Comparative Anatomical Analysis between Minipterional and Supraorbital Approaches in the Treatment of Anterior Circulation Aneurysms

Introduction: In vascular neurosurgery, most of recent discussions regarding the applicability of MIA included the comparative analysis between minipterional (MPT) and supraorbital (SO) approaches for the treatment of anterior circulation aneurysms. There exists a trend toward the treatment of middle cerebral artery (MCA) aneurysm trough a MPT approach, while the SO technique is usually preferred to treat anterior communicating artery (ACom) aneurysms. The aim of this work is to establish indications and limits of both techniques in the treatment of anterior circulation aneurysms, through a pertinent comparative anatomical analysis.

Methods: Area of exposure and surgical maneuverability provided by the SO and MPT were compared in five cadaveric heads. The area of exposure was selected based in the most relevant points in the anterior circulations that can be reached throughout the pterional approach. Surgical maneuverability was calculated by means of the Ammirati and Bernardo score that assess from how many directions the target can be approach, as such as the permissibility to perform microvascular dissection maneuvers. The surgical maneuverability was assessed for three selected target points, namely, (1) ipsilateral bifurcation of the middle cerebral artery (MCA); (2) ipsilateral bifurcation of the internal carotid artery (ICA); and (3) the anterior communicating artery (AComA). The points were selected to characterize the most representative surgical targets in the anterior circulation so that the exposure of these structures in both approaches could be evaluated.

Results: The MPT provided an increase of 21% in the area of exposure, in comparison to the SO (p < 0.05). Additionally, the MPT provided a better surgical maneuverability along the MCA (4 vs. 2.7, p = 0.005) and ICA bifurcation (4 vs. 2.1, p < 0.005). The SO affords a slightly better maneuverability around the AComA, although the statistical analysis did not reach significant differences (4 vs. 3.8, p > 0.05).

Conclusion: Our results demonstrate that the MPT is a versatile and minimally invasive approach that affords a larger area of exposure and better surgical maneuverability than the MSO to approach most of the anterior circulation aneurysms, including MCA, and ICA bifurcation aneurysms. AComA can be approach through both approaches, although limitations in the maneuverability and exposing paraclinoid and parasellar structures should be considered when choosing a SO. While SO provides a straight forward approach to AComA, the MPT offers the possibility to proximally dissect the Sylvian fissure, reducing the brain retraction and improving the surgical maneuverability.