Effect of topical 5-fluorouracil on closure time of myringotomies created by a radiofrequency surgical unit in guinea pigs

Animal models of chronic tympanic membrane perforation: a 'time-out' to review evidence and standardize design

OBJECTIVE

To review the literature on techniques for creation of chronic tympanic membrane perforations (TMP) in animal models. Establishing such models in a laboratory setting will have value if they replicate many of the properties of the human clinical condition and can thus be used for investigation of novel grafting materials or other interventions.

METHODS

A literature search of the PubMed database (1950-August 2014) was performed. The search included all English-language literature published attempts on chronic or delayed TMP in animal models. Studies of non English-language or acute TMP were excluded.

RESULTS

Thirty-seven studies were identified. Various methods to create TMP in animals have been used including infolding technique, thermal injury, re-myringotomy, and topical agents including chemicals and growth factor receptor inhibitors. The most common type of animal utilized was chinchilla, followed by rat and guinea pig. Twenty three of the 37 studies reported success in achieving chronic TMP animal model while 14 studies solely delayed the healing of TMP. Numerous experimental limitations were identified including TMP patency duration of <8 weeks, lack of documentation of total number of animals attempted and absence of proof for chronicity with otoscopic and histologic evidence.

CONCLUSION

The existing literature demonstrates the need for an ideal chronic TMP animal model to allow the development of new treatments and evaluate the risk of their clinical application. Various identified techniques seem promising, however, a need was identified for standardization of experimental design and evidence to address multiple limitations.

Animal models of chronic tympanic membrane perforation: in response to plasminogen initiates and potentiates the healing of acute and chronic tympanic membrane perforations in mice

Tympanic membrane perforations (TMP) are relatively common but are typically not treated in their acute stage, as most will heal spontaneously in 7–10 days. Those cases which fail to heal within 3 months are called chronic TMP which attract surgical intervention (e.g. myringoplasty), typically with a temporalis fascia autograft. New materials for the repair of chronic TMP are being developed to address deficiencies in the performance of autografts by undergoing evaluation in animal models prior to clinical study. However, there is currently a lack of ideal chronic TMP animal models available, hindering the development of new treatments. Various techniques and animal species have been investigated for the creation of chronic TMP with varied success. In the present commentary, we bring to the attention of readers the recent report by Shen et al. in Journal of Translational Medicine. The study reported the creation of a chronic TMP animal model in plasminogen gene deficient mice. However, the short observation time (9, 19 days), lack of success rate and the scarcity of solid evidence (e.g. otoscopic & histologic images) to confirm the chronicity of TMP warrant a more thorough discussion.

Levels of reactive oxygen species in rat tympanic membranes after incisional versus radiofrequency myringotomy

OBJECTIVE

A close relationship between reactive oxygen species (ROS) and myringosclerosis, which is a common complication of myringotomy, was recently reported. The objective of this study was to measure ROS levels directly in rat tympanic membranes using luminol-aided chemiluminescence (CL) in order to compare the levels of ROS after incisional and radiofrequency (RF) myringotomy.

METHODS

Fifteen Sprague-Dawley rats were separated into three groups of five animals each. Bilateral myringotomies were made using an appropriate myringotomy lancet in Group 1 and RF in Group 2. Group 3 served as the control group with no myringotomy. Twenty-four hours after the procedure, all tympanic membranes were inspected with an otomicroscope and then excised for the measurement of ROS using luminol-aided CL.

RESULTS

The mean ROS level in Group 1 was significantly higher than that in Groups 2 and 3 (p<0.05 for both). The difference in mean ROS level between Groups 2 and 3 was not significant (p>0.05). Otomicroscopy revealed increased vascularity and vessel dilation in all tympanic membranes that underwent myringotomy. Vascular dilation was observed in the annular region in the vessels that passed along the long arm of the malleus, in addition to the vessels feeding the anterior and posterior tympanomalleolar folds.

CONCLUSIONS

Although the relationship between ROS and the development of myringosclerosis after myringotomy has been demonstrated, the present study is the first to compare incisional and RF myringotomy based on the measurement of ROS levels. Our results indicate that the increase in ROS due to myringotomy was greater following incisional myringotomy than RF myringotomy.

Colchicine prolongs patency of myringotomy in an animal model

OBJECTIVE

Chronic otitis media with effusion (COME) is a frequently observed condition in childhood. The most common and effective surgical therapy for COME is myringotomy with insertion of a ventilation tube (VT). Our aims were to investigate the combined effect of myringotomy and the topical application of Colchicine solution to the external ear canal for the prolongation of patency in the treatment of patients with COME and to evaluate the ototoxicity of Colchicine applied directly to the middle ear.

METHODS

A prospective study on 47 ears in 26 fat sand rats was fashioned. In the first phase, solutions of different concentrations of Colchicine were applied to the middle ear cavity in order to determine the drug's ototoxicity, assessing inner ear function with ABR. In the second phase myringotomy was performed and a non ototoxic concentration of Colchicine applied to 12 external ear canals, while saline was applied to nine.

RESULTS

In the first phase, Colchicine concentration of 0.1% and higher applied to the middle ear cavity caused an ABR threshold elevation. In the second phase, the mean closure time after 0.01% Colchicine application was prolonged to >2.14 weeks (P<0.05).

CONCLUSION

Colchicine has a proven potential for prolongation of myringotomy patency when applied as a solution to the external ear as a 0.01% solution. Further investigations are required to validate these results in humans and to study the potential effect of repetitive Colchicine application on the duration of myringotomy patency for the treatment of COME.

Effect of topical use of mitomycin C and 5-fluorouracil on the closure time of myringotomies created by radiofrequency unit

CONCLUSION

Both mitomycin C (MC) and 5-fluorouracil (5-FU) had a significant effect in prolonging the patency rate of radiofrequency myringotomy.

OBJECTIVE

To compare the effect of topical use of MC and 5-FU on the closure time of myringotomies created by a radiofrequency unit.

MATERIALS AND METHODS

Myringotomies were performed using a radiofrequency unit on 80 tympanic membranes of 40 rats. Rats were divided into two study groups and one control group. MC (0.4 mg/ml) and 5-FU (50 mg/ml) pledgets were applied topically in the right ears (study groups, 20 ears each) for 10 min and saline pledgets in the left ears (control group, 40 ears). Animals were monitored using otomicroscopy weekly and patency rates were recorded until myringotomy closure.

RESULTS

The mean patency times were 4.85 weeks for the MC group and 3.90 weeks for the 5-FU group. The mean patency rate for the control side was 1.30 weeks. The log-rank test revealed both study groups to have a significantly longer patency time than the control group (p<0.0001). Although the patency rate was found to be higher in the MC-treated group than the 5-FU-treated group, this difference was not statistically significant (p>0.05).

Could radiofrequency myringotomy be an alternative to incisional myringotomy?

OBJECTIVE

To evaluate the usefulness of radiofrequency myringotomy (RFM) and the closure time of the myringotomy site in comparison to incisional myringotomy (IM).

METHODS

We performed conventional surgical myringotomy on the right ears and RFM on the left ears of 40 rabbits. In order to investigate the effect of the power of energy delivered on the patency period we arranged the animals into two groups: three power grade in RFM group 1 (RFMg1; n: 20) and six power grade in RFM group 2 (RFMg2; n: 20). The follow-up of the myringotomy procedure was performed on days 5, 8, 11, 14 and 17 with examination under the operating microscope.

RESULTS

At the first examination on day 5 after the procedure, all IM openings were found to be closed while seven and eight (36 and 44%) of the tympanic membranes in the radiofrequency groups 1 and 2 remained open, respectively. In these remaining ears, RFM site was patent up to days 11 and 14, respectively in the two RFM groups. None of the RFMs was patent on study day 17. The difference between the closure time of myringotomy sites of the radiofrequency and IM groups was statistically significant (p < 0.05). In comparison of the two RFM groups, we found approximately equal rates regarding the myringotomy patency (p > 005; chi2 yates: 0.02). The complication rates were 5 and 2% for the IM and RFM groups, respectively.

CONCLUSIONS

Radiofrequency myringotomies last longer than incisional myringotomies. With the low complication rate, it is possible to perform this bloodless RF procedure in an office setting. Increased power grade of radiofrequency has no effect on prolonging the myringotomy patency. RFM appears to be a safe and simple procedure that can be used as an alternative to IM.

5-Fluorouracil Ointment for the Treatment of Otitis Media With Effusion

OBJECTIVES/HYPOTHESIS

Our aim was to evaluate the combined effect of 5-fluorouracil (5-FU) and myringotomy for the treatment of otitis media with effusion (OME). OME is usually treated with medication, myringotomy, or insertion of a ventilation tube (VT). Except for VT insertion, however, treatment effects are short-lived. VT insertion has numerous sequelae: increased susceptibility to infection, large perforation of the tympanic membrane, cholesteatoma, and eventual hearing deterioration. We estimated the depressant action of 5-FU on normal cell proliferation in vitro. In addition, clinically, we assessed whether 5-FU has the potential to prolong the effect of myringotomy.

STUDY DESIGN

An in vitro study and a clinical study were conducted.

MATERIALS AND METHODS

In study I, fibroblasts harvested from the peritoneum of three green fluorescent protein transgenic mice were cultured with different doses of 5-FU. After 2 weeks, their proliferation rates were compared. In study II, patients (54 males, 47 females) were selected randomly from a group of patients with intractable OME. Myringotomy with or without a single dose of 5-FU ointment (approximately 0.10-0.30 mg) was performed in group I (n = 64) and group II (n = 37), respectively. The natural closure rates of the tympanic membrane were assessed in both groups.

RESULTS

In vitro, 5-FU inhibited the growth of fibroblasts in a dose-dependent manner. The average time to tympanic membrane closure was 20.5 days in group I and 8.1 days in group II. No adverse events were observed in either group.

CONCLUSIONS

Topical application of 5-FU ointment is useful in prolonging the effect of myringotomy. 5-FU ointment therapy is easy, safe, and cost-effective and may be of wide application.

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.