Applied Anatomic Study On Optic Canal And Its Adjacent Anatomic Structures

Objective:The anatomical data of the optic canal and its adjacent anatomic structures was obtained by dissection, observation and measurement under operation microscope. Based on it, we could get further understanding the mechanism of traumatic optic neuropathy, definitude localization of the optic canal, and obtain the anatomical data for transcranial optic canal decompression using by neurosurgery. The operative procedure of transpterional approach for optic canal decompression was simulated on intact cadaveric heads in order to offer reference for clinical application.Methods:Thirteen cases(26 sides) Chinese adult intact cadaveric heads fixed by 10% formalin. They were observed and measured by microanatomical mothod. The dissecting character in the course of transpterional approach for optic canal decompression on 2 intact cadaveric heads was observed. Under operative microscope, samples were dissected layer by layer according to operative approaches. The operative technique were analyzed. The photos were took by SONY digital camera. The data was treated statistically by the SPSS(America) microsoft and expressed with the average±standard deviation( x±s).Results:1.There were four walls and two openings for optic canal. The length of the canal wall was (8.94士1.09)mm,(7.15士0.98) mm, (11.01士1.12) mm, (8.20士0.90) mm in superior, inferior, internal and external walls respectively. Post of optic canal superior wall, dural fold formed falciform ligament, the width(anteroposterior diameter) was (1.98士0.33)mm , The optic nerve's impressions formed by falciform ligament were found (73.1%).The middle part of the optic canal was the narrowest, with a transverse area of (16.99士1.70)mm2. The adjacent structure of internal wall was best complicated. The ophthalmic artery commonly courses beneath the optic nerve in the dura. From cranial opening to orbital opening, its caliber varies littlely. And most of it courses from inside to outside under the optic nerve.2.The angle formed by cranial opening to glabella and orbital opening to glabella was (8.61±1.38o),and the angle formed by cranial opening to pterion and orbital opening to pterion was (11.97±1.89o). The axis of optic canal and midsagittal plane of skull formed an angle of(38.41士2.97 o). The transpterional approach for optic canal decompression had superiority.3.ACP formed the external wall of optic canal. The width of ACP root was (9.77士1.87)mm, and length of ACP was (9.20士1.32)mm . It can be resected from extradural approach. The resection of ACP was redound to decompression of optic canal. It must pay more attention to extradural exposure to the ACP and protection of adjacent cranial nerve.Conclusion: The results above provided the detail data of optic canal and its adjacent anatomic structures. Based on it, we could get further understanding the relation optic canal and its anatomic structures and the mechanism of traumatic optic neuropathy, definitude the localization of the optic canal, and obtain the anatomical for transcranial optic canal decompression using by neurosurgery. From simulating transpterional approach for optic canal decompression, we found that it could achieve good exposure, giving much space and convenience for the operation, and better chance for a fully decompression. Since the ophthalmic artery commonly courses beneath the optic nerve in the dura, it was safe to incise the dura vertically over it. The incision of dura reduced the pressure of the optic nerve which was traumatic and edematous. The ophthalmic artery, internal carotid and oculomotor nerve must be protected on transcranial approach for optic canal decompression because they adjoined the inferior wall and lateral wall of the optic canal.