Cadaveric Quantitative Comparison of Transorbital and Mini-Pterional Approaches for MCA Bifurcation Aneurysms

Objective: The middle cerebral artery (MCA) bifurcation aneurysms pose significant microsurgical challenges due to their location within the fissure, anatomical complexity, and proximity to eloquent neural structures. While the mini-pterional (MP) approach is widely adopted as the mainstream surgical exposure, the eyelid transorbital (TOA) approach has emerged as a minimally invasive alternative. This cadaveric study aims to quantitatively compare these two approaches in terms of surgical exposure, maneuverability, and working distance for the treatment of MCA bifurcation aneurysms. Methods: Five latex-injected human cadaveric heads were dissected via either the MP ( n = 5) or TOA ( n = 5) approach. Standardized microsurgical techniques of eyelid transorbital and mini-pterinal approaches were used to access the MCA bifurcation. Key surgical parameters including access depth, access angle (M1 angle) to first segment of MCA (M1), and horizontal and vertical angles of attack to the MCA bifurcation were evaluated quantitatively using neuronavigation. Statistical analysis was performed using the Wilcoxon Rank Sum test with a significance threshold of p < 0.05. Results: Both approaches provided adequate exposure to the MCA bifurcation and its branches. The working distance is similar in both approaches (MP 26.9 ± 7.48 mm versus TOA 31.0 ± 7.49 mm, p = 0.24). The MP approach offered significantly wider vertical angle of attack (86.1 ± 34.82° versus 45.3 ± 32.11°, p = 0.02) while the horizontal angle (25.0 ± 8.56° versus 33.6 ± 15.33°, p = 0.42) was comparable in both approaches. The TOA approach demonstrates a more perpendicular M1 angle (54.3 ± 17.37° versus 32.7 ± 17.2°, p = 0.03) favoring proximal control. Conclusion: The MP approach remains advantageous for broader exposure and maneuverability; however, the TOA represents a viable, cosmetically favorable alternative in selected cases of MCA bifurcation aneurysms. These findings support a tailored approach to aneurysm surgery, balancing anatomical exposure with patient-specific factors such as cosmetic preferences and prior surgical history. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany