本期为Worldneurosurgery定期连载的河南省人民医院张长远医师终审的《动脉瘤大师级神作--Seven Aneurysms》著作第二期。本期主要内容为 蛛网膜下腔的解剖，《Seven Aneurysms 》系列内容包括 Section I The Tenets：1. 在显微镜下操作；2. 蛛网膜下腔的解剖；3.脑牵拉；4.血管控制；5.临时阻断；6.永久夹闭；7.检测；8.脑皮层造瘘；9.术中破裂。Section II The Approaches: 10.翼点入路; 11.眶颧入路; 12.前纵裂入路; 13.远外侧入路。Section IIIThe Seven Aneurysms: 14.后交通动脉瘤; 15.大脑中动脉瘤; 16.前交通动脉瘤; 17.眼动脉动脉瘤; 18.胼周动脉瘤; 19.基底动脉分叉动脉瘤; 20.小脑后下动脉动脉瘤。
《Seven Aneurysms》著作第一期回顾：
神外医师基本功-- 在显微镜下操作技巧----Seven Aneurysms系列
Subarachnoid Dissection--蛛网膜下腔的解剖
The Subarachnoid Cisterns 蛛网膜下腔的脑池
The subarachnoid space is the arena of aneurysm surgery because it houses the brain’s arteries and provides a navigable labyrinth to deep targets that can be dissected without violating or harming the brain. Subarachnoid dissection,therefore, is a foundation of vascular neurosurgery.
蛛网膜下腔间隙是动脉瘤手术的地方，因为它容纳着脑动脉并提供了无需对脑造成伤害或损坏就可以分离到达深部目标的通道。因此，蛛网膜下腔的分离是血管神经外科的基础。
The subarachnoid space is compartmentalized into cisterns built with sheets of arachnoid tissue, bridged by internal arachnoid trabeculations, and filled with cerebrospinal fluid (CSF) (Fig. 2.1). Subarachnoid dissection opens and interconnects these cisterns en route to an aneurysm. Intercommunication between cisterns also drains CSF and untethers lobes and lobules of brain, thereby relaxing the brain, facilitating retraction, and widening surgical corridors. Every aneurysm is associated with a cistern. Middle cerebral artery (MCA) aneurysms reside in the sylvian cistern; posterior communicating artery (PCoA) and ophthalmic artery (OphA) aneurysms reside in the carotid cistern; anterior communicating artery (ACoA) aneurysms reside in the lamina terminalis cistern; pericallosal artery (PcaA) aneurysms reside in the callosal cistern (Fig. 2.2); basilar bifurcation aneurysms reside in the interpeduncular cistern (Fig. 2.3); and posterior inferior cerebellar artery (PICA) aneurysms reside in the lateral cerebellomedullary cistern and sometimes in the cisterna magna. The pathway to some aneurysms traverses several cisterns. For example, the pathway to ACoA aneurysms progresses from carotid to chiasmatic to lamina terminalis cisterns, and the pathway to basilar bifurcation aneurysms progresses from sylvian to
carotid to lamina terminalis to crural to interpeduncular cisterns (Fig. 2.4). Most of an aneurysm’s initial dissection has nothing to do with the aneurysm, and instead deconstructs cisternal architecture to open fissures, separate brain surfaces, and expose normal arterial anatomy.
蛛网膜下腔由蛛网膜组织层构成脑池，内由蛛网膜小梁连接，充满脑脊液（图2-1）。蛛网膜下腔的解剖可以开放和沟通其内相互连接的脑池直达动脉瘤。脑池的相互打通可以引流脑脊液、松解脑叶和小叶，因此可以使脑组织松弛，利于牵拉及扩大手术操作通道。每一个动脉瘤都与一个脑池相关。大脑中动脉瘤位于侧裂池，后交通动脉和眼动脉动脉瘤位于颈动脉池，前交通动脉瘤在终板池，胼周动脉瘤位于胼胝体池(Fig. 2.2);基底动脉分叉处动脉瘤位于脚间池（图2-3），小脑后下动脉动脉瘤位于外侧小脑延髓池，有时位于枕大池。然而，在一些动脉瘤，我们需要跨越几个脑池才能到达。例如，我们在处理前交通动脉动脉瘤时，需要先从颈内动脉池开始分离，然后视交叉池，最后才能到达终板池；显露基底动脉分叉动脉瘤从侧裂开始解剖，接着到达颈内动脉池，之后是终板池，然后到达大脑脚前方，最后显露脚间池。（图2-4）。多数情况下，在分离动脉瘤前进行的操作与动脉瘤无直接关系，而是通过打开脑池的结构，开放脑裂，分离脑叶之间的连结，暴露正常的动脉解剖。
Fig. 2.1 Basal subarachnoid cisterns, as viewed from beneath the brain. Middle cerebral artery (MCA) aneurysms reside in the sylvian cistern; posterior communicating artery (PCoA) and ophthalmic artery (OphA) aneurysms reside in the carotid cistern; anterior communicating artery (ACoA) aneurysms reside in the lamina terminalis cistern; pericallosal artery (PcaA) aneurysms reside in the callosal cistern; basilar bifurcation aneurysms reside in the interpeduncular cistern; and posterior inferior cerebellar artery (PICA) aneurysms reside in the lateral cerebellomedullary cistern. AmbC, ambient cistern; BA, basilar artery; CallC, collosal cistern; CarC, carotid cistern; ChiC, chiasmatic cistern; CruC, crural cistern; LCmC, lateral cerebellomedullary cistern; LTC, lamina terminalis cistern; MagC, cisterna magna; OlfC, olfactory cistern; PonC, prepontine cistern; SylC, Sylvian cistern.
图2-1 基底池，从大脑底面观。大脑中动脉瘤位于侧裂池，后交通动脉瘤和眼动脉动脉瘤位于颈动脉池，前交通动脉瘤在终板池，胼周动脉瘤位于胼胝体池，基底动脉分叉处动脉瘤位于脚间池，小脑后下动脉动脉瘤位于外侧小脑延髓池。AmbC, 环池；BA，基底动脉；CallC, 胼胝体池；CarC, 颈动脉池；ChiC, 视交叉池；CruC, 大脑脚池；LCmC，小脑延髓侧池；LTC, 终板池；MagC, 枕大池；OlfC，嗅池；PonC, 桥前池；SylC, 侧裂池。
Fig. 2.2 Midline subarachnoid cisterns, as viewed in the sagittal plane of the brain. The relationship between midline and paramedian aneurysms and their associated cisterns is shown. QuadC, quadrigeminal cistern.
图2-2 中线部位蛛网膜下腔脑池，从大脑的矢状面来观察。中线部位和中线旁部位动脉的关系以及与动脉瘤相关的脑池示意图。QuadC，四叠体池。
Fig. 2.3 Subarachnoid cisterns around the circle of Willis, as viewed from above the brain, which has been sliced axially. The relationship between aneurysms in the circle of Willis and their associated cisterns is shown.
图2-3 Willis环周围的蛛网膜下腔池，从已轴位切除的大脑上面观。起源于Willis环的动脉瘤和这些动脉瘤相关的脑池示意图。
Fig. 2.4 Pathway of subarachnoid dissection to the basilar apex begins with splitting the sylvian fissure (1) and opening the carotid cistern (2). The lamina terminalis cistern (3) is opened to mobilize the frontal lobe and fenestrate the lamina terminalis, thereby releasing cerebrospinal fluid (CSF) and relaxing the brain. Dissection along the anterior choroidal artery (AChA) opens the crural cistern (4) to detach the medial temporal lobe and facilitate retraction. Finally, the membrane of Liliequist is opened and the interpeduncular cistern (5) is entered to reach the basilar bifurcation aneurysm.
图2-4 蛛网膜下腔分离到基底尖的整个路径从（1）侧裂的分离开始，然后打开（2）颈内动脉池。牵开额叶打开（3）终板池并造瘘，释放脑脊液，松弛脑组织，沿着脉络膜前动脉分离打开（4）环池使颞叶内侧松解开便于牵拉。最后，Liliequist膜被打开，顺着（5）脚间池进入暴露基底动脉分叉处动脉瘤。
Arterial Landmarks 动脉的标志
Arteries define a trail through the center of the subarachnoid space that can be dissected continuously from the cortical surface to the circle of Willis. A single cortical artery invariably guides the dissection inward to larger branches and deeper trunks. Arteries are obvious in patients with unruptured aneurysms, untainted CSF, and clear cisterns. However, arteries in patients with subarachnoid hemorrhage (SAH) are buried in dense clot and require some excavation. Clot can be evacuated safely by suctioning outward from an arterial landmark, rather than suctioning inward toward an unidentified artery. Arteries lie centrally in subarachnoid spaces and therefore define the plane of separation between pial surfaces. Larger caliber arteries are identified as the dissection deepens. The angiogram is like a trail map, and angiographic information is translated constantly to the operative field.
大脑的动脉系统可以作为通往蛛网下腔中央的重要线索，你可以沿着动脉走行从大脑皮层表面连续分离至Willis动脉环。借助一支单一的皮层动脉完全可以帮助你一直向内分离到它的较大的分支和深部的主干。在未破裂的动脉瘤、脑脊液清亮、脑池清晰，因此动脉清晰可见。然而，在蛛网膜下腔出血的患者中，动脉可能被埋在血凝块中，需要清除血块。这时，血凝块的清除需要注意，安全的吸除方式是从一个动脉标志向外吸，而不是向内朝向一个还没有辨别清除的动脉方向吸。由于脑动脉走行在蛛网膜下腔的中央，因此在软脑膜之间有确定的分离平面。随着分离深入，动脉干越来越大。脑血管造影就仿佛是一个路线图，脑血管造影信息不断地在手术野展现出来。
Every artery has a safe surface to follow during subarachnoid dissection. Safe surfaces have smooth contours and few branches, whereas dangerous surfaces have perforating arteries, the aneurysm neck, or are poorly visualized (Fig. 2.5). For example, the superior surface of the M1 MCA segment gives off lenticulostriate arteries, and dissection along this surface can injure them. In contrast, the inferior surface of the M1 segment gives rise to the anterior temporal artery (ATA), which is easily seen and less vulnerable. Similarly, the superior surface of the P1 posterior cerebral artery (PCA) segment has thalamoperforators and leads directly to the neck of a basilar bifurcation aneurysm, whereas the inferior surface has no perforators. In addition, multiple perforating arteries close the dissection plane between artery and brain. Therefore, an artery’s safe surface is dissected preferentially.
蛛网膜下腔分离过程中，每一根动脉都有一个安全的分离面。这个平面轮廓光滑、分支少，相反，危险的分离平面有穿支动脉、动脉瘤颈或无法直视(Fig. 2.5)。例如，从大脑中动脉M1段的上表面发出豆纹动脉，沿着此面分离就会损伤豆纹动脉。相反，从M1深面（下方）发出的颞前动脉很容易被发现，因此很少会受到损伤。无独有偶，大脑后动脉P1段的浅层（上面）发出很多丘脑穿通动脉，P1段的浅层（上面）直接通向基底动脉分叉处动脉瘤的瘤颈。然而，P1段的下表面没有穿支血管。此外，动脉和大脑之间存在多个穿支动脉的情况使得无法在此处进行分离操作。因此，在处理动脉瘤时，要优先考虑从动脉的安全解剖面分离。
Fig. 2.5 Every artery has a safe surface to follow during subarachnoid dissection, with smooth contours, few branches or perforators, and opposite the aneurysm neck. The superior surface of the M1 MCA segment gives off lenticulostriate arteries, and dissection along this surface can injure them, but the inferior surface of the M1 segment is safe. Similarly, the superior surface of the supraclinoid internal carotid artery (ICA) and the inferior surface of the A1 anterior cerebral artery (ACA) segment are safe sides for dissection. Lent., lenticulostriate arteries; ON, optic nerve; PCA, posterior cerebral artery; SCA, superior cerebellar artery.
图 2-5 分离蛛网膜下腔过程中，每个动脉都可以沿着一个安全的界面——平滑的动脉轮廓、很少分支或穿支血管、位于动脉瘤颈的对侧。大脑中动脉M1的上表面发出豆纹动脉，沿着这个面进行分离会损伤它，但是在M1段的下表面进行分离是安全的。同样，在颈内动脉床突上段的上表面和大脑前动脉A1段下表面进行分离是安全的。Lent. 豆纹动脉；ON, 视神经；PCA，大脑后动脉；SCA，小脑上动脉。
Careful subarachnoid dissection should never require division or sacrifice of a small arterial branch. Branches travel to the brain they supply and can be mobilized in that direction, but sometimes the course may be indirect. Inspection from origin to destination will determine how to mobilize the artery. As a general rule, arteries supply only one lobe and therefore can be swept to that lobe safely. For example, an MCA branch that is adherent to the temporal lobe may appear, at first glance, to send branches to both the temporal and frontal lobes, but thorough dissection may demonstrate a loop that adheres to the temporal lobe but continues to supply the frontal lobe. This artery can be mobilized frontally.
严谨的蛛网膜下腔分离从来不会以离断或者牺牲小的动脉分支作为代价。供应脑组织的分支可以按走行方向牵移，但有时候血管走行可能是弯曲的。观察这些动脉的起点到终点的整个走行有助于决定怎么处理它们。通常的规律是，动脉只供应一个脑叶，因此将该动脉牵拉到它支配的脑叶是安全的。例如，一个大脑中动脉分支看上去与颞叶粘连，第一印象是既向颞叶又向额叶发出分支，但是彻底分离后可能会发现它在靠近颞叶的部分形成了一个血管袢，是继续走行供应额叶。这个血管可以牵向额侧。
Dissection Technique 分离技术
Subarachnoid dissection consists of three basic maneuvers with three simple instruments: cutting with microscissors, spreading with bipolar forceps, and probing with a slightly curved dissector (Rhoton No. 6 dissector; Codman; Raynham, MA). Microscissors incise and open cisternal walls. Blunt probing breaks apart many of the arachnoid webs inside cisterns and identifies resistant bands that require cutting. Subarachnoid tissues cut cleanly when under slight tension, which can be applied with the tip of the sucker or a fixed retractor. Microscissors blades surround the tissue precisely and under full visualization. The deep scissors blade lifts arachnoid away from underlying arteries and veins before cutting it, turning the microscissors into not only a cutting instrument but also a dissecting instrument that sets up its cuts.
蛛网膜下腔的分离是用三个简单的器械、由三个基本操作步骤组成：用显微剪剪断、用双极电凝扩张，用略微弯曲的剥离子(Rhoton 6号剥离子; Codman; Raynham, MA)探查。显微剪剪断并打开脑池壁。钝的探针可以撕开许多脑池内粘连的蛛网膜网、辨别比较坚韧的需要剪断的索带。当用吸引器吸头或固定牵开器保持蛛网膜轻度张力的情况下，蛛网膜组织很容易被剪断。显微剪的两个刃精确地剪除并保持剪刀刃完全在视野内。在剪之前，深面的剪刀刃将将蛛网膜轻轻抬离下方的动脉和静脉。显微剪刀不仅是用作剪断的工具，同时也是用作分离的工具。
Spreading dissection bluntly separates pial planes and opens fissures because pinched bipolar forceps have a gentle opening force that can be applied to brain tissues. Bipolar forceps are aligned parallel to arteries and parallel to pial surfaces, which in turn aligns the forceps’ opening force perpendicular to these brain surfaces. The opening force is distributed across a wide area of tissue to gently spread them apart. Bipolar forceps should not be aligned perpendicular to the arteries because the instrument’s opening force will not distribute to opposing brain surfaces and its tips might dig into the brain. The microscope and chair must be oriented to bring the bipolar hand and instrument into this parallel alignment. Spreading dissection is useful for splitting tight fissures in swollen brains, like the sylvian or interhemispheric fissures after SAH。
因为压闭的双极电凝镊具有轻柔的外张力，可以用于脑组织分离，所以钝性扩张性分离分开软脑膜平面，打开外侧裂。双极电凝镊在使用时应该平行于动脉血管方向和软脑膜平面进行分离，这反过来使镊子的张力垂直于脑表面。镊子的张力传到一个大的范围，可以轻柔的撑开组织，这样就能起到分离的作用。双极电凝镊不能垂体于动脉血管进行操作因为它的张力不是正好作用于脑表面，它的镊尖可能扎进脑组织。显微镜和椅子必须调整到你在使用双极电凝时器械正好能平行于血管方向。扩张分离有利于在肿胀的脑组织条件下分离粘连紧密的沟裂，例如在蛛网膜下腔出血后的外侧裂和大脑半球间裂。
Blunt dissection with a Rhoton No. 6 instrument helps probe anatomy, develop a feel for tissue planes, and mobilize arteries and nerves. This instrument is an extension of one’s index finger, and it allows the neurosurgeon to develop natural lines of dissection along arteries. Tight interfaces between arteries, veins, and arachnoid can be opened and enlarged safest with blunt dissection, transitioning to sharp dissection as these interfaces widen. Back-and-forth movements parallel the arachnoidal planes and avoid displacement of neural tissues. For example, the plane between the optic nerve and the inferior frontal lobe is opened with
side-to-side movements of the Rhoton No. 6, rather than up-and-down movements. Subarachnoid dissection cycles from blunt to sharp to spreading dissection, and back around again. The Rhoton No. 6 and bipolar forceps each have a discrete function, but the microscissors is more versatile. Closed microscissors can be used as a probing dissector, and carefully opening microscissors can perform spreading dissection. The complex art of subarachnoid dissection reduces to basic maneuvers with a few instruments. A simple routine enables the neurosurgeon to develop an efficient rhythm to the dissection.
用Rhoton 6号显微器械进行钝性分离可以帮助我们探测解剖结构，感知组织界面，移动血管和神经。它是食指功能的延伸，神经外科医生利用它可以沿着血管的自然行程进行分离。在动脉，静脉和蛛网膜之间紧密的界面能够用钝性分离技术打开和最安全地扩大，当界面增宽时即改为锐性分离。来回移动时要平行于蛛网膜面，避免牵拉神经组织。例如，用Rhoton 6号显微剥离子在视神经和额叶下方之间的平面进行侧向的开放而不是上下移动。蛛网膜下腔的分离是依靠钝性和锐性分离交替来回进行的。Rhoton 6号显微剥离子和双极电凝的功能单一。但是显微剪使用起来更灵活。闭合状态下的显微剪可以用做剥离探子，小心翼翼地打开剪刀可以用做扩大分离。蛛网膜下腔的解剖是一门复杂的艺术，用少数器械就减少基本的操作次数。这种简单的操作常规能够使神经外科医生形成高效的分离节奏。
Subarachnoid dissection remains “outside” of the brain by respecting and preserving pial boundaries. Pia is delicate, and subpial transgression can cause brain injury, swelling, and contusions. Safe subarachnoid dissection also remains outside of the vessels, respecting and preserving the arteries and veins that course through the cisterns. The neurosurgeon’s touch must be gentle and precise as he or she works between these boundaries. Developing the right touch is the biggest challenge with subarachnoid dissection.
蛛网膜下腔的分离是依靠珍视和保护软脑膜界面，从而保持在脑组织外进行操作。软脑膜是相当脆弱的，分离界面越过软膜到软膜下就会导致脑组织损伤、脑肿胀和脑挫伤，安全的蛛网膜下分离同样应该在血管外进行，珍视和保护脑池内走行的动脉和静脉。神经外科医生在这些界面之间进行操作时必须非常轻柔和精细。培养蛛网膜下腔分离所需的正确触觉对神经外科医生来说是个最大的挑战。
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