Endoscopic endonasal approach to the middle clivus. Close-up view of the lateral lateral limit of the approach on the left side. The left AICA arises from the basilar trunk and runs in between the fibers of the cisternal segment of the abducens nerve. The dural entry point of the abducens nerve is identified. The periosteal dura that covers the interdural segment of the abducens nerve has been removed. Note the lateral clival artery, as it runs just medial and parallel to the abducens nerve. This artery, which can either be a direct ICA branch or a branch of the meningo-hypophyseal trunk, may serve as a landmark to locate the interdural abducens nerve as we work from medial-to-lateral. In petroclival meningioma cases, the lateral clival artery might be enlarged and great care should be taken when coagulating it so to avoid injuring the adjacent abducens nerve. The clival bone has been removed to better expose the petrous apex, located behind the paraclival ICA. (Image courtesy of JC Fernandez-Miranda)