Kawashima Masatou, Matsushima Toshio, Sasaki Tomio
Department of Neurosurgery, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
J Neurosurg. 2003 Sep;99(3):517-25. doi: 10.3171/jns.2003.99.3.0517.
Most distal anterior cerebral artery (ACA) aneurysms arise at the pericallosal-callosomarginal artery (PerA-CMA) junction, which is usually located in the A3 segment of the ACA around the genu of the corpus callosum. Aneurysms in the PerA-CMA junction are divided into two types according to their location: supracallosal and infracallosal. Infracallosal distal ACA aneurysms are defined as those located in the lower half of the A3 segment, which makes it more difficult to gain proximal control. In this study, the authors examined the microsurgical anatomy of the distal ACA region, focusing especially on the relationship between the PerA and CMA located in the lower half of the A3 (infracallosal) segment, and present a surgical strategy for dealing with distal ACA aneurysms.
The microsurgical anatomy of the distal ACA region was examined in 22 adult cadaveric cerebral hemispheres after perfusion of the arteries and veins with colored silicone. The relationships of the infracallosal segment of the PerA to the CMA and the A2 segment of the PerA to the frontopolar artery were examined. The distance between the nasion and the site at which a parallel line directed along the long axis of the infracallosal PerA just proximal to the origin of the CMA artery crosses the forehead (which we have named the PC point) was also measured. Surgical approaches to distal ACA aneurysms were examined in stepwise dissections.
The PerA-CMA junctions were located in the supracallosal and infracallosal segments of A3 in 36 and 55% of cases, respectively. In the infracallosal region, it was difficult to identify the proximal PerA and to establish proximal control of the vessel. The infracallosal part of the proximal PerA coursed almost parallel to the frontal cranial base, and the PC point was 42.2 +/- 15.9 mm (mean +/- standard deviation) from the nasion. These findings indicate that there is only a limited space in which to access an infracallosal distal ACA aneurysm below the PC point and establish proximal control by the anterior interhemispheric approach. When the approach is made above the PC point, an anterior callosotomy may be necessary to establish proximal control before final aneurysm dissection and clip placement are completed. The PC point is an important surgical landmark in planning the surgical strategy for infracallosal distal ACA aneurysms.
大多数大脑前动脉（ACA）远端动脉瘤起源于胼周-胼缘动脉（PerA-CMA）交界处，该交界处通常位于胼胝体膝部周围的ACA A3段。PerA-CMA交界处的动脉瘤根据其位置分为两种类型：胼胝体上型和胼胝体下型。胼胝体下型ACA远端动脉瘤定义为位于A3段下半部分的动脉瘤，这使得获得近端控制更加困难。在本研究中，作者研究了ACA远端区域的显微外科解剖结构，特别关注位于A3（胼胝体下）段下半部分的PerA和CMA之间的关系，并提出了处理ACA远端动脉瘤的手术策略。
在22个成年尸体脑半球中，用彩色硅酮灌注动脉和静脉后，研究ACA远端区域的显微外科解剖结构。研究了胼胝体下段PerA与CMA的关系以及PerA A2段与额极动脉的关系。还测量了鼻根与沿着胼胝体下PerA长轴方向且恰好在CMA动脉起源近端的平行线与前额相交处（我们称之为PC点）之间的距离。通过逐步解剖研究了ACA远端动脉瘤的手术入路。
PerA-CMA交界处分别位于A3段胼胝体上和胼胝体下节段的病例占36%和55%。在胼胝体下区域，很难识别近端PerA并建立对该血管的近端控制。近端PerA的胼胝体下部分几乎与额颅底平行，PC点距鼻根42.2±15.9mm（平均值±标准差）。这些发现表明，在PC点以下进入胼胝体下型ACA远端动脉瘤并通过前纵裂入路建立近端控制的空间有限。当在PC点上方进行手术入路时，在完成最终的动脉瘤分离和夹闭之前，可能需要进行胼胝体前切开术以建立近端控制。PC点是规划胼胝体下型ACA远端动脉瘤手术策略时的一个重要手术标志。
