Cavernous Internal Carotid Artery Tortuosity Patterns: Anatomical Considerations for the Endonasal Transsphenoidal Transcavernous Approach

Objective: The cavernous segment of the internal carotid artery (ICA) is a critical structure during surgical exposure of the cavernous sinus in endonasal endoscopic approaches. Its tortuosity may alter the relationship between this vessel and the inferior cavernous sinus compartment space. This study aimed to classify cavernous ICA tortuosity based on angular measurements and evaluate its anatomical and surgical implications. Methods: One hundred individuals (200 cavernous ICAs) were analyzed using contrast-enhanced CT angiography. Posterior bend angle, posterior bend height, and inter-cavernous ICA distance were measured. Tortuosity was categorized into five types according to posterior bend angulation. Results: Mean posterior bend angle was 84.6° (SD 29.6), mean inter-cavernous ICA distance was 7.04 mm (SD 3.03), mean posterior bend height was 3.50 mm (SD 1.76). Increasing tortuosity demonstrated inverse correlation with posterior bend height (R = −0.869, p < 0.001) and positive correlation with inter-cavernous ICA distance (R = 0.643, p < 0.001). Five tortuosity types were identified: Type 1 (≥100°) 30.5%, Type 2 (80–99°) 27.5%, Type 3 (60–79°) 20.5%, Type 4 (40–59°) 13.0%, and Type 5 (<40°) 8.5%. The spheno-carotid triangle was defined with its base formed by the inter-cavernous ICA distance and its height by the posterior bend height, triangle height increased progressively, whereas its base narrowed stepwise with increasing tortuosity (p < 0.001). Conclusions: Greater posterior cavernous ICA tortuosity is associated with progressive narrowing of the inferior cavernous sinus compartment. Highly tortuous arteries may require increased caution during cavernous sinus exposure to reduce vascular injury risk.