Aim:This study aimed to identify the presence and delineate anatomical boundaries of the medial corridor (MC) within the cavernous sinus (CS) using the endoscopic endonasal transsphenoidal approach. Additionally, it sought to correlate these anatomical findings with clinical cases of pituitary adenoma invasion. Material and Methods:Ten cavernous sinuses (CS) from five adult cadaveric heads were examined using the endoscopic endonasal transsphenoidal dissection technique. Key anatomical landmarks and their corresponding distances were carefully measured and documented. Additionally, a clinical correlation was performed in 20 patients with pituitary adenomas demonstrating radiological evidence of CS invasion. Results:The medial corridor was consistently identified in all cadaveric specimens. The mean distance between the anterior genu of the internal carotid artery (ICA) and the pituitary gland was 5.0 ± 1.5 mm. Clinical data indicated that tumors frequently invade or extend into the superior compartment of the CS via the MC prior to extending laterally and posteriorly. The third cranial nerve served as a key anatomical landmark, demarcating the lateral boundary of the MC. Conclusion:A detailed understanding of the MC is essential for optimizing surgical planning, facilitating effective tumor resection, and reducing the risk of neurovascular injury. The anatomical reference of an average 5 mm distance between the anterior genu of the ICA and the pituitary gland provides a critical anatomical landmark for intraoperative navigation through the MC.