Study of pathology of ossicles in non-cholesteatomatous chronic suppurative otitis media, its repair and outcome

INTRODUCTION

“Chronic suppurative otitis media” prevalence varies in different parts of the world. It varies from one percent in some parts of the world to more than forty percent in other parts of the world. This variation is due to depending upon the whether the part of the globe is a developed country or the developing country. Many factors have been outlined as risk factors for “Chronic suppurative otitis media”. These include younger age, people living in overcrowded dwellings, lack of proper housing conditions, lack of proper hygiene, malnutrition, exposure to indoor or outdoor pollution, dysfunction of Eustachian tube etc.¹

If the ears have perforation of long standing durations, even without cholesteatomas, they remain infected. Three times as many operations were performed in the United States in 1978 for this disease as were performed for cholesteatoma.² Paparella and Kim reported that of 375 primary tympano-mastoid operations for chronic mastoidits, two-thirds were performed in ears with granulation tissue and without cholesteatoma.³

Ossiculoplasty represents the reconstruction of the ossicular chain in such a manner that it will transmit sound vibrations from the tympanic membrane to the oral window. The aim of ossiculoplasty is to restore the ossicular chain as near to normal as possible or to achieve continuity and transmission in an entirely different way after abandonment of natural system. In the last three decades, various ossiculoplasty methods have evolved and good results were achieved. Nevertheless ossicular reconstruction continues to be a process in evolution.⁴

This is a clinical study of patients presented to outpatient, department of Vijayanagar Institute of Medical Sciences, Bellary during the period of November 2004 to November 2005 with non-cholesteatomatous chronic suppurative otitis media. This study is aimed to study the various ossicular abnormalities encountered in non-cholesteatomatous chronic suppurative otitis media and their reconstruction techniques.

METHODS

This study study of pathology of ossicles in non-cholesteatomatous chronic suppurative otitis media, its repair and outcome was carried out at the Department of ENT, VIMS, Bellary.

The source of data for our study were the patients admitted in the department of ENT and operated for correction of hearing disability due to Non-cholesteatomatous chronic suppurative otitis media, and also patients referred from other departments of combined hospitals of VIMS, Bellary. This study is a prospective study, conducted for a period of 1 year from 1^st November 2004 to 31^st October 2005. The study was carried out on 30 cases (with unilateral ear problems, bilateral ear disorder patients were excluded from study). The complete data was collected in a specially designed case regarding form (CRF), from the patients by taking history of illness and by doing detailed clinical examination and relevant investigations. Finally, after diagnosis and after unsuccessful medical line of management, the patient was selected for surgery depending on inclusion/exclusion criteria.

For the present study, patients are selected with the following inclusion/exclusion criteria:

Inclusion criteria

Inclusion criteria were irrespective of age and sex; irrespective of socioeconomic status; cases of chronic suppurative otitis media with central perforation of tympanic membrane; cases of chronic suppurative otitis media with conductive hearing loss.

Exclusion criteria

Exclusion criteria were cases of chronic suppurative otitis media with attic or marginal perforation and/or retraction packet; cases of chronic suppurative otitis media with sensori-neural hearing loss; cases of chronic suppurative otitis media with cholesteatoma; cases with bilateral ear disease.

Follow up

All the cases in our study were admitted in our hospital for an average duration of 7 days. The initial follow up was weekly for a period of 21 days (3 weeks). Subsequently the patients were required to come at the end of 3 months and months from the date of surgery and at every 6 months thereon. Of the 30 cases operated, all the patients attended the follow up on the stipulated dates for the minimum period of 6 months post operatively, and the follow up range was from 6 months to 24 months.

The data collected was transferred into a master chart which was then subjected for statistical analysis. The various statistical parameters applied in the study include:

• 1. Standard deviation: it is defined as root-mean-square-deviation. The standard deviation is the most frequently used measure of deviation.

SD = √€(X-X)² / (n – 1)

• 2. Mean value: the mean is the average value, or the sum of all (Σ) of the observed values (X₁) divided by the total number of observations (N₁).

Mean = X = € (X-X₁₎ / (N₁)

• 3. Standard error: Instead of means, sometime we may have to test the significance of difference between two proportions or ratios have occurred y chance.

In this case we calculate the standard error of difference between two proportions.

Standard error = σ/√N = √σ² / N

• 4. Confidence interval: used as test to see whether a mean or proportion differ significantly from a fixed value. The most common situation for this is testing to see whether a risk ratio or an odd ratio differs significantly from the ratio of 1.0 (which means no difference)
• 5. P value: before doing any calculations to test the null hypothesis, the investigator must establish a criterion called the alpha level, which is the maximum probability of making a false positive error that the investigator is willing to accept. The level of alpha is usually set at p=0.05. This says that investigator willing to run a 5% risk of being in error when asserting that the treatment and control groups truly differ. It is used to perform tests of significance.

In our study ears, we have analyzed the age distribution, sex distribution, relationship between ossicular pathology and type of perforation of tympanic membrane and the hearing loss in relation to ossicular pathology and the site of perforation of tympanic membrane. Finally, the ears subjected to various types of tympanoplasty, have been studied to ascertain hearing gain, in relation to various reconstructive procedures adopted.

RESULTS

12 ears (40%) had central perforation (other than subtotal perforation) and 18 ears (60%) had subtotal perforation (Table 1).

The hearing loss in relation to ossicular pathology, have been summarized. In ears with single or multiple ossicular involvements, the average hearing loss was noted to be between 39.40 to 60 dB. The average hearing loss in patients with isolated erosion of lenticular process of incus was 50.72 dB with a Standard Deviation of 6.95 and 95% confidence interval of 44.29 to 57.15 (Table 2).

In our study, Autologous incus was used for ossicular reconstruction in 14 (46.67%) out of 30 patients. Homologous septal cartilage was used for ossicular reconstruction in 10 (33.33%) of the cases (Table 3).

Twenty-nine of the 30 cases underwent myringostapediopexy (type IIIb tympanoplasty) with the ossicular graft as short columella between the tympanic membrane graft and the stapes superstructure. Only one case had absence of the stapes superstructure and had to undergo myringoplatinopexy (type IIIc tympanoplasty) using the homologous septal cartilage graft as long columella between the tympanic membrane graft and the stapes footplate (Table 4).

The 14 patients who underwent surgery with autologous incus as the graft material had mean pre-operative Air bone gap of 35.03 dB with standard deviation of 10.88. Post-operatively their mean Air-Bone gap was 18.65 dB with standard deviation of 11.83. This is highly significant statistically with a p<0.001. The statistical significant of pre-operative and post-operative gap is calculated for each material using student’s test (Table 5).

DISCUSSION

Whatever the type of perforation of ear may be, it has been found usually that the incus gets commonly affected. In the present study, 90% of the cases have shown some kind of pathology. 23% of the cases have shown that the lenticular process got involved but it was isolated.

23% of the cases also have shown that the handle of malleus was affected. Usually there is resorption of the handle of the malleus. This is more commonly seen in cases of the central perforation than the perforation of the posterior type. This is due to complete exposure of “handle of malleus” in central type of perforation than the posterior type of perforation. Complete exposure leads to improper supply of blood which leads to necrosis. Stapes was involved only in 1 case (3%).

Austin explained the pathogenesis of necrosis. According to him, the vessels of the mucosa develop thrombotic disease.⁵ These vessels supply blood to the incus. Secondary squamous epithelium in growth occurs which results in the destruction of the arch of the stapes and the handle of the malleus. This destruction is due to the enzymes which are osteolytic.

In ears with single or multiple ossicular involvements, the average hearing loss was noted to be between 39.40 to 59.60 dB. It was 50.72±6.95 in patients having isolated erosion of lenticular process of incus. It was 50.10±15.48 in patients having isolated erosion of long process of incus.

Chronic form of disease of ear has perforation with ossicular interruption and 60% of them need surgery.⁵ Austin indicated that the typical hearing loss in worse at the lower frequencies and averages 38 dB.⁶ If the perforation is larger in size, then it will cause worse hearing loss. But the difference is not stable and can vary.⁷ In case the tympanic membrane is completely lost along with ossicles, then in that case, the contour of the hearing loss is the same as the previous group but more severe, averaging 50 dB.

Twenty nine of the 30 cases underwent myringostapediopexy (type IIIb tympanoplasty) with the ossicular graft as short columella between the tympanic membrane graft and the stapes superstructure. Only one case had absence of the stapes of superstructure and had to undergo myringoplatinopexy (type IIIc tympanoplasty) using the homologous septal cartilage graft as long columella between the tympanic membrane graft and the stapes footplate.

The results of tympanoplasty are frequently reported in terms of closure of air-bone gap. The prerequisites for success in tympanoplasty are that firstly the tympanic membrane must be intact and mobile post operatively. Secondly, there must be an efficient sound conducting mechanics. Smyth and Patterson concluded that for significant benefit to be achieved the postoperative air conduction (AC) average over the speech frequencies (0.5, 1.2 and 4 KHz) must be less than 30 db or the inter-aural difference reduced to less than 15 db. This figure of 15 db corresponds to the cross attenuation effect of the skull.⁸

In our study, the 14 patients who underwent surgery with autologous incus as the graft material had mean pre-operative air-bone gap of 35.03 dB with standard deviation of 10.88. Postoperatively their mean Air-Bone gap was 18.65 dB with standard deviation of 11.83. This is highly significant statistically (p<0.001)

In our study, 29 cases had an intact stapes. This group underwent myringostapediopexy. In this group 16 patients (55.17%) showed satisfactory results at 6 month post-operative follow-up (air-bone gap of 0-20 dB). Only 1 case had an absent stapes superstructure with only a mobile footplate. This patient underwent myringoplatinopexy. This patient had a postoperative air-bone gap of 30.90 dB.

The hearing results after ossicular reconstruction in other studies are: when the titanium prosthesis was used, as in studied by Hillman (45.3%).¹⁰ When the hydroxyapatite prosthesis was used as in studies by Grote (68%).⁹ and Shambaugh III (64.8%), and when plastipore prosthesis was used, as in studies done by Hillman (60%).¹⁰

CONCLUSION

Excellent results (post-operative Air-Bone gap between 0 to 10 dB) were noted only with the autologous incus graft. 28.57% of the total patients with autologous incus graft showed excellent post-operative results.

Good results (postoperative air-bone gap between 10 to 20 dB) were found for autologous incus, Homologous septal cartilage and teflon PORP, with percentage of 28.57, 50 and 25 respectively.

Funding: No funding sources

Conflict of interest: None declared

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

REFERENCES

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