The superior orbital fissure: a microanatomical study.

The superior orbital fissure (SOF) is a small (3 x 22 mm), but functionally very important, region. The microsurgical anatomy of the SOF was studied on five adult, formalin-fixed cadavers. The vascular structures of three of them were injected with latex. The SOF contains the third, fourth, and sixth nerves, the ophthalmic branch of the fifth nerve, and the superior orbital vein. It is divided by the two tendons of the lateral rectus muscle: the superior part contains the fourth nerve, the frontal and the lacrimal branches of the ophthalmic division of the fifth nerve, and the superior orbital vein; the inferior part contains the superior and inferior branches of the third, the nasociliary, and the sixth nerves. In regard to surgical access to lesions involving the SOF, the question is often raised as to whether the dissection should be started from the cranial or the orbital side. The following procedure is recommended: 1) frontotemporo-orbital craniotomy; 2) resection of the lesser wing of the sphenoid bone, of the anterior clinoid, and of the superolateral part of the orbital roof and opening of the dura along the Sylvian fissure, with an extension to the frontal lobe and another extension to the temporal lobe; 3) incision of the periorbita in its superolateral part and identification of the frontal nerve; and 4) dissection of the frontal nerve in an anteroposterior direction. The fourth nerve will be found medially and inferiorly to the frontal nerve. The third nerve will be found inferomedially to the frontal nerve in the SOF, and the sixth nerve will be found inferiorly to the inferior branch of the third nerve.