The petrous apex.

Petrous apex lesions are rare, but when present, they can usually be precisely defined. The key to their identity consists of answering five questions: 1) Is the abnormality arising in the petrous apex or from contiguous areas? 2) Are the bony walls of the apex and the septations in the air cells smoothly remodeled? 3) What are the MR imaging signal characteristics of the lesion? 4) Is there enhancement of the internal "matrix" of the lesion? 5) What is the relationship of the lesion to the carotid artery?