Quantitative Effect of Ethmoidal Artery Division on Supraoptic Triangle Exposure During Endoscopic Endonasal Surgery: A Cadaveric Study

Background: The supraoptic triangle (SOT) is a bony–dural region along the superolateral surface of the optic canal, bounded inferiorly by the optic nerve, laterally by the projection of the lateral optico-carotid recess, and superomedially by the planum sphenoidale. Despite extended transtuberculum–transplanum drilling, lateral access to the SOT remains restricted during endoscopic endonasal surgery. Ethmoidal artery division, often used to devascularize anterior skull base tumors, also permits lateral periorbital displacement, potentially widening the surgical corridor. Quantitative evidence supporting this effect is limited. Methods: Cadaveric dissections were performed via an endoscopic endonasal approach. SOT exposure was sequentially assessed: (1) baseline after transtuberculum–transplanum drilling, (2) after posterior ethmoidal artery (PEA) division, and (3) after combined anterior + posterior ethmoidal artery (AEA+PEA) division. Quantitative metrics included exposed SOT area (mm 2 ) and largest diameter (mm), obtained through calibrated image analysis in ImageJ. Calibration was performed using a microruler visible in the surgical field to convert pixel measurements into real distances, ensuring accurate calculation of areas and diameters. Results: Six sides were analyzed. Mean SOT area increased from 34.8 ± 24.1 mm 2 at baseline to 43.7 ± 28.9 mm 2 after PEA (25.6 ± 9.3%, p = 0.012) and 50.8 ± 36.1 mm 2 after AEA+PEA (43.9 ± 11.1%, p = 0.003 vs. baseline). The largest diameter expanded from 6.1 ± 0.4 mm at baseline to 7.0 ± 0.5 mm after PEA (15.2 ± 4.8%, p = 0.021) and 8.2 ± 0.4 mm after AEA+PEA (34.4 ± 6.9%, p < 0.001). Conclusion: PEA and AEA division provide stepwise, significant lateral expansion of the surgical corridor by enabling periorbital displacement. These findings support ethmoidal artery ligation as a practical adjunct to enhance supraoptic triangle exposure during endoscopic endonasal surgery. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany