Prognostic factors influencing anatomical and functional outcome of Myringoplasty

Objective: To assess the rate of healing of tympanic membrane, hearing status before and after operation and determine the factors influencing surgical outcome. Methods: This cross-sectional study was done in the department of Otolaryngology & HeadNeck Surgery of SSMC & Mitford Hospital, Dhaka, during the period of January, 2008 to December, 2009. A total of 60 patients was underwent myringoplasty operation and taken detailed history, clinical findings and post operative assessment. Analyzed data presented by various tables, graphs and figures. Results: The study included 60 patients of myringoplasty operation. Age of the patient was between 15-45 years. Out of 60 patients male was 60% and female was 40%. Highest number of patients was in the age group of 15-25 years. Conclusion: Hearing improvement after myringoplasty in anatomically successful cases improve quality of life of the patient.


Introduction
Chronic otitis media (COM) implies a permanent abnormality of the pars tensa or flaccida, most likely a result of acute otitis media, negative middle ear pressure or otitis media with effusion.Chronic otitis media equates with classic term 'suppurative' otitis media that is no longer advocated as COM is not necessarily a result of 'the gathering of pus'.However the distinction remaining between active COM where there is inflammation and production of pus and inactive COM, where this is not the case though there is the potential for the ear to become active at some time.A third clinical entity is healed COM where there are permanent abnormalities of pars tensa but the ear does not have the propensity to become active because the pars tensa is intact and there are no significant retraction of the pars tensa or flaccida 1 .
In Bangladesh, chronic otitis media (COM) is a common disease in clinical practice.Poor living condition, overcrowding, poor hygiene, malnutrition, lack of health education and inadequate health care all have been suggested as a basis for the widespread prevalence of chronic otitis media in our country.It is the single most important cause of hearing impairment in rural population.
Hearing loss arising from COM is a matter of serious concern because of its long term effects on communication, language development and educational process.
There is a significant quantitative correlation between the size and site of perforation and hearing loss, but this relationship is not constant and consistent in clinical practice seemingly identical perforation in size and location produce different degree of hearing loss. 2 Small perforations (10% of the membrane) produce losses of 10-15 dB below 3 KHz.Large perforations produce severe losses over the whole range particularly at higher frequencies, through these perforations the sound waves act directly on the round and oval windows.Small and moderate perforations (10-40% of the area) have far more severe effects when placed on the posterior and superior part of the membrane than when placed on the anterior and inferior part 3 However, non-marginal perforation with intact ossicular chain hearing loss is approximately 10-30 dB.The predominant hearing loss in mucosal disease is conductive in nature but a few cases of sensorineural hearing loss is also found. 4ny factors influence the surgical outcome of myringoplasty.The reported success rate is therefore variable, partly because of differences in the inclusion and exclusion criteria.In a study the overall success rate of myringoplasty was 86%.Posterior and inferior perforations had a 90% success rate for repair, compared to only 67% of anterior perforations. 5This was due to poor access to anterior perforations and better tissue perfusion in the posterior part.The success rate of sub-total perforation closure (92.5%) was as good as the closure rate for small perforations (94.1%) 6 .But the poorer results were seen in younger patients.Vrabec et al. 7 found better success rate with advancing age.This is due to lower incidence of upper airway infections and better Eustachian tube function in later age and the relative immaturity of immune system in younger children.Caylon et al 8 found no statistical difference between two groups.No significant difference was found when comparing the two surgical techniques of overlay and underlay, the success rate was 79.1% in the former and 83.2% in the later 9 .When hearing improvement was the main indication for surgery it was improved in 67%.All patients were operated under local anaesthesia.The incision was either postauricular, endaural or transcanal depending upon the size of the external ear canal and the position of the perforation.The graft was inserted onto the medial surface of the drum remnant, usually below the handle of the malleus ("underlay" technique).Gelfoam was used as the support material in middle ear.Betadine soaked packed was given over the gel foam in the external auditory canal which was removed after two weeks.Antibiotics were given in the postoperative period for four weeks.

Methods
During the follow-up, every patient was examined after one and three months of postoperative period.Outcome of surgery was regarded as successful if the ear was dry and the tympanic membrane intact and mobile.Postoperative pure tone audiometry was done on the third month of postoperative period.The results are presented as air bone gaps before and after operation by comparing audiometric graph.
Post-operative follow up was done at weekly interval for the first months and then as needed.The mean duration of follow-up 18 weeks (ranges from 12 weeks to 28 weeks).The function of Eustachian tube is a prerequisite for successful myringoplasty.However, there is no simple routine method for the accurate preoperative examination of Eustachian tube function.

Fig.-1: Effect of age on success rate
On the other hand, some authors have stated that tubal function may even improve following a successful myringoplasty 10 .It suggests that closure of a perforation may prevent irritation of the middle ear mucosa, which may encourage a return normal tubal function 11 .Patient age has generally been considered as influencing the surgical outcome.In our study, maximum success rate was in the age group 15-25 years (90%) followed by 85% and 66.67% in the age group of 25-35 years and 35-45 years respectively.This is due to lower incidence of upper airway infection and better Eustachian tube function in this age.
Male outnumbered the female (1.5:1).There was no significant difference in surgical outcome (88.89.vs 83.33 in male and female respectively).
Majority of the patients in our study came from middle class family (53.33%) and a significant number came from poor class family (30%).Previous history of intermittent otorrhoea (96.67%) and hearing loss (90%) were the major symptoms of this series.
Out of 60 patients, 30 patients had unilateral and 30 patients had bilateral diseases.The surgical success rate was equal in both unilateral and bilateral cases.Kessler et al 12 and denoyelle et al 13 who found that a pathological contralateral ear independently influence the risk of graft material, seems to be related to the fact that our cases did not show any inflammatory changes in the contralateral ear.
With regard to the role of size of perforation, small (100%) and medium size (88.23%)perforation had more success rate than the subtotal perforation (80%).
The site of perforation statistically affect outcome in our series as has been previously reported by others 14 .Success rate of posterior perforation (92.85%) and anterior perforation (88.46%) are more than the subtotal perforation (80%).Our finding of a higher rate of surgical failure in patients with anterior perforations in comparison to posterior perforations ,may have been due to the limited vascularization of the anterior part of the eardrum 15 and also due limited access to the anterior perforation.
Significant difference was found when comparing postauricular with endaural and transcanal approach.The success rate was 95.56% in postauricular, 80% in endaural and 80% in transcanal approach.Inwood et al 14 reported that surgical approach does not influence surgical outcome.

Conclusion
Myringoplasty in a dry ear significantly improves surgical outcome so preoperative inflammatory changes in the middle ear mucosa should be carefully evaluated and its medical treatment should be considered.Hearing improvement after myringoplasty in anatomically successful cases improve quality of life of the patients.
Total 60 patients who underwent myringoplasty were studied in the Department of Otolaryngology Head & Neck Surgery of SSMC & Mitford Hospital, Dhaka with their descriptive history, clinical findings, pre and post operative assessment during the period of January to December 2008.The assessment of the patient was done on the basis of history, clinical examination (Tuning fork test), radiological test (x-ray mastoid Towne's view, laboratory investigation and hearing function test (pure tone audiometry and impedance).

Table - V
Involvement of the ear.

Table - VI
Distribution of site of peroration.

Table - I
Age distribution of patients and graft take rate (n= 60)

Table - VII
Distribution of approach of operations.
16e overall success rate was 86.67% (52 out of 60).The surgical failure in five cases (8.33%) was characterized by evidence of graft failure at the last follow up visit.Two patients (3.3%) developed reperforation and one (I.67%)developedanteriorblunting .So total failure was observed in 8 patients (13.33%).Graft failure occurred during the first -8 weeks in five cases.None of the patient developed epithelial pearl medialization or lateralization of the graft.In a prospective study 60 cases ,Mangal Singh et al16showed overall success rate of 93.3% and hearing improvement(air-bone gap<10 dB) in 92.8%.