RESUMO
INTRODUCTION: Surgical treatment of conductive hearing loss runs the risk of damage to the inner ear in the mechanism of acoustic trauma. AIM: The aim of this study was to evaluate the function of the organ of Corti, expressed as bone conduction threshold at the frequency of 4000 Hz for selected operations: mastoidectomy and canal-wall-down procedure. MATERIAL AND METHODS: The material was collected from patients with chronic otitis media in the Department of Otolaryngology and ENT Oncology, Collegium Medicum of Nicolaus Copernicus University in Bydgoszcz in 2004-2009. All patients were examined with pure tone audiometry threshold before surgery and at least three years after surgery. The analyzed group of patients was divided into subgroups depending on the type of operation according to To classification and procedures for resection: mastoidectomy and canal-wall-down procedure. The results were statistically analyzed. RESULTS: In the analyzed period of three years after surgery there was no statistically significant difference between groups, although there were higher values for tympanoplasty type 1 with mastoidectomy compared with tympanoplasty type 1 without mastoidectomy - respectively 25.67 dB and 18.53 dB. In the study, there was no statistically significant the difference in bone conduction threshold for frequency 4000 Hz within the type 2 tympanoplasty according to Tosa comparing canal wall-up and canal-wall-down procedure. CONCLUSIONS: Mastoidectomy or canal-wall-down procedure do not affect the bone conduction threshold for a frequency of 4000 Hz after tympanoplasty in long-term observation.