Erosion of Stapes and Incus in Chronic Otitis Media and the Impact on Hearing

The aim of the present study is to assess the difference in hearing loss between patients with stapes erosion and patients with incus erosion without stapes destruction.

Material and Method: Inclusion criteria: incus or stapes erosion (partial or complete) and tympanic cavity occupied by cholesteatoma or granuloma confirmed during surgery for chronic otitis media and measurable pure tone thresholds before surgery. Twenty-four patients fulfilled the inclusion criteria, 13 men and 11 women with a mean age of 47 years. Hearing was assessed preoperatively with pure tone audiograms (air and bone conduction).

Results: The preoperative pure tone audiograms according to surgical findings were as follows: (1) stapes erosion and occupied tympanic cavity

Frequency	250 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz
Average gap	50.90	44.54	46.81	34.09	30.45
Median gap	50	45	50	40	30

(2) incus erosion, normal stapes, and occupied tympanic cavity

Frequency	250 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz
Average gap	33.88	27.77	32.22	19.44	30.0
Median gap	35	30	30	15	35

The difference between the two groups was statistically significant at 250, 500, 1000, and 2000 Hz (p < = 0.05).

Conclusion: Stapes erosion (partial or complete) contributes to a wider air bone conduction gap than incus erosion, although in both cases there is an ossicular chain discontinuity. The cholesteatoma or granulation tissue may bridge, at least partially, this discontinuity but it seems less effective in stapes erosion, although its contribution is variable and cannot be measured.