측두골 전산화단층촬영을 통한 만성중이염 수술 후 골도역치 상승에 관여하는 해부학적 인자의 분석

초록

Background and Objectives：Drill-generated noise during chronic ear surgery has been incriminated as a cause of sensorineural hearing loss in the operated ear. The safety of the inner ear during mastoid drilling depends on avoiding the transmission of amounts of energy to the labyrinthine fluid which will exceed the tolerance of the inner ear structure. It is induced by the conduction of drill noise through bone vibration to the inner ear or by impaired circulation around the inner ear. Until now, the noise levels have been considered to be influenced by the size of the burr, the type of the burr, and the duration of drilling. Materials and methods：The pure tone thresholds of 124 patients who underwent intact canal wall mastoidectomy with tympanoplasty type 1 were assessed preoperatively, and at 1 month, 3 months, and 6 months postoperatively. The patients were classified into 3 groups according to the degree of bone conduction threshold degeneration in the audible frequency range and at high frequency range. The soft tissue density of the epitympanum & the mastoid process, the size of the antrum & the mastoid process, the distance between the malleus head and tegmen tympani & lateral attic wall were measured on temporal bone CT. Results：Analysis of the relationship between each factor and postoperative bone conduction thresholds revealed a statistically significant degeneration in bone conduction threshold in both the audible frequency range and in the high frequency range when the density of the mastoid process density was increased. Also, there was a statistically significant decrease in the distance between the head of malleus and the lateral attic wall in the patient group with bone conduction threshold degeneration in the audible frequency range. Conclusion：We believe that in cases where the mastoid process is severely sclerotic, or when the malleus is close to the lateral attic wall on preoperative temporal bone CT, meticulous care should be taken in using the drill as a precaution against degeneration in postoperative bone conduction threshold.

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