Effect of Middle Ear and Mastoid Air Space Volume on Acoustic Transmission of Sound in Tympanic Membrane Perforation

Abstract

Background: Loss of hearing is a national health problem with significant social and psychosocial implications. Worldwide there are about 65-330 million people affected with hearing impairment, of which 60% suffers from significant hearing loss. Role of tympanic membrane and ossicular chain in the physiology of hearing is well documented. The emergence of the role played by mastoid air space volume in sound transmission is being critically evaluated these days. The present study is designed to analyze the effect of mastoid air space volume in tympanic membrane perforation with conductive hearing loss. Methods: 32 subjects both male and female with medium sized tympanic membrane perforation were included in the study. They were grouped into two (those with sclerotic and cellular mastoid). Hearing threshold assessed using pure tone audiometer. Mastoid air space volume evaluated using digital X-ray mastoid schuller’s view. Tympanic membrane perforation size assessed using otoscope. Results: The hearing loss in first group having cellular mastoid and second group with sclerotic mastoid were 22.82±6.28 and 27.82±5.66 respectively. Their p value was 0.026 which was statistically significant. Conclusions: Mastoid air space volume is inversely proportional to conductive hearing loss. Therefore mastoid air space volume also plays a key role in the sound transmission. The awareness of the pneumatisation status of the mastoid helps clinicians to choose appropriate line of management.