Bone conduction impairment in chronic ear disease.

The preoperative and postoperative bone conduction (BC) thresholds were prospectively investigated in 24 patients with chronic ear disease in the form of cholesteatoma, chronic suppurative otitis media, or adhesive otitis media. All underwent tympanoplasty with mastoidectomy. Ossicular reconstruction was performed in 14, and the remaining 10 were still awaiting second-stage ossicular reconstruction at the time of this investigation. In each group, the postoperative results were compared with the preoperative results by the paired-samples t-test. In the ossicular reconstruction group, the results revealed a significant improvement in the postoperative BC thresholds, as compared with the preoperative BC thresholds, at 250, 1,000, and 2,000 Hz, with the largest mean improvement observed at 2,000 Hz. No significant improvement was observed at any frequency for the group without ossicular reconstruction. Postoperative improvement of at least 10 dB at 2 or more frequencies was observed in 71% of the ossicular reconstruction group, as compared with 0% of the group that did not undergo ossicular reconstruction. The results support the theory that the elevated BC thresholds of patients with chronic ear disease result from the elimination, due to disease, of the middle ear contribution (from the inertial ossicular component and ossicular resonance) to the BC response. The results also suggest that the middle ear contribution to the BC response is restored with ossicular reconstruction.