A retrospective study on middle ear risk indices in analysing the post-operative outcome following tympanoplasty

INTRODUCTION

The goal of successful tympanoplasty is to eradicate the disease from middle ear and to create a sound conducting mechanism in a well aerated mucosal lined middle ear cleft.

The success rate of tympanoplasty is extremely variable, ranging from 60 to 99% in adults.¹

Middle ear risk index (MERI) was revised and updated in 2001 by Becvarovski et al and Kartush et al.^2,3 It combines the known preoperative and intra-operative risk factors for tympanoplasty prognosis into a numerical value.^4-7

The main aim of the study was to evaluate the effectiveness of MERI in determining postoperative graft uptake and air bone gap closure following tympanoplasty.

METHODS

A 1.5-years retrospective study was carried out in ENT department in a tertiary care medical centre from June 2018 to December 2019 on 96 subjects in the age group of 18-50 years who underwent tympanoplasty for chronic otitis media. Patients with squamosal type of chronic otitis media and previous use of ototoxic drugs were excluded from the study. After obtaining the institutional ethics committee clearance, data was collected from the hospital records. After detailed history and ENT examination, pure tone audiogram was done prior to surgery. All patients underwent tympanoplasty using post aural approach and temporalis fascia as graft material. Following surgery, intra-operative findings was obtained from operative notes. Based on these MERI score was calculated and categorized as mild, moderate and severe. Tympanic membrane status of operated ear at the end of one month was obtained from case records and postoperative audiogram at the end of 3 months was obtained from audiology database maintained by the department audiologist.

Note: M- malleus, S- stapes suprastructure, mild (1-3), moderate (4-6) and severe (7-16).

Statistical analysis

Data obtained were recorded in MS Excel work sheets and statistical analysis was done using IBM SPSS 22 programme running on windows operating system. Fischer’s exact test and Chi square test was used for statistical analysis. Data was expressed in terms of frequency and percentages. Data visualization was done using appropriate charts/graphs. A p value<0.05 were considered as statistically significant.

RESULTS

This was a retrospective study conducted to find the correlation between MERI and the result of tympanoplasty outcome and post-operative hearing gain. 96 patients were included in the study. The age range of participants in the study was 18-50 years with a mean±SD age was 34.70±10.22 years. There was a female predominance in the study (65.6%) (Figure 1). According to our data majority of the patients fell into the mild category (74%) followed by moderate (26%). There were no patients in severe category. Majority of our patients had mild conductive hearing loss in our study (44.8%). Of the 96 patients in our study graft was taken up in 84 patients (87.5%). There was no statistically significant difference between the various groups in terms of uptake of graft (p=0.073) (Figure 2).

According to Belluci criteria, there was no residual perforation in dry ears whereas in persistently wet ears there was 27.8% chance of graft rejection. There was a significant difference between the various groups in terms of distribution of graft status (p=0.004). According to our study patients with bilateral disease did not have a higher chance of graft rejection. Unhealthy middle ear mucosa included presence of congestion or discharge.

There was no granulation tissue in any of the cases. We noted that all the patients who had a residual perforation had unhealthy middle ear mucosa. There was an association between smoking and graft acceptance rate according to our study (p=0.001). According to our study the size of the perforation did not have a bearing on the success of the surgery. Incus was found to be most commonly affected ossicle followed by malleus. There was an improvement in AB gap in both mild (p value<0.001) and moderate categories (p value=0.002). We considered AB gap of less than 10 db as excellent hearing result and 10 to 20 db as successful hearing result as per Committee on Hearing and Equilibrium of the Academy of Otolaryngology- Head and neck surgery. We noticed that excellent hearing results were observed in 36.6% of patients with mild MERI. A successful hearing result was seen in 42.3% of mild MERI and 56% of moderate MERI.

DISCUSSION

The success of tympanoplasty is most often defined by the graft integration, disease control, an aerated ear and the results of hearing.⁸ There are many studies which discuss the prognostic factors and hearing results in tympanomastoid surgeries. In our study we used the middle ear risk index scale. Our sample size included adults between 18-50 years of age. The effect of age on the success of tympanoplasty is contradictory in different studies. The reason for poorer results in paediatric tympanoplasties was mostly related to continued Eustachian tube dysfunction and a low tympanometric volume.^9,10 However a study in elderly showed that elderly patients with low/medium MERI had a good surgical outcome.¹¹ There was a female preponderance in our study which was also noted in some of the studies.^12,13

A vast majority of our patients fell into MERI mild category (74%) with no patients in severe category. These results were similar to previous studies which showed that mild category of MERI was a majority.^4,5 The overall graft acceptance rate was 87.5% in our study. The various factors which were significantly associated with graft uptake were Belluci’s criteria (p=0.004), condition of the middle ear mucosa (p≤0.001) and smoking (p=0.001).

However, the size of the perforation and presence of bilateral disease (p=0.750) were found to have no association with graft uptake. In a study by Pinar et al it was found that bilateral disease and type of surgery were significantly associated with graft uptake whereas size and site of perforation had no significant association.¹ In a study conducted to assess the impact of perforation size on the success of tympanoplasty it was concluded that perforation size was not predictive or determinant of successful myringoplasty.¹⁴ The status of the ear (dry or wet) was not statistically related to surgical success in many studies.^4,8 However some studies showed that there are more likely chances of graft rejection in persistently wet ears.¹⁵

The effect of smoking on the middle ear can be classified as local (due to effect on mucociliary apparatus), regional (due to Eustachian tube obstruction) or systemic (due to immunosupression).⁸ A study conducted to review the effects of smoking on the success rate of tympanoplasty revealed that smoking was associated with a threefold increase in chance of long-term failure of graft. MERI was revised to include smoking as a risk factor based on this study.⁷

In our study there was no significant difference in graft uptake between the two categories (p=0.073). This is in contrast to other studies which showed that as the MERI score increases there are more chances of graft rejection. In a study by Aggarwal et al and Dev et al it was found that graft uptake was 91% in mild category but it was only 60% in moderate category (p=0.008).⁴ There was a 100% chance of graft rejection in ears with MERI score of 7-12 in the study by Nishant et al.⁵ This lack of correlation in our study could be explained by the fact that most of our patients belonged to mild category with no patients being in the severe category of MERI.

In our study the hearing loss was predominantly mild conductive hearing loss (44.8%). Ossicular involvement was seen in 14.5 % of the cases in which incus was the most common ossicle to be diseased (8.3%). When, it comes to the damaged ossicle as a predictor of hearing results in ossiculoplasties the literature data is controversial. Many studies showed that the presence of malleus is a better determinant of hearing results post-surgery regardless of the condition of the stapes.^16,17 The malleus handle contributes to the stability of the tympanic membrane and the ossicular chain. It further prevents graft lateralization and acts as a catenary lever.^18,19 However there are some authors who consider that the presence of stapes suprastructure is crucial in the hearing outcome.^18,20

There was a significant improvement in AB gap in both mild and moderate categories. This was in contrast to other studies which showed positive correlation between MERI score and hearing results.^2,4,12 However we noticed that excellent hearing improvement (AB gap <10 db) was seen in 36.6% of patients in mild MERI category.

The limitation of our study was that it was a retrospective study. So, our data was mainly based on the documented evidence. The study can be improved by adding Eustachian tube function tests along with MERI for best results.

CONCLUSION

In our study MERI did not have an overall effect in predicting the outcome of tympanoplasty. However certain components of MERI like otorrhoea and smoking had a positive correlation. We also assessed certain other prognostic factors in addition to the ones included in MERI. The purpose of doing this study is to help us in counselling the patients and give them the realistic expectations from the surgery.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

REFERENCES

1. 1. Pinar E, Sadullahoglu K, Calli C, Oncel S. Evaluation of prognostic factors and middle ear risk index in tympanoplasty. Otolaryngol Head Neck Surg. 2008;139(3):386-90.
2. 2. Singh A, Jain RK, Agarwal U, Chaudhary AK, Singh V. Prognostic parameters and their relevance in outcome of middle ear surgeries. Indian J Otolaryngol Head Neck Surg. 2020.
3. 3. Felek SA, Celik H, Islam A, Elhan AH, Demirci M, Samim E. Type 2 ossiculoplasty: prognostic determination of hearing results by middle ear risk index. Am J Otolaryngol. 2010;31(5):325-31.
4. 4. Aggarwal SK, Dev R. Comparative study of tympanoplasty and its outcome in various age groups using middle ear risk index scale. Indian J Otol. 2020;26:4-8.
5. 5. Kumar N, Madkikar NN, Kishve S, Chilke D, Shinde KJ. Using middle ear risk index and et function as parameters for predicting the outcome of tympanoplasty. Indian J Otolaryngol Head Neck Surg. 2012;64(1):13-6.
6. 6. Almazrou K, Alqahtani M, Alshehabi M. Middle ear risk index as a prognostic factor in pediatric ossicular reconstruction. Indian J Otol. 2013;19(1):23-36.
7. 7. Becvarovski Z, Kartush JM. Smoking and tympanoplasty: implications for prognosis and the Middle Ear Risk Index (MERI). Laryngoscope. 2001;111(10):1806-11.
8. 8. Lima JC, Marone SA, Martucci O, Gonçalez F, Silva NJJ, Ramos AC. Evaluation of the organic and functional results of tympanoplasties through a retro-auricular approach at a medical residency unit. Braz J Otorhinolaryngol. 2011;77(2):229-36.
9. 9. Shishegar M, Faramarzi M, Rashidi RM. Evaluation of middle ear risk index in patients undergoing tympanoplasty. Eur Arch Otorhinolaryngol. 2019;276(10):2769-74.
10. 10. Merenda D, Koike K, Shafiei M, Ramadan H. Tympanometric volume: a predictor of success of tympanoplasty in children. Otolaryngol Head Neck Surg. 2007;136(2):189-92.
11. 11. Sevil E, Doblan A. Significance of the middle ear risk index in predicting tympanoplasty success in the elderly. Eur Arch Otorhinolaryngol. 2020.
12. 12. Nallapaneni LS, Sudarshan SS, Krishnamoorthy S. A prospective study on middle ear risk index (MERI) and outcome of tympanoplasty with a note on quality-of-life (QOL). Indian J Otolaryngol Head Neck Surg. 2020.
13. 13. Basak B, Gayen GC, Das M, Dhar G, Ray R, Das AK. Demographic profile of CSOM in a rural tertiary care hospital. IOSR J Pharm. 2014;4(6):43-6.
14. 14. Wasson JD, Papadimitriou CE, Pau H. Myringoplasty: impact of perforation size on closure and audiological improvement. J Laryngol Otol. 2009;123(9):973-7.
15. 15. Vignadutt P, Shaik A. A retrospective study on middle ear risk indices in analysing the postoperative outcome following tympanoplasty. Int J Otorhinolaryngol Head Neck Surg. 2019;5(5):1234-39.
16. 16. Blom EF, Gunning MN, Kleinrensink NJ, Lokin AS, Bruijnzeel H, Smit AL, et al. Influence of Ossicular Chain Damage on Hearing After Chronic Otitis Media and Cholesteatoma Surgery: A Systematic Review and Meta-analysis. JAMA Otolaryngol Head Neck Surg. 2015;141(11):974-82.
17. 17. Dornhoffer JL, Gardner E. Prognostic factors in ossiculoplasty: a statistical staging system. Otol Neurotol. 2001;22(3):299-304.
18. 18. Kotzias SA, Seerig MM, Mello MFPC, Chueiri L, Jacques J, Silva MBCD, et al. Ossicular chain reconstruction in chronic otitis media: hearing results and analysis of prognostic factors. Braz J Otorhinolaryngol. 2020;86(1):49-55.
19. 19. Vos C, Gersdorff M, Gerard JM. Prognostic factors in ossiculoplasty. Otol Neurotol. 2007;28(1):61-7.
20. 20. Sousa A, Henriques V, Rodrigues J, Fonseca R. Ossiculoplasty in chronic otitis media: Surgical results and prognostic factors of surgical success. Acta Otorrinolaringol Esp. 2017;68(3):131-7.