Microanatomy And Virtual Imaging Anatomy Of Transanterior Approaches To The Clivus

Objectives:cadaveric heads were dissected under microscope, to provide the microanatomical information of the relative anatomical constructions for the transanterior approaches. The safety limits in bone removal of clivus and the methods to protect internal carotid artery and cranial nerves were investigated. The virtual anatomy was investigated via transanterior approaches in a virtual-reality (VR) setting, to establish a virtual anatomical model and explore the application value of the VR technology.Methods:The sphenoid sinus, internal carotid artery, cranial nerves, clivus dura and stuctures behind clivus dura were dissected, observed, measured and photographed under the operation microscope by using 7 adult cadaveric heads and 10 adult cranial bones.20 patients were given CT angiogram with Discovery Ultra 16 and 3.0T MRI lamellar examination. The datum were collected and inputted into the Dextroscope in the DICOM format. The virtual imaging anatomy of clivus and three-dimensional reconstruction and visualization research were carried out via the transanterior approaches in the virtual-reality (VR) setting.Results:1.The clivus was composed of three parts.the length of upper,middle and lower clivus was (17.8±4.2) mm (10.1～22.3mm),(17.3±3.9) mm (13.0～22.9mm),(12.0±4.0) mm (5.1～18.4mm). The bone thickness of upper,middle and lower clivus in the median line was (6.1±3.9) mm (0.5～11.5mm),(9.6±2.7) mm (5.1～13.4mm),(6.7±2.9) mm (4.3～12.2mm)2. The clivus bone windows of transnasal and sublabial transnasal approaches were the same. The laterial limits of clival bone removal were internal carotid arteries, the average distance between internal carotid arteries was (18.0±1.8) mm, the mininum was 15.2mm. Dorsum sellae and posterior clinoid process were difficult to reveal because the restriction of pituitary, the superior limits of clival bone removal was sellar floor. The inferior extending of clivus bone windows only reached to (27.9±1.3) mm below sellar floor as the restriction of the maxilla and hard palate.3. The limits of clivus bone window of transoral approach were sellar floor superiorly and inferior margin of clivus inferiorly, the distance between them was (40.7±5.4) mm. The laterial limits of clivus bone removal between sellar floor and hypoglossal canals were internal carotid arteries, the average distance between internal carotid arteries was (18.0±1.8) mm. Between hypoglossal canals and the inferior margin of clivus, the laterial limits were the inner margins of hypoglossal canals,the distance of them was (24.9±1.3) mm.4. The skull, sphenoid sinus, internal carotid artery, pituitary, brain stem and basilar artery were reconstructed through the automatic extraction function of the Dextroscope. And they were colored with the Color Mode to differentiate various anatomical structures. Moreover, the reconstructed structures could be combined randomly to observe spatial anatomical relationship. With the Stereo Mode and Three-Plane Mode, the reconstructed structures could be displayed in situ, cut and revolved multi-azimuthally and multi-angularly. Preoperative training could be conducted via simulating the surgical approach.5. The anatony structures which needed to be handle were different by simulating the transnasal, sublabial transnasal and transoral approaches in the virtual-reality (VR) setting. The laterial limits of clivus bone removal under the virtual-reality were the internal carotid arteries and hypoglossal canals.Conclusions:1. The morphosis of clivus is very important in transanterior approaches to clivus. Internal carotid arteries, abducens, basilar venous plexus and brain stem are important structures which need to be orientated exactly during the operation.2. The superior limits of clival bone removal is sellar floor. The inferior extending of clivus bone windows only reach to about 27mm below sellar floor as the restriction of the maxilla and hard palate. The laterial limits of clival bone removal of transnasal and sublabial transnasal approaches are internal carotid arteries.3. To reveal the upper clivus need to cut the soft palate and remove part of the hard palate via tranoral approach. The boundaries of clivus bone removal are sellar floor superiorly and inferior margin of clivus inferiorly. The laterial limits of clivus bone removal between sellar floor and hypoglossal canals are internal carotid arteries. Between hypoglossal canals and the inferior margin of clivus, the laterial limits are the inner margins of hypoglossal canals.4. By using the Virtual Reality Technology, virtual anatomical models of the transanterior approaches can be reconstructed, which disclose the adjacent relations and space allocation about different anatomic structures, and provide the reference for transanterior approaches in preoperative anatomic evaluation.5. The surgeon is allowed to observe dynamicly and stereoly the anatomic structures of transanterior approaches, especially the anatomic details and heteromorphosis of the sphenoidal sinus, Internal carotid arteries, abducens, basilar venous plexus and brain stem by Virtual Reality technology simulating transanterior approaches, to provide the reference for preoperative evaluation and operation planning.