Relation between the duration of disease and audiogram findings in tubotympanic type of chronic suppurative otitis media after myringoplasty

INTRODUCTION

CSOM is defined as a chronic inflammation of the middle ear and mastoid cavity which presents with recurrent ear discharges through a tympanic perforation. It is most likely a result of an earlier acute otitis media, negative middle ear pressure because of a non-patent eustachian tube or otitis media with effusion.¹ It is one of the commonest conditions encountered in OPD of otorhinolaryngology in most developing countries.

The most common presenting complaints include hearing loss and ear discharge.² In adults, the presence of this disease produces social stigma thereby affecting day to day activities. In adolescents, it results in disturbances socially and emotionally thereby causing reduction in academic performance. This can often pose a significant economic burden on the family.³

Histopathological changes can develop in middle ear and mastoid in CSOM which may or may not be due to inadequately treated episodes of acute otitis media.^4,5 Some changes are direct result of infection, while others like inflammation represent host response to the disease process. Adding up, these changes lead to the symptoms and signs which play an important role in determining the success or failure of tympan mastoid surgery.

Although CSOM is a multifactorial disease, microbial virulence factors including toxins and cell wall constituents such as lipopolysaccharide (LPS), peptidoglycan (PG) and lipoteichoic acid (LTA) are thought to be important in its pathogenesis. While bacterial toxins may directly damage the mucosal cells, they can also trigger an inflammatory reaction that may injure the mucosa of the middle ear.⁶ These changes can produce complications which are directly related to the disability faced by the patient. Thus, the early diagnosis and management of the disease becomes all the more necessary to achieve good results.

Pure tone audiometry is the easiest and the most basic procedure which needs to be performed on any patient who has a history of hearing loss irrespective of the nature of the disease and the cause surrounding it. Every initial evaluation for CSOM should include audiometric testing with air and bone along with pure tone thresholds. The degree of hearing loss is helpful in determining the severity of the middle ear disease.

Myringoplasty is defined as a surgical procedure in which the reconstruction is limited to closure of the tympanic membrane perforation which is aimed at preventing recurrent infection of the middle ear.⁷ Myringoplasty prevents the exposure of the middle ear mucosa to external pathogens thereby restoring the vibrating area of the neotympanum and improving the hearing capability.⁸

Based on the amount of hearing loss, it should be possible to grossly predict the duration of the disease, size and site of the perforation on pars tensa and the condition of the ossicular chain.

The aim of this study is to correlate the findings of the audiometry i.e. AB gap and AC threshold to the duration of the disease in the ear and also associate the same to the corresponding hearing changes after surgery.

METHODS

This was carried out at Meenakshi medical college and hospital, Kanchipuram from January 2017 to September 2018.

Patients presenting to the ENT OPD with hard of hearing, ear discharge and a dry central perforation of pars tensa on examination.

Sixty (60) patients were selected for the study and study type was prospective study.

Statistical Analysis carried out by performed using SPSS statistics 19 for Windows (IBM Corp., Armonk, NY, USA). Samples were compared and evaluated by means of a paired student t-test. A p value of <0.05 was considered statistically significant. The confidence interval was set at 95%.

All the patients were put thorough a detailed and complete clinical examination of ear, nose and throat. Special attention was given to otoscopic examination, tuning fork tests and audiometry. The hearing level was recorded with a pure-tone audiometer.

Inclusion criteria included perforation should be of central type i.e. in pars tensa with intact annulus. Mucosal type CSOM (tubotympanic disease), ear should be dry for at least 4 weeks pre-operatively, tuning fork tests should show hearing to be longer by bone conduction than air conduction i.e. pure conductive deafness, pure tone audiometry should reveal only conductive deafness, adequate cochlear function should be present i.e. good cochlear reserve, the disease should be limited to one ear with the other ear having normal anatomy. The normal opposite ear also helps as a control for reference, eustachian tube should be patent and patients should be willing to take part in the study.

Exclusion criteria excluded evidence of septic foci in nasopharynx, paranasal sinuses or throat. Squamous type of CSOM. Complications of CSOM, patients with Mixed or pure sensorineural hearing loss in the affected ear, disease present in the only hearing ear. Parameters for assessment included duration of the disease, duration of the disease affects the extent, presence or absence of complications and time required for recovery. The duration of disease is divided into following categories to aid in a detailed study- <1, 1-2, 2-3 and >3 years.

Pure tone audiometry. The pre-operative pure tone audiogram was taken before the surgery and the post-operative audiogram was taken 12 weeks after surgery.

Surgical procedure included myringoplasty with tragal perichondrium was performed under local anaesthesia. The procedure was done by the same surgeon to avoid bias. In all the cases an underlay technique was used.

RESULTS

The percentage of males in the study was 53% and females 47% (Figure 1). A large section of patients presented to the OPD with the disease being prevalent for at least one year (Figure 2) (Table 1).

It is clear that the hearing loss is much lesser if the duration of the disease is lesser than one year. As the diagnosis is delayed, both the AB gap and the mean AC threshold increase (Table 2).

The mean AB gap pre-operatively for a diseased ear of less than 1-year duration was found to be 14.82 dBHz and post operatively it was found to be 8.79 dBHz, improvement of 40.68%. The same values for a diseased ear between 1-2 years were found to be 21.17 and 13.76 dBHz, an improvement of 35%. The values for a diseased ear between 2-3 years were found to be 21.56 and 12.72 dBHz, improvement of 41%. The corresponding values for a diseased ear of more than 3 years were found to be 31.08 and 23.01 dBHz, an improvement of 25.96% (Tables 2 and 3). Thus, it can be argued that an early closure of perforation can significantly bridge the AB gap (Table 4).

The mean air conduction threshold pre-operatively for a diseased ear of less than one-year duration was found to be 31.93 dBHz and post operatively it was found to be 24.49 dBHz, an improvement of 23.3%. The same values for a diseased ear between 1-2 years were found to be 42.3 and 31.64 dBHz, an improvement of 25.2%. The values for a diseased ear between 2-3 years were found to be 43.84 and 32.19 dBHz, an improvement of 25.45%. The corresponding values for a diseased ear of more than 3 years were found to be 64.13 and 48.56 dBHz, an improvement of 24.29% (Tables 2 and 3). Although the mean air conduction thresholds in all the groups improve after surgery, there is no significant difference between groups. This indicates that the duration of disease does not affect the air conduction as much as it does to the AB gap (Table 4).

DISCUSSION

CSOM with perforation of pars tensa is one of the main causes of conductive hearing loss in developing countries like India.

Myringoplasty is defined as the reconstruction of the tympanic membrane without involving the ossicular chain. “myringoplastik” was a term introduced by Berthold in 1878 but the modern era of tympanoplasty did not begin until the 1950’s with the work of Zollner and Wullstein.⁹ Many different techniques and grafting materials have been used to close tympanic membrane perforations like full thickness skin graft, split skin, cornea, amniotic membrane, fat, vein, perichondrium and dura. Off late composite tissue grafts like temporalis fascia and perichondrium are becoming popular techniques because of their high take rate, easy availability in sufficient quantity and approachability in the vicinity of the operative field.^10,11

Sakagami et al observed CSOM as main cause of conductive hearing loss. In their study, 82 out of 91 cases undergoing myringoplasty, had a tympanic membrane perforation with an intact ossicular chain. In these cases, the secondary cause of conductive hearing loss was considered to be the rigidity of the ossicular chain. These changes which happen in the middle ear are variable. The quality of ear discharge and the amount of time the discharge has been present in the middle ear is directly proportional to the hearing loss.¹²

There have been extensive studies about the causes of hearing loss in patients with CSOM. Some studies have pointed out that changes in hearing are directly related to frequent episodes of otorrhoea.^13,14

Occasionally, elevated bone conduction threshold has been observed in various audiometric recordings in patients suffering from CSOM.¹⁵

In this study, we assess the relationship between the duration of disease in the middle ear and the changes in hearing thresholds. All the patients were taken up for surgery after proper consent and in accordance with the strict inclusion and exclusion criteria. The surgery was performed by the same surgeon with the same instruments and technique to prevent bias. The pre-operative audiogram was taken before the surgery and the post-operative audiogram 12 weeks after the surgery since it takes 12 weeks for the mucosa of the middle ear to regenerate, as documented in various past studies.¹⁶

Plenty of other researches have proved that the hearing of the patient (air conduction and AB gap) has improved after successful surgery irrespective of the method used with respect to the graft material, approach and anaesthetic technique.^17-20

Our motive was to appreciate the same in our sample group and associate it with the time of diagnosis and the time of surgery.

In our study, we found that the AB gap improved by 41% when the diagnosis was made within 1 year from the onset of the first symptom. However, the AB gap improved only by 26% when the diagnosis was made after 3 years from the onset of the first symptom. This can be explained by the various middle ear changes because of the disease, such as: rigidity of the ossicular chain because of calcification and granulation, tympanosclerosis and impairment of round window baffle effect.

On the same lines, although the AC threshold improved in separate groups, the range was between 23-25% which means that the AC threshold is independent of the changes in the diseased middle ear.

CONCLUSION

This study shows that AC threshold is independent of the changes in the diseased middle ear as compared to the AB gap. This shows that AB gap is a more sensitive tool of hearing assessment. Early closure of the perforation results in better bridging of the bone and air conduction thresholds. This can not only help in preventing complications but also aid in better hearing protection which in-turn helps in better social survival.

Funding: No funding sources

Conflict of interest: None declared

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

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