A descriptive analysis of endoscope-assisted endonasal, transorbital, and transcanal transpetrosal approaches to the pons

This study sough to determine the anatomical extents of anterior petrosectomy and corresponding exposure of the pons afforded by endoscopic endonasal, transorbital, and transcanal transpetrosal approaches. Anatomical dissections were performed in five human cadaveric heads. The expanded endoscopic endonasal transclival approach (EEA), endoscopic transorbital transpetrosal approach (ETOA), and endoscopic transcanal transpetrosal approach (ETCA) were executed consecutively in each cadaveric head. After that, the extents of anterior petrosectomy and surgical exposure of the pons were compared among the three approaches. For each endoscopic transpetrosal approach, the petrous segment of the internal carotid artery (petrous ICA) constituted the major limitation of anterior petrosectomy. Because the petrous apex drilling was restricted superiorly and laterally by the paraclival segment of the ICA and the horizontal portion of the petrous ICA near the foramen lacerum, the EEA provided inferior anterior petrosectomy with exposure of the pons positioned medially to the inferior petrous sinus. The horizontal portion of the petrous ICA formed the inferior delimitation of superior anterior petrosectomy, and the ETOA predominately revealed the supratrigeminal zone of the pons. Otherwise, the vertical portion of the petrous ICA composed the anterior boundary of fully anterior petrosectomy, and the ETCA mainly disclosed the peritrigeminal zone of the pons. The EEA, ETOA, and ETCA offer optimum visualization for different compartments of the pons. These three endoscopic transpetrosal approaches provide alternative means of access to safe entry zones of the pons.