The use of endoscopic endonasal approaches to the skull base provides an excellent view of the medial and inferior optic canal and affords the opportunity to address pathology in this region safely. Agosti et al. in their publication are reporting the detailed anatomical relationship of the optic nerve with the ophthalmic artery in the optic canal. They do so by studying 10 cadaveric specimens; they compare the anatomic relationship of the optic nerve and the ophthalmic artery from an endonasal perspective as well as from a top-down perspective via a craniotomy. Their results indicate that the ophthalmic artery can be located in an inferior, inferolateral, or inferomedial position in relation to the optic nerve, and they suggest that the dura over the optic nerve in the optic canal should be initially opened in the most superior third of the canal to avoid injury to the ophthalmic artery. The study is well done, and the results are sound.
While studies like the one presented in this manuscript have been performed before by other authors, the current study through analysis of additional anatomical specimens re-affirms the notion that the optic canal dura should be opened in its superior most aspect to avoid injury to the ophthalmic artery. In fact, the same conclusion has been drawn in several prior articles. For example, in 2008, Li et al. [2] write “the ophthalmic artery was inferomedial to the optic nerve in 9 sides (56%), inferior to the optic nerve in 4 sides (25%), and inferolateral to the optic nerve in 3 sides (19%).” In another article published in 2019, Guler et al. [1] conclude “The origin of the ophthalmic artery was inferior to the optic nerve in four samples (44.4%) and inferomedial to the optic nerve in five samples (55.5%) on the right side; inferior to the optic nerve in six samples (66.6%) and inferomedial to the optic nerve in three samples (33.3%) on the left side.” Then in 2021, in their study, Yilmazlar et al. [3] write “The ophthalmic artery was detected to run inferolaterally more distinctly than the optic nerve at a ratio of 61.6% after leaving the internal carotid artery.” For this reason, the novelty of their conclusions is perhaps the biggest question.
Along the same lines, surgeons that are considering addressing a pathology in the optic canal endonasally should study carefully the preoperative imaging, including dedicated vessel imaging, to evaluate the relationship of the optic nerve and ophthalmic artery at the level of the optic canal for each patient. Pathology in this region could distort the normal anatomy and can displace normal structures, so that the ophthalmic artery can present itself superomedial from a tumor that pushes the ophthalmic artery in a superomedial fashion from its normal inferomedial position. In this example, it would be a mistake to make the dural cut at the superomedial aspect of the canal. While knowledge of these anatomical relationships is useful when operating, the surgeon should take any possible measure to confirm the relative location of the ophthalmic artery to the surrounding structures either through preoperative imaging evaluation, through intraoperative navigation, or through the use of micro-Doppler ultrasound, to identify the characteristic sound of the ophthalmic artery pulsations that differs from that of the carotid artery.
References
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Yilmazlar S, Saraydaroglu O, Korfali E (2012) Anatomical aspects in the transsphenoidal-transethmoidal approach to the optic canal: an anatomic-cadaveric study. J Craniomaxillofac Surg 40(7):e198-205. https://doi.org/10.1016/j.jcms.2011.10.008
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Mathios, D., Schwartz, T.H. Considerations and limitations of anatomical studies delineating the relationship of the optic nerve and ophthalmic artery in the optic canal. Acta Neurochir 165, 535 (2023). https://doi.org/10.1007/s00701-022-05396-3
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DOI: https://doi.org/10.1007/s00701-022-05396-3