title: Magnetic resonance imaging and computed tomography of the internal auditory canal and cerebellopontine angle.
abstract: Computed tomography (CT) and magnetic resonance imaging (MRI) assessment of internal auditory canal lesions focuses on acoustic neurinomas (Schwannomas), a small percentage of which are entirely intracanalicular. MR is now the imaging method of choice and allows for the detection of intracanalicular tumors as small as 3 mm. Acoustic neurinomas are isointense relative to the pons on MR T1-weighted images, mildly hyperintense on MR T2-weighted images, and enhance intensely after i.v. administration of gadolinium-DTPA. The radiologic evaluation of the cerebellopontine angle first addresses lesions of the angle itself, other than acoustic neurinomas. On CT, meningiomas show calcifications in 25% of cases and homogeneous enhancement in 90%; on MR they demonstrate homogeneous gadolinium-DTPA enhancement. Epidermoids do not enhance on MR. Cholesterol granulomas are strongly hyperintense on MR T1- and T2-weighted images. Rare vascular lesions may mimic neoplasm in the posterior fossa and in the cerebellopontine angle: vertebral basilar dolichoectasia, vascular loop or aneurysm of the anterior inferior cerebellar artery. CT and MR characteristics of lesions extending into the cerebellopontine angle cistern are then reviewed: nonacoustic posterior fossa schwannomas, which have the same MR signal characteristics as the acoustic schwannoma; jugular fossa lesions, the most often encountered being the glomus jugular tumor; and rare intraxial posterior fossa tumors that extend into the cerebellopontine angle.
authors.affiliation: Department of Radiology, Massachusetts Eye and Ear Infirmary, Boston 02114.
authors.forename: A L
authors.initials: AL
authors.lastname: Weber
mesh_terms: D002528:Cerebellar Neoplasms / Q000175:diagnosis* / Q000473:pathology; D002530:Cerebellopontine Angle / Q000000981:diagnostic imaging / Q000473:pathology; D002784:Cholesterol; D003287:Contrast Media; D003560:Cysts / Q000175:diagnosis; D019786:Gadolinium DTPA; D006801:Humans; D008279:Magnetic Resonance Imaging; D008577:Meningeal Neoplasms / Q000175:diagnosis; D008579:Meningioma / Q000175:diagnosis; D009464:Neuroma, Acoustic / Q000175:diagnosis*; D009942:Organometallic Compounds; D004369:Pentetic Acid; D014057:Tomography, X-Ray Computed; D014652:Vascular Diseases / Q000175:diagnosis
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D004369:Pentetic Acid; D002784:Cholesterol; D019786:Gadolinium DTPA