2026 Poster Presentations
P448: KEY ANATOMICAL LANDMARKS FOR ENDOSCOPIC ENDONASAL SURGERY: AN ANATOMICAL "ROAD MAP" FOR SELLAR, PARASELLAR AND CLIVAL REGIONS
Rosaria Abbritti, MD1,2,3; Florian Moser1,2,4; Sandhya R Palit, MD1,2; Yohan Alexander, MD1,2; Luciano CPC Leonel, PhD1,2,5; Maria Peris-Celda, MD, PhD1,2,5; 1Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA; 2Mayo Clinic Rhoton Neurosurgery and Otolaryngology Surgical Anatomy Program, Rochester, Minnesota; 3Department of Neurologic Surgery, Lariboisière University Hospital, Université Paris Cité, Paris, France; 4Paracelsus Medical University, Salzburg, Austria; 5Department of Clinical Anatomy, Mayo Clinic College of Medicine and Science, Rochester, Minnesota, USA
Background: Surgery involving sellar, parasellar, and clival regions presents significant challenges due to the concentration of critical structures within these areas. Lesions originating or extending into these compartments may displace the normal anatomy.
Objective: To provide a surgical roadmap of the anatomical relationships of arteries and cranial nerves to the sellar floor and carotid segments, as encountered during endoscopic endonasal approaches (EEAs).
Materials and Methods: Nine formalin-fixed and latex-injected specimens (18 sides) were dissected endoscopically. Transsphenoidal transsellar, transcavernous, and transclival approaches were performed. The midpoint of the sellar floor (MSF) represented the reference point for measurements. For each structure, the superior–inferior and lateral distances from the MSF were recorded. The relationship of these structures to the internal carotid artery (ICA) segments was documented (Figs. 1 and 2).
Results: The main arteries originated from the cavernous internal carotid artery (cICA) superior to the MSF. The meningohypophyseal trunk (MHT) arose posteromedial to the posterior ICA bend, with a mean position 2.60 mm superior and 9.95 mm lateral to the MSF. Its three principal branches were identified lateral to the MSF along the medial aspect between the distal ICA and the superior portion of the proximal vertical ICA. In two sides (11.1%), the dorsal meningeal artery arose directly from the ICA.
The inferolateral trunk (ILT) originated lateral to the horizontal ICA in 15 sides (83.3%). Its posterior branch crossed inferolaterally the cavernous segment of the abducens nerve (CN VI) and the ophthalmic division of the trigeminal nerve (V1).
The location of CN III, CN IV, V1, and CN VI within the cavernous sinus (CS) and clival region were analyzed.
The interdural entry point of CN VI was located at the midclivus, 10.17 mm inferior and 11.53 mm lateral to the MSF medial to proximal vertical ICA. With an ascending route it ran medial to the petrous apex (PA) and superior and posterior to the foramen lacerum. Before entering the CS, CN VI passed superior to the PA and posterior to the proximal vertical ICA. Within the lateral wall of CS, the cavernous segment of CN VI was observed at two consistent positions:
- Proximal: lateral to the superior portion of the proximal vertical ICA and inferior to the horizontal ICA.
- Distal: lateral to the midpoint of the C-shape of the anterior ICA bend.
The ophthalmic nerve was found inferior and lateral to the cavernous CN VI. The entry points of CN III and CN IV into the CS were located between the distal segment of ICA and posterior bend, with CN IV coursing inferior and lateral to CN III. At their exit point from the lateral wall of CS toward the superior orbital fissure, CN III was found lateral to the distal ICA, whereas CN IV ran lateral to the superior edge of the anterior bend, inferior to CN III (Figs. 3 and 4).
Conclusion: The MSF and the ICA segments represent reliable landmarks for anticipating the location of arteries and cranial nerves during EEAs and avoiding iatrogenic vascular and neural injuries.
