Correlation of Air-Bone Gap on Pure Tone Audiometry with the Size of Perforation Assessed on Oto-Endoscopy.

Objective: To determine the correlation between the air-bone gap on pure tone audiometry with size of perforation oto-endoscopically.  Study Design: A descriptive study. Place and Duration of the Study: Department of ENT - Head and Neck Surgery, Dow University of Health Sciences (DUHS), from February 2020 to August 2021.  Methodology: A total of 43 patients with dry central pars tensa tympanic membrane perforation were diagnosed through oto-endoscopy during the study. The mean air-bone gap was calculated by assessing each air-bone gap through pure tone audiometry at different frequencies i.e., 250 Hz, 500 Hz, 1,000 Hz, 2,000 Hz, and 4,000 Hz. Air-bone gap was found to be the average value of these frequencies. The photograph of the tympanic membrane was taken oto-endoscopically, and the ratio between size of the perforation to the entire area of the tympanic membrane was measured.

Results: During the course of the study, a total of 43 patients agreed to provide consent for this study. Out of the 43 patients, 16 (37.2%) were males and 27 (62.8%) were females. The age range was from 18 to 50 years with average age of 38.302 ± 5.74 years. The mean perforation size was 28.255 ± 9.16% while the mean air-bone gap was 28.000 ± 3.89 dB. It was concluded that the Pearson's correlation coefficient is directly correlated to perforation size and air-bone gap (r = 0.898, p <0.001). Further, hearing loss decreases with decreased middle ear volume and mastoid pneumatisation. Moreover, no change was seen in the mean air-bone gap according to the location of perforation.

Conclusion: The hearing loss due to perforation of the tympanic membrane was correlated to the size of the perforation. Further, hearing loss decreases with reduced middle ear volume and mastoid pneumatisation.

Key words: Size of perforation, Hearing loss, Air-bone gap, Oto-endoscopy, Conductive deafness, Mastoid pneumatisation.