Microsurgical Anatomy of the Carotid Cave

BACKGROUND: The carotid cave was first described more than 20 years ago, but its relationships to the dural rings defining the clinoid segment of the internal carotid artery (ICA), the carotid collar, and the adjacent osseous structures need further definition. OBJECTIVE: To further define the microanatomy of the carotid cave and its relationships to the adjacent structures. METHODS: The cave and its relationships were examined in cadaveric specimens using 3 to 40x magnification. RESULTS: The cave is an intradural pouch, found in 19 of 20 paraclinoid areas, that extends below the level of the distal dural ring between the wall of the ICA and the dural collar surrounding the ICA. The distal dural ring is tightly adherent to the anterior and lateral walls of the ICA adjacent the anterior clinoid process and optic strut but not on the medial and posterior sides of the artery facing the upper part of the carotid sulcus where the carotid cave is located. The superior hypophyseal artery frequently arises in the cave. The depth and circumferential length of the cave averaged 2.4 mm (range, 1.5-5 mm) and 9.9 mm (range, 4.5-12 mm), respectively. Aneurysms arising at the level of the cave, although appearing on radiological studies to extend below the level of the upper edge of the anterior clinoid, may extend into and may be a source of subarachnoid space. CONCLUSION: The surgical treatment of aneurysms arising in the cave requires an accurate understanding of the relationships of the cave to the ICA, dural rings, and carotid collar.