A multidirectional extradural corridor for pretemporal endoscope-assisted orbitozygomatic–anterior petrosectomy

Surgical exposure of the ventral petroclival region remains technically challenging because of the complex three-dimensional relationships among the middle cranial fossa, petroclival junction, cavernous sinus, brainstem, and surrounding neurovascular structures. The orbitozygomatic (OZ) approach, anterior transpetrosal approach (ATPA), and pretemporal corridor are well-established approaches that provide complementary anatomical perspectives. This study aimed to define the continuous ventral petroclival corridor created by integrating extradural OZ–ATPA exposure with the intradural pretemporal corridor under endoscopic assistance. Five silicone-injected human cadaveric heads (10 sides) underwent standardized OZ craniotomy followed by extradural ATPA. The dissection was sequentially extended through a pretemporal intradural corridor and supplemented with 0° and 30° endoscopic inspection to evaluate anatomical continuity beyond the microscopic line of sight. Stepwise dissections were performed to characterize anatomical visualization during the sequential dissection along the ventral petroclival axis. Following anterior petrosectomy and dural opening, the ventrolateral brainstem between the dorsum sellae and the internal auditory canal (IAC) was visualized. Through the combined OZ–pretemporal trajectory, the optic tract, crural cistern, interpeduncular cistern, and mammillary bodies were identified from an inferior-to-superior perspective. Endoscopic inspection demonstrated deep and contralateral petroclival structures, including the contralateral abducens nerve and petrous apex, as well as inferior structures toward the cerebellopontine angle beyond the IAC. These findings document qualitative anatomical visualization; surgical freedom and the safety of instrument manipulation around the inferior and contralateral structures were not assessed. Stepwise integration of extradural OZ–ATPA exposure with the intradural pretemporal corridor and endoscopic inspection provides complementary anatomical views from the mammillary bodies to the cerebellopontine angle. This framework may support three-dimensional anatomical orientation and operative planning, but endoscopic visualization does not establish a safe working corridor to all visualized structures.