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DOI: 10.1055/s-0034-1384075
Surgical Microanatomy of the Anterior Clinoid Process for Paraclinoid Aneurysm Surgery and Efficient Modification of Extradural Anterior Clinoidectomy
Objective: Some anatomical variations of the anterior clinoid process (ACP) should be known before clinoidectomy to ensure a safe approach. This study describes the incidence of the caroticoclinoid foramen (CCF), interclinoid osseous bridge (IOB), and pneumatization of the ACP during extradural anterior clinoidectomy (EAC) for unruptured paraclinoid aneurysm. Here, we describe the problems and technical aspects of such cases. Material and Methods: A total of 144 sides in 72 paraclinoid aneurysm cases that underwent EAC were analyzed preoperatively using multidetector row computed tomography. Results: The CCF, IOB, and pneumatization of the ACP were observed in 16.6, 2.77, and 27.7% of cases, respectively. Pneumatized patterns were divided into the following three groups according to the route: pneumatization occurred via the optic strut (OS) in 74.1%; via the anterior root (AR) in 14.8%; and via both OS and AR in 11.1%. Discussion: CCF and IOB make it difficult to remove ACP completely extradurally. The ACP should not be moved even after drilling the lateral wall of the ACP, orbital roof, and OS; therefore, an intradural approach is sometimes needed. CCF also restricts the movability of the internal carotid artery and warrants careful removal to open the distal dural ring. An awareness of the routes of pneumatization of the ACP should reduce the risk of tears in the paranasal mucosa. Mucosa is pushed upward toward the optic nerve in AR cases and toward the optic strut in OS cases. If tears arise in the mucosa, suturing and closure are needed to prevent liquorrhea.