Comparative anatomical analysis between lateral supraorbital and minipterional approaches

Abstract

Background: The pterional craniotomy, described by Yasargil and Fox in 1975, constitutes the most traditional and important surgical access in vascular neurosurgery. Minimally invasive alternatives include the minipterional (MP) and lateral supraorbital (LSO) craniotomies, which avoid complications such as injury to the frontal branch of the facial nerve, temporal muscle dysfunction, depression of the craniotomy site, frontal sinus opening, and cosmetically unacceptable outcomes. We evaluated and compared the exposures provided by MP and LSO craniotomies through quantitative measurements of the surgical exposure area around the circle of Willis and parasellar regions, as well as angular and linear exposures of the internal carotid artery (ICA) bifurcation, middle cerebral artery (MCA), midpoint of the anterior communicating artery, and tip of the basilar artery (BA).

Methods: Seven fresh cadavers were dissected at the São Paulo Medical Examiner's Office, SP, and three at the skull base laboratory of Weill Cornell Medical College, New York, USA. The craniotomies were performed sequentially, initially with the LSO craniotomy followed by the MP. After the craniotomy, the surgical exposure area, craniotomy area, and angular exposures in the horizontal and vertical axes were determined.

Results: The MP craniotomy provided better angular exposure for the ipsilateral MCA, while the LSO craniotomy and BA provided better vertical axis exposures. The LSO craniotomy provided better angular exposure in the vertical axis for the midpoint of the anterior communicating artery and contralateral ICA bifurcation. Regarding surgical exposure and craniotomy area, there were no statistically significant differences.

Conclusion: The MP craniotomy offers a significantly larger surgical exposure compared to the LSO craniotomy, with specific advantages regarding angular exposure to important neurovascular structures. This study provides important quantitative data to guide the choice between these minimally invasive access techniques in vascular neurosurgery.

Keywords: Cerebral aneurysm; Lateral supraorbital; Minimally invasive approach; Minipterional craniotomy.

Figure 1:

Stepwise dissection in the lateral supraorbital and minipterional approach. (a) Positioning and marking of the incision for performing LSO and MP craniotomies on the left side; The curve define the skin incision made for the approach (b) after retracting the musculocutaneous flap, revealing the anatomical landmarks and reference points for the LSO and MP craniotomies; (c) marking of the LSO and MP craniotomies; and (d) exposition after performing the MP approach and the visualization before opening the dura mater. LSO: Lateral supraorbital, MP: Minipterional.

Figure 2:

Surgical view of the intradural space provided by the lateral supraorbital craniotomy (a) and the minipterional craniotomy (b) of the left side. ICA: Internal carotid artery, L: Left, ON: Optic nerve, R: Right.

Figure 3:

Photograph in superior view of the base of the skull of an anatomical specimen with an illustrative drawing of the six anatomical points used in the calculation of the exposure area for each craniotomy. (1) Most lateral point of the superior orbital fissure in the lesser wing of the ipsilateral sphenoid bone; (2) bifurcation of the ipsilateral middle cerebral artery; (3) most distal point of the ipsilateral posterior cerebral artery; (4) most distal point of the contralateral posterior cerebral artery; (5) most distal point of the contralateral middle cerebral artery; and (6) most lateral point in the lesser wing of the contralateral sphenoid bone. Courtesy of the Rhoton Collection, American Association of Neurological Surgeons/Neurosurgical Research and Education Foundation.

Figure 4:

Image of the hexagon and areas obtained in GeoGebra with the surgical exposure, including respective points of interest and obtained areas.