The clinoidal space: anatomical review and surgical implications.

This study describes the anatomy of the clinoidal space exposed after the anterior clinoid process (ACP) is removed. Five cadaver heads injected with colored latex in the arterial and venous systems were used. Each was cut in half to provide ten specimens for inspection. The bone that covered the medial side of the cavernous and clinoidal internal carotid artery (ICA) was removed. The ACP was removed and its dural layers were preserved. The removal of the ACP establishes an area called the clinoidal space. In this space, the clinoidal ICA is exposed. This space is delimited by two dural rings that anchors the clinoidal ICA. Most of the clinoidal space is located anterolateral to the artery where the ACP is found, but there is a small triangular space posterior to the artery and another space anteromedial to it. The clinoidal ICA is completely encased by connective tissue in this space. The clinoidal space is extracavernous, therefore, bleeding occurs only if the connective tissue layer is broken.