Optic Canal Size is an Indicator for the Accessory Optic Canal: Applications for Anterior Clinoidectomy

• Published in: World neurosurgery Vol. 181; pp. e826 - e832
• Main Authors: Zdilla, Matthew J., Cusick, Abbey M., Cowher, Abigail E., Choi, Janie S., Lambert, H. Wayne
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2024
• Subjects: Carotid Artery, Internal - surgery; Eye; Humans; Internal carotid artery; Neurosurgery; Neurosurgical procedure; Ophthalmic artery; Ophthalmic Artery - diagnostic imaging; Ophthalmic Artery - surgery; Optic nerve; Optic Nerve - diagnostic imaging; Optic Nerve - surgery; Sphenoid bone; Sphenoid Bone - diagnostic imaging; Sphenoid Bone - surgery; Optic nerve; ICA; Neurosurgery; Sphenoid bone; ACP; CT; Ophthalmic artery; OC; AOC; Internal carotid artery; Neurosurgical procedure; ON; OphA
• ISSN: 1878-8750; 1878-8769; 1878-8769
• DOI: 10.1016/j.wneu.2023.10.140

The ophthalmic artery normally travels with the optic nerve through the optic canal. However, sometimes, the ophthalmic artery travels through a foramen within the optic strut named an accessory optic canal, double optic canal, or ophthalmic canal. This variant puts individuals at an increased risk for blindness or death during anterior clinoidectomy due to unforeseen hemorrhage of the ophthalmic artery or internal carotid artery when the optic strut is separated from the body of the sphenoid bone. Several features make the accessory optic canal difficult to recognize on imaging: its variant nature, small size, and ability to masquerade as a caroticoclinoid foramen or a pneumatized sphenoidal structure. Hence, improved methods of presurgical identification are warranted. The aim of this study was to assess the size and shape of the optic canal, with and without a concomitant accessory optic canal, to determine whether measurement of the optic canal may provide useful information regarding the presence of an accessory optic canal. In 191 dry crania, optic canals with and without concomitant accessory optic canals were assessed for the following parameters: canal area, canal perimeter, circularity, solidity, the axes and aspect ratio of a best-fit ellipse, and roundness. Normal optic canals were found to have a larger area (P = 0.036), perimeter (P = 0.043), and minor axis of a best-fit ellipse (P = 0.031) than the optic canals that occurred alongside accessory optic canals. Asymmetry in optic canal size can help indicate the presence of a unilateral accessory optic canal before surgery.