Determinants of conductive hearing loss in tympanic membrane perforation

Tympanic membrane perforations are common, but there have been few studies of the factors determining the extent of the resulting conductive hearing loss. The aims of this study were to determine whether the size of tympanic membrane perforation, pneumatization of middle ear & mastoid cavity, and location of perforation were correlated with air-bone gap (ABG) of patients. Forty-two patients who underwent tympanoplasty type I or myringoplasty were included and preoperative audiometry were analyzed. Digital image processing was applied in computed tomography for the estimation of middle ear & mastoid pneumatization volume and tympanic membrane photograph for the evaluation of perforation size and location. Preoperative mean ABG increased with perforation size (P=0.018), and correlated inversely with the middle ear & mastoid volume (P=0.005). However, perforations in anterior versus posterior locations showed no significant differences in mean ABG (P=0.924). The degree of conductive hearing loss resulting from a tympanic membrane perforation would be expected with the size of perforation and pneumatization of middle ear and mastoid.