Expanded Endoscopic Endonasal Approach to the Inframeatal Area: Anatomic Nuances with Surgical Implications

BACKGROUND/OBJECTIVE: The inframeatal area represents a challenging region for skull base surgeons. Various surgical corridors have been described to access this area and frequently are used in combination. Recent studies describe the expanded endoscopic endonasal approach (EEA) as an established route for midline regions, particularly medial to the internal carotid arteries (ICA). We sought to evaluate the accessibility, maneuverability, and freedom of movement of the expanded endoscopic endonasal approach to the inframeatal region. METHODS: An EEA combining a middle and an inferior transclival corridor with an infrapetrous and a supra-condylar lateral expansion was performed in 5 embalmed human cadaveric heads. The area of exposure and the surgical freedom to access the inframeatal area were calculated. The angle of attack and distances from the lacerum segment of the ICA to several anatomical targets also were measured. Our database was searched to select clinical case examples. RESULTS: The EEA provided an exposure area of 101.26 +/- 16.66 mm(2) and an area of surgical freedom of 1208.50 +/- 507.01 mm(2). The angles of attack in both the sagittal and axial planes were wider at the lacerum segment of the ICA and narrower at the dural entrance zone of cranial nerves VII/VIII. Three chondrosarcomas are presented as case illustrations. CONCLUSIONS: The EEA is a feasible route to the inframeatal area. This approach provides a safe working corridor for lesions in this region, as shown by the anatomical and clinical findings presented here. Comparative studies and large case series are warranted to further establish its clinical value.