Background: The cavernous sinus (CS) is still one of the last frontiers of skull base surgery. Knosp 3B-4 subtypes of invasive pituitary adenomas pose significant difficulties since the endoscopic endonasal approach (EEA) is restricted to the medial compartment of the CS. The current study aims to validate the principle of 360° anatomic access around the CS and to demonstrate the clinical utility of the synergistic endoscopic biportal approach— combining EEA and the endoscopic transorbital approach (ETOA). Methods: Two silicon-injected cadaveric specimens were used to define the corridors EEA and ETOA and their respective access to the CS. A case series with two patients suffering from invasive pituitary adenomas is presented; both cases received a biportal approach, one staged and the other two staged. Results: The cadaveric study confirmed that EEA provides optimal access to the medial and inferior CS, whereas the ETOA corridor provided direct access to the superior and lateral compartments through the Mullan’s and Parkinson’s triangles. Clinically, a biportal approach in one case allowed for simultaneous dissection from medial and lateral trajectories, facilitating gross-total resection of a radiation-resistant recurrence. A second case demonstrated a staged uniportal ETOA for effective resection of a lateral CS recurrence, avoiding new cranial nerve deficits. Conclusion: The endoscopic biportal (transnasal and transorbital) approach is a feasible technique for invasive pituitary adenomas. This technique applies the concept of a 360° approach to the CS, allowing a panoramic dissection of tumors from complementary angles and overcoming the inherent limitations of a single surgical corridor.
Ng et al. (Fri,) studied this question.