| Objective: To obtain the anatomical data around posterior-lateralstructure of the foramen magnum from dissecting cadaveric adult heads underthe microscope, then observing, measuring and describing the region’s bones,nerves, blood vessels, dura mater, muscles and other structures about theiranatomical characteristic. We explore the methods and meanings about theremoval occipital condyle, the jugular tubercle and other bones, mastering themicroscopic anatomical features of far lateral suboccipital approach. Thepurpose was to provide a reference and anatomic basis for safely cutting theposterior circulation aneurysms.Methods:1Six （12sides） adult cadaveric heads with neck that were fixed with10%formalin, dissecting the cervical vessels, rinsing the thromboses, perfusingwith red and blue latex; then imitating the far lateral suboccipital approachunder the training microscope, dissecting the cervical muscles, resecting thearch and lateral mass of atlas, opening the dura mater, exposing the vertebralartery, posterior inferior cerebellar artery and other nerves to measure therelevant data.2In clinical, we chose five patients who got posterior circulationaneurysms, including3cases of posterior inferior cerebellar artery aneurysms:1case of vertebral artery aneurysm;1case of vertebrobasilar artery unionaneurysm; The far lateral suboccipital approach was adopted to clip posteriorcirculation aneurysms under the guidance of anatomy studies, then analyze thesurgical exposure and effect.Results:1Suboccipital triangle was an important anatomic landmark to exposethe vertebral artery, and the triangle was composed of three muscles, namely,superior oblique, inferior oblique and rectus capitis posteriormajor muscle.There was vertebral artery, muscular branches, vertebral venous plexus and the first cervical nerve via the triangle.2When vertebral artery goes through the transverse foramen of atlas, ittravels inward along the vertebral artery groove, bypasses the rear of theatlanto-occipital joint, then penetrates the dura mater reaching theintracerebral region, at last left and right vertebral arteries unite to form thebasilar artery in the junction of pons and the medulla oblongata. This segmentof vertebral artery （V3segment） is closely related to far lateral suboccipitalapproach, the left and right diameter of vertebral artery has big variation, andoften the difference of the diameter has more than1mm. The diameter ofvertebral artery（V3segment）: left side （3.54±1.21）mm, rightside（2.99±1.13）mm; the distance from the place of vertebral artery acrossingdura mater to the posterior median of foramen magnum: left side（22.70±4.48）mm, right side（22.73±2.34） mm; the distance from the place ofvertebral artery acrossing dura mater to the trailing edge of occipital condyle:left side （22.07±4.21）mm, right side （22.41±2.66）mm3Posterior inferior cerebellar artery has very large variation, and it runstortuously and forms vascular loops that have uncertain direction. Also theartery is closely related to the posterior cranial nerves and cerebellun.Sometimes, one side or both sides of posterior inferior cerebellar artery isabsent. One case in of this group who has one side of posterior inferiorcerebellar artery is absent. The diameter of the origin place of posteriorinferior cerebella artery: left side （1.39±0.30）mm, right sid e（1.47±0.484）mm.4The occipital condyle and jugular tubercle are two very importantanatomic landmarks in the operation; resection of them in moderation caneffectively increase the surgical exposure range and operating space,especially in the occlusion of vertebro-basilar artery union aneurysms,resection of part bones is necessary.5According to the score evaluation of GOS, the outcomes: in the5cases,3cases had good recovery,1case got mild disability,1case diedpostoperatively.Conclusions:1Being familiar with the anatomical level of muscles in the far lateralsuboccipital approach; grasping the traveling relations of the posterior inferiorcerebellar artery and vertebral-basilar artery, and their branches and variations; and understanding the relationships of these arteries and posterior cranialnerves, we can fully expose posterior circulation aneurysms and safety clipthem, simultaneously we can provide effective protection for posterior cranialnerves, cerebellum and brain stem.2Resecting of occipital condyle and jugular tubercle in moderation caneffectively increase the surgical exposure range and operating space of theventral and ventrolateral region of foramen magnum.3The vertebral artery, posterior inferior cerebellar artery, the confluenceof vertebral-basilar artery can be fully exposed by far lateral suboccipitalapproach, and vertebral artery can be early freed, the blood supply ofaneurysms can be early blocked too, so this approach is very ideal for safetyclipping posterior circulation aneurysms. |
