2026 Poster Presentations
P105: ENDOSCOPIC ACCESS TO THE MIDDLE FOSSA: A CADAVERIC COMPARATIVE ANALYSIS BETWEEN LATERAL TRANSORBITAL AND ENDONASAL TRANSPTERYGOID ENDOSCOPIC APPROACHES
Sergio Augusto Barbosa de Farias, MD1; Aysu Iyigun Kabakci, MD2; Gabriel Vargas Rosales, MD3; Elena Rosellini, MD4,5; Cezar Kabbach Calaça Prigenzi2; Cleiton Formentin, MD, PhD1; Enrico Ghizoni, MD, PhD1; Joao Paulo Almeida, MD, PhD2; 1Departament of Neurosurgery, State University of Campinas, Campinas, São Paulo, Brazil; 2Department of Neurosurgery, Neurosciences Institute, Indiana University, Indianapolis, IN, US; 3Department of Neurosurgery, Universidad Militar Nueva Granada, Hospital Militar Central, Colombia; 4Department of Biomedical Sciences, Humanitas University, Milan, Italy; 5Department of Neurosurgery, IRCCS Humanitas Research Hospital, Milan, Italy
Introduction: Endoscopic approaches has advanced in recent years for skull base lesions, and offers expanded approaches for laterally located pathologies, such as middle fossa. However, this region remains challenging due to critical neurovascular structures like the internal carotid artery. By using the endoscopic endonasal transpterygoid approach, the middle fossa can be accessed. Therefore, alternative approaches, such as lateral transorbital endoscopic approach, were introduced to access lateral skull base regions, bypassing some vital structures.
Objective: The primary objective of this study is to analyze two endoscopic pathways, the transpterygoid and the lateral transorbital approach for accessing the middle fossa. Through this comparison, we aim to delineate the distinct anatomical characteristics, surgical extension capabilities, and clinical applications of both acess routes.
Material and methods: Five formalin flushed silicon injected alcohol preserved (70%) cadaveric head specimen were dissected endoscopically for both approaches, and images were captured via rigid endoscopes, coupled to an endoscopic tower with a screen. This work involved a descriptive, qualitative anatomical study conducted through cadaveric dissection. Both approaches were performed on the same side of all cadaveric specimen to ensure a direct comparative analysis under identical anatomical conditions.
Results: During the endonasal transpterygoid endoscopic approach, after opening the posterior wall of the maxillary sinus, the pterygopalatine fossa was exposed, and after its removal, the access to the middle fossa was achieved. Key structures including the vidian nerve, maxillary nerve, pterygopalatine ganglion, mandibular nerve, sphenopalatine artery were identified, in addition to the medial and lateral pterygoid muscles. The middle fossa access required controlled drilling the pterygoid process, to enhance the exposure of the maxillary (V2) and mandibular (V3) branch of the trigeminal nerve, the maxillary strut, located between the inferior orbital fissure and V2, and the mandibular strut located between V2 and V3. In contrary to the previous studies the vidian nerve was preserved in this specimen after drilling of pterygoid process. Previous studies show that sacrifice of the sphenopalatine artery is generally necessary to access the middle fossa through the transpterygoid approach. For the lateral endoscopic transorbital approach, an incision was made in the superior palpebral fissure extending to the lateral wall of the orbit. The orbicularis muscle was opened to expose the periosteum, followed by exposure of the greater wing of the sphenoid to reveal the middle fossa. During the exposure, key structures should be identified, such as the lateral pterygoid muscle inferiorly. The ophthalmic, maxillary, and mandibular branches of the trigeminal nerve were observed. Laterally, the foramen spinosum with the middle meningeal was visible. Superiorly, the lesser wing of the sphenoid and posteriorly, the greater superficial petrosal nerve were seen. This approach represents an alternative access to the middle fossa besides the endonasal endoscopic approaches, with the main advantage of avoiding neurovascular structures visualized in the transpterygoid approach.
Conclusion: The present study demonstrates that the lateral endoscopic transorbital approach offers a viable alternative for accessing the middle fossa when compared to the transpterygoid approach, avoiding neurovascular structures which are frequently encountered and potentially compromised in the transpterygoid route.