Clinically Applied Anatomy Of The Hypoglossal Canal Area

PartⅠMicrosurgical anatomy of the osseous hypoglossal canal and its osseous adjacent structures.Purpose:To study the morphology,dimension and relation of the osseous hypoglossal canal(HC) and its adjacent bony structures for further study of surgical approach in this area.Methods:The osseous hypoglossal canal(HC)and its adjacent osseous structures were observed and measured anatomically,and bilateral differences in distance were statistically analyzed on 25 dry specimens of adult skull base bone and 15 dry specimens of atlas.Three wet specimens of randomly selected adult standard head and neck were made axis line,and coronal CT scanning before they were seperated by thin-layer slices(cross-sectional,1case; sagittal,1;coronal plane,1).Results:In the view of the base skull,the long axis of the occipital condyle and the outer edge of the foramen magnum parallel to the first half;hypoglossal canal was hidden in between occipital condyle and anterior, medial and inferior to the jugular foramen.The angle formed by HC and sagittal plane in left and right side was 42.2±3.4(34.5～47),42.5±3.5(34～47.8)degrees respectively.The angle formed by HC and condylar canal which was present 64% was about 48 degrees.Occipital condyles from the posterior pole to deutostoma of condylar canal left 4.8±1.0(3.5～7) mm,right 3.9±1.1(2.1～6) mm.The distance between jugular tubercle and the surface of nodules on the hypoglossal canal wall was about 5mm.The distance between jugular foramen and hypoglossal canal endostoma was about 9mm.The distance between the posterior edge of occipital condyle and intracranial orifice or extracranial orifice of hypoglossal canal was 13.08±2.3mm(left),16.8±2.4 mm;13.24±2.3 mm,17.1±2.5 mm(right). Transverse process of atlas were left around the length of 9.27±1.6(6.5～12.5) mm;right 9.29±1.8(6.1～12.3) mm.Occipital cervical process is located in between mastoid and occipital condyle,and the posterior medial of styloid process,and it is the landmark of of posterior edge the jugular foramen.Transverse sinus and sigmoid sinus is a turning point in the former asterion,and the occipital protuberance to the zygomatic arch outside the root symbol was connected to transverse sinus.Asterion is the importance of readily identifiable anatomical landmark,but the relationship between the transverse sinus and it is not constant, and exists variation,15 lateral(30.0%) sites are located in transverse sinus,17 sides(34.0%) upper the transverse sinus groove,18 sides(36.0%) under the groove of the transverse sinus.Conclusion:Hypoglossal canal is located deeply and it is very difficult to expose it.Occipital condyle,jugular tubercle,transverse process of atlas are the main obstacles in the access to the hypoglossal canal region; asterion,mastoid,styloid process,jugular tubercle,occipital condyle are the main osseous signs of lateral approach to the hypoglossal canal region;occipital condyle, jugular tubercle are the most important osseous landmarks and objectives by far lateral approach to deal with condylar,cranial nervesⅨ,Ⅹ,ⅪandⅫand the lesions of ventral brain stem in the middle and lower clivus. Part 2 Microsurgical anatomy features of the hypoglossal canal and its adjacent structures the microsurgical anatomy featuresPurpose:To investigate the Microsurgical anatomy features of the hypoglossal canal(HC) and its adjacent structures for the further study of surgical approach in this area.Methods:The microsurgical anatomy of the extracranial muscles,nevres and vessels in the caniocervical junction region(CCJR) were investigated in 8 cadaveric head-neck specimens posterolaterally and anterolaterally, respectively.Then the transverse process of the atlas(TPA),occipital squama, occipital condyle and jugular tubercle were removed to observe the content of HC and the relationship of nerves and vessels with in HC and between HC and its adjacent structures.Results:1.caniocervical junction region(CCJR) can be divided into the lateral side of the former parapharyngeal space and hind suboccipital area by transverse process of the atlas,the former is the main access to the skull base arteriovenous large blood vessels(ICA,ECA,IJV,EJV) and cranial extracellular latter cranial nerve and so on,the latter is mainly the suboccipital suboccipital muscles and the vertebral artery and vertebral venous plexus.In the parapharyngeal space,the stylid diaphragm is an important anatomical landmark and the parapharyngeal space is subdivided into prestyloid and poststyloid compartments by the stylid diaphragm.There were internal carotid artery,internal jugular vein and theⅨ,Ⅹ,Ⅺ,Ⅻcranial nerves in the retroparapharyngeal space.The suboccipital triangle and ventral branch of C2 nerve were the important marks,and rectus capitis lateralis was the important symbol to identify the jugular foramen.2.The hypoglossal nerve(HN) path and contents of HC The HN is divided into three main parts:cisternal,intracanalicular and extracranial.It is the newly described 'hypoglossal' triangle in the anterior neck that is bordered by the descending hypoglossus laterally,transverse hypoglossus inferiorly and inferior border of the stylohyoid muscle superiorly.The structure is constant,and easily identifiable.HC wall is made up from compact bone.In the mill the emergence of the compact bone from cancellous bone that wall mean reaching the HC.From the former direction to the rear there are the venous plexus mainly,hypoglossal nerve, ascending pharyngeal artery through the hypoglossal canal and hypoglossal nerve is envelopped by the whole hypoglossal nerve sheath.Conclusion:TPA can serve as an important landmark in identifying important structures in suboccipital area, however it is also a big handrance which blocks the access to extracranial orifice of HC posterolaterally.Styloid is the key to anatomy of parapharyngeal space.Hypoglossal nerve can be identified safely according to its features of either extracranial or intracranial part.HC wall is the first forecasting set preserving hypoglossal nerve.The venous plexus of HC is a landmark to identify HC and aslo is the second forecasting set preserving hypoglossal nerve.Hypoglossal nerve sheath is the final barrier to protect hypoglossal nerve against injury.'hypoglossal' triangle in the anterior neck is an important anatomical landmark in order to find extracranial hypoglossal nerve,master of whose anatomical characteristics is conducive to the anterior lateral approach in the identification of nerves,accurate positioning and retrograde exploration from hypoglossal hypoglossal nerve to extracranial orifice of HC.Part 3 3-D CT reconstruction of Hypoglossal canal and its adjacent structures and digital simulation for surgical approach-related qualitative and quantitative analysisObjective:Construction of 3D visualization of the CCJR model,preliminary exploration of the function of the model,Clarify the anatomy of the HGCA structure and the distribution of spatial relations,for the HGCA clinical treatment of surgery figures provided by the choice of three dimensional anatomical basis.Methods:Specimens of 10 cases of normal adults were selected randomly by the 64-slice spiral CT examination(including C4-dorsum sellae and CT enhance,the scanning slice thickness 0.3 mm).CT data were entered into the computer using the materialise interactive medical image control system (Mimics) software to deal with three-dimensional reconstruction of hypoglossal canal and adjacent structures,construction of the the CCJR that contains craniocervical arteries,venous system.The hypoglossal canal and the approach-related adjacent structures were made anatomical observation and measurement,and comparative analysis to autopsy results,the quantitative analysis of simulation for surgical approach to cut the main bone obstacles for expanding the scope of perspective.Results:Three-dimensional visualization model of CCJR was set up.Through observation and measurement of two-dimensional and three-dimensional space for models,the level of results and autopsy was illustrated with consistent results including anatomical layer,the important point of view and distance.Conclusion:The CCJR virtual human data can be reconstructed by Mimics software.This model relations in the structure adjacent to the display, intuitive and easy to quantify positioning measurement of the structure has advantage s such as functional;But the current virtual human data collection and the establishment of the visualization model can not meet the research of some fine anatomical struc ture,still can not be used for the true simulation training of the surgical approach,waiting to be continuously improved and developed.