ORBITAL VENOUS DRAINAGE INTO THE ANTERIOR CAVERNOUS SINUS SPACE - MICROANATOMIC RELATIONSHIPS

OBJECTIVE: Microsurgical anatomy and relationships in the region of th e superior orbital fissure and anterior part of the cavernous sinus we re studied, with special attention to the venous structures. METHODS: Microanatomic dissections were performed in 24 specimens from human ca davers, fixed in formalin, with the aid of a microdrill and operating microscope. RESULTS: A protocol of dissection was developed, enabling plane-by-plane exposure of the cranial nerves passing from the caverno us sinus to the superior orbital fissure and farther, on disclosure of the junction between the ophthalmic veins and the anterior cavernous sinus space. The main draining vessel was the superior ophthalmic vein . The inferior ophthalmic vein was much thinner and it was identified in 91.7% of cases. These two vessels fused together to form a common v enous confluence approximately 5 mm in length that entered the anterio r cavernous sinus space in its anterior or anteroinferior aspect. The shape of this venous drain varied greatly, from that of a typical vein to that of a venous lake. The latter was characterized by a relativel y narrow opening into the anterior cavernous sinus space and lacunar w idening of the vessel in its central part. No case of a separate entra nce of the superior and inferior ophthalmic veins into the anterior ca vernous sinus space was encountered. The anterior cavernous sinus spac e was described as a slit-like venous chamber located in front of the anterior genu of the intracavernous segment of the internal carotid ar tery. The anteroposterior diameter of this space was 3.2 +/- 0.4 mm; i t was filled with blood, and no venous structures inside this space we re observed. CONCLUSION: The knowledge of the anatomic details describ ed may be useful for elaborating surgical approaches to this region an d for planning the treatment of carotid-cavernous fistulas.