Sheet Sectional And Microsurgical Anatimic Studies Of Orbital Apex Region

Objective To provide detail morphological basis for imaging diagnosis and surgery by studying sheet sectional and microsurgical anatomy of the optic apex region. Methods (1)We observed the serial sheet sections of the optic apex region obtained using collodion microtomy in 4 adult cadaver heads; (2)High resolution CT scanning and three dimensional images of the optic apex region were observed and measured in 10 adult volunteers; (3)High resolution magnetic resonance images of the optic apex region were observed in 5 adult volunteers; (4)We observed and measured the osseous structures and contents of the optic apex region in 30 dry skulls and 15 cadaver heads of adult Chinese; (5)Transcranial approaches to the optic apex region were performed in 3 cadaver heads under operating microscope and endoscope.Results (1)We described the morphological characteristics, relationship and the variation's law of the optic apex region and its contents in the serial sheet sections. (2)The osseous structures of optic apex could be demonstrated well using high resolution CT and three dimensional rendering techniques. The intraorbital and intracanalicular segments of optic nerve could be showed in the same transverse plane in 80.00%, which Reid's base line was used as baseline. (3)The nerves, vessels and extraocular muscles passing through the optic apex region could be showed well using high resolution MRI. In frontal and oblique frontal planes, the appearance rate of the inferior branch of oculomotor nerve was 100% and that of ophthalmic artery was 90.00%. In frontal and transverse planes, the appearance rates of medial and lateral rectuses were 100%. (4)The optic apex region was formed by optic canal and superior orbital fissure. The superior, inferior, medial and lateral walls of optic canal were 8.87 2.01mm, 5.89+ 1.32mm, 8.45 + 1.54mm and 8.01 1.45mm in length respectively.The length of superior, medial and lateral the wall of superior orbital fissure was 19.09 2.65mm, 7.42 1.24mm and 18.95 2. 50mm in turn. (5)The mostly structures passing through optic canal were optic nerve and ophthalmic artery. Optic nerve was divided into intraocular, intraorbital, intracanalicular and intracranial segments, which was sigmoid in the orbit. All of the ophthalmic arteries were divided from internal carotid arteries. Ophthalmic artery lay to the inferomedial of optic nerve in 62.07% in the cranial orifice of optic canal, to the inferolateral in 86.21% in the orbital orifice of optic canal, which was divided into three segments and formed two curves in the orbit. (6)Superior orbital fissure was divided into lateral, central and inferior area by the anulus of Zinn. Lacrimal, frontal and trochlear nerves and superior ophthalmic vein passed the lateral area. The superior and inferior branches of oculomotor nerve, nasociliary and abducent nerves and the sensory and sympathetic roots of ciliary ganglion went via the central area. The structure passing through the inferior area was only inferior ophthalmic vein. (7)Transcranial approach to the orbital apex region was divided into three types: medial, central and lateral approaches. The medial approach exposed the medial part of the orbital apex region well. The central approach only exposed the midportion of the intraorbital segment of optic nerve. The lateral approach exposed the lateral part of the orbital apex region well, as well as superior orbital fissure region. Conclusions (1)Serial sheet section combined with embedding in collodion was applied to study the sectional anatomy of orbital apex region as well as that of other part. The method was simply, practicably and could be oriented accurately. (2)The frontal plane demonstrated the orbital apex region and its contents well which helped to clinic diagnosis. (3)High resolution CT and MRI and three dimensional rendering techniques were the best methods to study the morphology of orbital apex region in vivo. (4)When the disease of orbital apex region took place, MRI was the best examination method and CT was used as assistant method.