The Effect of Chronic Otitis Media to Bone Conduction Threshold

Abstract

Despite a number of clinical and histologic studies on the relation between chronic otitis media (COM) and bone conduction threshold, questions remain. The majority agree that COM is associated with decrease of bone conduction threshold and that

some aspect of COM is the causative agent. We performed this study to investigate the relation between COM and bone conduction threshold, and further analyze the each COM factors. We also compared the preoperative and postoperative changes of bone conduction

thresholds.

Among the 893 patients with COM who underwent chronic ear surgery from June 1994 to March 1997, 430 unilateral COM patients were reviewed retrospectively who met the following criteria: no history of head trauma, meningitis, post-traumatic

tympanic membrane perforation, labyrinthine fistula, or coexisting otologic condition of either ear. The audiograms were analyzed for any changes of bone conduction threshold, between diseased and normal ears. Pre- and postoperative changes of bone conduction

threshold were also analyzed.

Significant decrease of bone conduction threshold differences were observed between normal and COM ears at all frequencies. In diseased middle ear mucosa and ossicular erosion groups showed decreased threshold at all frequencies. We also found

significant decrease of bone conduction threshold at 1 KHz and 2 KHz frequencies in cholesteatoma group. We could not find any effect of tinnitus and dizziness on bone conduction threshold. Postoperative changes of bone conduction threshold were minimal

except on 2 KHz frequency.

We observed significant decrease of bone conduction threshold in COM patients especially on high frequencies. Chronic damages on normal middle ear structures such as diseased mucosa, ossicular erosion and cholesteatoma could be causative factors

of above results.