Microsurgical Anatomy On Orbitaol Apex Region And Frontotemporal Orbitozygomatic Surgical Approach

Objective:The orbital apex is an anatomical region surrounded by the anterior clinoid process, optic canal and superior orbital fissure. It is the important cranio-orbital junction structure, and the neighber structure in anterior and middle fossa. This area space is small, complex structures assembled by the intensive and important blood vessels and nerves, and other tissues.lesions in this Area often extend to the orbital and intracranial two-way, and have the close relationship with the important nerves and blood vessels.Total remove of the lesions in this area is difficut and always leads to the postoperative complications. This is a complex problerm faced by neurosurgeons. Frontotemporal orbitozygomatic cranio-orbital approach to the orbital apex region is studied and applied most,and is regarded as the most valuable approach and the preferred surgical approach for removal of lesions of the orbital apex.It provide a good perspective and fully exposed space, and the surgical path is short.but this approach has more operative trauma,complex time-consuming, somepostoperative complications. We designed and carried out this study in order to learn in detail microsurgical and imaging anatomy of the orbital apex region,deal with the problems related to operative approaches, to provide direct anatomical diagrams of microsurgery and imaging as well as the detailed anatomical parameters for clinical operation,and more important,to improve the operative efects of the lesions in this area.Method:Ten cases (20 sides) Chinese adult cadaver heads fixed by 10% formalin. Age and sex couldn't be exactly judged. clean thrombosis of the arterial and venous system, Then red latex mixed with red dye was injected into arterial systems and blue latex was injected into venouss ystems,in order to identify arteries and veins, to maintain the caliber of blood vessels normal, and to improve photo quality. Fifteen dry Chinese adults' skulls (30 sides) were used to observe and measure bone structures. Frontotemporal-orbi- tozygomatic approach is the most representative anterolateral approach. Under operative microscope, samples were dissected layer by layer according to frontotemporal-orbitozygomatic approach, and observed with the micro- structure in orbital apex and the anatomic structure of this region through Traveling the important nerves and blood vessels and adjacent relationship. Referring to imaging anatomy, we measured the anatomical structures accurately and took photos. All data were statistically processed and presented in the MD±SD style.Results:This group of samples were dissected layer by layer according to frontotemporal-orbitozygomatic approach,for observing and measuring extracranial skull bone flap,improving operative technology. Under the operating microscope important anatomic structures in orbital apex and the adjacent structures was observed and measured . The important structures of orbital apex anatomy include: the anterior clinoid process, optic canal, superior orbital fissure, Zinn tendon loop, and the total important nerves and blood vessels walking through this area.(1)The optic canal is an important bone crevice for communication betweenthe cranium and orbit,with four walls and two port. The Cranial aperture is horizontal oval,and orbital aperture vertical oval. The superior wall of optic canal is more long than the inferior wall. Normally we say the lenghth of the superior wall of optic canal as the optic canal, withn meaning lenghth 8.9 (5.5~11.5) mm. The interal wall is adjacent with sphenoid sinus and(or) ethmoidal sinus, 51.50% with sphenoid sinus. around 25% of the optic canal is completely surrounded by ethmoid air room. Cranial dura mater of skull base come back at the Cranial aperture of optic canal, and coated the optic nerve into the optic canal. the dura mater is called sickle-back fold, where only the dura mater covering the optic nerve.(2)Superior orbital fissure is the largest important bone crevices for communication between the cranium and orbit, which was divided by the tendon ringin to three areas, the lateral, middle and inferior. We measure three walls of the superior orbital fissure, which length are 16.04土2.18mm(the superior),19.58±2.50mm(the lateral), 9.05±1.57(the inferior). (3)The anterior clinoid process is a bone extending in small wing of sphenoid. The shape of the anterior clinoid process is Pyranlidal. The lenghth, width and thickness are 9.56±1.10 mm, 13.06±2.50 mm, 5.96±1.93mm. The anterior clinoid process is a posterio and medial continunation, next to SOF on anterior lateral, next to the lessor wing of the sphenoid bone on anterior lateral, next to optic canal on anterior and be jioned with strut, ICA pass by ACP,s internal, Cavernous sinus on ACP,s lateral side. (4) Zinn tendinous ring is formed by the periosteum of the orbital apex, dura of the superior orbital fissure and optic canal and optic nerve sheath dura elements together. Four rectus muscles originate in the Zinn tendon, and form muscle pyramid which is an important clinical anatomic symbol. (5)After the Cavernous sinus internal carotid artery walk upward and backward, named Clinoid segment. 75%of the ophthalmic artery originated from the medial wall of the internal carotid artery, together With the optic nerve into the orbit through the optic canal. After the lateral wall of the cavernous sinus cranial nerves with the upper and lower eye veins come into the orbit through superior orbital fissure, specifically: trochlear nerve, frontal nerve, lacrimal nerve and the ophthalmic vein pass by lateral, the lower branch of oculomotor nerve, fabducens nerve, nose and eyelashes nerve and ciliary ganglion of the sympathetic and sensory root by the central Ministry. (6) Frontotemporal-orbitozygomatic approach is complex and time-consuming, especially bone formation. there are limitations for traditional one piece of bone craniotomy,as well as improving two piece of bone craniotomy. We improve the craniotomy technology, firstly removing zygomatic arch,then using one piece of bone craniotomy. This simplify the craniotomy, save time and reduce bone defect with good results.Conclusion:1 Orbital apex as a anatomic concet is not yet a clear anatomical definition.We define this area as the region surrounded by the anterio clinoid process, optic canal and superior orbital fissure .2 The orbital apex is an important structure to communicate the Cranial cavity and orbit.In this narrow regional there are intensive cranial nerve and internal carotid artery and other important structures, these structures are difficult to separate.3 For large tumors in orbital apex and cranio-orbital tumors ,there are more difficulties to exposure, to separatation from the important vessels and nerves and excision. the frontotemporal-orbitozygomatic approach to this area provide a good exposure of lesion, surgical operations and perspective space, and more angle for lesions removed. So it is the most widely used approach for skull base surgery.4 This study explores to modify the tradition craniotomy to simplify the operation, saving craniotomy time, reduce surgical trauma and improve operative effection.5 The frontotemporal-orbitozygomatic approach have some limits , more trauma, complex and time-consuming craniotomy, the lack of standards ,and other limitations.This should be further developed.