Image diagnosis of internal auditory meatus and surrounding areas

Abstract

The internal auditory meatus (IAM) is a bony canal which contains nerves and vessels. The inside of the IAM is covered with dura mater and arachnoid and, the IAM is filled with cerebro-spinal fluid (CSF). Because of advantage that bone causes no artifact, MRI is now the gold standard in the image diagnosis of lesions in the IAM and surrounding areas such as acoustic neuromas, petrous ridge meningiomas or facial neurinomas. Recent advances in MRI technology enables detailed study of the lesions and, especially, the constructive interference in steady state (CISS) pulse sequence clearly visualize the nerves and vessels in the IAM and cerebello-pontine angle. By CISS image, the state of the fundus of IAM, whether it is invaded by the tumor or not, can be recognized, and the possibility of success can be roughly predicted in hearing preservation surgery of acoustic neuromas. The X-ray CT also plays an important roll in the diagnosis of lesions eroding temporal bone or in the treatment of the lesions.