The Study On The Microanatomy Of Operative Approaches To The Aneurysms Of The Posterior Circulation

Objective 1.To study anatomy of the posterior circulation,and therefore provide anatomical bases for relevant clinical operations in this area such as the aneurysms and the intervention operation.2.Mimicking approaches to the aneurysms of the posterior circulation,describle operative approaches of the scope and compare difference of these operative approaches.Methods 1.The vertebro-basilar artery of 15 formalin-fixed adult brain specimens (30 sides)with intact dura mater were dissected under the surgical microscope.The length,diameter were measured and counted;their shapes,courses,branches and connections were observed and recorded.2. The approaehes were made respectively on fifteen cadaverie head specimens, including pterional approach,subtemperal approach,orbitozyogmatic approach,extended middle fossa approach,supra-and infra-tentorial transpetrosal presigmoid approach,far lateral approach. The skull base surgical technic related to these approaches were drilled and summarized. The advantages and disagvantages of these approaches were evaluated.Results 1.The branches,the course and variability of vertebro-basilar artery was observed on cadaverie head specimens.Significant asymmetry of caliber of V4 are 4 cases,shifting and curve V4 are 3 cases. Variation of origination of the posterior inferior cerebellar artery is more common. The shape of basilar artery is irregular. The superior cerebellar artery is latent symmetry, there are two trunks on one side sometimes. The posterior communicating artery is enlargement in two cases and their blood supplying came from internal carotid artery of same side.2. From the process of pterional approach we observed comparatively large variation of the second interspace. The exposure to apical of basilar artery was enlarged if we elevated the CNâ…¡or ICA. The exposure angle was enlarged after removing the anterior clinoid process.we can gain better expose after removing posterior clinoid process and elevating CNâ…¡.3.Subtemprol approach permit observation from anterior and lateral direction to top of basilar artery.Trough the visual fields of subtemprol approach we can expose posterior communicating artery,anterior choroidal artery,oculomotor nerve and posterior cerebral artery.Elevating posterior communicating artery and oculomotor nerve made for the exposure of basilar artery.The discussion of tentorium of cerebellum extend exposure of superior segment of basilar artery.4. Through orbitozyogmatic approach we removed anterior clinoid process and opened lateral wall of cavernous sinus which increase the exposure to top of basilar artery.5. We observed dependency structure and anatomy of extended middle fossa approach. Microsoftiddle meningeal artery,GSPN,arcuate eminence are important mark of this approach.Through this approach we can expose middle and superior segment.6. Through supra-and infra-tentorial transpetrosal presigmoid approach we observe the distance of PS point to important structure in petrous bone. We also observed canal for facial nerve and drilled how to cut dura mater and tentorium of cerebellum.Through two degree measures observe basilar artery trunks.7. Relevant anatomy of far lateral approach was surveyed.In this approach we can observe the origin of posterior inferior cerebellar artery.Conclusion 1.Normal and variable vertebro-basial artery have important significance on neurosurgery and angiograms.2.Combined anterior approach adding manipulate of cavernous sinus and tentorium of cerebellum can increase exposure.3.Through petrous bone approach can arrive the aneurysms of basilar artery trunk. Combining petrous part approach and subtemporal approach adding dissection of tentorium of cerebellum can extend the exposure.4.We can treat the aneurysms of vertebral artery trunk through far lateral approach. Shifting vertebral artery, removing occipital condyle and jugular eminence can increase internal exposure.5.This study focused on the posterior circulation aneurysms,for the first time systematically studied relevant microanatomy of approaches,which has important reference value on surgical treatment of posterior circulation aneurysms.