Extended Endoscopic Transorbital Approach for the Posterior Cranial Fossa

The endoscopic transorbital approach (ETOA) for the anterior and middle cranial fossa has become a common technique among neurosurgeons. Although pioneers of endoscopic neurosurgery expanded the indications of ETOA, the posterior fossa pathologies or the petroclival tumors are still challenging. Compared to conventional craniotomy, it has a longer distance to the surgical site, limited view by the orbital cavity, and is hindered by the temporal lobe. Moreover, the complex neurovascular anatomy surrounding the petroclival area is further complicated by the limited view provided by the orbital cavity. We introduce the extended endoscopic transorbital approach (EETOA) which is ETOA accompanied by extending osteotomy, including the superior and lateral orbital rim as well as a part of the frontal bone to maximize the surgical corridor. EETOA can replace the conventional anterior petrosal approach (APA) for the treatment of the petrous apex lesions as well as anterolateral brainstem pathologies. EETOA shows a similar surgical view to the pretemporal APA, which is anterior to posterior direction, in contrast to the subtemporal APA, which is lateral to medial direction. Cranial nerve positions and routes are also slightly different from subtemporal APA. We also demonstrated the removal of a large petroclival meningioma grown along the lateral wall of the cavernous sinus and extended into the posterior fossa using EETOA.