Effects of tympanic membrane perforation, middle ear cavity volume, and mastoid aeration on hearing impairment

Aims: To investigate the effects of the location and size of tympanic membrane (TM) perforation and middle ear cavity volume on conductive hearing loss in patients with TM perforation. Methods: Data were collected via a retrospective medical chart review. Results: We enrolled 128 patients with a mean age of 45.6 ± 10.1 years. The mean perforation size was 21.2 ± 8.6% of the TM area, and the mean air-bone gap (ABG) was 20.2 ± 8.6 dB HL on pure tone audiometry. Patients were divided into two groups based on mean ABG. Patients with a large ABG had a significantly larger TM perforation area and smaller mastoid volume. The TM perforation was most commonly located in the central section. However, regression analyses showed that the proportion of the perforated TM area was the only independent predictor of a large ABG (odds ratio, 1.053; 95% confidence interval, 1.022–1.085; p = 0.001). When we analyzed the frequencies in which hearing loss occurred due to TM perforation, we confirmed that hearing loss occurred mainly in the low-frequency range. Conclusion: In patients with TM perforation, conductive hearing loss occurs mainly at low frequencies and in proportion to the size of the TM perforation.