Tympanic Membrane Perforation Research Articles

Comparison of Total Endoscopic Ear Surgery and Microscopic Postauricular Canal-Wall-Down Approach on Primary Acquired Cholesteatoma.

This study aimed to compare total endoscopic ear surgery (TEES) and microscopic postauricular canal-wall-down tympanomastoidectomy (CWD) in cholesteatoma surgery in our clinic. This study included 59 patients, of whom 30 and 29 were operated on with CWD in 2016-2018 and TEES in 2019-2021, respectively and compared regarding intraoperative findings, hearing outcomes, long-term outcomes, and recidivism rates between groups. This study excluded patients in stage IV according to the European Academy of Otology and Neurotology/Japan Otological Society Staging System on Middle Ear Cholesteatoma, aged < 18, with congenital cholesteatoma, who underwent revision surgery. Two patients in the TEES group had recidivism (6.9%), with recurrent disease observed in both patients and residual disease in none, whereas 3 patients in the CWD group had recidivism (10%), including recurrent disease in 2 and residual disease in 1 patient. Tympanic membrane perforation occurred in 2 (6.9%) and 1 (3.3%) patients in the TEES and CWD groups, respectively. The 2 groups revealed no significant difference in terms of recidivism and perforation rates (P=1.000, P = .612). The CWD group had a longer mean operation time (225.54 ± 47.86 minutes) than the TEES group (160.55 ± 24.98 minutes) (P < .001). The 2 groups demonstrated no significant difference regarding pre- and postoperative air-bone gap (ABG) and ABG gain (P = .105, P=.329, P=.82, respectively). Total endoscopic ear surgery provides similar results in terms of hearing, recidivism, and long-term outcomes with the microscopic CWD approach. However, the CWD approach is still important, especially in patients in advanced stages.

Tough and self-adhesive zwitterionic hydrogels with mechano-responsive release of bFGF for tympanic membrane repair

The tympanic membrane (TM) is constantly in a state of vibrating. However, there is currently a lack of drug-delivery scaffolds suitable for the dynamic environment of TM perforation. In this study, a mechano-responsive tough hydrogel was developed. It consists of basic fibroblast growth factor (bFGF)-loaded sodium alginate (SA) microspheres, polysulfobetaine methacrylate (polySBMA), and gelatin methacrylate (GelMA). This hydrogel was designed to serve as a TM scaffold to promote perforation healing under dynamic conditions. bFGF was encapsulated in SA microspheres, which were then incorporated into polySBMA-GelMA hydrogels through photo-initiated free radical polymerization. The mechanical properties, tissue adhesiveness, swelling properties, and degradation of the hydrogels were evaluated before and after microsphere incorporation. It was observed that incorporating bFGF-loaded SA microspheres did not significantly impact the adhesion and degradation mechanisms of the hydrogel. The compressive strength and tensile strength of the microsphere-incorporated hydrogel were up to 6.6 MPa and 64.1 kPa, respectively, suitable for a TM scaffold. The release behavior of bFGF from the hydrogel could be controlled by vibration stimulation without significantly affecting the hydrogel's mechanical properties, indicating a mechano-responsive nature of the hydrogel. The in vitro cytotoxicity assay demonstrated that the hydrogels showed no cytotoxic effects. Moreover, cell culture assays demonstrated that vibration stimulation could enhance the release of bFGF, significantly promoting cell proliferation and migration. The results demonstrate the significant potential of the mechano-responsive hydrogel as a scaffold for repairing TM perforations.

Advances in 3D printing for the repair of tympanic membrane perforation: a comprehensive review.

Tympanic membrane perforation (TMP) is one of the most common conditions in otolaryngology worldwide, and hearing damage caused by inadequate or prolonged healing can be distressing for patients. This article examines the rationale for utilizing three-dimensional (3D) printing to produce scaffolds for repairing TMP, compares the advantages and disadvantages of 3D printed and bioprinted grafts with traditional autologous materials and other tissue engineering materials in TMP repair, and highlights the practical and clinical significance of 3D printing in TMP repair while discussing the current progress and promising future of 3D printing and bioprinting. There is a limited number of reviews specifically dedicated to 3D printing for TMP repair. The majority of reviews offer a general overview of the applications of 3D printing in the broader realm of tissue regeneration, with some mention of TMP repair. Alternatively, they explore the biopolymers, cells, and drug molecules utilized for TMP repair. However, more in-depth analysis is needed on the strategies for selecting bio-inks that integrate biopolymers, cells, and drug molecules for tympanic membrane repair.

Plasminogen - safe for treatment of chronic tympanic membrane perforation: a phase 1 randomized, placebo-controlled study

Background There is a need for a simpler and accessible intervention to heal tympanic membrane perforations than myringoplasty that is todaýs golden standard. Experimental studies have identified plasminogen as a promising agent for medical treatment of chronic tympanic membrane perforation. Aims/Objectives This was a phase 1, prospective, randomized, placebo-controlled study with the main objective to evaluate the safety of injecting plasminogen in the vicinity of the tympanic membrane in subjects with chronic tympanic membrane perforation. Material and Methods Adults diagnosed with a dry chronic tympanic membrane perforation were recruited for an injection schedule with Human plasminogen 10. Adverse events, audiometry, VAS fluctuations and size of perforation, were monitored throughout the length of the study. Results It was possible to perform the injections according to schedule in all subjects. None of the subjects experienced any severe adverse events. Most common adverse event was ear pain. No signs of ototoxicity were reported. Conclusions and Significance This pilot study suggests that plasminogen injections close to the tympanic membrane as treatment for chronic tympanic membrane injections are safe and feasible, encouraging further dose-escalating studies.

Airbag Deployment and Tinnitus Emergence Following Car crash, a Case Report and a Brief Literature Review

Automatic airbag deployment during car accidents undoubtedly plays a vital role in preventing injuries. However, it may occasionally lead to aural damage, including noise-induced hearing loss, tympanic membrane perforation, and tinnitus. Here, we present a case of left curtain airbag deployment immediately following a low-speed car accident, which resulted in the driver experiencing tinnitus. In addition to the case presentation, we have included a brief literature review on potential otologic and nonotologic injuries caused by airbags

Endoscopic ear surgery in the treatment of chronic otitis media with atelectasis.

Atelectasis otitis media (AtOM) is a chronic condition where the tympanic membrane (TM) becomes retracted towards the middle ear and the ossicular chain. Surgical treatment for this condition could be indicated based on stage of atelectasis, patient's clinical condition and hearing loss. Over the years, AtOM has been treated with various types of tympanoplasty under microscopic view. The aim of this study is to present the results of endoscopic ear surgery in AtOM. Forty-five patients who underwent endoscopic trans-canal tympanoplasty were included in the study. Preoperative features, intraoperative findings and postoperative outcomes were collected. Preoperatively, none of the study's patients were classified with a Sadè Grade I, whereas grades II, III and IV were 3 (6.6%), 23 (32.1%) and 19 (67.8%) respectively. The 3 patients with Sadè grade II showed a conductive hearing loss higher than 20dB and a continuous ear fullness, therefore they were surgically treated. The postoperative graft success rate was estimated at 95.5%. During follow-up, 2 patients showed a TM perforation (at 6 and 12months after surgery) whereas 1 patient experienced a recurrence of atelectasis in the TM (16months after surgery). The overall success rate at the final follow-up was calculated at 88.8%. The average preoperative air-conduction threshold was 51.1 ± 21.5, which reduced to 34.6 ± 22.1 (p = 0.04) at follow-up. The preoperative air-bone gap decreased from 28 ± 7.2 to 11.8 ± 10 (p = 0.002) after surgery. Atelectasis otitis media might be suitable for exclusive endoscopic surgical treatment, as it appears to exhibit a low recurrence rate and promising audiological outcomes.

Endoscopic push through tragal cartilage tympanoplasty: A 10-year retrospective review of our technique and outcomes

BACKGROUND Endoscopic ear surgery (EES) provides a magnified, high-definition view of the otological surgical field. EES allows otologists to avoid surgical incisions and associated postoperative complications. It is an ideal technique for the performance and teaching of tympanoplasty. AIM To examine the efficacy of total Endoscopic Push Through Tragal Cartilage Tympanoplasty (EPTTCT), at our institution over a 10-year period. METHODS A retrospective analysis of 168 cases of EPTTCT for closure of small to medium tympanic membrane perforations from 2013-2023 was conducted. Patient sex, age range (pediatric vs adult), etiology of injury, success rate, complications, and postoperative hearing status were collected. RESULTS Graft uptake results indicated success in 94% of patients, with less than a 2% complication rate. Postoperative pure tone audiometry demonstrated hearing status improvement in 69% of patients. CONCLUSION EPTTCT has been shown to be effective in tympanic membrane perforation closures with minimal complications. This study further demonstrates the efficacy and safety of these procedures in a single-center review.

A Novel Combined Cartilage-Fascia Technique for Anterior Perforation in Type-1 Underlay Tympanoplasty

Background: Biomaterials and surgical techniques for reconstructive tympanic membrane surgery are under development. Objectives: The objective of this study is to analyze the functional and surgical outcomes of a novel fascia with cartilage reinforcement technique for anterior tympanic membrane perforation in tympanoplasty. Methods: Records of 198 patients with anterior tympanic membrane perforation who underwent tympanoplasty between August 2018 and March 2021 were prospectively reviewed. Patients with dry anterior quadrant perforations of the tympanic membrane were included and underwent tympanoplasty using two methods: Type 1 tympanoplasty with temporalis fascia only, and tympanoplasty with fascia and cartilage reinforcement. Postoperative functional and surgical outcomes were analyzed. Results: Comparing the pre-operative and post-operative air conduction levels and air-bone gaps showed significant improvement in both groups (P &lt; 0.001). Additionally, no significant difference was observed between air-bone gap closure (P = 0.316) and increase in air conduction levels (P = 0.222) according to graft type. Conclusions: Both temporalis muscle fascia and temporalis muscle fascia with cartilage reinforcement revealed satisfactory functional and surgical outcomes. Furthermore, the novel combined cartilage-fascia technique had a comparable graft take rate and hearing results in anterior perforations, with no significant change in tympanic membrane vibratory properties.

The Prognostic Value of Active Otitis Media on Tympanoplasty Success Rate-A Systematic Review.

The aim is to investigate the influence of an active otitis media on the success rate of tympanoplasty in patients with a chronic otitis media (COM) and a tympanic membrane perforation. PubMed, Embase and the Cochrane Library. The inclusion criteria were studies on closure rates of tympanoplasty performed in COM patients of any age with a tympanic membrane perforation caused by COM. The exclusion criteria were studies on patients undergoing concomitant mastoidectomy, ossicular chain reconstruction, tuboplasty, adenoidectomy, revision tympanoplasty, patients with perforations due to other conditions than COM, and letters to editors, commentaries, conference abstracts and case reports. The included articles were critically appraised using the QUIPS tool. Data on tympanic membrane closure rate were extracted, odds ratio (OR) and 95% confidence intervals (CI) of the closure rate with a wet versus a dry ear were calculated. The search was performed on 1 February 2023. Of 4671 articles, 16 studies were included and critically appraised. Of these observational studies (nine prospective, seven retrospective), with a total of 1509 patients (dry ear group n = 1003; wet ear group n = 506), two studies stated a significant difference in success rate, one in favour of a dry ear and one in favour of a wet ear at time of surgery. All other studies did not show a statistically significant difference. Overall, the risk of bias was considered moderate to high. We found no significant prognostic value of having an active otitis media during tympanoplasty on tympanic membrane closure rates. Because the overall risk of bias was considered moderate to high, no strong conclusions can be made. To be able to answer this question with higher levels of evidence, high-quality prospective or randomized studies are needed.

Comparison of four ventilation tubes commonly used in the pediatric population: A retrospective cohort study.

To assess differences in otorrhea, tympanic membrane perforation, and time to extrusion in children receiving one of four commonly used, short-term ventilation tubes for the first time. Retrospective chart review of 2 years of postoperative follow-up to analyze patient outcomes after insertion of either a Paparella type-I Activent, Armstrong Beveled, Modified Armstrong, or Armstrong Microgel ventilation tube. Incidence of complications was determined by reviewing provider notes. Adjusted multivariate logistic regression models were used to determine odds ratios of complications among the four tube types. A total of 387 patients were reviewed. The mean age was 2.4 years and 35.9% were female. Armstrong beveled tubes had the highest odds of otorrhea. Paparella type-I tube had the shortest time to extrusion of about 9 months, while Armstrong Beveled had the longest, at almost 19 months. When evaluating episodes of otorrhea each child experienced on average, per month, Armstrong beveled tubes had the highest monthly rate of otorrhea and Paparella type-I the least. No significant differences were found regarding tympanic membrane perforation. This retrospective chart review showed that no tube was clinically superior across all complications. The findings from this study may give otolaryngologists an opportunity to consider choosing a specific type of tube according to the clinical situation. The large variations in extrusion times should be considered in terms of patient age, seasonality, and desired duration of tube placement. 4.

Efficacy and safety of a self-expandable retainer in endoscopic ear surgery.

During endoscopic ear surgery (EES), it is important to maintain a clear view of the endoscopic camera to achieve a clean field. In this study, a self-expandable external auditory canal (EAC) retainer was developed to enable a more efficient and safer EES. This study aimed to evaluate the retainer's efficacy and safety in EES. Among adult patients scheduled for endoscopic tympanoplasty, 50 participants were recruited. They were assigned to either the retainer or control group in a 1:1 ratio. The anatomical characteristics, number of endoscopic cleanings during surgery, surgeon's satisfaction, and other factors were evaluated. No differences were observed in the surgical direction, EAC size measured on preoperative temporal bone computed tomography scans, location and size of tympanic membrane perforation, or bleeding degree between the two groups. When comparing the surgical time, including retainer insertion and removal, the time was similar between groups (retainer group, 35min; control group, 33.2min). The frequency of endoscopic cleaning per minute was statistically significantly lower in the retainer group than in the control group (0.18 times per minute, p = 0.048). No side effects, including sensory abnormalities or allergic reactions, were reported in any patient who used the retainer. A reduction in unnecessary endoscopic cleaning during EES was observed while using the self-expandable retainer, leading to increased surgeon satisfaction and efficiency. Furthermore, as a safe method without side effects, the retainer could be widely used to various indications for EES beyond tympanoplasty.

Platelet rich fibrin augmented tympanoplasty versus cartilage tympanoplasty: a randomized clinical trial.

The aim of the current study was to evaluate the efficacy of PRF-augmented fascia tympanoplasty versus cartilage tympanoplasty in repair of large TM perforations. This randomized clinical trial included 156 patients with dry large tympanic membrane perforations. Patients were randomly allocated into 2 groups, cartilage tympanoplasty group (n = 77) and platelet rich fibrin (PRF) augmented tympanoplasty group (n = 79). Graft take rates, hearing outcomes, operative time, and postoperative complications were documented and compared. Graft take rate was 96.1% in the cartilage group and 93.7% PRF group with no statistically significant difference. Operative time was significantly longer in the cartilage group. No differences in the hearing outcomes and postoperative complications were reported. Application of PRF on the fascia in tympanoplasty promotes healing of the tympanic membrane. PRF is safe, cheap, readily available, and easily prepared and applied. It increases the success rates of large tympanic membrane perforations without the need for cartilage grafts.

Outcomes of endoscopic modified cartilage-perichondrium tympanoplasty on different sized perforations

ObjectivesTo evaluate the anatomic and functional outcomes of type1 tympanoplasty with endoscopic modified butterfly cartilage-perichondrium technique. MethodsIn our modification, perichondrium was elevated circumferentially till the attached part of the composite graft was approximately same size and shape of the perforation, cartilage was trimmed based on the perforation but 0.5 mm larger. Cartilage portion of the graft was placed medial to the edge of the perforation, then perichondrium was rolled out and draped on the circumferential raw surface of remaining tympanic membrane around. ResultsAt 4 months postop, the anatomic integrity rate of the tympanic membrane perforation for small & medium sized perforation and large sized perforation group were 100 % and 94 % (p > 0.05). For the small & medium perforation group, the mean pre and 4 months postop ACs were 30 ± 8 dB and 18 ± 6.4 dB (p < 0.01). The mean pre and 4 months postop ABGs were 19 ± 11 dB and 9 ± 3 dB (p < 0.01). For the large perforation group, the mean pre and 4 months postop ACs were 43 ± 12.5 dB and 21.5 ± 7 dB (p < 0.01). The mean pre and 4 months postop ABGs were 34 ± 8.5 dB and 12.5 ± 6 dB (p < 0.01). The differences of mean 4 months postop ACs and mean 4 months postop ABGs between the two groups were not significant (p > 0.05). ConclusionsCompared to the conventional inlay butterfly cartilage tympanoplasty technique, large or marginal perforations can be sealed more securely by this modification.

Endoscopic Double Flap Tympanoplasty.

This study is aimed to compare the outcomes of the two techniques (endoscopic single flap tympanoplasty- ESFT versus endoscopic double flap tympanoplasty - EDFT) of endoscopic tympanoplasty for repairing large tympanic membrane (TM)perforations with limited anterior remnant. In this randomised controlled trial, forty patients with large sized TM perforations were included and randomised in the ESFT and EDFT arms with twenty patients in each group. Both the groups underwent endoscopic tympanoplasty using temporalis fascia graft. The graft uptake rates and hearing results were compared. Graft success rate was 85% (17/20 cases) in the ESFT group and 90%(18/20 cases) in the EDFT group. The ABG (air-bone gap) improvement median with interquartile range(IQR) was 5 dB (3.12 dB-10 dB) in the ESFT group and 8.75 dB (5dB-11.87 dB) in the EDFT group. The difference was not statistically significant. In our study, there was no statistically significant difference in the graft success rate or hearing gain in ESFT or EDFT group. Moreover, there was longer operative time and need for an extra incision while raising the anterior flap. This lack of statistically significant results in our study may be since the study has a very small sample size. Whether the same conclusion is reproducible needs to be further explored by a larger sized randomised controlled trial.

Correlation of hearing impairment with site of tympanic membrane perforation

Correlation of hearing impairment with site of tympanic membrane perforation

Myringoplasty Using Human Birth Tissue Allografts to Repair Large Tympanic Membrane Perforations.

Examine outcomes among a series of pediatric patients who underwent myringoplasty using human birth tissue (BT) for repair of large tympanic membrane (TM) perforations. Case series. Single-institution pediatric hospital. Retrospective chart review of patients treated with BT during a 4-year study period. Subjects who underwent myringoplasty for large (size 40% or greater) TM perforations were included for this study. Patients with a stable perforation of at least 1 month's duration preoperatively who then followed up for at least 3 months postoperatively met inclusion criteria. Six subjects were included in this study. One subject underwent bilateral repair; thus, this series includes a total of 7 perforations. TM perforations ranged from 40% to 70% of the TM. At initial follow-up (median of 2 months), 5 of the 7 perforations had healed. One of these 5 had evidence of a 10% recurrent perforation at 5 months, which subsequently healed. Of the 2 patients not healed at initial follow-up, 1 had only a residual pinpoint perforation that subsequently healed; the other had a persistent 30% perforation that was possibly related to their postoperative recovery period, which was complicated by a respiratory viral illness. For large TM perforations, myringoplasty with BT grafts may be a viable alternative to longer, more invasive procedures like tympanoplasty. Larger, randomized, prospective studies are needed.

Role of Tympanometric Ear Canal Volumes in Determining Outcome of Myringoplasty in Chronic Suppurative Otitis Media Patients.

Middle ear aeration is a predictive indicator of myringoplasty's successful outcome and tympanometric ear canal volume is a novel investigation that can estimate the volume of middle ear cleft and mastoid air cells. Our aim of this study is to determine the role of tympanometric ear canal volume on myringoplasty outcome in Chronic Suppurative Otitis Media Patients. Prospective analysis involving 50 patients of CSOM was performed on patients undergoing myringoplasty from April 2022 to December 2023. Smokers, Patients with squamosal COM, Bilateral COM, Otitis Externa, and Revision surgery were excluded from the study. The successful outcome of surgery was defined as no tympanic membrane perforation on postoperative follow-up. Analysis was carried out using SPSS. V. 25 and P-value less than 0.05 was considered significant. A total of 50 patients were included in the study with a mean age of 24.4 ± 8.965 and male predominance. Overall graft uptake was 64%. Graft uptake had no significant statistical correlation with age, gender, type, location, or size of perforation. However, there is a significant effect of tympanometric ear canal volume of pathological ear and interaural tympanometric ear canal volume difference on graft uptake with p-values of 0.023 and 0.033 respectively. Tympanometric ear canal volume can predict middle ear aeration and the higher the interaural tympanometric canal difference more are the chances of successful graft uptake.

Experimental Study of Needle Insertion into Gerbil Tympanic Membrane.

The perforation characteristics and fracture-related mechanical properties of the tympanic membrane (TM) greatly affect surgical procedures like myringotomy and tympanostomy performed on the middle ear. We analyzed the most important features of the gerbil TM perforation using an experimental approach that was based on force measurement during a 2-cycle needle insertion/extraction process. Fracture energy, friction energy, strain energy, and hysteresis loss were taken into consideration for the analysis of the different stages of needle insertion and extraction. The results demonstrated that (1) although the TM shows viscoelastic behavior, the contribution of hysteresis loss was negligible compared to other irreversible dissipated energy components (i.e., fracture energy and friction energy). (2) The TM puncture force did not substantially change during the first hours after animal death, but interestingly, it increased after 1week due to the drying effects of soft tissue. (3) The needle geometry affected the crack length and the most important features of the force-displacement plot for the needle insertion process (puncture force, puncture displacement, and jump-in force) increased with increasing needle diameter, whereas the insertion velocity only changed the puncture and jump-in forces (both increased with increasing insertion velocity) and did not have a noticeable effect on the puncture displacement. (4) The fracture toughness of the gerbil TM was almost independent of the needle geometry and was found to be around 0.33 0.10kJ/m2.

Video Otoscopy as a Novel Teaching and Remote Otolaryngology Consultation Tool at an Academic Medical Center.

Assess the use of video otoscopy (VO) as a tool for teaching Emergency Department (ED) residents and remote Otolaryngology consultation. Survey and retrospective chart review. Tertiary care center. Emergency Medicine resident physicians completed an otologic skill self-assessment and pathology followed by an interactive training on VO and postintervention assessment after 9 months of use. Outcomes compared change in pre- to posttraining scores. ED consultations using VO during this time period were reviewed to detect differences between the presumed diagnosis/treatment based only on phone consultation and VO image compared to the final diagnosis/treatment after in-person Otolaryngology consultation. Forty-six (63.1%) ED residents participated. Diagnostic accuracy improved by 20.7% overall. The most improved diagnoses were of a normal ear canal (+75%), tympanosclerosis (+58.4%), and ear canal foreign body (+57.1%); most challenging were external auditory canal cyst (-13.6%), hemotympanum (-11.3%), and cerumen (-1.9%). Cholesteatoma did not improve because all responses were incorrect; neither did tympanic membrane perforation because all were correct. Confidence in the otologic exam and anatomy also increased (P < .01). Thirteen consults used VO and 3 (23.1%) had a change in diagnosis/treatment after in-person Otolaryngology evaluation. Training on the use of VO significantly improves the confidence and diagnostic skills of ED providers for many pathologies. This application suggests the efficacy of an otologic e-consultation model.

Efficacy of Empirical Co-Amoxiclav Vs Culture Directed Treatment in Chronic Suppurative Otitis Media. A Double Blind Randomized Controlled Trial

Background: Chronic suppurative otitis media (CSOM) is common middle ear inflammatory condition secondary to tympanic membrane perforation and superimposed infection, which causes increased discharge from middle ear mucosa. This is a common condition seen in relatively low socioeconomic status and in younger population. The effective treatment of this disease is essential as un-treated patients often lead to various complications like mastoiditis, facial nerve paralysis, labyrinthitis and abscess formation. A huge number of hearing loss in paediatric population is due to this condition. The treatment of CSOM includes aural toilet, topical antibiotics and in some cases systemic antibiotics. In this study we will compare the results of patients who were given culture sensitivity directed antibiotics with the ones who were given Co-Amoxiclav as an empiric treatment Methodology: A two-year observational cross-sectional study was conducted at PIMS, a total of 396 patients were enrolled and randomly divided into two group i.e., Group A and Group B with 198 patients in each. Group A included those who were given culture specific antibiotics and group B included those who were given Co-Amoxiclav as a part of empiric therapy. Their results were compared after 12 days of treatment in terms of response seen as clean and dried, external auditory canal along with middle ear mucosa. Results: Out of 198 patients in Group A, 177 patients had clean and dried middle ear mucosa which shows success rate of 89.39% and in Group B 170 patients out of 198 (85.85%) showed positive response. Conclusion: Empiric treatment of CSOM (Tubotympanic Type) with co-amoxiclav must be considered as its response is comparable to culture sensitivity directed treatment in terms of clean and dried external auditory canal and middle ear mucosa.