Microsurgical anatomy of the superior orbital fissure.

The microanatomy of the superior orbital fissure (SOF) was studied in 96 sides of cadaver specimens. The SOF is a narrow bony cleft that lies at the apex of the orbit between the greater and lesser wings of the sphenoid. Through this fissure, many important structures enter the orbit from the middle cranial fossa including the third, fourth, sixth cranial nerves, and the ophthalmic branch of the fifth nerve. In addition, the superior opthalmamic vein exits the orbit to drain into the cavernous sinus via the SOF. The fissure can be divided into three anatomical regions by the annulus of Zinn (common annular tendon): the lateral, central, and inferior regions. The lateral wall of the SOF can also be divided between the upper and lower segments, and the angle between them was measured to be 144.27 degrees +/- 20.03 degrees . Defining these regions is useful in describing the course and placement of the nerves and vasculature in the SOF. Managing lesions at the orbital apex requires an extensive knowledge of the cranial base and the intracranial and extracranial relationships of the anatomical structures coursing through the SOF. The goal of this study was to describe the microanatomy of the SOF region in detail and to provide a reference for surgical procedures involving the orbital apex.