CT Findings of Automastoidectomy: Comparison with Postmastoidectomy Defect of the Temporal Bone

ABSTRACT

PURPOSE: To describe the CT findings of automastoidectomy caused by cholesteatoma, and to evaluate the natural course of cholesteatoma by comparing it with the postmastoidectomy defect of the temporal bone. MATERIALS AND METHODS: We retrospectively reviewed the CT findings of 15 cases of automastoidectomy in 13 patients with cholesteatoma and of 14 cases of postmastoidectomy in 13 patients. RESULTS: In automastoidectomy, the posterior walls of bony defects of the temporal bone were thinner (mean thickness in automastoidec/postmastoidec tomy2mm/3.5 mm) and smoother(n=10) than those of bony defects in postmastoidectomy(n=6). Defects of the posterosuperior wall of the bony external auditory canal were present in all cases of automastoidectomy(100%) andmost of postmastoidectomy(79%). there were gross defects of the lateral bony cortex of the mastoid(71%), Henle'sspine(100%), and the postero superior extension of the exit of bony defect(100%) in cases of postmastoidectomy(n=10), but there were rare findings in cases of automastoidectomy(20%, 21%, 23%, respectively).There were soft tissue densities within the bony defect and sinus tympani in all cases of automastoidectomy(100%)and in some cases of postmastoidectomy(64% and 36% respectively). CONCLUSION: When comparing automastoidectomyand postmastoidectomy, CT findings concerning bony defects were different with regard to the remaining posteriorwall, the extent of bony defect, and the presence of findings which suggested an active disease process. These differences are helpful in differentiating automastoidectomy and postmastoidectomy and in understanding thenatural course of cholesteatoma.