Extended Kawase Approach to the “True” Petrous Apex: Anatomical Considerations and Quantitative Volumetric Study

Objectives: The “true” petrous apex is hidden behind critical neurovascular structures and remains incompletely exposed through the standard Kawase approach. The extended Kawase technique, involving mobilization of the trigeminal ganglion after opening Meckel’s cave, may provide a wider surgical corridor. This study aims to compare the exposure achieved by standard versus extended Kawase approaches using CT-based volumetric analysis, and to describe the stepwise anatomical maneuvers required for the extended technique. Methods: Twelve cadaveric heads (24 sides) underwent sequential standard and extended Kawase approach. After each stage, high-resolution CT scans were obtained, and volumetric reconstructions were performed to quantify the extent of petrous bone removal. Results: The extended Kawase approach, designed as a stepwise modification of the standard Kawase corridor, provided progressive expansion of the surgical window toward the “true” petrous apex. Stepwise extension involved: (1) enlargement of the foramen ovale to mobilize V3; (2) dissection and coagulation of the superior petrosal sinus with dural opening above the porus trigeminus; (3) transection of the posterior petroclinoid ligament to enter the posterior compartment of the cavernous sinus; (4) opening the lateral wall of Meckel’s cave along the trigeminal root–V3 axis; and (5) superior mobilization of the trigeminal ganglion to uncover the true petrous apex. ( Fig. 1A-E ) These maneuvers enabled direct visualization of the petrosal process of the sphenoid bone (PPsb), inferior petrosal sinus, and abducens nerve. Volumetric CT analysis demonstrated that the standard Kawase approach achieved a mean bone removal volume of 1137 ± 105 mm 3 . The extended Kawase approach increased this by an additional 1042 ± 98 mm 3 , corresponding to nearly 92% more exposure of the true petrous apex region. ( Fig. 1F ). Conclusion: The extended Kawase approach nearly doubles the exposure of the “true” petrous apex compared with the standard approach. By systematically opening Meckel’s cave and mobilizing the trigeminal ganglion, this technique provides a safe and effective microsurgical corridor to the petroclival junction, PPsb, and related neurovascular structures, with significant implications for managing lesions involving the upper petroclival and petrous apex regions. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany