2025 Proffered Presentations
S236: EXPANDING THE LIMITS OF THE ENDOSCOPIC ENDONASAL APPROACH TO THE PETROUS APEX THROUGH THE ADDITION OF THE CONTRALATERAL TRANSMAXILLARY CORRIDOR AND STEPWISE MOBILIZATION OF THE PARACLIVAL INTERNAL CAROTID ARTERY
Liang Xia; Maria Karampouga; Jiabin Zhan; I-sorn Phoominaonin; Rakhmon Egamberdiev; Kyle Affolter; Carl H Snyderman; Eric W Wang; Garret W Choby; Georgios Zenonos; Paul A Gardner; Department of Neurological Surgery, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, United States
Objective: The petrous apex has traditionally been considered one of the lateral boundaries of the endoscopic endonasal approach (EEA), as its reach is primarily constrained by the paraclival, lacerum, and petrous segments of the internal carotid artery (ICA). However, the addition of the contralateral transmaxillary approach (CTMA) has been shown to enhance petrous apex exposure, by allowing access from a more lateral direction to the posteromedial aspect of the paraclival ICA through the anteromedial petrous (Gardner’s) triangle. This study aims to further extend the limits of petrous apex resection via the EEA and CTMA by incorporating stepwise mobilization of the carotid artery.
Methods: Anatomic dissections were performed in five latex-injected cadaveric heads (10 sides), using standard endoscopic equipment and instrumentation. The ICA (from its parasellar to its horizontal petrous segment) was mobilized in 3 steps and 4 volumes were obtained (before mobilization and after each step): 1. after lingual process removal, 2. after dissection of the pterygosphenoidal fissure, removal of the pterygoid tubercle, and partial detachment of the Eustachian tube, 3. after sectioning of the parasellar ligaments. The bone removal was achieved with CTMA, assisted with endoscopic visualization and dissection through EEA. Both the degree of ICA lateralization and the pyramidal bone volume amenable to removal in each step were calculated using stereotactic measurements taken with image guidance.
Results: The mean distance of ICA mobilization, measured at the horizontal level of its midclival portion, was 3.01 mm, 6.74 mm, and 10.08 mm in after steps 1, 2, and 3, respectively. This significantly increased the exposure and resection volume of the petrous apex, from 187.78 mm³ in the non-mobilization first measurement to 332.70 mm³, 509.00 mm³, and 869.59 mm³ in the 1-3 ICA mobilization levels. Utilizing this technique maximized the surgical corridor to the petrous apex from a ventral perspective, allowing for progressively greater removal of the petrous bone. Additionally, a structure referred to as the Supramedial Petrous Pyramid has been proposed, representing the maximum pyramid-shaped bone removal achievable through EEA and CTMA when combined with ICA mobilization.
Conclusion: Although challenging, the mobilization of the paraclival ICA via EEA and CTMA constitutes a novel surgical approach for managing complex lesions in the petrous apex and clival regions. This technique significantly broadens the lateral surgical exposure, expanding the potential clinical applications of ventral endoscopic skull base procedures. Mastery of this technique requires extensive laboratory training and a thorough understanding of the anatomy to overcome its steep learning curve, whereas further clinical studies are needed to validate the technique’s safety and efficacy for patients.
Keywords: Endoscopic; Endonasal; Contralateral Transmaxillary Approach; Carotid Mobilization; Petrous Apex
Figure 1 Intradural view of maximal drilling of the petrous apex following the stepwise mobilization of the paraclival ICA through the ENCTM.
Figure 2 The Supramedial Petrous Pyramid was defined based on the resected areas following ICA mobilization.(Supramedial Petrous Apex Pyramid: The limit of bone removal from the petrous bone achievable with the ENCTM)