Clinical Application of Modified Technique of Temporal HRCT for Dehiscence of Tympanic Segment of Facial Nerve

Oh, Seung Chul; Hwang, Hee Young

Abstract

BACKGROUND AND OBJECTIVES: High Resolution Computed Tomography(HRCT) of the temporal bone is the most accurate diagnostic tool and is popularly used in the chronic otitis media with cholesteatoma. However, the bony dehiscence of tympanic segment of the facial canal may be difficult to evaluate by the conventional HRCT of the temporal bone. This study was undertaken to develop a modified technique of axial CT scan for evaluation of bony dehiscence of tympanic segment of the facial canal.
MATERIALS AND METHODS
A prospective study was performed in 33 patients with chronic otitis media with cholesteatoma. These patients had also underwent canal down mastoidectomy from August of 1996 through July of 1997. A correlation study of the CT and surgical findings at 40 degree and 30 degree axial scans was carried out.
RESULTS
The sensitivity and specificity of this method for dehiscence of tympanic segment of the facial canal were 88.9% and 95.6%, respectively and the diagnostic predictability was 93.9%. However, the sensitivity, specificity, and diagnostic predictability of the 30 degree axial scan were 77.8%, 83.3%, and 81.8%, respectively.
CONCLUSION
We think that the modified technique of axial CT scan of temporal bone is an effective method for detecting the dehiscence of tympanic segment of facial canal.