Indian J Otolaryngol Head Neck Surg (2023) 75:S216–S221

https://doi.org/10.1007/s12070-022-03320-w

ORIGINAL ARTICLE

A Prospective Study on Correlation of MERI (Middle Ear Risk

Index) Score with Surgical Outcome of Tympano‑mastoid Surgery
in Patients of CSOM
Mahesh Chand Gupta1 · Shraddha Sharma1 ·
Pragya Rajpurohit1 · Yogesh Aseri1 · P. C. Verma1

Received: 11 November 2021 / Accepted: 28 November 2022 / Published online: 19 December 2022
© Association of Otolaryngologists of India 2022

Abstract Chronic otits media (COM) is surgically treat- Introduction

able disease which includes complete removal of disease and
improving hearing via ossicular reconstruction. Therefore, Chronic otitis media (COM) is the chronic inflammation of
thorough assessment of the disease, ossicles and various the mucoperiosteal lining of the middle ear cleft present-
factors causing it plays a major role in surgical outcome ing with or without recurrent ear discharge. The definitive
prediction. MERI (Middle ear risk index) is one such tool management of COM is surgical and the goals of the sur-
being used worldwide. Our aim was to evaluate the surgical gery are to achieve a safe ear, eradicate disease, stabilize or
outcome of tympanomastoid surgery using MERI and find improve hearing by reconstructing the tympanic membrane
out correlation between them as well as categorize cases into and ossicular chain. Tympanic membrane perforation asso-
their severity score in a developing country. Observational ciated with COM are considered as the major indication for
prospective study conducted in a tertiary care center. 200 tympanoplasty and other tympanomastoid surgeries [1].
patients were included. After complete history and examina- But, in order to restore the normal anatomy and hearing,
tion, they were given MERI scores and prediction of surgical the reconstruction process has always been a challenge to the
outcome was done. Postoperatively it was compared with the otologist. The life of an otologist can become much easier if,
real outcome of the surgery. Out of 200 patients, 71.5% had he can predict the outcome of the surgery for better patient
mild, 15.5% had moderate and 13% had severe MERI scores counseling and to decide the intraoperative procedure. For
preoperatively. There was a success rate of 88.5% in graft such dilemmas many methods have been used, out of which
uptake and the mean score of hearing benefit (A-B gain) one is Middle Ear Risk Index (MERI) score.
among patients was 8.75 ± 8.82 dB postoperatively. MERI In 1994, the MERI was proposed by Kartush which gen-
may be used as a prognostic indicator for predicting surgi- erates a numeric value corresponding to the severity of dis-
cal outcome. Based on the MERI score, chances of surgical ease and the likelihood of a successful outcome following
success and hearing benefit can be explained to the patient surgery [2]. Both, the preoperative and intraoperative factors
with certain limitations. are combined into a numerical value for assessing prognosis
of tympanoplasty. The factors included are otorrhoea, tym-
Keywords MERI index · COM · Tympanomastoid panic membrane perforation, presence or absence of chole-
surgery steatoma, ossicular status, presence of middle ear granula-
tion or effusion and history of previous middle ear surgery.
Kartush in 2001 further added smoking as a risk factor [3].
MERI score can be helpful in deciding intraoperatively
whether to proceed with canal wall up or canal wall down
mastoidectomy. The score can also be used to compare the
* Pragya Rajpurohit hearing improvement by using different types of prosthesis
lakhirjp@gmail.com
in ossiculoplasty. Many studies have been done to justify
1
Department of Otorhinolaryngology and Head and Neck the use of MERI in tympanomastoid surgeries but none
Surgery, Jawahar Lal Nehru Medical College, Ajmer, India have discussed the difficulties which a developing country

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Indian J Otolaryngol Head Neck Surg (2023) 75:S216–S221 S217

face due to limited factors included in the scoring system. or conchal cartilage (allograft) were reshaped and used. In
Hence our present study was conducted to find out correla- patients with incus erosion, ossicular prosthesis was placed
tion between MERI, and surgical outcomes based on graft between stapes head and handle of malleus. In patients with
uptake and hearing improvement and its usefullness in a erosion of stapes, ossicular graft was placed between the
developing country like India. footplate of stapes/oval window and malleus. In case of mal-
leus and incus erosion, ossicular graft was placed between
stapes and TM. Hence ossiculoplasty was done based on the
Methods ossicular erosion. The temporalis fascia graft was placed by
underlay technique. Gel foam was placed in middle ear and
The prospective, observational study has been conducted in external ear canal. Merocel™ ear wick was placed in exter-
a tertiary care hospital of a Medical College of North India. nal canal. Wound was closed in two layers. Mastoid dressing
Target population comprises of adult COM patients of more was applied. The middle ear risk index score was calculated
than 18 years to 60 years of age planned for tympnomastoid for each patient. The patients were stratified into those with
surgery. Patients with moderately severe mixed or sensory mild (0–3), moderate (4–6) and severe (≥ 7) MERI.
neural hearing loss, and patients undergoing revision sur- Intravenous antibiotics and the analgesics were given in
geries were excluded. Total 200 patients were enrolled for the immediate postoperative period. Postoperatively patients
the study. Study was approved by Institutional Ethical Com- were prescribed tablet amoxicillin with clavulanic acid and
mittee. Written and informed consent was obtained from tablet diclofenac sodium for 10 days. Stitches and ear canal
the patients wherein they were explained about the study. packing was removed on 7th postoperative day. Topical
A detailed history was taken from the patient such as the ear drop containing ciprofloxacin with dexamethasone was
nature of ear discharge, hearing loss, other medical illness, started twice per day for 1 month. The outcome of surgery
history of smoking, previous ear surgery and long term use was assessed based on graft status and hearing improvement.
of ototoxic drugs. Otoscopic examination was done to find Graft status was analysed by oto-endoscopy: (a) Success-
the presence or absence of perforation, granulation tissue ful—The healed graft with proper middle ear aeration, (b)
and cholesteatoma. Tuning fork tests were performed to find Atelectatic graft and (c) Graft failure or perforation of graft.
the type of hearing loss. Those with sensorineural and mixed Post operative PTA was performed after third post-operative
hearing loss were excluded from the study. Examination of month. The mean air bone gap was calculated (from the air
nose and paranasal sinuses and throat was done to rule out bone gaps at 0.5 kHz, 1 kHz, 2 and 4 kHz). Based on the
septic foci such as adenotonsilltis and sinusitis. Basic inves- preoperative and postoperative air bone gaps, the hearing
tigations such as complete blood counts were done prior benefit was calculated in terms of Air-Bone gap closure.
to surgery. Otoendoscopy and otomicroscopy were done to These outcomes were statistically analyzed for patients with
confirm the otoscopic findings and also in large perforations, mild, moderate and severe MERI scores. Statistical analysis
the middle ear mucosa, any polypoidal changes in middle of these results was done using the opera-otic software. Sta-
ear, the ossicles, and attic were inspected. The pre and 3rd tistics were made using one-way analysis of variance and the
month post-operative hearing evaluation were performed by chi-square test. The results were assessed at a significance
pure tone audiogram (PTA) using ALPS AD 2100 audiome- level of p < 0.05.
try machine in a sound proof audiometry room, using Hugh-
son and Westlake method modified by Carhart and Jerger.
The type and degree of hearing loss was noted. The mean Results
air-bone gap was measured from the air and bone conduc-
tion thresholds at 0.5 kHz, 1 kHz, 2 kHz, and 4 kHz (Fig. 1). The age of the 200 patients included in the study ranged
The patients were planned for surgery after proper inves- from 18 to 60 years. The commonest age group was 21–30
tigations and pre anaesthetic check-up. Lidocaine sensitivity years having 76 (38%) patients. The mean age of study
testing of all the patients was performed. The procedures population who underwent tympano-mastoid surgery was
were undertaken under local or general anaesthesia. The 39.10 + 2.46 years. There were 66 (33%) males 134 (67%)
post auricular approach was used. Temporalis fascia was females. Female preponderance was seen in the study with
exposed and prepared in situ. Ossicular status was assessed sex ratio 0.49:1. Ear discharge was the most-common symp-
and noted. The type of tympanoplasty and mastoidectomy tom amongst the patients, followed by hearing impairment.
was decided intra operatively based on the extent of disease On preoperative otoscopic and microscopic examination
in middle ear and mastoid. Temporalis fascia graft was used of the ear undergoing tympanomastoid surgery, maximum
for all patients. The mastoid cortex was drilled using electri- patients had wet ear 51% (n = 102), cholesteatoma was pre-
cal burr and any granulation, cholesteatoma or serous effu- sent in 35 patients (17.5%) and edematous mucosa in 40
sion were removed. For ossiculoplasty, the eroded ossicles patients (20%). Intact ossicular chain (M + I + S) was seen

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S218 Indian J Otolaryngol Head Neck Surg (2023) 75:S216–S221

Cases of chronic suppurative otitis media admitted

in a tertiary care hospital.

Detailed history, clinical examination, routine

investigations, pure tone audiometry, x-ray
mastoid,otoscopic examination,examination under
microscope. 350 Pts were evaluated

Case inclusion (200 pts) Case exclusion (150 pts)

Cases of chronic suppurative otitis media

between 18 to 60 years of age operated for 1. Patients with SNHL, mixed (100pts)
tympano-mastoid surgery 2. Age <18 years and >60 years.
(50pts)
3. Revision ear surgery

Tympanomastoid Surgery
(Tympanoplasty/ Mastoid Quantitative Assessment
intact Canal Wall
Tympanoplasty/ Canal Wall
Middle Ear Risk Index
Down Tympanoplasty)
(MERI)

Follow up at 1 and 3

Otomicroscopic
examination
Audiometry

Data analysis

Fig. 1  Flow-chart of the study

in 130 patients (65%) who underwent intact canal wall type 6 and 15 dB with mean of 13.24 ± 8.04 and 20% (n = 60)
I tympanoplasty. In the rest group of patients, 17% under- had air-bone gap between 26 and 40 decibels with mean of
went intact canal wall type II cartilage tympanoplasty, 8% 24.10 ± 13.53dB.
intact canal wall type III cartilage tympanoplasty and 10% Postoperatively, after 3 months there was significant
modified radical mastoidectomy with type III cartilage tym- improvement in the mean air conduction. Maximum patients
panoplasty. (Table 1) Postoperatively, 88.5% of cases had 64% (n = 128) had minimal conductive hearing loss with
successful graft uptake and only 11.5% had graft failure. mean of 27.05 ± 13.11dB. Whereas improvement in the
Preoperatively, the average hearing loss of study group bone conduction level in 57.5% (n = 115) of the cases was
was found to be 37.70 ± 15.14 dB. Most of the patients, found to be between 6 and 15 dB, with mean of 11.99 ± 6.9
62% (n = 124) had bone conduction threshold between dB, which was not significant. The A-B gap improved from

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Indian J Otolaryngol Head Neck Surg (2023) 75:S216–S221 S219

Table 1  Intraoperative findings in operated ear Table 3  Graft uptake according to MERI score

Number of Graft status Mild Moderate Severe

patients
Graft taken up 138 24 15
Middle ear findings Graft rejected 5 7 11
Edematous mucosa 32
Glue 10
Granulation 15
patients. Therefore, higher the MERI score lower was the
Cholesteatoma 35
hearing improvement.
Ossicular status
M+I+S 130
Defect of I 35
Discussion
Defect of I, S/ossicular head fixation 20
Defect of I, M/S fixation 10
COM is an otorhinolaryngeal problem seen more in develop-
Defect of M, I, S 5
ing countries [4]. In general, complete removal of disease
M Malleus, I Incus, S Stapes and hearing improvement amongst COM cases is difficult
to achieve, due to the extent of pathology in the middle ear
and mastoid which affects the outcome. Hence, these fac-
24.10 ± 13.53 to 15.09 ± 11.73 dB, making the AB gain 13 tors are summarized and assigned a numerical value, the
dB (mean 8.75 ± 8.82 dB), highly significant. (Table 2) MERI score, which helps us identify the extent of disease
MERI score was calculated for all 200 participants. Out and thereby predict the surgery outcome. This study was
of them 143 patients had mild (1–3) score, 31 patients had done to find if MERI score can be effectively used as a tool
moderate (4–6) score and 26 patients were with severe (≥ 7) for this purpose.
score. When the MERI score was mild, graft uptake was In the present study, mean age at which the disease mani-
seen in 138 patients and rejection in only 5 patients. When fested was 39.20 ± 2.46 years and females (67%) were more
the MERI score was moderate, the graft uptake was present commonly affected than males. Bijan Basak et al. also stated
in 24 patients and rejected in only 7 patients. But, when that COM (both tubotympanic and atticoantral type) is com-
the MERI score was high, graft rejection was seen in 11 mon in the age group 11 to 30 years with female predomi-
patients and uptake in 15 patients. (Table 3) Thus, there was nance [5]. Lack of proper nutrition and reduced literacy rate
an inverse relation between the MERI score and the rate of and hence poor hygienic practices among females may con-
graft uptake. Therefore, higher the MERI score, lower was tribute to higher incidence in them.
the rate of graft taken up in patients and patients with lower The reason to include patients between the age of 18 to 60
MERI had higher rate of graft uptake. years in the study was due to limited causative factor spec-
Similar relation was seen with hearing improvement. Out trum of the MERI. In the developing country like ours, chil-
of the total, 151 patients (75%) had hearing improvement dren ( below 18 years) are prone to recurrent upper respira-
post operatively. When MERI score was mild (n = 143), tory tract infections, adenoid hypetrophy leading to higher
hearing benefit was observed in 117 patients, for moder- frequency of COM. In other words, recurrent episodes of
ate (n = 31), hearing benefit was observed in 26 patients, otorrhea. MERI does not include any of these factors, hence
for high (n = 26), hearing benefit was observed for only 8 inclusion of children will give erroneous outcome. Simi-
larly, in elders (above 60 years) sensory neural hearing loss
and co-morbidities like diabetes sets in, which are again not
Table 2  Comparison of pre and post-operative hearing included in the index.
The success rate in our study has been explained with
Total (n = 200) Hearing thresh- Hearing thresh- p-value
reference to two different entities—graft status and hear-
old old
(preoperative) (postoperative) ing benefit. The overall success rate of tympanoplasty was
Mean (dB) ± SD Mean (dB) ± SD 88.5% according to graft status. Grafts which were rejected,
were taken as failures, which was 11.5%. The studies con-
Air conduction 37.27 ± 15.14 27.05 ± 13.11 0.002 (S) ducted by Andersen et al. [6] also showed that graft uptake
Bone conduc- 13.24 ± 8.04 11.99 ± 6.19 0.0475 (NS) rate after type 1 tympanoplasty was 93% at 2 to 6 months
tion
and 86.6% at the end of 12 months.
Air-bone gap 24.10 ± 13.53 15.09 ± 11.73 0.002 (S)
Success of hearing reconstruction procedure also depends
A-B gain 8.75 ± 8.82
on the preoperative ossicular status. In the current study,
S Significant, NS Non significant 35 patients had erosion of incus. According to the studies

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S220 Indian J Otolaryngol Head Neck Surg (2023) 75:S216–S221

conducted by Ghodrat Mohammadi, incus is the most com- of mastoidectomy and have better realistic outcomes after
monly eroded ossicle similar to our study [7]. The most middle ear surgeries [12].
common ossicle to be eroded is the long process of incus Sayal et al. [13] studied hearing results of tympano-mas-
due to the nature of blood supply (poor) to the lenticular toidectomies using Titanium Prostheses in patients with
process. However, defect of malleus is given a higher score mild, moderate and severe MERI .They concluded that in
in MERI as compared to incus erosion. As in several stud- developing countries, where they have limited resources,
ies it has been seen that intact handle of malleus has bet- should take the advantage of MERI score to decide the type
ter prognosis for hearing outcome, also shown in study by of ossicular reconstruction.
Wilson et al. [8]. The above studies in common agree to the point that mild
The air conduction i.e., the hearing of most of the patients to moderate MERI scores give good surgical outcome. But
improved after surgery and it showed significant change but there is merely any discussion about the result of poor MERI
improvement in bone conduction was non-significant. In score. Some of them have given inconclusive relation. We
2001, Karthush et al. conducted studies on 74 cases (includ- have tried to assess the correlation between poor score and
ing both smokers and non smokers) of type I tympanoplasty. outcome also. Present study concluded that there is higher
There was 100% graft uptake. The average improvement graft rejection rate for patients with higher MERI scores
in air-bone gap was 5.3 dB with no gain [3]. Whereas, and vice versa.
in our study the A-B gap improved from 24.10 ± 13.53 Other parameters like Ossiculoplasty outcome param-
to 15.09 ± 11.73 dB, making the AB gain 13 dB (mean eter staging (OOPS) and surgical prosthetic infection tissue
8.75 ± 8.82 dB), highly significant. eustachian tube (SPITE) scores can also be used to assess
Factors like cholesteatoma, TM perforation, status of the surgical outcomes. Many comparative studies have been
the ossicular chain, and the overall sum of the MERI were done between above two and MERI although we have not
highly significant pre-operative negative prognostic factors done any comparision.
influencing the outcome of tympanoplasty in our study. In a recently published retrospective study from Repub-
Similarly, Pinar et al. in 2008, studied the role of middle lic of Korea Jung et al. analysed MERI score and OOPS
ear risk index and other factors such as age, sex, systemic of COM patients and reported that there was no significant
diseases, site and size of perforation, period of dryness, pres- difference in hearing outcome in three follow-up groups of
ence of myringosclerosis, nasal pathology, status of opposite patients according to MERI score. However they reported
ear and type of surgery on the outcome of tympanoplasty. that the patient with low OOPS score had better postopera-
They concluded that low MERI scores, smaller perforation, tive hearing results [14].
healthy opposite ear, absence of myringosclerosis and more In another study Judd et al. retrospective evaluated pre-
than 3 months dryness were good prognostic factors [9]. Our diction of hearing outcome after ossiculoplasty using MERI,
study also found these factors as significant . OOPS, and surgical prosthetic, infection, tissue, eustachian
In 2009, Viktor Chrobok et al. studied the prognostic tube (SPITE) scores. For prediction of hearing outcome after
factors for hearing preservation in surgery of chronic oti- ossiculoplasty, they found that none of the three scores could
tis media. They compared the MERI score of patients with predict poor post-operative outcome, though low SPITE was
hearing benefit after surgery and showed that patients with found to be associated with better hearing outcome [15].
a generally lower MERI had better pre-operative and post- However our study showed that higher MERI score conse-
operative air and bone conduction than patients with a higher quently resulted in poor graft uptake.
MERI score. They concluded that MERI is a significant
prognostic factor for predicting the outcome [10]. A similar
correlation between low MERI score and better postopera-
tive air conduction was seen in our study. Conclusion
In a recent retrospective case-control study by Torre
Carlos et al. on pediatric patients with tympanic membrane MERI score is an easy to calculate prognostic factor and
perforation mild MERI before tympanoplasty was found the extent of disease for management of COM. Based on
to be associated with significantly better chances of suc- the MERI score, chances of surgical success and hearing
cessful tympanoplasty in comparison to severe MERI [11]. benefit can be explained to the patient. Our study had a suc-
Although our study excludes pediatric group but the correla- cess rate of 88.5% in graft uptake(proportionately more with
tion of MERI score and output still shows similarity. low MERI score). The mean score of hearing benefit (A-B
Another similar study by Sevil et al. compared the role gain) among patients is 8.75 ± 8.82 dB. Attempts should be
of MERI score with surgical outcome in elderly patients of made to reduce the middle ear disease where ever possible
≥ 60 years and patients of 18–59 years. They concluded that (otorrhoea and granulation) preoperatively to improve the
low and medium MERI scores will have less requirement success rate of tympanoplasty.

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Indian J Otolaryngol Head Neck Surg (2023) 75:S216–S221 S221

But still MERI could not make its place as a mandatory 7. Mohammadi G, Naderpour M, Mousaviagdas M (2012) Ossicu-
routine tool in each ear case and in the entire world due lar erosion in patients requiring surgery for cholesteatoma. Iran J
Otorhinolaryngol 24(68):125–128
to the lacunae discussed above. More work is required to 8. Wilson KF, London NR, Shelton C (2013) Tympanoplasty with
improvise it according to the needs of developing country intact canal wall mastoidectomy for cholesteatoma: long-term
like ours as different countries have different prevailing hearing outcomes. Laryngoscope 123(12):3168–3171
factors. 9. Pinar E, Sadullahoglu K, Calli C, Oncel S (2008) Evaluation of
prognostic factors and middle ear risk index in tympanoplasty.
Otolaryngol Head Neck Surg 139(3):386–390
10. Chrobok V, Pellant A, Meloun M, Pokorny K, Simáková E, Man-
Funding None. dysová P (2009) Prognostic factors for hearing preservation in
surgery of Chronic Otitis Media. Int Adv Otol 5(3):310–317
Declarations 11. Torre Carlos DL, Carolina V, Perla V (2021) Middle ear risk index
(MERI) as a prognostic factor for tympanoplasty success in chil-
Conflict of interest Authors declare that we have no potential con- dren. Int J Pediatr Otorhinolaryngol 144:110695
flict of interests. 12. Sevil E, Doblan A (2021) Significance of the middle ear risk
index in predicting tympanoplasty success in the elderly. Eur Arch
Otorhinolaryngol 278(10):3689–3695
13. Sayal A, Taneja V, Gulati A (2013) Preliminary hearing results of
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