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Introduction: Endoscopic endonasal approaches are frequently employed to access lesions in the cavernous sinus (CS). This approache often involve opening the anterior wall of the cavernous sinus, and removing the medial wall of the cavernous sinus (MWCS), which can be achieved through two primary techniques: lateral-to-medial and medial-to-lateral. Using sharp instruments to incise the anterior wall of the CS dura carries a risk of internal carotid artery (ICA) injury, particularly if the vessel has tortuous trajectory or abuts the dura due to its anatomical course or tumor presence. Adjunctive tools such as doppler ultrasound are recommended to map the course of the cavernous ICA before incising the anterior wall, but a safe entry zone may not always be identifiable due to the ICA's trajectory. The aim of this paper is to present the relation between the geometry of the ICA configuration and the pituitary gland, as the surgical implication during the resection of the MWCS.
Methods: Twenty-seven fresh cadaveric specimens underwent meticulous bilateral dissections using an endoscopic endonasal approach. A detailed anatomical analysis focused on the ICA geometry in the parasellar and paraclival regions was performed. The relationship between ICA geometry, the pituitary gland, surrounding neurovascular structures, and implications for surgical planning was further classified and analyzed.
Results: This study analyzed the ICA geometry in 27 cadaveric specimens (54 side) within the parasellar and paraclival regions using the Cebula classification. Distribution was: 12 type I (pronounced curvature), 8 type II (mild curvature), 24 type III (linear course), and 10 type IV. Complex ICA geometries indicated varied surgical risks. Type I ICAs, closer to the pituitary gland, presented higher risks and potential doppler mapping false positives. The trajectory of the inferior hypophysial artery was horizontal in 26 cases and superior in 28 cases. Type III geometry was more favorable for pituitary hemi-transposition and medial wall resection due to its linear course. Types I and II, with complex curvatures and reduced distances to critical structures, required additional precautions. These findings highlight the importance of ICA geometry in surgical planning to reduce the risk of ICA injury.
Conclusion: Understanding the structural variability of the parasellar and paraclival ICA anatomy around the pituitary gland provides valuable insights for planning safer and more precise dissections during the endoscopic transcavernous approach. When the ICA is closely associated with the pituitary gland, the risk of arterial injury may increases. Therefore, recognizing these anatomical nuances is crucial for minimizing surgical risks and improving patient outcomes.