Methods and materials The study was performed on 43 rats that were divided into three groups. Study groups (A and B) and control group (C) after bilateral cold-knife myringotomy, we applied Mitomycin C (MMC) 4mg/ml to group A, 5-Fluouracil (5FU) 50mg/ml to group B, and normal saline to group C. An examination of all ears of rats was carried out by otoscope on days 0, 1, 3, 5, 7, and then every five days up to 70 days. Each day's closed myringotomies of all groups were examined. Results The mean of post myringotomy opening time was 37, 16, and 12 days respectively in MMC, 5FU, and saline. Patency duration of MMC group was significantly long (p<0.0001), but in histopatholgical examinations, sclerosis of tympanic membrane in MMC group showed the highest patency duration (p<0.0001). Conclusion Mitomycin C significantly prolonged the duration of myringotomy patency time - longer than 5-Fluouracil and saline but with the adverse effects of tympanic membrane fibrosis.

Effect of treatment at different time intervals for traumatic tympanic membrane perforation on the closure

CONCLUSION

Treatment of traumatic tympanic membrane (TM) perforation with everted or involute edge flaps at different time intervals within 1 week after the injury did not affect the perforation closure rate and mean closure time.

OBJECTIVE

To retrospectively analyze the effect of treatment at different time intervals for traumatic tympanic membrane perforation with gelatin sponge patch and edge approximation plus gelfoam patching.

METHODS

Patients with traumatic TM perforation visited at different days since the injury for medical treatment (1, 2, 3, 4, and 5-7 days post trauma). These patients were treated with the following prominent methods of treatment: gelatin sponge patch treatment and edge approximation plus gelfoam patching. Measurement indicators were perforation closure rate and mean closure time at 3 months.

RESULTS

In the group treated with the gelatin sponge patch technique, the patients sought medical treatment at different time intervals since the injury. Accordingly, the outcome of the treatment varied in terms of the perforation closure rates achieved in different patients in this group. The respective perforation closure rates were 100%, 100%, 96%, 94%, and 89% in accordance with the time interval at which the patients were treated since the injury. The results were not significantly different when compared by statistical analysis (p > 0.05); the mean closure times in each of the different sets of cases in this group were calculated and the following values were reported: 7.1 ± 2.3, 8.2 ± 1.6, 8.7 ± 1.2, 9.2 ± 3.1, and 10.7 ± 3.9 days. On the other hand, in the edge approximation plus gelfoam patching group, the perforation closure rates were 100%, 97%, 96%, 97%, and 94%, respectively. This was in accordance with the time elapsed since the injury for the patients who visited the hospital on different days. Statistical analysis confirmed that the perforation closure rates for the different cases of this group did not have any significant difference (p > 0.05); the mean closure times were 7.6 ± 1.9, 7.9 ± 2.2, 9.2 ± 2.8, 8.5 ± 3.6, and 11.2 ± 4.1 days, respectively, indicating that differences were not significant even in terms of mean closure rates for the different cases of this group (p > 0.05).

Mitomycin C-associated radiofrequency microelectrocautery used in myringotomy in an animal model

This study aimed at describing an alternative surgical technique to the insertion of a ventilation tube in the tympanic membrane: myringotomy by radiofrequency alone and associated with mitomycin C.

AIM

to show a surgical approach that can be simple to execute, not subject to complications arising from the ventilation tube.

MATERIALS AND METHODS

we compared myringotomy by microknife and by radiofrequency microcautery (0.3 mm and 0.7 mm tips) alone and associated with mitomycin C, considering the time of tympanic closure in Wistar rats. Experimental study.

RESULTS

there was a statistically significant difference between radiofrequency myringotomy and knife myringotomy. As we analyze the radiofrequency approach with the 0.7 mm tip associated with mitomycin C (Wilcoxon test), the p value found was lower than 0.001, showing a statistical significance. The maximum tympanic membrane closure time was 44 days and the median found was 14 days.

CONCLUSION

the radiofrequency myringotomy (with the larger diameter tip) associated with mitomycin C enhances the tympanic membrane healing time.

Angiogenesis, fibrinogenesis and presence of synechiae after exeresis of a swine vocal fold mucosal microflap and use of topical mitomycin-C

PURPOSE: To evaluate swine vocal fold healing in a period of 30 days after topical mitomycin-C application. METHODS: Twelve swine underwent exeresis of mucosal flaps from the free edge of the anterior third of both vocal folds with a cold instrument (laryngeal scissors). The animals were divided into two groups: EG (Experimental Group), consisting of 6 animals undergoing topical MMC application (4 mg/dL) on the operated area for 4 minutes; CG (Control Group), 6 animals undergoing topical saline solution application on the operated area for 4 minutes. After 30 days, the animals were sacrificed and the larynges were collected and examined for the presence of synechiae as well as a histological immunohistochemical assessment of immature and mature collagen deposition, number of blood vessels and myofibroblasts. RESULTS: Mature collagen deposition in the EG was 452.12 μm² and 1332.31μm² in the CG; immature collagen deposition was 1511.73μm² in the EG and 1020.61μm² in the CG. The number of myofibroblasts was 1.556 in the EG and 3.583 in the CG. The number of blood vessels was 2.565 in EG and 6.917 in the CG. There were no synechiae in the two studied groups. CONCLUSIONS: There was an increase in immature collagen deposition in the experimental group when compared with the control group. There was a decrease in mature collagen deposition in the experimental group when compared with the control group. There was a decrease in the number of myofibroblasts in the experimental group when compared with the control group. A decrease in blood vessels was observed in the experimental group when compared with the control group. There was no synechia formation in either studied group.

Topical mitomycin-C for the treatment of anal stricture

BACKGROUND

Anal stricture is a well-known and feared consequence of anorectal surgery. Daily dilatations are often prescribed in the immediate postoperative period to avoid stricture of the anus. Nonetheless, stricture may still occur and, particularly in older children, may require multiple dilatations under anesthesia. Topical mitomycin-C has been found to be effective in the treatment of strictures at various anatomical locations. In this article, we review our experience with topical mitomycin-C as an adjunct to anal dilatation for children with anal stricture.

MATERIALS AND METHODS

Cases of children with anal stricture who were treated with a single application of topical mitomycin-C as an adjunct to anal dilatation between 2000 and 2008 were analyzed retrospectively. Anal diameter was measured with Hegar dilators. Cottonoid swabs soaked in mitomycin-C were placed on the anal mucosa for 5 minutes after dilatation. Treatment success was defined by sustained improvement in anal size, decrease in symptoms, parental satisfaction, and need for additional intervention.

RESULTS

Ten children with anal stricture who underwent anal dilatation with application of topical mitomycin-C were identified. All children presented with severe constipation. Average increase in anal size after dilatation under sedation was 5.7 mm (+/-3.2 mm). Average improvement in anal diameter on first clinic visit after mitomycin-C application was 3.7 mm. On follow-up, only 1 child required repeated intervention for stricture after treatment with mitomycin-C. No complications were associated with the use of mitomycin-C.

CONCLUSIONS

All children treated with mitomycin-C showed early improvement in their anal size after dilatation under sedation. A single application of topical mitomycin-C allowed them to retain an increased anal diameter over time and avoid additional dilatations. Furthermore, the application of mitomycin-C in our population was straightforward and safe. Therefore, we advocate its use as an adjunct to anal dilatation under sedation in the treatment of severe anal stricture.

Study of wound healing in rats treated with topical and injected mitomycin-C

Experimental study in animals. Introduction: Mitomycin C has been used as a fibroblasts inhibitor, thus reducing the scaring process in surgical wounds.

Aim

This paper aims at assessing the use of Mitomycin C to reduce the scaring process through its topical use and later injected reinforcements.

Materials and Methods

We used a model of a creating a wound in the dorsum of rats, removing a circular piece of skin and letting it heal by itself. We used 18 rats, divided in three groups. The first group - Control, the second with topical use, and a third group with injected mitomycin C reinforcement, monthly for 2 months. After 3 months the animals were slaughtered and the scars were surgically removed and sent for histology study.

Results

We noticed, under different criteria, that healing with topical mitomycin is less intense; however, when it was injected, the parameters were again comparable to those from the control group.

Discussion

We believe that injected mitomycin C in the scar, since it is highly toxic, it destroys tissue and brings about scar neoformation.

Conclusions

Mitomycin C reduces the scaring process when used topically; however, it increases scar tissue formation when injected in these wounds.

Study of Wound Healing in Rats Treated with Topical and Injected Mitomycin C

Objectives:

Mitomycin C, a widely used chemotherapeutic drug, has been proposed as a potential adjuvant for the control of scar tissue in surgical wounds because of its capacity to inhibit fibroblast proliferation. The current study used a combination of topical and injected mitomycin C to slow the healing process of surgical wounds in rats.

Methods:

An experimental model of surgical wounding at the dorsum of rats was used. A total of 43 animals were subdivided into 3 groups: Control, topical mitomycin C, and a combination of topical treatment and intradermal injections of the drug at 30 and 60 days after the initial topical treatment. After 3 months, the animals were painlessly sacrificed and the surgical scars were removed for microscopic analysis.

Results:

The group that received only topical mitomycin C presented milder inflammatory signs and consequently had a less intense healing process than the control group. The group treated with a combination of both topical and injected mitomycin C presented results comparable to those of the control group.

Conclusions:

The toxic characteristics of mitomycin C were most likely responsible for the greater tissue damage that occurred when it was used in the injected form, causing increased scar tissue formation. Mitomycin C slows the healing process of surgical wounds when used topically, but causes enhanced scar tissue formation when injected.

Comparative study of laser versus radiofrequency myringotomy in rabbits: The effectiveness of mitomycin C application

OBJECTIVE

To compare laser-assisted tympanostomy (LAT) with radiofrequency myringotomy (RFM), as well as the effectiveness of mitomycin C (MC) on the above techniques, in rabbits.

STUDY DESIGN

Experimental animal research protocol.

SETTING

University of Crete, School of Medicine, Medical Experimental Education and Research Center.

METHODS

Bilateral myringotomies were performed under general anesthesia on 40 rabbits. LAT was performed on 20 animals (40 ears) and RFM on the remaining 20 animals (40 ears). MC (0.3 mg/mL) pledgets were applied to the right ears and saline pledgets to the left ears. Animals were monitored weekly using otomicroscopy until myringotomy closure. Kaplan-Meier survival techniques were used to compare myringotomy patency times.

INTERVENTIONS

Under general anesthesia, bilateral LAT was performed on 20 rabbits and bilateral RFM on 20 rabbits.

MAIN OUTCOME MEASURES

Myringotomy patency time.

RESULTS

The mean patency times of the saline-treated ears were: 1.85 weeks (95% confidence interval [CI], 1.556-2.144 wk) for the LAT group and 1.70 weeks (95% CI, 1.494-1.906 wk) for the RFM group. This difference was not significant (p > 0.5). MC application significantly prolonged mean patency time (p < 0.0001) in both LAT and RFM groups. The mean patency times in the MC-treated ears were 5.45 weeks (95% CI, 5.226-5.674 wk) for the LAT group and 5.55 weeks (95% CI, 5.285-5.815 wk) for the RFM group. This difference was not significant (p > 0.5).

CONCLUSION

There is no significant difference in myringotomy patency times between LAT and RFM techniques in rabbits, whereas MC significantly prolongs the patency rate of either technique.

A comparison of the effectiveness of mitomycin C and 5-fluorouracil in the prevention of peridural adhesion after laminectomy

Object

The effectiveness of the topical application of mitomycin C (MMC) or 5-fluorouracil (5FU) in preventing peridural adhesion after laminectomy was compared in this study.

Methods

Laminectomies were performed at L-1 in 30 rats. Cotton pads soaked with 0.1 mg/ml MMC, 25 mg/ml 5FU, or 9 mg/ml saline (control) were applied to the operative sites. To evaluate neurological deficits pre- and postoperatively, somatosensory evoked potentials were monitored and the Basso-Beattie-Bresnahan locomotion test was performed. Four weeks postlaminectomy the rats were killed, and peridural scar adhesion was evaluated histologically. The level of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts were determined. The degree of peridural adhesion was classified according to the Rydell standard.

Results

No obvious adhesion formed in the rats in the MMC group, but severe peridural adhesions were found in those in the 5FU and control groups. The content of hydroxyproline, the area of peridural scar tissue, and the number of fibroblasts in the MMC group were significantly lower than those in the 5FU and control groups.

Conclusions

The topical application of MMC rather than 5FU may be a successful method of preventing post-laminectomy peridural adhesions.

Effect of Mitomycin C on Anterior Urethral Stricture Recurrence after Internal Urethrotomy

OBJECTIVES

Urethral stricture is one of the oldest known urologic diseases and remains a common problem with high morbidity. Internal urethrotomy refers to any procedure that opens the stricture by incising or ablating it transurethrally. The most common complication of internal urethrotomy is stricture recurrence. The curative success rate of internal urethrotomy is approximately 20%. Mitomycin C has antifibroblast and anticollagen properties and in sporadic reports of animal and clinical studies it has increased the success rate of trabeculectomy and myringotomy. This study evaluated the efficacy of mitomycin C in the prevention of anterior urethral stricture recurrence after internal urethrotomy.

PATIENTS AND METHODS

Forty male patients with anterior urethral strictures were randomized to undergo internal urethrotomy with or without urethral submucosal mitomycin C injection. Using general anaesthesia, the urethrotomy was performed under direct vision. Mitomycin C (0.1mg) was injected submucosally at the urethrotomy site in 20 patients. The patients were re-evaluated after 6 mo and the stricture recurrence rate was compared between the two groups (chi(2) analysis).

RESULTS

Urethral stricture recurred in 2 patients (10%) in the mitomycin C-treated group and in 10 patients (50%) in the other group. This difference in stricture recurrence between the two groups was statistically significant (p=0.006).

CONCLUSIONS

To our knowledge, this is the first prospective, randomized, clinical trial to evaluate the efficacy of mitomycin C application in internal urethrotomy. Submucosal injection of mitomycin C significantly reduced stricture recurrence after internal urethrotomy. Further investigations are warranted to confirm its efficacy and safety.

Inhibition of epidermal growth factor receptor by erlotinib: wound healing of experimental tympanic membrane perforations

HYPOTHESIS

Inhibition of epidermal growth factor receptor (EGFR) may arrest wound healing of experimental tympanic membrane perforation in rats.

BACKGROUND

An animal model of chronic tympanic membrane perforation is needed for experiments on supporting wound healing of tympanic membrane perforations. The EGFR has been implicated in the regulation of wound healing.

METHODS

Thirty animals were administered 80 or 40 mg/kg/d EGFR tyrosine kinase inhibitor, or vehicle only for 5 days. The right-sided tympanic membrane of each animal was perforated at Day 2. Rat ears were inspected repeatedly to analyze the status of perforation. Tympanic membranes were examined histologically.

RESULTS

Unfortunately, five animals in the 80-mg/kg group and four in the 40-mg/kg group died before they reached their scheduled endpoint. Taking into account the small sample sizes, we observed a delayed closure of perforations in the 80-mg/kg group and differences in the histologic parameters between treated groups and control group.

CONCLUSION

The inhibition of EGFR by systemic application of erlotinib seems not to be suitable to create a chronic tympanic membrane perforation in rat.

Topical Application of Mitomycin C to the Middle Ear Is Ototoxic in the Gerbil

HYPOTHESIS

Mitomycin C is ototoxic when applied topically to the structures of the middle ear.

BACKGROUND

Mitomycin C is a topically applied medication widely used in a variety of surgical procedures to prevent excessive scar tissue formation. Its safety for use during otologic procedures has not been fully evaluated.

METHODS

A laboratory study was undertaken using the Mongolian gerbil as an animal model. Both acute and chronic effects on cochlear function of mitomycin C were assessed with measurements of compound action potential (CAP) thresholds of the auditory nerve, CAP input/output functions, distortion product otoacoustic emissions, and endocochlear potentials. Morphologic changes were assessed with light microscopy using hematoxylin-eosin staining as well as transmission electron microscopy.

RESULTS

Five-minute applications of mitomycin C (0.5 mg/ml) to the entire surface of the middle ear adversely affected CAP thresholds, input/output functions, distortion product otoacoustic emissions, and the endocochlear potential. Ninety-minute exposures of mitomycin C solely to the round window produced similar changes. Histologic evaluation of animals 1 week after treatment showed damage to cochlear hair cells, the stria vascularis, and spiral ganglion neurons when compared with controls.

CONCLUSION

Mitomycin C can produce substantial sensorineural hearing loss when applied topically to the gerbil middle ear for even brief periods. Consequently, its safety for topical use in the human middle ear is highly questionable.

Topical mitomycin-C for obstructing endobronchial granuloma

An elderly woman with post-tuberculous stricture of the lower trachea and main bronchi underwent laser re-canalization, balloon dilation, and silicone stent insertion in the lower trachea and main bronchi. Subsequently she had recurrent dyspnea develop due to obstructing granulomas, which necessitated four endoscopic procedures in 2 years. The tracheal stent was removed and topical mitomycin-C was applied using saturated pledgets at a dose of 0.5 mg/mL for 2 minutes each over the lower trachea and both orifices of the main bronchi. Follow-up for 24 months showed no recurrence of symptoms. Bronchoscopy and spirometry performed at 2, 6, and 12 months showed resolution of the granulomas.

Topical application of transforming growth factor-β1 in acute traumatic tympanic membrane perforations: an experimental study in rats

High transforming growth factor-beta1 (TGF-beta1) expression in combination with fibrotic scar was observed in human tympanic membranes containing a chronic perforation. The purpose of this study was to investigate whether application of exogenous TGF-beta1 to experimentally created tympanic membrane perforations might induce a nonhealing tympanic membrane perforation. Bilateral myringotomies were performed in 20 rats. In 10 animals, a single dose of TGF-beta1 (0.1 microg) was topically applied to the left tympanic membrane after perforation. In the second part of the study with 10 animals, repeated applications of TGF-beta1 at a higher concentration were tested. In both groups, the opposite ears received vehicle alone. Tympanic membranes were observed for a total of 5 weeks. The effect of TGF-beta1 on the healing of the tympanic membranes was evaluated by closure rates and histology. In the single application group, the healing process was not delayed. Repeated applications of TGF-beta1 did cause a faster perforation closure and a thicker tympanic membrane. Topical TGF-beta1 applied to a traumatic tympanic membrane perforation does not create a chronic perforation at the concentrations and modes of application used in this study.

Topical Application of Mitomycin C in Combination with Dexamethasone: Effective Delay of Myringotomy Closure

The object of this study was to investigate the efficacy of topical mitomycin C (MMC) in combination with subsequent topical dexamethasone to prolong the patency of myringotomies. Bilateral instrumental myringotomies were performed in 12 rats. On both sides, a solution of MMC (2 mg/ml) was applied to the intact tympanic membrane for ten minutes before myringotomy. Dexamethasone (4 mg/ml) was applied to one tympanic membrane of each animal at days 3, 6, 9 and 14. Tympanic membranes were observed weekly for a total of 9 weeks. The mean healing period was found to be 17.5 days (range 4.5-45.5 days) in the group with MMC alone, and 32 days (range 17.5-59.5 days) in the group MMC + dexamethasone. The difference was significant. A combination of topical MMC and subsequent dexamethasone did delay the healing rate of myringotomies in rat tympanic membranes longer than MMC alone.

Topical Application of Mitomycin C before versus after Myringotomy: An Experimental Study

The objective of this animal study was to compare topical mitomycin C (MMC) before and after nonlaser myringotomy. Bilateral myringotomies were performed in 12 rats. On the left side, MMC was applied to the intact tympanic membrane for 10 min before myringotomy (preapplication group). On the right side, MMC was applied to the tympanic membrane following myringotomy. Tympanic membranes were observed for a total of 8 weeks. By day 35, all myringotomies with application of MMC after perforation of the tympanic membrane were closed, whereas 42% of the myringotomies with application of MMC prior to perforation remained patent. One tympanic membrane in the preapplication group showed an enlargement of the perforation with partial destruction of the malleus. The present study showed that the application of MMC to the intact tympanic membrane prolongs the patency of nonlaser myringotomies in rats. Specific side effects of the MMC application must be kept in mind.

Radiofrequency Myringotomy with the Topical Use of Mitomycin C: An Experimental Study

OBJECTIVE

To assess the use of radiofrequency myringotomy in combination with mitomycin C as an alternative myringotomy technique on rabbits.

STUDY DESIGN

Experimental animal research protocol.

SETTING

University of Crete, School of Medicine, Medical Experimental Education and Research Center.

METHODS

Radiofrequency myringotomies were performed under general anesthesia on both ears of 20 rabbits. Mitomycin C (0.3 mg/ml) pledgets were applied in the right ears (study group) and saline pledgets in the left ears (control group). Animals were monitored using otomicroscopy weekly until myringotomy closure. Kaplan-Meier survival techniques were used to compare myringotomy patency time between the two sides.

INTERVENTION

Radiofrequency myringotomy under general anesthesia on both ears of 20 rabbits.

MAIN OUTCOME MEASURE

Myringotomy patency time.

RESULTS

The mean patency time of the study group was 5.45 weeks (95% confidence interval, 5.185-5.715 weeks). The mean patency rate for the control side was 1.60 weeks (95% confidence interval, 1.38-1.82 weeks). The Breslow (generalized Wilcoxon) test showed the study group to have significantly longer patency of radiofrequency myringotomy than the control group (p<0.0001).

CONCLUSION

The patency period of radiofrequency myringotomy was not long enough to be proposed as an alternative to the insertion of ventilation tubes, although mitomycin C had a significant adjunct effect in prolonging the patency rate of radiofrequency myringotomy on rabbits.

Effects of topical application of mitomycin-C and 5-fluorouracil on myringotomy in rats

OBJECTIVE

The effects of topical application of Mitomycin-C (MMC) and 5-fluorouracil (5-FU) for maintaining myringotomy patency were investigated in this experimental study.

STUDY DESIGN

We performed simple myringotomy with a knife on 140 tympanic membranes of 70 rats. Rats were divided in two study groups and a control group. Each study group had 60 tympanic membranes, and the control group had 20. We applied Mitomycin-C (0.4 mg/ml) in Group A, 5-fluorouracil (50 mg/ml) in Group B topically, and sterile saline in the control group for 10 minutes. Examination was made with otoendoscope on days 1, 3, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, and 70, and patency rates were recorded.

RESULTS

MMC and 5-FU Groups remained open for a mean of 46.17 days and 14.62 days, respectively. The control ears healed within 10.4 days. Fibrosis of the MMC-treated group was the same as that of 5-FU-treated groups. Fibrosis of both study groups was significantly lower than that of the control group.

CONCLUSIONS

MMC is more effective than 5-FU, which is more effective than the simple myringotomy procedure in extending the patency of myringotomies in rat tympanic membranes (p < 0.05). Both medications are useful as an adjunct in preventing myringotomy closure.

The Effect of Radiofrequency and Mitomycin C on the Closure Rate of Human Tympanostomy

OBJECTIVES

To conduct a prospective, randomized, controlled trial determining the feasibility of radiofrequency with or without topical mitomycin C application in delaying the closure time of human tympanostomy and screening its efficacy in management of recurrent acute otitis media and otitis media with effusion.

METHODS

From November 2002 to January 2004, 96 patients (180 ears) who were to undergo surgical intervention for recurrent acute otitis media or otitis media with effusion were included in this study. Sixty ears with a diagnosis of recurrent acute otitis media were equally randomized to three procedures: cold knife myringotomy (Group A), radiofrequency tympanostomy (Group B), and radiofrequency tympanostomy with topical mitomycin C application (Group C). One hundred twenty ears diagnosed as having otitis media with effusion were equally randomized to the last two procedures only. Patients were followed-up every week in the first month, every 2 weeks in the second month, and monthly after that until closure of the tympanostomy. A special follow-up setting was designed 3 months after tympanostomy closure where tympanograms and pure-tone audiograms were obtained.

RESULTS

Groups B and C showed a significantly slower rate of closure than Group A. At the same time, Group C demonstrated a slower rate when compared with Group B. The mean closure time of Group B was 3.5 weeks, with no difference between recurrent acute otitis media and otitis media with effusion. In contrast, the mean closure times for Group C were 5.3 and 7 weeks in cases of otitis media with effusion and recurrent acute otitis media, respectively, with the latter demonstrating a significantly slower closure rate. No recurrence of acute otitis media was reported in 10, 45, and 80% of Groups A, B, and C, respectively. Fifty-nine percent of Group C showed no clinical or tympanometric signs of otitis media with effusion 3 months after closure of tympanostomy. In contrast, Group B reported a lower cure rate (28%), with a statistically significant difference between both groups. Absence of recurrence and improvement in tympanometry signs correlated significantly with the duration of patency of tympanostomy (p < 0.01). The success rate was higher in patients who underwent adenoidectomy, but this did not reach statistical significance except in Group C (p < 0.01).

CONCLUSION

Radiofrequency and mitomycin C delay the closure rate of human tympanostomy. The efficacy of mitomycin C seems to be amplified in the presence of an inflamed tympanic membrane. Radiofrequency-assisted mitomycin-enhanced tympanostomy is a precise, safe, and cost-effective procedure that provides a viable approach in the management of recurrent acute otitis media and otitis media with effusion, especially when used in conjunction with adenoidectomy.

Use of mitomycin C for treatment of keloid: a preliminary report

OBJECTIVES

Mitomycin C (MC) is an anti-neoplastic agent with an anti-proliferative effect on fibroblasts. We set out to evaluate the effect of MC application following keloid excision.

STUDY DESIGN AND SETTING

Patients with keloid in a tertiary referral center were enrolled in a prospective study. The scar was excised and prior to skin closure, a pledget with 1 cc of MC 0.4 mg/mL was applied for 5 minutes. Patient satisfaction and keloid thickness were assessed.

RESULTS

All patients were satisfied with the results, although complete disappearance of the keloid was evident only in two. Keloid thickness was measured and ranged from 5 to 26 mm. Following surgery and treatment at 2 months thickness ranged from 0 to 8 mm.

CONCLUSIONS

MC application following scar resection appears to be effective in treatment of keloid.

SIGNIFICANCE

As no specific effective treatment for keloid is currently available, utilization of this readily available therapeutic agent may improve treatment outcome.

Otologic Effects of Topical Mitomycin C: Phase I-Evaluation of Ototoxicity

HYPOTHESIS

To determine ototoxicity of topical mitomycin C when placed in the middle ear at varying concentrations.

BACKGROUND

Despite meticulous surgical technique and diligent postoperative care, some patients develop excessive scar and granulation tissue in the middle ear or mastoid cavity. Poor wound healing may result in infection, tympanic membrane perforation, or conductive hearing loss, which may necessitate further surgery. Use of topical mitomycin C in the ear may be beneficial in reducing scar and granulation tissue formation. This phase of the study was developed to determine the safety of topical mitomycin C in the rat model relative to ototoxicity.

METHODS

Twelve Sprague-Dawley rats were evaluated with auditory brainstem response testing before and after treatments. Topical mitomycin C was injected in the middle ear of the right ear of eight animals. Varying concentrations of 0.125 to 0.5 mg/ml were used. Saline was injected in the left ear of each animal to serve as a control. Four separate animals were evaluated with placement of topical mitomycin C on Gelfoam into the middle ear. In two animals, Gelfoam was placed in the middle ear for 1 minute and then removed. In two animals, Gelfoam was placed in the middle ear and left in place. Auditory brainstem response testing was performed at 4 weeks and at 8 weeks.

RESULTS

Using a high concentration of mitomycin C (>0.25 mg/ml) resulted in ototoxicity, with an increase in the auditory brainstem response threshold at 4 weeks and at 8 weeks. At low concentrations (<0.20 mg/ml), no change in auditory brainstem response threshold was noted. Animals treated with Gelfoam soaked in mitomycin C showed no change in auditory brainstem response threshold.

CONCLUSION

The results of this study indicate that topical mitomycin C on Gelfoam applied in the middle ear appears safe when low concentrations are used, even in the rat, which has a higher susceptibility to gentamycin toxicity than humans. Higher concentrations may lead to ototoxicity based on changes in Wave V on auditory brainstem response. This treatment may prove to be an important option for patients suffering from chronic granulation tissue or scar tissue in the external or middle ear.

[An improved animal model for chronic perforation of the tympanic membrane]

BACKGROUND

An inexpensive and valid animal model of chronic tympanic membrane perforation is needed.

METHOD

Twelve male rats were selected for different surgical procedures (subtotal tympanic membrane perforation with local microflaps, re-perforation without flaps, partial excision of the handle of malleus). The inhibition of spontaneous healing was accomplished by the application of prednisolon or mitomycin directly onto the tympanic membrane.

RESULTS

Only by additional partial excision of the handle of malleus followed by local application of mitomycin were we able to achieve a persistent tympanic membrane perforation.

CONCLUSION

Chronic tympanic membrane perforation using this procedure may be useful in further investigations of the medical impact of tympanic membrane healing.

Clinical and Histological Healing of Surgical Wounds Treated With Mitomycin C

OBJECTIVES/HYPOTHESIS

The proven ability of mitomycin C to inhibit fibroblasts in vitro has stimulated its use in research animals and in humans to control healing. The objective of the study was to follow the healing process of surgical wounds in the dorsum of rats treated topically with mitomycin C.

STUDY DESIGN

Prospective experimental study.

METHODS

Two distinct surgical wounds were made to the dorsum of 10 adult rats. One of the wounds received topical mitomycin C diluted at 0.5 mg/mL during a 5-minute period, and the other wound was used as a control. The healing process was followed clinically and histologically after the rats were killed at different post-treatment periods. The degree of fibrosis was evaluated histologically by two different pathologists.

RESULTS

Surgical wounds treated with mitomycin C presented delayed healing when compared with the untreated wounds, with remission of scabs 7 days after the control wounds. Histological analysis at 1 month after treatment revealed a significant reduction in fibrosis of the wounds treated with mitomycin C when compared with the untreated wounds. After the third month the degree of fibrosis was comparable in both wounds.

CONCLUSION

Topical mitomycin C delays the healing of surgical wounds in rats up to the fourth week following treatment, but the degree of fibrosis is comparable in both treated and untreated wounds after 12 weeks. In otolaryngology this characteristic of the drug may be useful in the treatment of external ear canal stenosis, choanal atresias, nasal cicatricial stenosis, laryngeal stenosis, and keloids.

Dose-Response Relationship of Topically Applied Mitomycin C for the Prevention of Laser Myringotomy Closure

OBJECTIVE: We sought to determine a dose-response curve for topical mitomycin C when used to prolong the patency of laser-assisted myringotomies.

STUDY DESIGN AND SETTING: Bilateral myringotomies were performed using the argon laser in 40 guinea pigs with normal ears. Pledgets with (0.05, 0.2, 0.4, or 2.0 mg/mL) mitomycin C were applied topically. Monitoring consisted of weekly or biweekly otomicroscopy.

RESULTS: As in previous studies, all saline-treated myringotomies closed by day 7. By day 14, all myringotomies (100%) in the 0.05 mg/mL group were closed. By contrast, all myringotomies (100%) remained patent in the 0.2 and 0.4 mg/mL treatment groups, and 56% of the myringotomies remained patent in the 2.0 mg/mL group at day 14. By day 56, all myringotomies were closed in the 2.0 mg/mL group, 5 (50%) myringotomies were patent in the 0.4 mg/mL group, and 1 (11%) myringotomy was patent in the 0.2 mg/mL group. The study was terminated on day 84 (12 weeks). At that time, only the 0.4 mg/mL group had patent myringotomies (n = 3; 30%). The highest dose (2.0 mg/mL) of mitomycin was significantly associated with otorrhea. Otorrhea also appeared to be associated with earlier myringotomy closure.

CONCLUSION: There is a dose-response curve for topical mitomycin C when used for prolonging my-ringotomy patency in doses up to 0.4 mg/mL. Higher doses do not appear to prolong patency and are associated with greater otorrhea, suggesting middle ear toxicity.

O comportamento clínico e histológico da pele do rato submetida ao uso tópico e injetável de Mitomicina C

OBJETIVO: A Mitomicina C é um quimioterápico que apresenta a capacidade de inibir fibroblastos in vitro. Esta característica a levou a ser usada experimentalmente em animais de laboratório e no ser humano, principalmente em oftalmologia, para inibir o processo cicatricial. Este trabalho visa acompanhar o processo de cicatrização de feridas cirúrgicas feitas em dorsos de ratos e tratadas topicamente com Mitomicina C, comparando-as com feridas no mesmo local, não tratadas. Propõe-se também a avaliar a resposta da pele quando injetada com concentrações diferentes do medicamento. FORMA DE ESTUDO: Experimental. MATERIAL E MÉTODO: Foram feitas, em 10 ratos, duas feridas cirúrgicas em seus dorsos. Uma delas foi tratada topicamente com Mitomicina C na diluição de 0,5 mg/ml por 5 minutos e outra não. O processo de cicatrização destas feridas foi acompanhado clinicamente. Posteriormente, os ratos foram sacrificados em períodos diferentes, e suas feridas estudadas histologicamente quanto ao grau de fibrose por dois anatomopatologistas. Posteriormente, três ratos foram submetidos a injeções intradérmicas com concentrações diferentes de Mitomicina C, e o comprometimento local foi avaliado clínica e histologicamente, sendo que apenas na concentração de 0,01mg/ml não se observou necrose tecidual. RESULTADOS: As feridas tratadas com Mitomicina C tiveram seu processo cicatricial retardado, com o desaparecimento das crostas locais 7 dias após o das feridas não tratadas. Ao exame histológico, observado separadamente por dois anatomopatologistas, observou-se no primeiro mês uma nítida diminuição do grau de fibrose nas feridas tratadas com Mitomicina C em relação às não tratadas. Este grau de fibrose se iguala, nas duas feridas, no terceiro mês. Quanto às diluições injetadas, notou-se clínica e histologicamente uma necrose tecidual proporcional ao grau de concentração (0,5; 0,1; e 0,05 mg/ml), que não foi observada na concentração de 0,01mg/ml. CONCLUSÃO: A Mitomicina C usada topicamente em feridas cirúrgicas em ratos retarda seu processo de cicatrização até a 4ª semana. Na 12ª semana este processo se equaliza. Quando usada intradermicamente, causa necrose tecidual apenas em concentrações elevadas. Estas características da Mitomicina C podem ser usadas, em otorrinolaringologia, como coadjuvante no tratamento de estenoses do meato acústico externo, imperfurações coanais, sinéquias nasais, estenoses laríngeas e quelóides.

Effects of topical mitomycin on inner ear: a light and electron microscopic study

Providing maintenance of myringotomy patency without use of ventilation tubes in the treatment of secretory otitis media has been one of the important study areas. For this reason, laser and Mitomycin C (MMC) are used together in experimental studies. But there has been no ultrastructural studies concerning whether leakage of MMC to middle ear during application of this procedure has an ototoxic effect or not and if so, to what extent. In this study, we searched the ultrastructural changes which occurred in the middle ear by direct applications of MMC to the middle ear for different time durations. The study was carried out over thirty adult guinea pigs without ear diseases. Bilateral myringotomy was performed and MMC was applied only to the right middle ear of each guinea pig. The first group received MMC once for 10 minutes, the second group received it once for 20 minutes, and the third group took it each day for 10 minutes during a one week period. The left ears of the samples were accepted as the control group. On the 8th day, sacrification was carried out. After electron and light microscopy examination, significant changes in the inner ear were observed in the third group though no significant change was observed for the first and the second groups. As a result it was concluded that the application of MMC to the middle ear once for a short duration causes no toxic effect on the inner ear.