Hearing Loss In Chronic Suppurative Otitis Media (CSOM)

Objectives: To evaluate the type and degree of hearing loss in CSOM and also to find out any relationship between the hearing loss and disease duration. Methods: This was a cross sectional study which was carried out in the departments of Otolaryngology and Head-Neck Surgery of BSMMU and Dhaka Medical College Hospital during the period of July’2011 to December’2011. A total 80 cases of CSOM were collected. Patient below the age of 5 years and patients above the age of 50 years were excluded from this study. The diagnosis of CSOM was established on the basis of clinical examinationotoscopy and tunning fork test. Pure tone audiogram (PTA) was done for hearing assessment. Thus, 80 cases of CSOM were collected with their PTA reports of 117 ears. Results: The study included 80 patients of CSOM, of them 60 were with tubo-tympanic type and 20 were with attico-antral disease. Highest number of patients was in 2 decade in both type of disease. 44.79% of ears of tubo-tympanic type were associated with mild (26-40 dB) hearing loss and 42.85% attico-antral variety was with moderate (41-55 dB) hearing loss. Conductive type of hearing loss was common in both types of disease. 98% of ears in tubotympanic and 81% of ears in attico-antral disease had conductive hearing loss. Mixed type (2.08%) of hearing loss was found in tubo-tympanic disease. Attico-antral disease was also associated with mixed (14.28%) and SNHL (4.76%). Conclusion: The above study revealed that hearing loss in CSOM is mostly conductive in nature rarely sensorineural in type.


Introduction
Chronic suppurative otitis media (CSOM) is a worldwide health problem and is still prevalent in the modern antibiotic era. The disease usually presents with hearing loss and aural discharge.
Hearing loss arising from chronic suppurative otitis media is a matter of serious concern globally, particularly in children, because of its long-term effects on early communication, language development, educational process and achievement. Hearing disability in adults is a burden to the individual and also to the family and entire society.
Considering the epidemiological prevalence of CSOM, a protocol was designed to conduct a survey in Bangladesh to find out the effect of CSOM on hearing in the prevailing socioeconomic and climatic condition of Bangladesh which showed that 16.95% of mild to moderate conductive hearing loss in children and young adult was due to CSOM. 1,2 The main possibilities of hearing loss in CSOM were impairment of tympano-ossicular impedance matching mechanism, reduction of baffle effect on round window and cochlear dysfunction. There was also a relationship between the thresholds of hearing and the duration of aural discharge. 3 The degree of hearing loss varies with the size and position of tympanic membrane defect, impairment of ossicular chain and presence of middle ear pathology. It is more in attico antral disease associated with cholesteatoma. 4 There was a significant quantitative correlation between the size and site of perforation and hearing loss. Non-marginal perforation with intact ossicular chain shows hearing loss approx. 10-30 dB; in postero-superior marginal perforation with disruption of ossicular chain hearing loss is 40-60 dB and in total or subtotal perforation with loss of malleus and incus, the stapes remaining mobile, hearing loss is 60-80 dB. 5,6 The predominant hearing loss in chronic otitis media was conductive in nature. But a few cases of sensorineural hearing loss was also found. 7 In another study, out of 897 patients with CSOM, sensorineural hearing loss was observed in 10% of patients and hearing loss was significantly more common in patients with cholesteatoma. 8 The relationship of cochlear losses associated with otitis media or sensorineural hearing loss caused by otitis media has been documented and confirmed by a number of authors. 9,10 The round window membrane was a site of pathological involvement especially in CSOM. The mechanism by which sensorineural loss (especially high tone loss) occured in presence of CSOM appeared to involve chemical contamination, i.e. toxins being absorbed through round window membrane. 9 In a retrospective study of 87 patients with uncomplicated and unilateral CSOM confirmed the evidence of increased bone conduction thresholds on the diseased side when compared with normal opposite ears. Furthermore, there was a greater loss of bone conduction with longer duration of the disease. They postulated, based on their findings, that abnormal bone conduction threshold in CSOM may well be due to changes in the mechanics of sound conduction. 10 Long standing use of locally instilled antibiotics was thought to be one of the important causes of sensorineural hearing loss. 11 A study showed in individuals with CSOM, mixed hearing impairments were common. But it was unclear whether the raised bone conduction thresholds were a reflection of the pathologic process affecting the inner ear or a combination of high prevalence of sensorineural hearing impairments in the population along with artificial elevation of bone conduction thresholds associated with a conductive defect. 12 Bone conduction losses increasing in severity with the increasing duration of the disease was reported on 404 patients with CSOM. 13 A significant bone conduction reduction was seen in 195 patients with CSOM. It was also documented that the changes were not related to the patient's age at the onset of CSOM but were related to the disease duration. An average increase of 5.5 dB for every 10 year duration was noticed. 14 Early diagnosis and treatment of CSOM have a great role in prevention of further hearing impairment and in the improvement of hearing. Since only few studies have been done in our country to assess the effect of CSOM on hearing, this study will be of great help in identifying the type and degree of hearing loss and also in planning the modern micro surgical treatment for preservation and improvement of hearing and also rehabilitation in some cases.

Objectives:
1. To observe the type and degree of hearing loss in CSOM 2. To correlate the degree of hearing loss with duration of disease.
3. To compare the hearing loss in tubotympanic and attico-antral types of CSOM.

Materials and Methods:
Study design : Cross-sectional study. In the 80 patients, out of their total 160 ears, 117 ears satisfied the criterion for having CSOM, 96 being tubo-tympanic and 21 atticoantral.

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The distribution of CSOM (n= 80) shows that tubo-tympanic variety was in 60 patients (75%) and attico-antral variety in 20 patients (25%). Central perforation was most common in tubotympanic cases (98.33%). In attico-antral type where attic perforation was common (70%).  Most of the ears of tubo-tympanic (97.92%) and attico-antral type (80.95%) were associated with conductive type of hearing loss. Few ears (14.28%) were associated with mixed hearing loss in attico-antral disease. In the present study, tubo-tympanic type of CSOM was found in 75% of patients and attico-antral type in 25% of patients. The majority was young adults in their 2 nd and 3 rd decade. In tubo-tympanic disease 33.34% was in 2 nd decade and 26.67% was in 3 rd decade. In attico-antral disease incidence was highest 54.93% in the 2 nd decade which exactly corresponded with many workers 15 .
Patients below the age of 5 years were excluded from this study because pure tone audiogram (PTA) could not be done due to difficulty and non co-operation of the patients. Patients above the age of 50 years were excluded from the study because patient about 50 years might have some degree of age related hearing loss.
There was no difference in the incidence between men and women. 15 But a considerable male predominance was found in another study. 16 In this series, males (63.75%) were more affected than female (36.25%) with a male female ratio of 1.75:1. This might be due to increase prevalence of CSOM among the male or it might be simple reflection of overall high male attendance in hospital outpatient department. Female are also reluctant to come forward for treatment in our country.
Regarding the type of perforation in this series, central perforation (98.33%) was more Maximum ears (48.71%) were presented with 6-10 years disease duration and minimum ears (2.57%) were presented with less than 1 year disease duration.
common in tubo-tympanic disease. There was a single case of marginal perforation (1.67%). This is similar to the author, where marginal perforations were considered to be more sinister, because they may be associated with the formation of cholesteatoma. 17 In attico-antral disease, 70% of patients had attic perforation and 30% had marginal perforation. These findings are more or less similar to other series where attic perforation was more than the marginal perforation. 18 In  19 More or less similar findings were also shown by others. 1,3. In the present study, in case of CSOM of attico-antral type, out of 21 ears 9 (42.85%) had moderate and 7 (33.33%) had moderately severe (56-70 dB) hearing loss. This is supported by the author where hearing loss was 10-60 dB, according to the condition of ossicular chain in attico-antral disease. 7 Hearing impairment is more in attico-antral type than tubo-tympanic disease. 3,4,8. Hearing thresholds vary considerably in case of CSOM. Some patients have normal hearing, while others have a severe mixed hearing loss or even a dead ear. 34 In this series, in tubotympanic disease (97.92%) ears had conductive hearing loss and (2.08%) ears had mixed type of hearing loss. Mixed type of hearing loss in tubo-tympanic disease was also reported by others. 10 year disease duration respectively. This gradual increase in hearing loss with disease duration was more or less similar to the author who studied with 218 patients with uncomplicated CSOM. That study showed that hearing loss was increased by 8-7 dB in patients with less than 10 years disease duration and 12.2 dB increased in 10-20 years duration. 22 But an increase of 5.5 dB for every 10 years duration in bone conduction threshold was found by another author 19 which is less than this series. It was found that sensorineural hearing loss increased as the duration of CSOM had increased. 13 Sensorineural hearing loss might be due to either prolong use of topical antibiotics or absorption of chemicals or toxins of CSOM through round window membrane. 9,11 Conclusion: From the study, it can be concluded that CSOM is the major cause of hearing impairment in our society. Findings of the present study suggest that early diagnosis and audiological assessment are needed for the patients with CSOM. This will help in the treatment of this disorder especially in bilateral cases and cases of young individual for restoration of hearing either by medical treatment or by surgery or by hearing aids and subsequent rehabilitation. For prevention more attention should be given for epidemiological survey and public awareness.