侧裂池蛛网膜结构及其与大脑中动脉分级关系的解剖学研究

Anatomical study of arachnoidal structures around sylvain fissure and it's relationship to the branches of middle cerebral artery

目的研究颅内侧裂池蛛网膜层次及其和大脑中动脉(MCA)各级分支间的关系及其临床意义。方法取成人尸头6例(12侧),显微镜下观察外侧裂膜性结构层次及侧裂池构成,解剖MCA各支分布及其和膜性层次间的关系。结果侧裂池由外向内共有4层蛛网膜结构,分别是远外侧侧裂膜(FLSa)、外侧侧裂膜(LSa)、中间侧裂膜(MiSa,内层和外层)和内侧侧裂膜(MeSa)。12侧标本中,4层膜性结构均完整的6侧。FLSa通常菲薄,覆盖在侧裂浅静脉表面,和静脉外膜粘连紧密;LSa相对致密,构成了侧裂池的真正外侧壁,并分隔MCAM3和M4段;沿MCAM3段走行,有相对菲薄的MiSa浅层覆盖并将其固定在侧裂池内;在M2和M3段交汇处,见相对致密的MiSa深层,包绕M3段起始部,并将侧裂池分为前后两部,3侧标本中该层菲薄稀疏,呈网眼状;而在M1和M2段间有非常致密的MeSa,分隔侧裂池和颈内动脉池,5侧标本中,该膜菲薄呈网眼状。结论侧裂池蛛网膜的分层分布和MCA各级动脉关系密切,掌握其解剖特点有利于术中充分解剖侧裂池和颈内动脉池。其膜性分布的个体化差异,可能影响MCA动脉瘤的出血方式。

Objective This study aims to investigate the layers of arachnoidal structures and illustrate the relationship between the arachnoid membranes with branches of middle cerebral artery（MCA）.The related clinical issues are discussed. Methods Six cases of adult cadaveric heads（twelve sides） were dissected under the microscopy. The construction of Sylvain fissure cistern and the different layers of arachnoidal membranes were observed. The course of MCA＇s branches and its relationship to the aforementioned membranes were analyzed. Results A total of four layers of membranes composed the sylvain fissure cistern. From outer to inner, it was far lateral sylvain arachnoid（FLSa）, lateral sylvain arachnoid（LSa）, middle sylvain arachnoid（MiSa） and median sylvain arachonid（MeSa） respectively. Among the 12 sides of specimens, four layers of fully complete and intact membranes were observed in 6 cases. FLSa was always thin with covering among the superior sylvain vein and fusing with the vascular extima. After opening the FLSa, a related thicker membrane named LSa actually served as the lateral wall of sylvain fissure cistern. It existed in all cadavers and separated M3 and M4 segments of MCA. With deeper dissection along the distribution of M3 segment, the outer layer of MiSa was observed to fix artery in the sylvian cistern. A significant inner layer of MiSa was identified around the original part of M3, and divided sylvian cistern into anterior and posterior parts. In 3 cases, this membrane was thinner and cancellous- like in appearance. The deepest layer of membranes was MeSa, which separated M1 and M2 segments. It served as the inner wall of sylvain fissure cistern and lateral wall of internal carotid artery cistern. In five sides of specimens, this membrane was thin and cancellous. Conclusion Stratification distribution of sylvain arachnoidal membrane shows close relationship with different segments of MCA. Its individualized contribution might influence the bleeding characteristics of MCA aneurysm.