Determinants of Cochlear Dysfunction in Chronic Otitis Media: Mucosal Disease.

The nature of association between chronic otitis media (COM)-mucosal disease and sensorineural hearing loss is controversial. Identifying the risk factors which influence the bone conduction threshold in these patients can help the clinician in counselling the patients for surgery at the earliest to achieve optimum hearing outcomes. The present study was undertaken to determine the association between COM-mucosal disease and cochlear dysfunction. The study also aimed at identifying the determinants and their influence on the bone conduction thresholds of the diseased ear. In this study, 72 patients with unilateral chronic otitis media-mucosal disease were enrolled consecutively. All patients were enquired in detail about their presenting ear symptoms. All the patients underwent a pure tone audiogram in a sound treated room. Patients were categorised into two groups according to the presence of conductive hearing loss only or with a sensorineural component. The bone conduction thresholds were calculated and compared for frequencies at 0.5, 1, 2 and 4 kHz. The average hearing threshold for air conduction and bone conduction were calculated across 0.5, 1 and 2 kHz. Bone conduction threshold more than 20 decibels (dB) in any of the frequencies were considered significant and indicative of having sensorineural hearing loss component. The contralateral healthy ear served as control to cancel out the confounding factors such as presbyacusis, noise induced hearing loss, congenital hearing loss, etc. Multivariate linear regression models were used to evaluate the relationships between bone conduction thresholds and chronic otitis media-mucosal disease. In the present study, 18.05% of participants had a sensorineural component. The difference between the bone conduction threshold in the diseased ear and normal ear ranged from 5.41 dB at 0.5 kHz to 3.77 dB at 4 kHz ( < 0.001). Bone conduction thresholds at 4 kHz were greater than that for speech frequencies ( < 0.5). 84.6% of participants with sensorineural component had a disease duration of less than 5 years and the remaining 15.4% had a duration of greater than 15 years. There was no statistically significant difference in the incidence of sensorineural component based on the site of the perforation ( = 0.341). 21.9% of participants who used topical antibiotic drops developed a sensorineural component, while 15% of participants who did not use antibiotic ear drop preparation developed a sensorineural component. Multivariate linear regression analysis revealed that increasing age was the only factor associated with increase in bone conduction thresholds of the diseased ear ( = 0.002). Chronic otitis media- mucosal disease appears to be associated with higher bone conduction thresholds, signifying cochlear dysfunction. A statistically significant higher bone conduction thresholds are seen across 0.5 to 4 kHz in the diseased ears compared to the normal ears, signifying the vulnerability of the inner ear against chronic otitis media. In our analysis increasing age is the most significant predisposing factor associated with higher bone conduction thresholds. Higher frequencies are more affected than lower speech frequencies. Sensorineural hearing loss can occur early in the disease process and early surgical intervention in COM-mucosal disease is recommended to prevent increase in bone conduction thresholds and achieve optimum hearing outcomes.