A study on correlation of size and site of tympanic membrane perforation with degree of conductive hearing loss in chronic otitis media

 

 

Abstract              Background: Tympanic membrane perforations are common cause of hearing loss. This study was designed to analyze the relation between tympanic membrane perforation and conductive hearing loss. Materials and Methods: In this prospective study, patients with dry tympanic membrane perforations of safe type were included. The patients were divided into groups in according to size, site and duration of perforation. Based on the inclusion and exclusion criteria a total of 100 patients were included in this study. All the patients clinical data was analyzed statistically using paired t-test. Results: Hearing loss increased as the size of perforation increased. Posterior quadrant perforations were associated with more hearing loss as compared to anterior quadrant perforations. Also duration of disease was in linear relation with mean hearing loss. Conclusions: The degree of conductive hearing loss as a result of tympanic membrane perforation would be expected with the size, site and duration of perforation.

Key Words: Tympanic membrane, Conductive hearing loss, Perforation, hearing loss, posterior quadrant, ear.

 

INTRODUCTION

Tympanic membrane separates middle ear from the external ear, measuring 9-10 mm vertically and 8-9 mm horizontally. It transmits sound in middle ear¹. Apart from conduction of sound waves across the middle ear, the tympanic membrane, also sub-serves a protective function to the middle ear cleft and round window niche². Chronic otitis media (COM) has been defined as a longstanding inflammatory condition of the middle ear and mastoid associated with or without a perforation of the tympanic membrane³. COM with a perforation often is accompanied by a past and present history of intermittent otorrhea and conductive hearing loss. Chronic Suppurative Otitis Media (CSOM) is a wide spread disease of the developing countries like India especially in the rural areas^4,5. It is one of the commonest causes of hearing loss that mainly results due to a tympanic membrane perforation. The large effective surface area of an intact and normally vibrating tympanic membrane plays a major role in the middle ear transformer mechanism. Perforation of the tympanic membrane is a common cause for hearing loss due to loss of effective area of vibration. Perforations can result from various reasons including middle ear disease, trauma. Tympanic membrane (TM) perforation reduces the total ratio of surface area, allowing the sound waves to directly pass through the middle ear. It is a highly prevalent condition and an important cause of preventable hearing loss⁶. Perforated eardrum results in conductive hearing loss, and this range is reported not to exceed 50dB^7-9. Accurate assessment of the TM Perforation and its relationship with hearing loss is important as it enables the clinician to optimally assess the condition and offer an appropriate solution. The objective of this study was to analyze the correlation between tympanic membrane perforation and hearing loss.

 

MATERIALS AND METHODS

Source of data

Patients attending ENT OPD BGS GIMS in the study period from April 2019 to Jan 2020 who have Tympanic membrane perforation.

Study design

A prospective study design was made and sample size was set at 70 perforated ears in 49 patients and safe CSOM. The patients were divided into 2 to 3 groups depending on size of perforation. The site of perforation was recorded and a pure tone audiogram is performed on the patient.

Inclusion criteria

Subject should have central TM perforation due to trauma or CSOM. All subjects should have dry ears (duration 3 months). Patients with intact ossicular chain. Age between 15-50 years.

Exclusion criteria

Patients with Attico antral disease – presence of cholesteatoma or granulation tissue. Active CSOM. Patients with Ossicular chain pathology. Patients who cannot give a valid and consistent PTA response. Patients with sensorineural hearing loss

Data collection

This study was approved by Institutional Human Ethics Committee (IHEC). A thorough history was taken in each case and patients underwent detailed ENT examination. The type, degree and frequency of hearing loss were determined by PTA (Pure Tone Audiometry). Average AC threshold was calculated at 500, 1000 and 2000 Hz. Depending upon the area of perforation of tympanic membrane, patients were divided into 3 groups.

Group-I: Small perforation

Group-II: Medium perforation

Group-III: Large perforation

Depending upon the site of perforation of tympanic membrane, patients were divided into 3 groups.

Group-A: Anterior (Antero inferior and antero superior quadrant) perforation.

Group-B: Posterior (Postero inferior and postero superior quadrant) perforation.

Group-C: Central (Multiple quadrants) perforation.

Depending upon the duration of disease, patients were divided into 3 groups.

Group-1: <1year; Group-2: 1-5years; Group-3: >5years

The association of degree of hearing loss was matched with the characteristics of perforation and result thus obtained was evaluated.

Statistical analysis

The data was expressed in number, percentage, mean and standard deviation. Statistical Package for Social Sciences (SPSS 16.0) version used for analysis. Paired t test applied to find the statistical he results of our study were analysed on SPSS Software using paired t test.

 

RESULTS

Table 1: Distribution of patients based on the size of perforation

Graph 1: Comparison of mean hearing loss between the groups

 

Table 2: Distribution of patients based on the site of perforation

 

Graph-2: Comparison of mean site of perforation between the groups

 

Table 3: Distribution of patients based on the duration of perforation

 

Graph 3: Comparison of mean duration of perforation between the group

A total of 49 patients with unilateral or bilateral CSOM (total perforated tytmpanic membranes=70) were included in the study. Maximum patients were in age group of 20 to 30. In our study number of males was 29 and females were 21 with Male: Female ratio of 1.38:1. Bilateral CSOM was seen in 21 patients, left CSOM in 19 patients and right CSOM in 9 patients. Otorrhea was the presenting complaint in 100% patients followed by impaired hearing. On comparing the mean hearing loss of group I, group II and group III, difference was found to be statistically significant (p<0.001). Thus there is significant increase in mean hearing loss from small perforation to medium perforation and most in the large perforation (Table-1). On comparing the mean hearing loss of group A, group B and group C, difference was found to be statistically significant with p<0.001. Thus we concluded that there is significant increase in mean hearing loss from anterior perforation to posterior perforation (Table-2). From the above result, we observed that mean hearing loss increased significantly as the duration of disease increased (Table-3).

 

DISCUSSION

The study included 49 patients, 21 patients had involvement of both ears so total number of ears involved in this study were 70. In this study, most common affected age group was 20– 30 years. The possible reason could be that this group is socially more active and is more health conscious. This finding is in accordance with Deepak et al. and Prasansuk et al..^10,11 The number of males in the study group was higher than the number of females (M:F=1.38:1). Rafique et al. in their study found M:F ratio of 1.25:1. Kurian also reported higher incidence of disease in males. The most common symptom was ear discharge (on and off) from the diseased ear which is consistent with study of Kumar et al. 13,14. The size of perforation comparing the degree of hearing loss with various size of perforation, it was observed that hearing loss increased with increased size of perforation. Our result was comparable with Vijayshree et al., Kumar et al. and Pannu et al..^6,14,15 Baumann et al. also reported a linear relation between the size of perforation and amount of hearing loss.¹⁶ Site of perforation in this study posterior quadrant perforations have higher mean hearing loss than anteriorly located perforations with statistically significant p value. However, hearing loss was highest in perforations involving multiple quadrants. This view has been supported by Vijayshree et al., Bianca et al. and Malik et al..^6,17,18 This can be attributed to the direct exposure of round window to the sound waves resulting in cancellation of phase difference between the oval and round windows. However, Herkat et al., Kumar et al. and Pannu et al. differed in this view in their study.^14,15,19.In our study, hearing loss increased as the duration of disease increased. On comparing hearing loss in all the three groups, it was observed that average hearing loss increased significantly as the duration of disease increased. Our observation regarding the duration of disease is similar to Pannu et al..¹⁵

 

CONCLUSION

Tympanic membrane perforation causes hearing loss ranging from mild to moderate. From our study, we concluded that the hearing loss increased with size of perforation and with posterior location of tympanic membrane perforation. A thorough knowledge of all these results would allow us to clinically predict the hearing loss based on size and site of perforation.

 

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