Maximizing Access to the Petroclival Region: An Anatomic Comparison of the Transcranial Preauricular Subtemporal Infratemporal Fossa and Endoscopic Contralateral Transmaxillary Approaches with Clinical Case Series

Objective: Extradural petroclival lesions lie at the junction of transcranial and extended endoscopic skull base corridors, presenting unique challenges. This study examines the anatomic reach of two complementary techniques designed to maximize exposure to this region: the transcranial preauricular subtemporal infratemporal fossa (PSI) and the endoscopic contralateral transmaxillary (CTM) approach. Methods: Five embalmed cadaveric heads underwent PSI and CTM on opposite sides. Quantitative metrics included drilled petrous and clival bone volumes (measured by pre- and post-dissection CT segmentation) and angular degrees of freedom to critical landmarks assessed with stereotactic navigation. Three-dimensional renderings and photogrammetry were used to depict the surgical windows. Additionally, a clinical series of extradural petroclival lesions was analyzed to compare resection extent and morbidity between PSI and CTM. Results: Stepwise dissections are shown for PSI ([ Fig. 1 ]) and CTM ([ Fig. 2 ]). PSI yielded greater petrous bone removal (3.31 ± 0.4 cm 3 vs 0.99 ± 0.2 cm 3 ; p = 0.008), while CTM removed more clival bone (4.30 ± 0.8 cm 3 vs 2.23 ± 0.90 cm 3 ; p = 0.02). Total bone volume drilled was comparable. Three-dimensional reconstructions are provided ([ Fig. 3 ]). PSI offered wider freedom of movement at the petrous apex (41.5 ± 4.3° vs 27.3 ± 1.9°; p = 0.008), jugular tubercle (34.0 ± 19.9° vs 19.4 ± 4.3°; p = 0.016), Meckel’s Cave (33.8 ± 4.7° vs 23.6 ± 3.7°; p = 0.016), and vertical/horizontal petrous ICA (50.7 ± 16° vs 25.5 ± 4.7°; p = 0.008). Ten PSI cases (4 chordoma, 6 chondrosarcoma) and 20 CTM cases (7 chordoma, 13 chondrosarcoma) were reviewed. Gross total resection rates were similar (PSI 50% vs CTM 55%). Residual tumor was most often clival after PSI and at the petrous apex after CTM. Common permanent morbidity was facial numbness (30%) and conductive hearing loss due to eustachian tube sacrifice with PSI and abducens palsy (30%) with CTM. One PSI patient required malocclusion correction. CSF leak rates were 1% (PSI) and 1.5% (CTM). No strokes or carotid injuries occurred in either group. Conclusion: The PSI and CTM represent complementary strategies for extradural petroclival pathology. PSI affords broader access to the petrous bone with complete ICA control but is limited at the midline clivus, while CTM enables near-total clival exposure but is constrained posterolaterally at the internal auditory canal. Used in combination, they provide comprehensive access to the petroclival skull base for giant lesions. With proper selection and technique, both can be executed with low morbidity. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany