Differential Diagnosis between Chronic Otitis Media with and Mass Effect

PURPOSE: In order to determine specific differences, we compared the temporal bone CT findings of chronic otitis media(COM) with and without cholesteatoma, focusing on bone change. MATERIALS AND METHODS: Between 1997 and 1998, 82 patients(84 cases) underwent temporal bone CT and were shown to have COM, with or without cholesteatoma after mastoidectomy and tympanoplasty. There were 36cases of COM with cholesteatoma(26 patients, M:F=11:15; age range, 16 -61 [mean, 36.2] years), and 58 cases without cholesteatoma(56 patients, M:F=25:31, age range, 15 -61 [mean, 36.2]years). The findings of temporal bone CT were analyzed at the point of bony changes including erosion and medial displacement of ossicles(malleus, incus, and stapes), erosion or destruction of the scutum, tegmen, facial canal, and lateral semicircular canal, and ballooning of the tympanic cavity and mastoid antrum. In addition, the soft tissue changes seen on temporal bone CT were analyzed at the site of lateral bulging of soft tissue in Prussak's space, perforation of the pars flaccida, tympanic membrane retraction, and tympanosclerosis. We retrospectively compared the findings of temporal bone CT with the surgical findings, and to assess statistical significance, the Chi-square test was used. RESULTS: Bone erosion or destruction was seen in 36.2 % of COM cases without cholesteatoma, and in 96.2% of cases with cholesteatoma. Comparing COM with and without cholesteatoma, the erosion of ossicles includ-ing the malleus(81%, 24%), incus(88%, 14%), stapes(58%, 10%), scutum(88%, 10%), facial canal(8%, 0%), and lateral semicircular canal(8%, 0%), was more common in COM with cholesteatoma(p-value<0.05), with the exception of erosion of the tegmen(8%, 3%). Other bony changes including medial displacement of ossi-cles (27%, 3%), ballooning of tympanic cavity and mastoid antrum(96%, 16%), and the soft tissue changes including lateral bulging of soft tissue in Prussak's space(58%, 14%) and perforation of the pars flaccida(35% ,9%) were more common in COM with cholesteatoma (p-alue<0.05). Soft tissue in Prussak's space(58%, 72%), retraction of the tympanic membrane(1%, 9%), and tympanosclerosis(8%, 10%) were not however,important findings(p-value>0.05). CONCLUSION: Bone erosion or destruction was seen in COM without cholesteatoma, but expansile bone erosion or destruction with mass effect suggested COM with cholesteatoma. These findings of temporal bone CT in COM demonstrate the existence and extent of combined cholesteatoma, and are therefore valuable.