Petrous apicitis: surgical anatomy.

Various surgical approaches to the petrous apex for exposure and drainage of suppurative processes are available to the otologist. The petrous apex may be conveniently divided into anterior and posterior portions by a line in the coronal plane through the internal auditory canal. The approach to the posterior petrous apex follows fistulous tracts in the sinodural angle, the subarcuate fossa, and the infralabyrinthine tract. The anterior petrous apex may be entered by means of a radical mastoidectomy. Fistulous tracts into an infected anterior petrous apex may be found through the hypotympanum, below the cochlea, through a triangle anterior to the cochlea, below the middle fossa dura, and above the carotid artery. In this approach to the petrous tip, one must have a thorough knowledge of the anatomical relationships around the carotid artery and cochlea: the carotid artery lies within 1.69 +/- 0.70 mm of the cochlea anteriorly, and the carotid artery may be exposed within the middle ear.