Microanatomy studies of orbital oculomotor nerve

Objective To provide anatomic data for avoiding damage to the orbital oculomotor nerve during the intraorbital operation.Methods The microsurgical anatomy of the orbital oculomotor nerve and its branches and adjacent structures through their intraorbital courses were observed and measured in each side of 30 adult cadaveric heads fixed in formalin,in which the arteries and veins were injected red and blue latex.Results The oculomotor nerve of total 60 eyes were divided into superior and inferior divisions before the superior orbital fissure in 95.0%(57 eyes)and 5.0%(3 eyes)of the nerve divided into the two divisions in the superior orbital fissure.The transition point of the branch from the superior rectus to levator palpebrae superior muscle located proximally in the middle of the orbit in 96.7%(58 eyes).The ciliary ganglion originated mostly in one-third proximal of the inferior division in 86.7%(52 eyes).Conclusions The oculomotor nerve has a complex course and adjacent relationship.The microanatomical knowledge of the nerve can reduce the bleeding and injury in the orbital operation.The transition point of the branch from the superior rectus to levator palpebrae superior muscle and ciliary ganglion is critical key points to the various orbital approaches.