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S265: INFERIOR AND LATERAL ACCESS TO THE PETROUS APEX: A COMPARATIVE ANATOMICAL STUDY OF THE TRANSORAL AND CONTRALATERAL TRANSMAXILLARY APPROACHES
Sandhya R Palit, MD^1,2; Rosaria V Abbritti, MD^1,2,3; Florian Moser, MD^1,2,4; Yohan Alexander, MD^1,2; Luciano CPC Leonel, PhD^1,2,5; Jake Eide, MD⁶; Maria Peris-Celda, MD, PhD^1,2,5; Jamie J Van Gompel, MD^1,2,5; ¹Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA; ²Mayo Clinic Rhoton Neurosurgery and Otolaryngology Surgical Anatomy Program, Rochester, Minnesota, USA; ³Department of Neurologic Surgery, Lariboisière University Hospital, Université Paris Cite, Paris, France; ⁴Paracelsus Medical University, Salzburg, Austria; ⁵Department of Clinical Anatomy, Mayo Clinic College of Medicine and Science, Rochester, Minnesota, US; ⁶Department of Otolaryngology-Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota, USA

Introduction: The medial to lateral view provided by endoscopic endonasal and contralateral trans maxillary (CTM) corridors limit their effectiveness for resecting petrous apex (PA) pathologies that grow primarily in an inferior direction. Conversely, the transoral approach to petrous apex (TOPA) offers a beneficial inferior-to-superior trajectory. This study compared the maximal inferior and lateral drilling achievable by the CTM and TOPA approached while sparing soft palate incision. 

Methods: Six sides of three formalin-fixed cadaveric head specimens with colored latex injection were used for the anatomical dissections to compare the TOPA and CTM. The cadavers were positioned supine, with the head secured in a Mayfield head holder and slightly extended. To facilitate access and avoid a palatotomy, a key step involved elevating the soft palate by inserting red rubber tubes through the nose and into the choana. The tubes were then retrieved through the oral cavity, effectively creating a sling that lifted and held the soft palate superiorly (Fig. 1). This technique provided an unobstructed view of the posterior nasal cavity and nasopharynx. The initial point of entry and orientation was the vomer-sphenoid junction, a critical landmark for identifying the midline and the subsequent surgical trajectory to the petrous apex (Fig.1). 

The CTM approach was performed through an antrostomy into the contralateral maxillary sinus. The posterior wall of the sinus was then partially removed to access the pterygopalatine fossa. This was followed by a posterior septectomy to widen the surgical corridor, providing a direct trajectory to the retro carotid portion of PA (Fig. 2). 

Results: The soft palate elevation successfully established a clear, inferior-to-superior and medial-to-lateral surgical corridor to the PA without requiring a palatotomy. The transoral approach achieved a greater mean lateral extent of bone resection (19.33 mm vs. 18.67 mm) and a higher mean proportion of petrous apex bone resection (81.08% vs. 78.52%) compared to the CTM approach when measured and maximized to the level of the jugular bulb/foramen (Fig. 3). The transoral approach offered a clearer visualization of the jugular bulb and the jugular foramen. Conversely, during the CTM approach, the medial wall of the maxillary sinus restricted the inferior angulation of the drill when attempting to move inferiorly and obscuring the visualization of the inferior structures like the jugular bulb and jugular foramen. This qualitative difference highlights the inherent advantage of the inferior-to-superior trajectory offered by the transoral corridor for accessing the most inferior, lateral and retro carotid aspects of PA. 

Conclusions: This comparative anatomical study confirms the surgical potential of the soft palate-sparing transoral approach to the petrous apex. By comparison with the CTM approach, the transoral corridor offers a modestly wider, and qualitatively superior window for accessing the inferior and lateral petrous apex, particularly the jugular bulb and jugular foramen. 

 

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