Tympanic membrane changes resulting from different methods of transmyringeal middle ear ventilation

This experimental study was designed to evaluate the morphologic changes of the tympanic membrane in the rat after different methods of transmyringeal ventilation. Artificial ventilation was obtained in two principal ways, either by making tympanic membrane perforations with delayed healing or by inserting a tympanostomy tube. Perforations occupying the upper rear quadrant of the tympanic membrane were made by diathermy or by a carbon dioxide laser with healing times of 12 to 15 days and 18 to 21 days, respectively. Compared with the healing times of perforations made by lancet (9 to 11 days), the healing pattern was considerably delayed. The structural changes of the healed tympanic membrane were minimal, but the connective tissue remained thickened for several months. Repeated insertion of tympanostomy tubes caused a remarkable thickening (30-fold) of the tubulated quadrants. The thickened tympanic membranes were characterized by a hyperplastic, dense connective tissue containing sclerotic plaques. Similar changes, though less pronounced, were also seen after reiterated myringotomies without tube insertion.     

Tissue-engineered calcium alginate patches in the repair of chronic chinchilla tympanic membrane perforations

OBJECTIVE: Chronic tympanic membrane perforations are a common problem in the United States. A high number of these cases results from placement of pressure equalization tubes. These perforations may initially be treated with paper patch techniques and although safe and well tolerated, the procedure demonstrates poor efficacy. The ideal treatment for small perforations should be rapid, minimally invasive, and efficacious. Calcium alginate-based tissue engineered tympanic membrane patches represent an attractive option, but in vivo data are required. METHODS: A controlled prospective study of tympanic membrane perforation repair using a well-known chinchilla model of chronic tympanic membrane perforation was performed. Calcium alginate-based tympanic membrane patches were created using computer-aided design techniques. A previously described chinchilla model of chronic tympanic membrane perforations was used to create stable perforations ranging from 2 to 5 mm. Ears with chronic perforations were divided into three groups: control (no patch), paper patch, and calcium alginate plugs. At 10 weeks postimplantation, all animals were killed and inspected both grossly and histologically for healing. RESULTS: In the chinchilla model, the alginate grafts demonstrated significantly improved healing rates over both the untreated control group (spontaneous repair) and the paper patch group; nine of 13 healed in the alginate group versus two of nine healed in the paper patch group (P < .05) versus one of 11 healed in the control group (P < .05). CONCLUSION: Calcium alginate tympanic membrane perforation patches offer a significant advantage in the repair of chronic perforations over traditional techniques in the chinchilla perforation model and may offer attractive opportunities in the clinical setting.     

Embryonic stem cells enhance the healing of tympanic membrane perforations

OBJECTIVE: Tympanic membrane perforations may cause hearing impairment and otorhea. It is a common indication for ear surgery. The aim of the study was to test whether stem cells may enhance the healing of fresh tympanic membrane perforations. METHODS: In a first assay, the status of the tympanic membrane at 5 days after myringotomy was tested in five Mongolian gerbils that were treated on one side with embryonic stem cells and on the other side with control substance. In a second assay, nine gerbils were treated in the same way, except that fluorescent-labeled embryonic stem cells were used. The integration of the stem cells into the surface layer of the healing tympanic membrane was assessed with fluorescence microscopy, as well as the differentiation of these cells. RESULTS: In the first assay, all perforations in the treated ears were closed, whereas only two of the untreated ears were closed. The strength of the healed perforation was greater in the stem cell treated tympanic membranes (mean rupture pressure 120 daPa in three treated ears compared to 60 daPa in the one control ear). Two stem cell-treated tympanic membranes remained intact throughout the whole sequence of pressures, whereas only one control tympanic membrane remained intact. In three tympanic membranes in the second assay, a group of fluorescence-doped cells was detected in the region of the perforation. CONCLUSION: These findings indicate that stem cells enhance the healing of tympanic membrane perforations, possibly by differentiation and integration into the tympanic membrane tissue.     

A new ventilation tube for long-term middle ear ventilation

OBJECTIVES: The treatment of secretory otitis media often requires repeated tubulation of the tympanic membrane as the standard ventilation tubes are extruded before the disease of the middle ear has remitted. The T-tube and its modification have been developed to remain longer in situ, often requiring surgical removal. The rates of subsequent persisting tympanic membrane perforations and granulations around the tube have been unacceptably high. In the search for a long-term ventilation tube with fewer complications, the Duravent tube (Smith and Nephew) has been developed. The aim of the study was to estimate duration in situ and observe complications in using the Duravent tube compared with standard tubes and T- tubes. STUDY DESIGN: Retrospective study. METHODS: In all, 51 patients have been treated with the Duravent tube over a 2-year period. In all, 72 Duravent tubes have been inserted. All patients were subsequently invited for a follow-up examination at a median time of 28 months (range, 11-43 mo) after the tube insertion and were followed up for 5 years. RESULTS: The duration in situ was optimal with a median duration of 17 months. The Duravent tube was extruded spontaneously in all but four cases in which surgical removal was necessary. The rate of persisting perforations of the tympanic membrane was low (4.2%) compared with 24% after the use of the T-tube. Likewise, the usual complications connected with long-term ventilation tubes were less frequent (14% compared with 35% when using the T-tube). CONCLUSIONS: In the present study, the Duravent tube has proved superior to other known long-term ventilation tubes. The problem of granulations, otorrhoea, and tube occlusion was significantly less than reported in other studies using the T-tube.     

Tympanic membrane healing process and biocompatibility of an innovative absorbable ventilation tube.

OBJECTIVE: To investigate tympanic membrane healing process and biocompatibility of pressure-equalizing (PE) tubes, made of a novel biodegradable, absorbable material, in an animal model. BACKGROUND: Myringotomy and pressure-equalizing tube insertion is a frequent otologic procedure in children. However, results may vary because of the unpredictable extrusion rate of tubes. Furthermore, tubes that are no longer required need a surgical procedure to be removed. The ideal pressure-equalizing tube should remain in place for the time selected by the otologist, with no need for subsequent removal. This objective could be met with pressure-equalizing tubes made from a self-disintegrating material. METHODS: Pressure-equalizing tubes, made of poly-bis(ethylalanate)phosphazene, were inserted in 55 ears of 28 Hartley guinea pigs, with survival times of 10, 30, and 60 days after tube insertion. In vivo reactions between the poly-bis(ethylalanate)phosphazene pressure-equalizing tubes and the tympanic membrane were studied. Tympanic membranes, middle ears, and tubes were examined by scanning electron microscopy. RESULTS: There was neither infection nor inflammatory reaction to the tube in any animal. The healing process of tympanic membranes revealed neither residual perforation nor inward spread of skin epithelium into the middle ear cavity. At 30 days, 53% of the tubes had disintegrated. At 60 days, tubes were functioning in 25% of ears. CONCLUSION: These new poly-bis(ethylalanate)phosphazene pressure-equalizing tubes are promising. The healing process of tympanic membranes is excellent, with no complications. The tube disintegration rate can be controlled by varying the formulation of the polymer, obtaining tubes with predictable resorption rates, to adapt treatment to the needs of each single patient.     

Fresh tympanic membrane perforations heal without significant loss of strength.

HYPOTHESIS: The mechanical and structural properties of the tympanic membrane change after a perforation has healed. BACKGROUND: In previous studies, efforts have been made to enhance the healing process of tympanic membrane perforations. The strength of the healed perforation has been tested with moiré interferometry in gerbils, but in no other species. METHODS: A laser myringotomy was made on 10 Sprague-Dawley rats and 10 CBA mice, and assessments were made after 2 or 4 weeks with moiré interferometry and light and electron microscopy. RESULTS: The mean peak displacement at pressure loads of +350 daPa and of -350 daPa did not differ significantly in the healed perforations as compared with the untouched tympanic membranes. Morphologic assays showed fivefold increased thickness at the site of the perforation due to invaded fibroblasts and extracellular matrix. CONCLUSION: Moiré interferometry was successfully performed in the rat ears, whereas in mouse ears the method was not easily applicable due to technical difficulties. The stress-strain curve of the rat tympanic membrane displays an S-shape. The strength of the spontaneously healed tympanic membrane after myringotomy was not significantly impaired. The site of the perforation became significantly thickened at 2 and 4 weeks post-myringotomy. This information is of clinical importance, because recently closed perforations will be challenged by pressure gradient in everyday life.     

Spontaneous healing of traumatic tympanic membrane perforations in man: a century of experience.

Widespread controversy exists concerning the treatment of traumatic tympanic membrane perforations. To elucidate the issue, a reference value for the rate of spontaneous tympanic membrane closure in man, to which the healing rates following different techniques of early surgical repair should be compared, was established on the basis of a review of more than 500 texts covering a century's literature on the traumatically perforated tympanic membrane. The spontaneous healing rate appeared to be close to 80 (78.7 per cent) in 760 evaluable cases of traumatic tympanic membrane perforations of all sorts diagnosed within 14 days post injury. A relative, causal-related variation of spontaneous healing could be demonstrated, and a pathogenetic classification of direct traumatic tympanic membrane perforations into ruptures induced by air-pressure changes, heat or corrosives, solids, and water pressures, is of proved clinical value and may have medico-legal validity. There is an obvious need for clinically controlled studies on the spontaneous healing of all kinds of traumatic perforations of the tympanic membrane in humans, and important elements in the design of future studies are advocated.     

Homograft tympanic membrane in cats

A total of 91 cats were evaluated to determine the effectiveness and nature of closure of total tympanic membrane perforations with homografts preserved in buffered formaldehyde, 70 percent alcohol, benzalkonium in Tis-U-Sol (1:750 solution), or Cialit (1:5,000 aqueous solution). Controls consisted of unoperated ears, ears with partial and total perforations that were not grafted, ears in which the total tympanic membrane was removed and immediately replaced, and ears grafted with fresh homograft tympanic membranes. The study revealed that the removal of the tympanic annulus was necessary to prevent spontaneous regrowth of a new tympanic membrane. The percentage of successful closures of tympanic membrane perforations according to the preservative was formaldehyde 50 percent, alcohol 50 percent, benzalkonium 45 percent, and Cialit 30 percent. The rate of successful closures with fresh autograft tympanic membranes was 40 percent and with fresh homografts 25 percent. The homografts preserved in formaldehyde or alcohol were more rigid and easier to handle than were those preserved in benzalkonium or Cialit. The histologic findings were similar in ears that had developed a new tympanic membrane after grafting with preserved homograft tympanic membranes and in ears with fresh homografts or autografts. The graft served as an inert scaffold for the new tympanic membrane to grow across. Gelfoam used in the middle ear to support either a homograft or an autograft became incorporated into the new tympanic membrane and was associated with a foreign-body reaction. There was, however, no evidence of an immunologic reaction to the homograft.     

Behandlung von Trommelfellperforationen mit Fibringel

Background

The goal of this study was to evaluate the effects of a fibrin gel on the healing of tympanic membrane perforation in rats.

Methods

Prolonged tympanic membrane perforations in 12 rats were created by application of mitomycin C to the intact tympanic membranes followed by bilateral myringotomy. Repeated applications of a fibrin gel to the perforation site of one tympanic membrane were performed in each animal. Tympanic membranes were observed for a total of 8 weeks.

Results

One perforation in each group was already patent at the end of the observation period. The mean healing period of the remaining tympanic membranes was found to be 16.7 days in the fibrin gel group and 19.6 days in the control group.

Conclusion

A fibrin sheet does not seem to promote the wound healing process of tympanic membranes. However, the sheet might serve as a drug-delivery system for growth factors in the treatment of tympanic membrane perforations, because of its biocompatibility.     

Traumatic perforations of the tympanic membrane: immediate clinical recovery with the use of bacterial cellulose film

IntroductionPerforation of the tympanic membrane is a reasonably frequent diagnosis in otorhinolaryngologists’ offices. The expectant management is to wait for spontaneous healing, which usually occurs in almost all cases in a few weeks. However, while waiting for healing to be completed, the patients may experience uncomfortable symptoms. Although some research suggests the use of various materials to aid in the recovery of the tympanic membrane, none presented robust evidence of improvement in the cicatricial process. Nevertheless, the occlusion of the perforation with some material of specific texture and resistance can alleviate the patients’ symptoms and accelerate the healing process.ObjectiveTo evaluate the clinical (symptomatic and functional) improvement after the placement of bacterial cellulose film (Bionext®) on tympanic membrane perforations (traumatic).MethodsWe evaluated 24 patients, victims of traumatic perforations of the tympanic membrane, who were evaluated in the Otorhinolaryngology Emergency Room. Following otoscopy and audiometric examination was performed, before and after the use of cellulose film occluding the tympanic membrane perforation.ResultsTwenty-four patients were included, whose degree of overall discomfort caused by the tympanic membrane perforation and the presence of symptoms of autophonia, ear fullness and tinnitus were investigated. The mean score attributed to the overall annoyance caused by tympanic membrane perforation was 7.79, decreasing to a mean value of 2.25 after the film application. Symptom evaluation also showed improvement after using the film: autophonia decreased from a mean value of 6.25 to 2.08, tinnitus from 7 to 1.92 and ear fullness from 7.29 to 1.96. The auditory analysis showed mean threshold values still within the normal range at low and medium frequencies, with slight hearing loss at acute frequencies, but with significant improvement at all frequencies, with the exception of 8000 Hz, after film use.ConclusionThe use of bacterial cellulose film fragment on traumatic perforations of the tympanic membrane promoted immediate functional and symptomatic recovery in the assessed patients.     

The effect of epidermal growth factor on the pseudo-healing of traumatic tympanic membrane perforations

IntroductionTraumatic tympanic membrane perforations tend to heal spontaneously. However, in this study, several perforations exhibited abnormal healing, where the morphology of healing tympanic membranes differed from that of non-perforated tympanic membranes. Pseudo-healing of the tympanic membrane was characterized by the accumulation of thickened tissue in the perforated area.ObjectiveThe purpose of this study was to evaluate the utility of epidermal growth factor in cases showing pseudo-healing of traumatic tympanic membrane perforations.MethodsA total of 26 traumatic tympanic membrane perforations showing pseudo-healing were included in this study. In all cases, tissue that accumulated in the perforated area was removed, which subsequently caused a new perforation to form. An epidermal growth factor solution was applied to the tympanic membrane once daily to keep the tympanic membrane moist. Closure rates and times were evaluated at 6 months.ResultsDuring the 6 months follow-up period, two patients were lost. Of the remaining 24 patients, the closure rate was 100% (24/24) and the closure time was 6.1 ± 2.3 days (range: 3–12 days). The morphology of the healed tympanic membrane was not significantly different from that of the remnant tympanic membrane.ConclusionsPseudo-healing of traumatic tympanic membrane perforations affects sound conduction. This can be associated with various symptoms, including tinnitus, aural fullness, and ear discomfort. The excision of excessive epithelial tissue and topical application of epidermal growth factor can correct the pseudo-healing of traumatic tympanic membrane perforations.     

鼓膜外伤性穿孔自然修复的实验研究

目的研究大鼠鼓膜不同类型穿孔的自然修复过程，探讨鼓膜穿孔的修复机制。方法50只(100耳)大鼠，鼓膜完整，随机分5组，每组10只：①鼓膜紧张部中央2．5mm穿孔；②鼓膜紧张部中央1mm小穿孔；③紧张部后方边缘性穿孔；④紧张部3／4切除后铬酸烧灼锤骨柄；⑤松弛部中央1．5mm穿孔。光镜下观察鼓膜穿孔修复的组织改变。结果鼓膜紧张部穿孔后早期上皮退缩，锤骨柄和鼓环处上皮细胞增殖，上皮细胞的增生还出现在远离穿孔的正常鼓环区域。纤维层的增生晚于上皮层，上皮细胞的堆积首先封闭穿孔，不同大小穿孔的愈合时间差别无统计意义。单侧耳鼓膜穿孔，健侧耳鼓膜无明显变化。鼓膜后方边缘穿孔的上皮细胞未进入鼓室，破坏锤骨柄上皮后穿孔仍可愈合；松弛部穿孔愈合快，伴有紧张部鼓环上皮增殖。结论鼓膜紧张部的穿孔修复依赖于上皮细胞的移行，细胞的增殖中心位于鼓环和锤骨柄，中耳手术对鼓环和锤骨柄的保护有重要的意义。     

The prevention of tympanic membrane perforation following the removal of long-term Paparella type II ventilation tubes

Residual perforation following the extrusion or removal of a long-term ventilation tube may occur in between 8.5% and 25% of cases. This prospective clinical trial concerns Paparella II ventilation tubes and demonstrated that (a) extracting (pulling) a tube from the tympanic membrane gives a 6-month perforation rate of 20%, (b) excising (freshening) the edge of the defect at the time of removal decreases the 6-month perforation rate to 3%, and (c) excising the edge significantly accelerates the healing of the tympanic membrane. There was no correlation in this study between the incidence of perforation and age, sex, ear affected, tympanosclerosis, ventilation tube position, tube in situ time or discharge. The study confirmed a high rate of tympanosclerosis (76%) to be associated with ventilation tubes. Long-term discharge (68%) was identified as a problem of Paparella II ventilation tubes.     

Ventilation time of the middle ear in otitis media with effusion (OME) after CO2 laser myringotomy

OBJECTIVE: The aim of this study was to investigate the transtympanic ventilation time, the healing course of the tympanic membrane, the early and late complications, and the recurrence rate of otitis media with effusion (OME) within 6 months after CO2 laser myringotomy with the CO2 laser otoscope Otoscan. STUDY DESIGN: Prospective clinical study. MATERIALS AND METHODS: In this study, laser myringotomy was performed with the CO2 laser otoscope Otoscan in a patient population comprising 81 children (159 ears) with a history of otitis media with effusion (OME) associated with adenoidal and sometimes tonsillar hyperplasia. The procedure on the tympanic membrane was accordingly combined with an adenoidectomy, a CO2 laser tonsillotomy, or a tonsillectomy and therefore performed under insufflation anesthesia. In all ears, approximately 2 mm circular perforations were created in the lower anterior quadrants with a power of 12 to 15 W, a pulse duration of 180 msec, and a scanned area of 2.2 mm in diameter. RESULTS: None of the children showed postoperative impairment of cochleovestibular function such as sensorineural hearing loss or nystagmus. Otomicroscopic and videoendoscopic monitoring documented the closure time and healing pattern of tympanic membrane perforations. The mean closure time was found to be 16.35 days (minimum, 8 days; maximum, 34 days). As a rule, an onion-skin-like membrane of keratinized material was seen in the former myringotomy perforations at the time of closure. At the follow-up 6 months later, the condition of the tympanic membrane of 129 ears (81.1%) could be checked by otomicroscopy and videoendoscopy and the hearing ability by audiometry and tympanometry. The CO2 laser myringotomy sites appeared normal and irritation-free. Two of the tympanic membranes examined (1.6%) showed atrophic scar formation, and 1 (0.8%) had a perforation with a diameter of 0.3 mm. The perforation was seen closed in a control otoscopy 15 months postoperatively. OME recurred in 26.3% of the ears seen intraoperatively with mucous secretion (n = 38) and in 13.5% of the ears with serous secretion (n = 37; P <.05). CONCLUSION: The most important principle in treating OME is ventilation of the tympanic cavity. CO2 laser myringotomy achieves this through a self-healing perforation in which its diameter roughly determines the duration of transtympanic ventilation. Laser myringotomy competes with ventilation tube insertion in the treatment of OME. It may be a useful alternative in the surgical management of secretory otitis media.     

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.     

Repair of large traumatic tympanic membrane perforation using ofloxacin otic solution and gelatin sponge

IntroductionTraumatic large tympanic membrane perforations usually fail to heal and require longer healing times. Few studies have compared the healing and hearing outcomes between gelatin sponge patching and ofloxacin otic solution.ObjectivesTo compare the healing outcomes of large traumatic tympanic membrane perforations treated with gelatin sponge, ofloxacin otic solution, and spontaneous healing.MethodsTraumatic tympanic membrane perforations >50% of the entire eardrum were randomly divided into three groups: ofloxacin otic solution, gelatin sponge patch and spontaneous healing groups. The healing outcome and hearing gain were compared between the three groups at 6 months.ResultsA total of 136 patients with large traumatic tympanic membrane perforations were included in analyses. The closure rates were 97.6% (40/41), 87.2% (41/47), and 79.2% (38/48) in the ofloxacin otic solution, gelatin sponge patch, and spontaneous healing groups, respectively (p = 0.041). The mean times to closure were 13.12 ± 4.61, 16.47 ± 6.24, and 49.51 ± 18.22 days in these groups, respectively (p < 0.001).ConclusionsGelatin sponge patch and ofloxacin otic solution may serve as effective and inexpensive treatment strategies for traumatic large tympanic membrane perforations. However, ofloxacin otic solution must be self-applied daily to keep the perforation edge moist, while gelatin sponge patching requires periodic removal and re-patching.     

Effect of pentoxifylline on the healing of guinea pig tympanic membrane

Although most tympanic membrane perforations heal spontaneously, persistent perforations frequently require treatment by otolaryngologists. Initial management strategies include keeping the ear dry, ensuring aural hygiene, and using topical antibiotics. For persistent perforations, paper patching or myringoplasty may be required. Recently, agents such as hyaluronic acid and epidermal growth factor have been used to promote tympanic membrane healing. Similarly, pentoxifylline, a pharmaceutical agent with hemorrheological and antithrombotic properties, has been shown to increase perfusion and accelerate wound healing. This double-blinded prospective study attempts to examine the effect of pentoxifylline on tympanic membrane healing of 50 guinea pigs subjected to myringotomy. Serial examinations and histopathologic sectioning of the tympanic membranes revealed no significant difference in rate of healing or quality of repair between the pentoxifylline and control groups.     

Results of middle ear ventilation with Goode's tubes

The results of a retrospective study of the effect and outcome of middle ear ventilation by Goode's tubes are presented. 83 ears from 50 patients were analyzed both as a group and in age-related sub-groups over a mean follow-up period of 1.83 years. The mean period of ventilation by Goode's tubes before removal or extrusion was 18.4 months. The tubes became infected in 70.4% and were spontaneously extruded in 44.9% of patients. Permanent perforation of the tympanic membrane ensued in 47.5% of patients and significantly more often in those aged between 10 and 20 years (P less than 0.002). Patients aged less than 10 years were significantly less likely to develop a retraction of their tympanic membranes after removal of the Goode's tube than those older (P less than 0.02). No significant relationship was found between the development of these complications and the period of ventilation, past experience of otitis media, consistency of effusion, degree of tympanosclerosis or the preoperative presence of tympanic retraction.     

"Window shade" tympanoplasty for anterior marginal perforations

OBJECTIVES/HYPOTHESIS: Anterior marginal perforations of the tympanic membrane often present a reconstructive challenge to the otolaryngologist. Poor surgical outcomes are often due to inadequate exposure, a lack of residual tympanic membrane, impaired vascular supply, and delayed healing. This study reports on the success of the "window shade" technique, combining aspects of both the traditional underlay and overlay tympanoplasty techniques, for the management of anterior marginal tympanic membrane perforations. STUDY DESIGN: Retrospective review of patients undergoing window shade tympanoplasty from July 1, 1994, to July 1, 2003, at a tertiary care referral center. METHODS: Only patients found to have anterior tympanic membrane perforations and who underwent a window shade tympanoplasty were included in the study. Tympanoplasty success rate was studied by examining postoperative complications of recurrent perforation, tympanic membrane lateralization, or anterior blunting. RESULTS: The authors identified 164 patients who underwent window shade tympanoplasty during the study period. The overall success rate for tympanic membrane repair was 94.5%. There were no cases of tympanic membrane lateralization or significant blunting. The average healing time was 4 weeks. The surgical technique is described in detail. CONCLUSION: The window shade tympanoplasty is an excellent surgical option for repair of anterior marginal perforations of the tympanic membrane.     

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.