The "Crista Ovale": A Reliable Anatomical Landmark in Transorbital Endoscopic Approaches to the Middle Cranial Fossa

BACKGROUND:Transorbital endoscopic approaches (TOEAs) have emerged as adjunct and alternatives for accessing the middle cranial fossa (MCF). Nuances of the skull base anatomy from a ventral transorbital endoscopic viewpoint remain to be fully described.OBJECTIVE:To assess the anatomy of the "crista ovale" (COv), described transcranially as the midsubtemporal ridge (MSR), from a ventral transorbital perspective and evaluate its role as a landmark in TOEA to the MCF.METHODS:Lateral TOEAs to the MCF were performed in 20 adult cadaveric heads (40 sides). The presence of the COv/MSR was evaluated under endoscopic visualization. Anatomic relationships between COv/MSR and surrounding structures were assessed. The presence of COv/MSR was also examined in 30 cadaveric head computed tomography (CT) scans (60 sides).RESULTS:The COv/MSR was identified in 98% (39/40) of sides at the MCF, as 1 of 4 major configurations. The COv/MSR was found anterolateral to the foramen ovale and foramen spinosum (mean distance: 9.2 +/- SD 2.4 mm and 12.3 +/- SD 2.6 mm, respectively) directly anterior or anteromedial to the petrous apex (mean distance: 26.2 +/- SD 2.6 mm) and at a mean 47.6 +/- SD 4.7 mm from the approach's surgical portal. It was recognized in 95% (57/60) of CT scans.CONCLUSIONThe COv/MSR can be readily identified during TOEA to the MCF and on CT. It serves as a reliable landmark to localize the foramen ovale, foramen spinosum, and petrous apex. Further studies may confirm its surgical significance in transorbital endoscopic procedures.