MRI of unusual lesions in the internal auditory canal

We report the MRI findings of six unusual lesions of the internal auditory canal: three haemangiomas, one lipoma, one metastasis and one traumatic neuroma. We compare the findings to those of 20 intracanalicular schwannomas. We noted the site and size of the tumour, its signal intensity, borders and the homogeneity of enhancement were studied on T1-weighted images before and after intravenous contrast medium and T2-weighted images. Most schwannomas were homogeneous lesions, isointense on T1- and T2-weighted images, and strongly enhancing. Spontaneous high signal on T1-weighted images, heterogeneous contrast enhancement and extranodular enhancement were helpful for recognising lesions other then schwannomas; site, size and signal on T2-weighted images were not. All the haemangiomas had a specific pattern of contrast enhancement, with an anterior core intensely enhancing portion and a posterior portion which enhanced moderately or not at all. Received: 4 November 1999/Accepted: 19 July 2000