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 skul l base. Surgical exposure of the clivus, the posterior aspect of the p etrous bone, the ventral aspect of the brain stem, and of all the intr adural structures in the area, remains difficult because of the presen ce of the so-called ''petrous and peripetrous complex''. However, the lateral approach to the skull base is the most suitable approach if th e lesion lies lateral to the cavernous portion of the internal carotid artery, and of course if the lesion develops laterally behind the pet rous apex. Consequently, neurosurgeons should be familiar with the ana tomy of the intrapetrous cavities and their contents, and with the rel ationships in the area. Middle cranial fossa dissections (dry and fres h specimens) allow us to study the anatomical relationships between th e intrapetrous carotid artery, the facial nerve, the porus, the cochle a, the geniculate ganglion and the petrosal nerves, the trigeminal gan glion and nerve, the auditory tube and the middle ear. While briefly r eviewing some approaches (anterior petrosectomy, sub-temporal preauric ular infratemporal fossa approach, pre-sigmoid approach), we explore t he concept of the approach and the limitations of surgical technique a nd exposure.