The anatomic determinants of conductive hearing loss secondary to tympanic membrane perforation

OBJECTIVES: Recent studies have introduced middle ear volume (MEV) as a novel determinant of perforation-induced conductive hearing loss (CHL) in a mechanism driven by trans-tympanic membrane pressure differences. The primary aims of this preliminary report are to: 1) correlate CHL with perforation size; 2) describe the relationship between CHL and MEV; and 3) compare CHL across a range of cholesteatoma involvement. DESIGN: A retrospective pilot study was performed in 31 subjects with audiometry indicative of conductive hearing loss, temporal bone CT scans, and no prior middle ear surgery. Perforation size and MEV were analyzed with respect to CHL in a cohort of 10 perforated ears with no cholesteatoma. CHLs were compared in 3 groups defined by extent of cholesteatoma involvement. RESULTS: Ears with large and small perforations showed mean ABG values of 32.0 ± 15.7 dB and 16.0 ± 16.4 dB, respectively. A direct relationship was observed between MEV and CHL for ears with large perforations across all frequencies, whereas this relationship for small perforations was frequency-dependent. Finally, a statistically significant increase in CHL was found across ears with increasing cholesteatoma involvement at 1000 Hz (χ(2)(2) = 9.786, p = 0.008), 2000 Hz (χ(2)(2) = 8.455, p = 0.015), and 4000 Hz (χ(2)(2) = 8.253, p = 0.016). CONCLUSIONS: These pilot data suggest that greater perforation-induced conductive hearing losses may be associated with larger perforation sizes and cholesteatoma. The correlation between MEV and CHL may require additional study.