Microanatomic Study Of The V4 Segment Of The Vertebral Artery

Objective:The microstructure of the V4 segment(intracranial segment)of the vertebral artery in the suboccipital approach was studied by anatomical of cadaveric head.We can be familiar with the operation field of vision which can be exposed by this approach,observing and measuring the anatomic datas of the important branches of the V4 segment of vertebral artery accurately.Anatomical basises for the operation of clinical surgery can be acquired by observing the relationship between the V4 segment of vertebral artery and the adjacent nerves.Reducing or avoiding the possibility of injury for important vessels and nerves in clinical surgery,reducing the incidence of postoperative complications.Methods: Arteries and veins of 10(20 sides)of the cervical adult cadaver head specimes with cervix were dissected after soaked with medical alcoho,and the thrombuses in the arteries and veins are repeatedly rushed out,pouring red and blue perfusion which is well prepared well into arteries and veins.The perfused cadaver heads are anatomized through surgical microscope for training by suboccipital far lateral approach.The muscles and arteries were dissected,and the bone flap was removed routinely,removing the posterior arch and lateral mass of atlas and part of the occipital condyle,exposuring the intracranial branchs of the vertebral artery by opening the dura,observing and measuring accurately the datas of length and diameter of arterial branches.These datas can be benefit to know more aboat the location and relationship of the vertebral artery and its branches with peripheral nerves and tissues.Results:1 Suboccipital triangle is a triangular space made up of superior oblique,inferior oblique and musculi rectus capitis posterior and it is great significant to identify vertebral artery.Vertebral artery,C1 nerve and the venous plexus surrounding the vertebral artery across horizontally in the suboccipital triangle.Therefore,we can judge the position of vertebral artery by the adjacent relation for muscles in suboccipital triangle and the venous plexus around the vertebral artery.2 The bilateral vertebral arteries are formed the basilar artery in front of the brain stem after they entering the dura.The relationship between the posterior cranial nerve and the vertebral arteries is related closely in the course of the vertebral artery.The length of the V4 segment of left vertebral artery is(33.13 + 1.12)mm,the rightside is(32.95 + 1.22)mm.The mean diameter of the V4 segment of the left vertebral artery is(4.04 + 0.85)mm,the rightside is(3.96 + 0.95)mm.The main branches of the intracranial vertebral artery areanterior spinal artery,posterior spinal artery and posterior inferior cerebellar artery.Among them,the posterior inferior cerebellar artery is the largest branch of the intracranial segment of the vertebral artery and a good place for the intracranial aneurysms.The posterior inferior cerebellar artery can be divided into five parts(Ant.Wed.Seg,Lat.Wed.Seg,Ton.Wed.Seg,Telo.Velo.Ton.Seg,Cortical.Segment),mainly supplying medulla and cerebellum.The variation of the initial point of the posterior inferior cerebellar artery is large,which is mainly origined from the middle and upper part of the intracranial segment of the vertebral artery.In the same specimen,the origin of the posterior inferior cerebellar artery is not identical,and the posterior inferior cerebellar artery is absent in some specimens.In the the formation process,the posterior inferior cerebellar artery have a lot of vascular loops whose size and direction are changeable,and it is more closely linked with the surrounding nerves and the organizations.The posterior inferior cerebellar artery and the posterior cranial nerve are adjacent to the inferior complexux.The posterior inferior cerebellar artery contribute to transformation of these nerve roots.The initial crater of the left posterior inferior cerebellar artery is(1.42 + 0.31)mm,and the crater of the right posterior inferior cerebellar artery is(1.53 + 0.46)mm.The distance between the starting part of the left posterior inferior cerebellar and the position vertebral artery entering the dura is(17.32 + 3.41)mm,while the distance between the initial part of the right cerebellar artery and the position vertebral artery enter the dura is(18.10 + 3.72)mm.The variation of the starting point of the posterior spinal artery is large,posterior spinal artery usually start from the position where vertebral artery entering the dura,and posterior spinal artery of some specimens origin from the posterior inferior cerebellar artery.Part of the posterior spinal artery is accompanied by the vertebral artery in the position of the vertebral artery entering the dura,so the posterior spinal artery should be protected when the dura is cut in the far lateral suboccipital approach.The starting point of anterior spinal artery located in the ending of vertebral artery,bilateral anterior spinal artery are merged alone in the anterior median fissure,then the artery walking down the line.The initial part of the anterior inferior cerebellar artery vary largerly,and a majority of the anterior inferior cerebellar artery is located at the lower end of the basilar artery,a small number of the anterior inferior cerebellar artery origin from the upper part of the V4 segment of the vertebral artery.The anterior inferior cerebellar artery usually downward under the outer side after origining from the origin,bypassing the middle cerebellar peduncle,forming vascular loop.The anterior inferior cerebellar artery is closely related to the facial nerve.Conclusions : Mastering the course of vertebral artery and paying attention to isolation and protection for vertebral artery,being familiar with the far lateral approach to the revealation of the V4 segment of vertebral artery,mastering the adjacent relationship of vertebral artery and its branches with surrounding tissues and nerves,paying attention to protect the branches of the V4 segment of vertebral artery,providing anatomic datas support for clinical surgery.