A Study Of Microanatomy Associated With Anteriolateral Epidural Approach To Skull Base

For improving the surgical efficacy of the skull-base tumors, the microanatomy of superior orbital fissure and anterior cavernous sinus, optic canal, anterior clinoid process and applied anatomy of anteriolateral epidural approach were conducted on 35 formalin fixed cadaveric heads in which vessels were perfused with colorful silicone and 15 dry adult cadaveric head specimens. Epidural approaches for anterior and lateral fossa were used in patients to improve the operative effect of refractory skull base tumors.Part I Microanatomy of superior orbital fissure and anteriorcavernous sinusObjective: To provide the microsurgical anatomical basis for the operation of cranio-orbital region tumors and tumors related to superior orbital fissure(SOF) and cavernous sinus. Materials and Methods: (1) The osseous structures of superior orbital fissure were observed in 30 sides of dry adult cadaveric head specimens; (2) The course and relationship of nerves and vascular structures passing through superior orbital fissure were studied in 30 sides of formalin fixed cadaveric heads in which vessels were perfused with colorful silicone under the microscope; (3) Explored how to incise temporal tip dural fold and anulus of Zinn and how to expose superior wall and lateral wall of cavernous sinus. Results: (1) The superior orbital fissure is a narrow cleft through which the orbit communicates with the middle cranial fossa; (2) Detachment of the temporal tip dural fold (depth^ 5mm) vertically to the superior orbital fissure introduces the interdural space, where the cavernous sinus is present, without opening the meningeal dura. This may avoid damaging the lacrimal nerve, the frontal nerve, trochlear nerve and the superior ophthalmic vein; (3) With the dissecting technique, we began the dura incision along the surface of V 2 at foramen rotundum and V3 at foramen ovale, in sequencely, we reflected the dura from trigeminal ganglion, cavernous sinus lateral wall and whole middle fossa; (4) The anulus of Zinn should be incised between the superior rectus and the lateral rectus toexpose the central sector of the superior orbital fissure; (5) The cavernous sinus is situated behind the orbital apex and the superior orbital fissure. The fissure is divided into three sectors by the annular tendon: that are the lateral, central and inferior sector. The lateral sector is pass by the trochlear, frontal and lacrimal nerves and the superior ophthalmic vein. The central sector transmits the superior and inferior of divisions of the oculomotor nerve, the abducens and nasociliary nerves and the sensory and sympathetic roots of the ciliary ganglion. The inferior sector is pass by the inferior ophthalmic vein. (6) At the fissure, the dura covering the middle fossa and cavernous sinus blends into the periorbital of the orbital apex and the annular tendon from which the extraocular muscles arise. The annular tendon surrounds the anterior end of the optic foramen and the adjacent part of the superior orbital fissure. The fibrous components, which blend together to form the annular tendon, are the periorbita covering the orbital apex, the dura lining the fissure and optic canal, and the optic sheath. The annular tendon is also attached to the lateral margin of the fissure at the junction of the narrow lateral and larger medial parts. Conclusions: (1)Detachment of the temporal tip dural fold (depth< 5mm) vertically to the superior orbital fissure introduces the interdural space, where the cavernous sinus is present, without opening the meningeal dura. This may avoid damaging the lacrimal nerve, the frontal nerve, trochlear nerve and the superior ophthalmic vein; (2)The central sector and the oculomotor foramen could be opened with an incision directed through the annular tendon between the origin of the superior and lateral rectus muscles. It is important to remember that the superior ophthalmic vein exits the extraocular muscle cone bypassing between the origin of the superior and lateral muscles from the annular tendon. Wh...