Clinical Anatomy Of The Lateral Skull Base

ObjectiveThe goals of this study were to obtain more detailed microanatomic information of the lateral skull base, to study the sectional anatomy and imaging and to build the 3D reconstruction model and the replica of the lateral skull base to explore vascular landmarks and spatial relationships of the important structures, for providing the morphological basis for clinical image diagnosis and lateral skull-base surgery. To examine the feasibility and reliability of cranial surface anatomic fiducials to register computed tomographic images of the lateral skull base by using StealthStation navigation system. Methods1. The distance between bony landmarks and foramina in the lateral skull base were determined by measurement of 50 (100 sides) dry lateral skulls. We established a three-dimensional cooradinate system of the skull base on the basis of the principle of analytical geometry and measured the three-dimensional coordinate values of bony landmarks of 20 (40 sides) adult lateral skull base.2. Ten lateral skull base blocks were obtained from five human cadavers, a plastination technique was used to make equidistant serial thin sections on the coronal, sagittal, and axial planes with 1.0mm in thickness, comparing with the images of HRCT and MRI.3. On SGI workstation, a Contours + Marching Cubes algorithm was selected to reconstruct the temporal bone, intratemporal structures, parapharyngeal space, and jugular foramen in three-dimensions. The improved Medview 1.0 software was used to convert the mcb format of the 3-D data to STL format, then the STL file input into the rapid apparatus ZIPPY III, the 3D stereo physical model of the lateral skull base was built.4. Using 15 (30 sides) adult cadaver heads, rm'crosurgical anatomy and measurement were performed by mimicking the preauricular subtemporal -infratemporal and presigmoid approach. We observed the infratemporal fossa, parapharyngeal space, styloid diaphragm, jugular foramen, the anatomic relationships of the muscles, arteries, nerves, and veins were carefully recorded, special attention was given to the internal carotid, cranial nerves and labyrinth and their relationship to the structures in the temporal bone.5. Using 10 adult cadaver heads, surface anatomic fiducials such as the tip of the mastoid process, the umbo of the tympanic membrane, Henle's spine, the root of the zygoma and various sutures were used for registration of CT-images of the lateral skull base. The registration error and target localization error were determined.Results1. The distance from the lateral border of the carotid canal to the root of the styloid process is 10.36 ?.14mm (left) and 9.58 ?1.87mm (right), to the posterior root of the zygomatic arch is 29.31 + 2.69mm (left) and 29.66 +2.98mm (right), to the mastoid tip is 34.01 ?.53mm (left) and 33.01 ?.26mm (right). The carotid canal, the foramen spinosum and the outer orifice of pterygiod canal form a right angle triangle, so do the carotid canal, the mastoid tip and the hypoglossal canal.2. We measured 17 bony landmarks in internal surface and 11 bony landmarks in external surface of the lateral skull base, and three-dimensional coordinate values of 53 measured points were obtained.3. Ten thin serial plastinated slices of 1.2mm in thickness of axial, coronal, and sagittal orientations were obtained. The impregnation with epoxy resin results in transparent, odorless, durable slices demonstrating excellent distinction of connective tissue, muscles, nerves, blood vessles, and the intratemporal organs of the lateral skull base. We found a good overall correlation between plastinated slices, CT and MRI images.4. On a SGI workstation, the final 3D reconstruction model contains many of the important structures encountered during lateral skull base operation such as the labyrinth, cochlea, facial nerve, auditory ossicles, auditory tube and the carotid artery, sigmoid sinus, jugular bulb, among others. The reconstructed structures can be displayed singly...