Microanatomic Study Of Basilar Artery Bifurcation Through Pretemporal Approach

Part I Comparative Microanatomic Study of Pterional Approach and Pretemporal Approach to the top of the Basilar ArteryObjective: Comparative study of pterional approach and pretemporal approach to the top of the basilar artery and its surrounding structures with the head in the same position revealed the scope of the anatomical differences.Methods: Red latex-injected internal carotid arteries and vertebral arteries of 8(16 specimens) formalin-fixed cadaver heads were prepared. Both of the standard pterional craniotomy and pretemporal craniotomy were performed. The surgical exposure of basilar artery bifurcation and the surrounding critical anatomic structures were observed through interspace lateral to internal carotid artery of pterional approach and from the straight view of the pterional approach to the strictly lateral view of the subtemporal approach in pretemporal approach under microscope. Data obtained were analyzed with SPSS 10.0.Results: The vertical field of pterional in pretemporal approach provided exposure of the trunk of the basilar artery in 13例(81.25%)with a length of 5.02±0. 85mm through the interspace lateral to internal carotid artery and its bifurcation exposed in 12(75%)specimens. View of the temporal pole in pretemporal approach provided exposure of the trunk of the basilar artery in 5例(31.25%) with a length of 2.86±0.06 mm and its bifurcation exposed in 14(87.5%)specimens. The field of subtemporal provided exposure of the trunk of the basilar artery in 10例(62.5%) with a length of 3.01±0.45mm and its bifurcation exposed in 11(68.5%)specimens.Conclusions: 1.Basilar artery bifurcation and the surrounding critical anatomic structures can be exposed from pretemporal approach, ranging from the straight downward view of the pterional approach to the strictly lateral view of the subtemporal approach, but the trunk of the basilar artery is not exposed very well.2. In the case of low-positioned aneurysms, blockage with uncus of temporal, the big posterior clinoid process, pretemporal approach can be chosen.Part II Microanatomic Study of Interspace Lateral to OMN udner the view of Temporal pole and the Clinic Significance to Widen itObjective:To investigate the anatomic features of the interspace lateral to OMN from the view under the view of temporoplar then make improvements of pretemporal approach in order to achieve proximal control to contribute to operations of Aneurysm clipping in basilar artery bifurcation.Methods: Red latex-injected internal carotid arteries and vertebral arteries of 8(16 specimens) formalin-fixed cadaver heads were prepared. A standard pretemporal craniotomy was performed. The length BC between Intersection B of OMN and PCA to vertical point of intersection C of the tentorial free edge,AB between the point A of OMN into the tentorium and Intersection B and AC were measured from the view under temporoplar using an operating microscope. OMN sheath was amputated between OMN and tentorium cerebelli in the interspace later to OMN, moved the OMN inwards, cut tentorium cerebelli at the region which angle B corresponds to about 8mm parallel to the lateral margin OMN and so on to widen the interspace later to OMN then observed the increase the range of exposure. Data obtained were analyzed with SPSS 10.0.Results: Under the view of temporal pole, the length BC between Intersection B of OMN and PCA to vertical point of intersection C of the tentorial free edge is 2.15±0.90mm; AB between the point A of OMN into the tentorium and Intersection B is 4.74±0.75mm;the length of AC is 4.08±0.67mm. 2 (12.5%) of the origin of the SCA can be seen through the interspace lateral to internal carotid artery OMN.The SCA can be exposed in 16(100%)specimens. 3 (18.7.5%) of SCA arise as a double (or duplicate) trunk. The mean diameter of 13 single trunk of SCA at the point of intersection with the OMN is 1.56±0.10 mm. The increased exposure of the trunk of the basilar artery with a length of 5.42±0.17mm by amputating OMN sheath between OMN and tentorium cerebelli, cutting tentorium cerebelli between the OMN and the trochlear nerve sneak, moveing the OMN inwards under the tentorium. The length of the trunk of the basilar artery is 8.53±0.24mm, adding cutt tentorium cerebelli along the OMN between the OMN and the trochlear nerve. The range of perforating branches is from 1 to 4.Conclusions: 1.The triangle of interspace lateral to OMN is composed of three Margins, Lateral border of the oculomotor nerve, part of tentorium cerebelli and the border of Intersection B of OMN and PCA to vertical point of intersection C of the tentorial free edge.2.The contents of interspace lateral to OMN under the temporal view include part of the OMN sheath and part of the SCA. 3. The operation through interspace lateral to OMN, OMN and SCA should be identified and protected. 4.Tentorial incision along the direction of OMN at region corresponds to the angle between the lateral margin of OMN and the vertical line from the intersection point of OMN and the PCA to the tentorial free edge is relatively safe.5. Under the view of temporal pole, Increased exposure of the trunk of the basilar artery from the interspace lateral to OMN in order to achieve proximal control of Aneurysm clipping in basilar artery bifurcation can be achieved by cutting tentorium and moving the OMN inwards.