Clinical anatomy of optic nerve and chiasma

Objective:To study the construction features and surgical significance of optic nerve and chiasma.Methods:The morphologic characteristics and adjacent relations of optic nerve and chiasma were observed on 15 cadaveric human head specimens under an operating microscope.Results: The length of falciform fold along optic nerve was 0.4～4.6mm.One third of optic nerve bulged.All of the tuberculum sellae were flat.The majority of posterior margins of optic chiasma were posterior to dorsum sella.Optic nerve was mainly supported by superior anterior hypophyseal artery.About half of superior anterior hypophyseal arteries gave out a branch that runs anteriorly along optic never.Superior surface of optic chiasma was supported by anterior cerebral anterior communicating artery complex.Medial part of inferior surface of optic chiasma was mostly supported by superior hypophyseal artery,but lateral part was supported by internal carotid artery and posterior communicating artery.A sheet of arachnoid covered the superior surface of optic nerve.A sheet of pia mater lining inferior surface of gyrus recuts was just superior to the arachnoid.Conclusions: Because the edge of Chinese tuberculum sellae cannot be easily defined,it is difficult to type optic chiasma in traditional methods.So it is proper to judge prefixed optic chiasma or postfixed optic chiasma according to the distance between limbus sphenoidalis and anterior edge of optic chiasms.If a small artery coursing optic nerve was damaged in operation,coagualted must be extraordinarily carefully.Lifting gyrus rectus along optic nerve is a procedure in which dissociaton is done along a less adhesive interface.Fibrous trabeculae presenting in the interface should be cut in half number of cases.