Overview of the Endoscopic Endonasal Internal Carotid Artery Classification. A, 0-degree endoscopic views after complete exposure of the ICA on the left side and partial exposure on the right. B, A schematic diagram of the proposed classification. Six ICA segments are proposed: parapharyngeal, petrous, paraclival, parasellar, paraclinoid, and intradural. (Images courtesy of AL Rhoton, Jr.)