[Clinical study of the bone conduction thresholds before and after tympanoplasty in chronic suppurative otitis media].
ABSTRACT To study the relative factors of the changes of preoperative and postoperative bone conduction thresholds in chronic suppurative otitis media.
The preoperative and postoperative bone conduction thresholds were prospectively investigated in 45 patients with unilateral chronic suppurative otitis media after tympanoplasty. Preoperatively (within 3 days before operation), 10 dB or more depression of bone conduction threshold at least in consecutive 2 frequencies between 0.25 kHz and 8.00 kHz was considered to be significant. Similarly in the postoperative period (3 months after operation), 10 dB or more improvement or impairment of bone conduction threshold at least in consecutive 2 frequencies between 0.25 kHz and 8.00 kHz was regarded as significant.
Thirty-five of 45 cases (77.8%) were found to have depressed bone conduction threshold before operation, 6 of 35 cases (17.1%) had improved bone conduction thresholds and 5 of 45 cases (11.1%) had depressed bone conduction thresholds after tympanoplasty.
In cases with chronic suppurative otitis media, successful results could be achieved after tympanoplasty disregarding air conduction threshold, the air-bone gap and deteriorated bone conduction threshold. Impairment of bone conduction thresholds could be induced by chronic suppurative otitis media itself and could also be induced by touching the ossicle chain crudely and by the noise of drilling during the operation.