MR Imaging of the Internal Auditory Canal and Inner Ear at 3T: Comparison between 3D Driven Equilibrium and 3D Balanced Fast Field Echo Sequences

OBJECTIVE: To compare the use of 3D driven equilibrium (DRIVE) imaging with 3D balanced fast field echo (bFFE) imaging in the assessment of the anatomic structures of the internal auditory canal (IAC) and inner ear at 3 Tesla (T). MATERIALS AND METHODS: Thirty ears of 15 subjects (7 men and 8 women; age range, 22-71 years; average age, 50 years) without evidence of ear problems were examined on a whole-body 3T MR scanner with both 3D DRIVE and 3D bFFE sequences by using an 8-channel sensitivity encoding (SENSE) head coil. Two neuroradiologists reviewed both MR images with particular attention to the visibility of the anatomic structures, including four branches of the cranial nerves within the IAC, anatomic structures of the cochlea, vestibule, and three semicircular canals. RESULTS: Although both techniques provided images of relatively good quality, the 3D DRIVE sequence was somewhat superior to the 3D bFFE sequence. The discrepancies were more prominent for the basal turn of the cochlea, vestibule, and all semicircular canals, and were thought to be attributed to the presence of greater magnetic susceptibility artifacts inherent to gradient-echo techniques such as bFFE. CONCLUSION: Because of higher image quality and less susceptibility artifacts, we highly recommend the employment of 3D DRIVE imaging as the MR imaging choice for the IAC and inner ear.

The Significance of a Hypoplastic Bony Canal for the Cochlear Nerve in Patients with Sensorineural Hearing Loss: CT and MRI Findings

PURPOSE: The purpose of this study is to evaluate the significance of the hypoplastic canal for the cochlear nerve in patients with sensorineural hearing loss (SNHL) and the relationship between the hypoplastic bony canal and aplasia or hypoplasia of the cochlear nerve. MATERIALS AND METHODS: A retrospective review of high resolution temporal CT(HRCT) and MRI findings was conducted. The narrow bony canal of the cochlear nerve and the relative size of the internal auditory canal were correlated with the cochlear nerve deficiency on MRI. The comparative size of the component nerves (facial, cochlear, superior vestibular, inferior vestibular nerve), and the relative size of the internal auditory canal and the bony canal of the cochlear nerve were measured. The clinical history and the results of the clinical examination were reviewed for each patient. RESULTS: High resolution MRI showed aplasia of the common vestibulocochlear nerve in one patient and a deficiency of the cochlear nerve in 9 patients. These abnormalities occurred in association with a prominent narrowing of the canal for the cochlear nerve and a stenosis of the internal auditory canal, which was observed on temporal bone CT in 9 patients with congenital SNHL. Three patients had normal IAC, despite the presence of a hypoplastic cochlear nerve on the side on which they had SNHL. In one patient, the narrowing of the canal for the cochlear nerve and internal auditory canal were not found to be associated with acquired SNHL. CONCLUSION: The hypoplastic bony canal for the cochlear nerve might be more highly indicative of congenital cochlear nerve deficiency than that of the narrow internal auditory canal, and the position of the crista falciformis should also be carefully.

High Grade Hemangioendothelioma of the Temporal Bone in a Child: A Case Report

Hemangioendothelioma is a rare vascular tumor characterized by endothelial tumor cells and variable malignant behavior, and it's not common for this lesion to involve the bone. Although there are a few reports of cranial involvement by hemangioendothelioma, only rare cases arising in temporal bone have been published. We present the radiologic findings of a 7-year-old boy who had a high grade hemangioendothelioma involving the temporal bone with intracranial extension. Evidence of flow voids on MR images suggested a tumor of vascular origin, and the ill-defined margins, cortical destruction and intracranial extension on the CT and MR images were correlated with the tumor's high histologic grade.

The Usefulness of MR Imaging of the Temporal Bone in the Evaluation of Patients with Facial and Audiovestibular Dysfunction

OBJECTIVE: To evaluate the clinical utility of MR imaging of the temporal bone in patients with facial and audiovestibular dysfunction with particular emphasis on the importance of contrast enhancement. MATERIALS AND METHODS: We retrospectively reviewed the MR images of 179 patients [72 men, 107 women; average age, 44 (range, 1-77) years] who presented with peripheral facial palsy (n=15), audiometrically proven sensorineural hearing loss (n=104), vertigo (n=109), or tinnitus (n=92). Positive MR imaging findings possibly responsible for the patients' clinical manifestations were categorized according to the anatomic sites and presumed etiologies of the lesions. We also assessed the utility of contrast-enhanced MR imaging by analyzing its contribution to the demonstration of lesions which would otherwise not have been apparent. All MR images were interpreted by two neuroradiologists, who reached their conclusions by consensus. RESULTS: MR images demonstrated positive findings, thought to account for the presenting symptoms, in 78 (44%) of 179 patients, including 15 (100%) of 15 with peripheral facial palsy, 43 (41%) of 104 with sensorineural hearing loss, 40 (37%) of 109 with vertigo, and 39 (42%) of 92 with tinnitus. Thirty (38%) of those 78 patients had lesions that could be confidently recognized only at contrastenhanced MR imaging. CONCLUSION: Even though its use led to positive findings in less than half of these patients, MR imaging of the temporal bone is a useful diagnostic procedure in the evaluation of those with facial and audiovestibular dysfunction. Because it was only at contrast-enhanced MR imaging that a significant number of patients showed positive imaging findings which explained their clinical manifestations, the use of contrast material is highly recommended.

Chondrosarcoma of the Temporal Bone: A Case Report

Chondrosarcoma of the temporal bone is a rare lesion. Clinically it has been confused with chordoma, glomus jugulare tumor and meningioma, among other conditions, and due to its anatomic location, cranial nerve palsy is frequently observed. We report a case involving a 50-year-old woman with chondrosarcoma of the temporal bone.

Cholesteatoma of the Temporal Bone: MR Findings

PURPOSE: The purpose of this study is to evaluate the diagnostic capability of MR imaging for distinguishingcholesteatoma from other causes of inflammation. MATERIALS AND METHODS: We prospectively evaluated the MR imagesof 17 patients with a fully opacified middle ear in whom CT of the temporal bone suggested cholesteatoma. Allpatients underwent middle ear surgery and cholesteatoma was verified in 15 cases, granulation tissue in 15,cholesterol granuloma in four and hemotympanium in one. For each lesion, MR and pathologic findings werecorrelated. RESULTS: All cases of cholesteatoma showed low to intermediate signal intensity on T1-weightedimages. On T2-weighted images, 11 cases showed high signal intensity, while seven were less than CSF and four werethe same. Four cases revealed central low signal intensity with peripheral rim of high signal intensity. On GdDTPA-enhanced images, peripheral or marginal enhancement due to surrounding granulation tissue was noted in 12cases. Two appeared to be totally enhanced. One case of congenital cholesteatoma showed no enhancement. OnT2-weighted images, all cases of granulation tissue showed high signal intensity, and on neither T1- norT2-weighted images could these be distinguished from cholesteatoma. On Gd DTPA-enhanced study, all cases ofgranulation tissue were enhanced, and on T1WI, all cases of cholesterol granuloma showed homogeneous bright signalintensity on T1WI. One case of cholesterol granuloma in the mastoid showed bright signal intensity mixed withirregular areas of dark signal intensity. A further comparison of MR imaging with CT is that two case oflabyrinthitis and one of meningitis were diagnosed on Gd- enhanced T1-weighted images. CONCLUSION: Todifferentiate cholesteatoma from granulation tissue and cholesterol granuloma by the evaluation of their signalintensities and enhancement patterns, MR imaging is superior to CT. When there are cholesteatoma-associatedcomplications such as labyrinthitis or meningitis, postcontrast MR imaging can provide better information.