Radiographic Analysis of the Vidian Canal and Its Utility in Petrous Internal Carotid Artery Localization

BACKGROUND: Endoscopic endonasal surgery of the skull base requires expert knowledge of the anatomy and a systematic approach. The vidian canal is regarded as a reliable landmark to localize the petrous internal carotid artery (pICA) near the second genu, which can be used for orientation in deep skull base approaches. There is controversy about the relationship between the vidian canal and the pICA. OBJECTIVE: To further establish the vertical relationship between the vidian canal and the pICA to aid in surgical approaches to the skull base. METHODS: We utilized a collection of institutional review board-approved computed tomographic (CT) angiograms (CTAs). Fifty CTAs were studied bilaterally for 100 total sides. The vidian canal was visualized radiographically to determine whether it terminates below, at, or above the level of the pICA. RESULTS: Sixty-six of 100 vidian canals terminated inferior to the pICA (66%), which was the most common relationship observed. The average distance inferior to the pICA was 1.01 mm on the right, 1.18 mm on the left, and 1.09 mm of the total 66 sides. Less commonly, the vidian canal terminated at the level of the pICA canal in 34 sides (34%). The vidian canal was not observed to terminate superior to the pICA in any of the 50 CTAs studied. CONCLUSION: The vidian canal terminates inferior to the pICA most commonly, but often terminates at the level of the pICA. Careful drilling clockwise inferior to superior around the vidian canal should allow for safe pICA localization in most cases.