|Year : 2014 | Volume
| Issue : 1 | Page : 10-15
Tympanic membrane perforation: Its correlation with hearing loss and frequency affected - An analytical study
Vijayshree Nahata1, Chandrakant Y Patil1, Rashmi K Patil1, Gaurav Gattani2, Ashish Disawal1, Amitava Roy1
1 Departments of Ear, Nose and Throat, Acharya Vinoba Bhave Rural Hospital and Jawaharlal Nehru Medical College, Wardha, Maharashtra, India
2 Department of Gen Surgery, Acharya Vinoba Bhave Rural Hospital and Jawaharlal Nehru Medical College, Wardha, Maharashtra, India
|Date of Web Publication||1-Apr-2014|
Sanjeevani Nursing Home, 103 Polo Ist, Paota, Jodhpur - 342 001, Rajasthan
Source of Support: None, Conflict of Interest: None
Objective: The correlation between tympanic membrane perforations and hearing loss was studied. Study Design: Cross sectional prospective study design. Setting: E. N. T OPD, at a tertiary referral center. Materials and Methods: 100 perforated ears in patients of CSOM safe were selected from May 2011 to September 2013. Instruments used for data collection/processing included questionnaires, oto-endoscopy and micro-otoscopy, Pure tone audiometer and image J software. Results: Sixty-three patients (27-males, 36-females), aged 10-56 years (mean age 23.2 years ± 11.8 years) with 100 perforated eardrums were studied. 37(58.7%) had bilateral TM perforations, 7(11.1%) right unilateral and 19(30.2%) left unilateral. The various sizes of perforation and their hearing loss were as follows: Group I (0-8 mm 2 ), n=18, with mean hearing loss 29.41 ± 4.39. Group II (8.1-30 mm 2 ), n=39, with mean hearing loss 34.69± 4.96. Group III (>30.1 mm 2 ), n = 43, with mean hearing loss= 38.79± 3.44. Difference was significant, P value 0.000. The various sites of perforations were Central (69 ears. Mean hearing loss 35.64 dB ± 5.31), Posterior (16 ears, mean hearing loss 39.99 dB ± 2.79) and Anterior (15 ears, mean hearing loss 30.1 dB ± 2.98). Difference was significant, P value 0.000. Lower frequencies were affected more than higher frequencies. Inverted 'V' pattern of audiograms was observed at 2000 Hz. Conclusion: A linear relationship existed between size and degree of hearing loss. Posterior perforations had a higher hearing loss. Lower frequencies were affected more in general. Inverted 'V' pattern of audiograms was observed with turning point at 2000 Hz.
Keywords: Hearing loss in CSOM, Site of tympanic membrane perforation, Size of tympanic membrane perforation, Tympanic membrane perforation and hearing loss
|How to cite this article:|
Nahata V, Patil CY, Patil RK, Gattani G, Disawal A, Roy A. Tympanic membrane perforation: Its correlation with hearing loss and frequency affected - An analytical study. Indian J Otol 2014;20:10-5
|How to cite this URL:|
Nahata V, Patil CY, Patil RK, Gattani G, Disawal A, Roy A. Tympanic membrane perforation: Its correlation with hearing loss and frequency affected - An analytical study. Indian J Otol [serial online] 2014 [cited 2019 Apr 20];20:10-5. Available from: http://www.indianjotol.org/text.asp?2014/20/1/10/129796
| Introduction|| |
Chronic suppurative otitis media (CSOM) is defined as a stage of ear disease in which there is chronic infection of the middle ear cleft; and a nonintact tympanic membrane (TM) and discharge are present.  It is a highly prevalent condition and an important cause of preventable hearing loss. According to a classification by World Health Organization (WHO) for burden of CSOM, India was put into highest (>4%) prevalence group. 
CSOM often presents with hearing loss and for understanding deafness we need to understand the mechanics of sound transmission in diseased middle ears. It has been an area of constant research among otologists and has been studied extensively in cats by Wever and Lawrence  and Payne and Githler  and on temporal bones by Voss et al.,  and Mehta et al. 
In the recent years, several clinical studies have been conducted in patients of CSOM to correlate the hearing loss with the characters of the perforation such as size and site. Most authors have generally stated that the hearing loss is dependent on the site and size of perforation, but their results were found to be conflicting and inconclusive.
In the studies by Kumar et al.,  and Pannu et al.,  it was observed that the degree of hearing loss increases with the size of perforation and has no relation with the site of perforation. However, Malik et al.,  in his study observed that the degree of hearing loss did not vary with the size of the perforation but was dependent on the site of perforation. Frequency dependence of hearing loss was also not correlated well with the site and size of hearing loss.
Considering the high incidence of CSOM in our country and conflicting reports of various studies this study were undertaken as an effort to validate the above facts with the following aims and objectives:
- Study of various sites and size of perforation in patients of CSOM safe
- Study of relationship between the site and size of perforation with the degree of hearing loss and frequencies affected.
| Materials and Methods|| |
A cross-sectional prospective study design was made and sample size was set at 100 perforated ears from patients of CSOM safe. Unilateral/bilateral CSOM of safe type with no history of ear discharge for atleast 6 weeks were selected randomly irrespective of age and gender. Patients of unsafe CSOM, traumatic perforations, mixed hearing loss, and ossicular chain fixation/disruption were excluded.
Prior to starting the study, all recruits were explained the nature of the study and informed consent was taken.
All the cases underwent detailed history taking and ENT examination. Pure tone audiometry was done and the pure tone average of AC threshold was calculated by at 500, 1000, and 2000 Hz. The degree of hearing loss was assessed according to the WHO classification of hearing impairment. Paper patch test was done to rule out ossicular abnormality.
Otomicroscopy and Otoendoscopy was performed and images of perforations were saved using a TV tuner card (iBall Claro TV18 TV Tuner Card ) . These images were then subjected to computer software analysis by Image J (version 1.35j) package. The following equation was then generated to calculate the size of perforation:
Percentage of perforation = P/T × 100%, where P is the area (in pixels) of the YM perforation and T is the total area (in pixels) for the entire TM (including the perforation).
Assuming the total area of the TM to be 90 mm 2 , the area occupied by the perforation in square millimeter was then calculated as following:
Area of perforation in mm 2 = 90 × percentage perforation/100.
The perforations were then classified into three groups based on their size: Group I (small) - area in range of 0-8 mm 2 , Group II (medium) - area in range of 8.1-30 mm 2 , Group III (large) - area in range ≥ 30.1 mm 2 [Table 1].
|Table 1: Distribution of perforation according to area occupied with mean hearing loss (n=100)|
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The TM perforations were divided into the following three categories based on their location on the pars tensa.
Anterior - perforations occupying area only anterior to handle of malleus on the pars tensa Posterior - perforations occupying area only posterior to handle of malleus on the pars tensa Central - perforations occupying area on either side of handle of malleus on the pars tensa [Table 2].
|Table 2: Distribution of perforation based on site with mean hearing loss (n=100)|
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Statistical analysis with one-way analysis of variance test and multiple comparisons Tukey's honestly significant difference was done. The criteria for statistical significance was set at P < 0.05.
| Results|| |
A total of 63 patients with unilateral or bilateral disease (total ears = 100) were found suitable and included in the study.
The age group of patients in the study ranged from 10 to 56 years with maximum involvement in younger age groups. Females and bilateral involvement was more common. Otorrhea was the most common presenting complaint. The demographic profile of the patients is described in [Table 3].
Various sizes of perforation
On basis of area three groups of perforations were made. Maximum number of patients were seen in Group III (43), followed by Group II (39) and Group I (18) [Table 1].
Various sites of perforation
Three groups of perforations were made based on their location in relation to the handle of malleus. Maximum number of patients were seen in central group (69), followed by posterior (16) and anterior (15) groups [Table 2].
Hearing loss irrespective of site and size of perforation
The hearing loss ranged from 23.3 dB to 45 dB in all 100 ears. Based on WHO grades of hearing impairment, the ears were classified and maximum ears were seen to have a mild hearing loss (81 ears), followed by moderate loss (16 ears) and normal hearing (3 ears) [Table 4].
Irrespective of site and size of perforation the hearing loss was observed to be highest at the frequency of 500 Hz, that is, 41.05 ± 6.32 dB and lowest at 8000 Hz, that is, 22.72 ± 8.84 dB. The frequency of 2000 Hz was seen to be least affected in comparison to its adjacent frequencies.
Hearing loss and size of perforation
In our study, it was observed that with increasing size of the perforation the degree of hearing loss increases. Mean hearing loss in each group was as follows, Group I: 29.41 ± 4.39 dB, Group II: 34.69 ± 4.96 dB, and Group III: 38.79 ± 3.44 dB, respectively (P value 0.000, highly significant, [Table 1]).
Hearing loss and site of perforation
In our study it, was observed that posterior perforations have the greatest hearing loss, that is, 39.99 dB ± 2.79 dB, followed by central perforations, 35.64 ± 5.31 dB and anterior perforations, 30.1 ± 2.98 dB, respectively (P value 0.000, highly significant).
Frequency dependence of hearing loss
Effect of size
It was observed that the hearing threshold was highest at 250 Hz for Group II perforations and at 500 Hz for Groups I and III perforations. All three groups had the lowest hearing threshold at 8000 Hz. Hence, the relationship between size of perforation and frequencies affected is not a linear rising line [Figure 1].
|Figure 1: Hearing threshold at various frequencies in three groups of perforation based on their size|
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Effect of site
Highest hearing threshold was seen at 250 Hz in anterior perforations and at 500 Hz for central and posterior perforations. Again, 8000 Hz was the least affected frequency [Figure 2].
|Figure 2: Hearing threshold at various frequencies in three groups of perforation based on their site|
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| Discussion|| |
In patients with perforated TM, a precise otoscopic examination with special attention to perforation size and location would enable us to predict the expected hearing loss. If the clinical judgment and audiometry findings differ, a high index of suspicion of underlying middle ear pathology should be kept. The goal of our study was to validate the existing suppositions and fulfill lacunae of scientific research in this field.
Our study showed that the highest incidence of CSOM was seen in patients in younger age group (15-24 years). Our observation was similar to studies of Shyamala and Reddy  and Agrawal et al.  This finding can be explained by presence of a straighter and shorter Eustachian tube More Details in children predisposing easy passage of infection from nose to ear, lower immunity and recurrent upper respiratory tract infection (URI's) in this age group.
Also, the number of females in the study group was higher than the number of males (male: female ratio was 3:4). Our results differed from the studies of Singh et al.,  and Afolabi et al.,  where a male preponderance was seen. This variation could arise due to difference in literacy levels in different geographical locations where women visit hospitals less frequently.
B/L involvement was more common in our study, possibly due to presence of large number of younger population in the sample, where causes like adenoid hypertrophy or recurrent URI's in childhood would have predisposed to bilateral disease.
Otorrhea was the most common presenting complaint, consistent with other studies as that of Kumar et al.
Hearing loss irrespective of site and size of perforation
Until recently, the effects of TM perforations on middle-ear sound transmission were not well-characterized and there was no general agreement among clinicians about the magnitude and the configuration of the hearing loss that is caused by various types of TM perforations. In our study, the hearing loss ranged from 23.3 to 45 dB. Other studies, those by McArdle and Tonndorf  and Merchant et al.,  observed the hearing loss to range from negligible to 50 dB in cases of central TM perforations.
Most of the studies investigating the relationship between the TM perforations and hearing thresholds at various frequencies concluded that sound transmission loss in the case of perforated eardrums is frequency dependent with most serious losses on low frequencies.  The same was observed in studies of Bigelow et al.,  on rats, on temporal bones by Mehta et al.,  and in clinical studies of Bhusal et al. 
It has also been noted that our audiograms revealed a consistent frequency pattern, similar to an inverted V shape of the audiogram with a turning point around 2000 Hz irrespective of the site and size of the perforation. Below 2000 Hz, the ABG is larger for the lower frequencies, and above 2000 Hz, the ABG gets bigger again in the higher frequencies. These observations are similar to those made by Lerut et al.  As the inherent frequency of the TM has been calculated to be at 2000 Hz, that is, the TM vibrates the most at 2000 Hz, the least loss of sound transmission (or best hearing) has been observed around 2000 Hz.
Size of perforation and hearing loss
When comparing the various sizes of perforation with the degree of hearing loss, it was observed that the hearing loss increases with increasing size of perforation. Results were comparable with studies of Kumar et al.,  and Pannu et al.;  however, Mallik et al.,  in his study observed that there was no relation between the size of perforation and the degree of hearing loss. The primary mechanism of hearing loss due to a TM perforation is a reduction in the ossicular coupling caused by a loss in the sound pressure difference across the TM.
Site of perforation and hearing loss
We observed in our study that hearing loss was more in posterior perforation, followed by central perforations and anterior perforations. This view has been supported by Bianca et al., and Malik et al.,  in their studies. They attributed this effect to the direct exposure of the round window to the sound waves resulting in cancellation of the phase difference between the two windows and resultant nonmovement of perilymph. However Pannu et al.,  and Kumar et al.,  differed from this view in their study and suggested that location of perforation does not affect the degree of hearing loss.
Frequency dependance of hearing loss
Our results are comparable with other studies in general that lower frequencies are affected more than higher frequencies. Yet, no other study has made observations over such a wide range of frequencies as ours; hence, more research is needed in this area to compare our findings.
Effect of size
A linear relationship between perforation size and frequency affected could not be established. Small and large sized perforations had highest hearing threshold at 500 Hz and moderate size perforation were worst affected at 250 Hz. All three sizes had the lowest threshold at 8000 Hz. Our findings are similar to those of Ahmad and Ramani  who observed greater hearing loss in the lower frequencies, increasing with the size of the perforation. However, Austin  stated that the presence of perforation does not significantly affect the frequency response of the middle ear, since a flat hearing loss was observed for the frequencies studied for each size of perforation.
Effect of site: Anterior perforations had a higher hearing threshold at 250 Hz, whereas 500 Hz was worst affected in central and posterior perforations. Bhusal et al.,  observed that hearing loss is greater in lower frequency when compared with higher frequencies, for all sites of perforation. Matsuda et al.,  observed frequency dependence of hearing loss and the highest hearing threshold was of the perforations in anteroinferior quadrant.
| Conclusion|| |
A TM perforation usually causes a range of hearing loss, from mild to moderate. Our study gives a first hand knowledge about when to expect a plain TM perforation and when to look for a middle ear pathology based on closely observing the pattern of hearing loss in the patient.
From our study, we concluded that the hearing loss increases with increasing size of perforation and with a posterior location on the TM. Also, frequency dependence of hearing is a complex phenomenon based on several interrelated parameters. 2000 Hz being the inherent vibrating frequency of the TM is least affected in comparison to its adjacent frequencies.
This study aimed at giving us an insight into various patterns of hearing loss in different types of perforations. A thorough knowledge of these attributes would allow us to decide upon the most effective interventions for the patients of CSOM at the correct time.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]