[Microsurgical Anatomy of the Petrous Part of the Temporal Bone]

For a surgeon to become skilled at skull base surgery, they should have mastered the three-dimensional anatomy of the petrous part of the temporal bone. The anatomy encountered during surgery is demonstrated from the superior, posterior, and lateral aspects of the petrous bone. The landmarks of the superior aspect of the petrous bone are the third division of the trigeminal nerve, the petrous ridge, the arcuate eminence, the greater superficial petrosal nerve, and the internal carotid artery. Drilling of the rhomboid area surrounded by these structures results in the exposure of the internal auditory canal and the posterior fossa dura. A key landmark of the posterior surface of the petrous bone is the dural fovea which marks the apex of the endolymphatic sac. After a dura flap is raised in a "U" shape just beyond the fovea, the internal auditory canal is opened to resect an intacanalicular portion of a vestibular schwannoma. Mastoidectomy is then performed from the lateral aspect of the petrous bone. Drilling of the mastoid leads to the exposure of the sigmoid sinus, mastoid antrum, fallopian canal, and lateral semicircular canals. Knowledge of the precise surgical anatomy of the petrosal bone is required to perform safe and secure skull base surgery.