Anatomical references beyond the vidian canal in petrous apex endoscopic approaches: A radiologic study and clinical...

The vidian nerve is a well-recognized landmark in endoscopic endonasal skull base surgery, as it helps identify the internal carotid artery at the foramen lacerum and allows surgeons to safely approach the petrous region. However, to the best of the authors' knowledge, there are no clearly defined landmarks when the surgical corridor advances posteriorly and superiorly through the petrous bone, behind the internal carotid artery. This study aimed to provide anatomical and radiological references, based on patient-specific anatomy, for approaching the petrous apex through endoscopic endonasal approaches. Twenty petrous bones from ten patients were analyzed, defining skull base landmarks and their posterior projections, namely the newly named naso-vidian, naso-carotid, and naso-paraclival lines. The distance between these projections and other standard skull base landmarks was measured to establish their anatomical correlations. The posterior projections of the naso-vidian and naso-carotid lines deviated by a mean of 2.5mm and 2.1mm, respectively, when measured against the internal acoustic meatus. In postoperative CT scans of endonasal petrosectomies performed at our center, the average distance from the bone edge reached to the antero-inferior border of the internal acoustic meatus was 1.7mm. The naso-vidian and naso-carotid lines may function as suitable references when approaching the petrous apex, as they commonly project towards the internal acoustic meatus, aiding in preoperative planning for endonasal skull base approaches to this region.