The C5 section of the bedrock of the brain begins at the proximal dural ring and ends at the distal dural ring where the internal carotid artery enters the subarachnoid space, which is a short section between the distal and proximal dural rings, and the shortest section of the internal carotid artery among all the ends of the internal carotid artery, with a length of about 4-6 mm, which is an interdural structure. The internal carotid artery is divided into seven segments in the order of proximal to distal, namely: C1 cervical segment, C2 rock segment, C3 rupture segment, C4 cavernous sinus segment, C5 bedrock segment, C6 ophthalmic segment, and C7 transportation segment. The two hard dural rings adjacent to the C5 segment (bedrock segment) of the brain play a role in restricting the rupture of the aneurysm below to form an intracranial subarachnoid hemorrhage. The distance between the internal carotid arteries on both sides and the paramedian segments is the closest and the most superficial, and the bone of the internal carotid artery prominence is missing in some patients, and the mucosa of the paranasal sinuses is in direct contact with the dura mater. Therefore, this is the most common area of internal carotid artery injury in endoscopic transsphenoidal surgery.