CT Findings of the Osteoma of the External Auditory Canal

PURPOSE: We wanted to report the CT image findings of the osteoma of the external auditory canal. MATERIALS AND METHODS: Temporal bone CT scanning was performed on eight patients (4 males and 4 females aged between 8 and 41 years) with pathologically proven osteoma of the external auditory canal after operation, and the findings of the CT scanning were retrospectively reviewed. Not only did we analyze the size, shape, distribution and location of the osteomas, we also analyzed the relationship between the lesion and the tympanosqumaous or tympanomastoid suture line, and the changes seen on the CT scan images for the patients who were able to undergo follow-up. RESULTS: All the lesions of the osteoma of the external auditory canal were unilateral, solitary, pedunculated bony masses. In five patients, the osteomas occurred on the left side and for the other three patients, the osteomas occurred on the right side. The average size of the osteoma was 0.6 cm with the smallest being 0.5 cm and the largest being 1.2 cm. Each of the lesions was located at the osteochondral junction in the terminal part of the osseous external ear canal. The stalk of the osteoma of the external auditory canal was found to have occurred in the anteroinferior wall in five cases (63%), in the anterosuperior wall (the tympanosqumaous suture line) in two cases (25%), and in the anterior wall in one case. The osteoma of the external auditory canal was a compact form in five cases and it was a cancellous form in three cases. One case of the cancellous form was changed into a compact form 35 months later due to the advanced ossification. CONCLUSION: Osteoma of the external auditory canal developed in a unilateral and solitary fashion. The characteristic image findings show that it is attached to the external auditory canal by its stalk. Unlike our common knowledge about its occurrence, osteoma mostly occurred in the tympanic wall, and this is regardless of the tympanosquamous or tympanomastoid suture line.

Nerve Canals at the Fundus of the Internal Auditory Canal on High-Resolution Temporal Bone CT

PURPOSE: To identify and evaluate the normal anatomy of nerve canals in the fundus of the internal auditory canal which can be visualized on high-resolution temporal bone CT. MATERIALS AND METHODS: We retrospectively reviewed high-resolution (1 mm thickness and interval contiguous scan) temporal bone CT images of 253 ears in 150 patients who had not suffered trauma or undergone surgery. Those with a history of uncomplicated inflammatory disease were included, but those with symptoms of vertigo, sensorineural hearing loss, or facial nerve palsy were excluded. Three radiologists determined the detectability and location of canals for the labyrinthine segment of the facial, superior vestibular and cochlear nerve, and the saccular branch and posterior ampullary nerve of the inferior vestibular nerve. RESULTS: Five bony canals in the fundus of the internal auditory canal were identified as nerve canals. Four canals were identified on axial CT images in 100% of cases; the so-called singular canal was identified in only 68%. On coronal CT images, canals for the labyrinthine segment of the facial and superior vestibular nerve were seen in 100% of cases, but those for the cochlear nerve, the saccular branch of the inferior vestibular nerve, and the singular canal were seen in 90.1%, 87.4% and 78% of cases, respectively. In all detectable cases, the canal for the labyrinthine segment of the facial nerve was revealed as one which traversed anterolaterally, from the anterosuperior portion of the fundus of the internal auditory canal. The canal for the cochlear nerve was located just below that for the labyrinthine segment of the facial nerve, while that canal for the superior vestibular nerve was seen at the posterior aspect of these two canals. The canal for the saccular branch of the inferior vestibular nerve was located just below the canal for the superior vestibular nerve, and that for the posterior ampullary nerve, the so-called singular canal, ran laterally or posteolaterally from the posteroinferior aspect of the canal for the saccular branch. CONCLUSION: Five bony nerve canals in the fundus of the internal auditory canal were detected by high-frequency on high-resolution temporal bone CT. Familiarity with these structures can prevent confusion with, or misinterpretation as, a fracture line, and further study such as MR imaging may be required when any enlargement or erosion of these nerve canals is present.

Temporal Bone CT Findings of Tuberculous Otitis Media: Comparison with Chronic Otitis Media

PURPOSE: To compare the differential findings of tuberculous otitis media(TOM) with those of chronic suppurative otitis media with or without cholesteatoma, as seen on high resolution temporal bone CT. MATERIALS AND METHODS: We retrospectively reviewed 14 cases of TOM, 30 cases of chronic suppurative otitis media(CSOM), and 30cases of chronic otitis media with cholesteatoma(Chole). All had been pathologically confirmed. We evaluated thepreservation of mastoid cells without sclerotic change, the location and extension of soft tissue to the externalauditary canal, the erosion of ossicles, the tegmen tympani, scutum, bony labyr inth, facial nerve canal andsigmoid sinus, and the presence of intracranial co mplications. RESULTS: Soft tissue in the mastoid antrum wasseen in all cases of TOM(100%), 29 cases of CSOM(96.7%), and 26 cases of Chole(86.7%). In contrast, the softtissue in the entire middle ear cavity was noted in 13 cases of TOM(92.8%), 7 cases of CSOM(23.3%), and 12 casesof Chole(40%). Soft tissue extended to the superior aspect of the external auditory canal in 4 cases of TOM(28.6%) and 5 cases of Chole (16.7%). Mastoid air cells were seen in 9 cases of TOM (64.3%), 4 cases of CSOM(13.3%), and 3 cases of Chole(10%). Ossicular erosion was noted in 6 cases of TOM (42.9%), 12 cases of CSOM (40%),and 26 cases of Chole(86.7%), while in one case of TOM (7.1%), 5 cases of CSOM (16.7%), and 15 cases of Chole(50%)there was erosion of the scutum. In one case of TOM, follow-up CT study after 9 months of antituberculousmedication without surgery revealed complete clearing of previously noted soft tissue in the middle ear cavity. CONCLUSION: Specific CT findings of TOM were not seen, but if there were findings of soft tissue in the entiremiddle ear cavity, soft tissue extension to the external auditory canal, preservation of mastoid air cells withoutsclerotic change, and intact scutum, TOM may be differentiated from other chronic otitis media.

Three Cases of Tuberculous Otitis Media

We report the imaging features of three cases of tuberculous otitis media. All three patients underwenttemporal bone CT scanning, and in two, additional MRI scanning was performed. The three cases showed soft tissuedensity in the external auditory canal, and in two, destruction of the trabeculation and internal cortex of themastoid bone was noted. In two patients with facial palsy, erosion of the facial canal was seen. On MRI, abundantgranulomatous tissue was noted in the middle ear cavity and mastoid air cells. In one case, abnormal enhancementof the cochlea, and of the facial and eighth cranial nerve in the internal acoustic canal was seen. Another caseshowed enhancement of the vestibule and lateral semicircular canal. If radiologic evaluation of chronic otitismedia reveals destruction of the tegmen and trabeculation of the mastoid bone, together with abundant granulationtissue and enhancement of the internal ear, tuberculous otitis media may be included in the differentialdiagnosis.

Tympanosclerosis of the Middle Ear: Radiologic-Surgical Correlation

PURPOSE: Tympanosclerosis is a common problem causing conductive hearing loss accompanied by chronic otitismedia. The purpose of this study was to evaluate the CT findings of tympanosclerosis, and correlate them with thesurgical findings. MATERIALS AND METHODS: The CT scans of 17 patients with surgically-proven tympanosclerosis andthose of a control group of 34 patients with nontympanosclerotic chronic otitis media were reviewed. According totheir location, they were assigned to one of three groups; tympanic membrane, epitympanum, or ossicles. RESULTS: Tympanosclerosis was found during surgery to be located in the tympanic membrane (n=11), the epitympanum (n=6), oraround the ossicles(n=8). Calcification of the tympanic membrane, ossicular thickening, narrowing of theepitympanum and calcification of the tympanic cavity occurred to a significant extent, and were more often afeature of tympanosclerosis than of nontympanosclerotic chronic otitis media (p <0.05). As an indicater of tympanicmembrane involvement, sensitivity and specificity of calcification of the tympanic membrane were 73% and 83%,respectively. As an indicator of ossicular involvement, the corresponding figures for ossicular thickening were50% and 93% ; as an indicator of involvement of the tympanic cavity (especially the epitympanum) the figures fornarrowing of the epitympanum and calcification of the tympanic cavity were 50% and 50% (respective sensitivities),and 89% and 93%(respective specificities). CONCLUSION: Tympanosclerosis usually appears on CT as ossicularthickening, narrowing of the epitympanum, calcification of the tympanic membrane and/or tympanic cavity. CT isvery helpful in evaluating ossicular involvement and determining the appropriate surgical treatment oftympanosclerosis.

Cochlear Otosclerosis (Otospongiosis): A Case Report

Otosclerosis occurs when the normal ivory-like endochondral bone of the otic capsule is replaced by foci of spongy vascular irregular new bone. Eventually these foci of haversian bone become more solid. There anr two typesof otosclerosis : fenestral and retrofenestral or cochlear. The cochlear type is much less common and rarely occurs without fenestral involvement. Otosclerosis occurs very rarely in blacks and orientals ; in otolaryngologic articles in Korea there are few reports of otosclerosis, and then only the fenestral type. This is a case reportof cochlear otosclerosis that can be diagnosed on temporal bone CT.

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

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 tomy :2mm/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.

Aberrant Internal Carotid Artery in the Middle Ear: A Case Report

Aberrant internal carotid artery in the middle ear is a rare disease which, if unrecognized on radiological studies, can lead to serious complications during tissue biopsy. We report the imaging features of a case with aberrant internal carotid artery in the middle ear. A 60-year-old woman visited our hospital because of hearing difficulty on the right side. Temporal bone CT showed a well-defined mass of the right middle ear and lateral bony defect in the carotid canal adjacent to the mass. After arterial phase temporal bone CT with spiral CT andangiography, the mass could be diagnosed as aberrant internal carotid artery in the middle ear.