Surgical anatomy and dissection of the petrous and peripetrous area. Anatomic basis of the lateral approaches to the skull base.

The purpose of this study is to review the topographic anatomy of the petrous and peripetrous structures, with emphasis on the relationships important to the lateral approaches to the posterior and lateral skull base. Surgical exposure of the clivus, the posterior aspect of the petrous bone, the ventral aspect of the brain stem, and of all the intradural structures in the area, remains difficult because of the presence of the so-called "petrous and peripetrous complex". However, the lateral approach to the skull base is the most suitable approach if the lesion lies lateral to the cavernous portion of the internal carotid artery, and of course if the lesion develops laterally behind the petrous apex. Consequently, neurosurgeons should be familiar with the anatomy of the intrapetrous cavities and their contents, and with the relationships in the area. Middle cranial fossa dissections (dry and fresh specimens) allow us to study the anatomical relationships between the intrapetrous carotid artery, the facial nerve, the porus, the cochlea, the geniculate ganglion and the petrosal nerves, the trigeminal ganglion and nerve, the auditory tube and the middle ear. While briefly reviewing some approaches (anterior petrosectomy, sub-temporal preauricular infratemporal fossa approach, pre-sigmoid approach), we explore the concept of the approach and the limitations of surgical technique and exposure.