本期为Worldneurosurgery定期连载的《动脉瘤大师级神作--Seven Aneurysms》著作第十二期。本期主要内容为 前纵裂入路，《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.临时夹闭；6.永久夹闭；7.夹闭后的检查；8.必要的脑切除；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】往期回顾
第六期：动脉瘤手术基本功--永久夹闭
第七期：动脉瘤手术基本功--夹闭后的检查
第八期：动脉瘤手术基本功--必要的脑切除
第九期：动脉瘤手术基本功--术中破裂
第十期：神外入路丨翼点入路
第十一期：神外入路丨眶颧入路
第十二期：Anterior Interhemispheric Approach--前纵裂入路
■ Position, Incision, and Extracranial Dissection--体位、切口和颅外解剖
Pericallosal artery (PcaA) aneurysms originate from a right or left-sided bifurcation of the anterior cerebral artery (ACA), but are midline aneurysms deep to the falx. Therefore, the anterior interhemispheric fissure needs to be accessed only on one side, and the craniotomy is eccentric to that side. The right side is chosen for these aneurysms to avoid complications in the dominant hemisphere resulting from the craniotomy, venous sacrifice, or retraction.
胼周动脉（PcaA）动脉瘤起源于右侧或左侧大脑前动脉（ACA）分叉处，为中线部位动脉瘤，位于大脑镰深部。因此，仅需在前纵裂的一侧进行操作，开颅则偏向于该侧。这类动脉瘤手术多选右侧，以免在优势侧因开颅、静脉损伤或脑组织牵拉引起相关并发症。
The patient is positioned supine with the head in neutral position (nose up) and the neck extended slightly (Fig. 12.1A). A bicoronal skin incision is needed to mobilize the scalp flap inferiorly enough for a craniotomy cut that runs across the anterior cranial fossa floor (Fig. 12.1B). The incision begins at the right zygoma and ends at the contralateral superior temporal line because the craniotomy is eccentric to the right side. The scalp is folded to expose supraorbital frontal bone from the ipsilateral superior temporal line to the contralateral glabella. Pericranium is harvested during the opening to make it available during the closure to cover the frontal sinus, if it has been entered. It is easier to harvest pericranium as a separate layer as the scalp flap is elevated, rather than to peel it away from a folded scalp flap at the end of the procedure.
病人仰卧位，头部正中（向上），颈部略后伸（图12.1A）。行双侧冠状切口，尽量向下分离皮瓣，开颅显露前颅窝底（图12.1B）。切口从右侧颧弓到对侧颞上线，开颅偏向右侧。翻起皮瓣，显露从同侧颞上线到对侧眉间的眶上额骨。在手术期间保留颅骨外膜，如果额窦开放，关颅时可用于封闭额窦。翻起皮瓣时单独分离颅骨外膜，比手术结束时再从折叠的皮瓣上剥离更容易一些。
■ Craniotomy--开颅
Pericallosal artery aneurysms are exposed optimally with a craniotomy flap whose medial border crosses the superior sagittal sinus (SSS) to the contralateral (left) side (Fig. 12.1C). Midline exposure enables the dura to be opened to the edge of the SSS and directly accesses the interhemispheric fissure without any overhanging bone. The craniotomy flap is extended inferiorly as close to the anterior cranial fossa floor as possible. Crossing the midline with this cut sometimes requires drilling down the ridge of bone on the inner table in the midline. The lateral cut extends to the superior temporal line, and the temporalis muscle is left undisturbed. The posterior cut extends to the coronal suture.
为充分显露胼周动脉动脉瘤，开颅手术骨瓣内侧缘应过上矢状窦（SSS）到对侧（左侧）（图12.1C）。暴露中线部位，使硬脑膜打开到上矢状窦边缘，直接进入纵裂而没有任何骨质的干扰。扩大开颅骨瓣向下尽可能接近前颅窝底。这种骨窗过中线有时需要磨除中线处内板的骨嵴。骨窗外侧至颞上线，保留颞肌。向后至冠状缝。
The SSS is crossed carefully with the craniotome. Its epidural location is established visually before crossing the sinus by aiming light into the cut of bone and irrigating enough to see intact dura. If a dural tear is detected, the flap is taken in two pieces. The craniotomy flap can be raised safely as one flap in younger patients with dura that is not adherent to the inner table of the skull, and in many women with a shallow bony sulcus of the SSS. However, this craniotomy flap is raised in two pieces in elderly patients or those with thin, adherent dura. The first piece is a unilateral (right) frontal flap taken up to, but not across the SSS. After removing this bone flap first, dura containing the SSS is dissected from the inner table of the skull under direct visualization to minimize the risks of sinus injury or excessive bleeding from the emissary veins. The second portion of the craniotomy safely crosses the SSS twice, with the dura retracted away from the skull.
开颅时器械应小心谨慎跨过上矢状窦。在通过静脉窦前，颅骨切开处充分照明、注水并可见完整硬膜，确保器械位置在硬膜外。如果发现硬脑膜撕裂，则将开颅骨瓣分成两片。年轻患者的硬脑膜与颅骨内板附着并不紧密，并且许多女性颅骨内板的上矢状窦沟较浅，可将开颅瓣整块安全剥离。然而，对于高龄或硬脑膜较薄、粘附明显的患者，可将开颅骨瓣分成两块。第一块为单侧（右侧）额瓣，但不过上矢状窦。先去除这块骨瓣，然后直视下从颅骨内板分离硬脑膜，包括上矢状窦，以最大限度降低静脉窦损伤或导静脉大出血的风险。第二部分开颅，器械需要安全地跨过上矢状窦两次，并将硬脑膜从颅骨上剥离。
The inner table of the frontal bone in the inferior midline is drilled until flat (Fig. 12.1D), in a manner analogous to drilling the sphenoid bone for a pterional approach. This additional bone removal increases visualization along the anterior cranial fossa floor for accessing proximal control of low-lying PcaA aneurysms. This bone removal may also enter and cranialize the frontal sinus, which requires coverage with a pericranial graft during the closure.
中线下部额骨内板打磨平整（图12.1D），某种程度上类似于翼点入路打磨蝶骨。这种额外的骨质磨除增加了前颅窝底的可视性，用于进行低位PcaA动脉瘤的近端控制。这种骨质移除也可能进入和破坏额窦，关颅期间应该使用颅骨膜植入覆盖。
■ Dural Opening--打开硬脑膜
Dura is opened with a semicircular flap based against the SSS. Bridging frontal veins are preserved when they are large and more posteriorly located. A vein that fuses with the dura before reaching the SSS can be saved by dividing the dural flap on both sides of the vein and elevating two flaps instead of one. These cuts fashion a sleeve of dura over the vein that preserves the vein. Venous infarction is a potentially devastating complication that is difficult to predict, which means that bridging veins should be preserved whenever possible.
以上矢状窦为基部，半圆形打开硬脑膜。当额部桥静脉比较粗大以及位于更后方时需要保护。在汇入上矢状窦之前与硬脑膜融合的静脉，可以在静脉两侧将硬脑膜瓣剪开后予以保护。这种切口使硬脑膜在静脉上形成袖套样，保护静脉。静脉栓塞是一种潜在的灾难性的并发症，难以预测，这就需要我们随时注意保护桥静脉。
■ Gravity Retraction--重力牵拉
Pericallosal artery aneurysms that lie along the A4 or A5 segments are rare, but their distal location on the body of the corpus callosum allows for a modified anterior interhemispheric approach that uses gravity to retract the right hemisphere. The patient is positioned supine with bolsters under the left shoulder. The head is turned 90 degrees to the right with the sagittal midline parallel to the floor, and angled 45 degrees upward (lateral neck flexion) (Fig. 12.2A,B). This position allows gravity to retract the dependent right hemisphere and open the interhemispheric fissure.
位于A4或A5段的胼周动脉动脉瘤少见，不过其位于胼胝体远端，可以采用改良前纵裂手术入路，借助重力牵拉右侧大脑半球。病人仰卧位，左肩下垫枕。头部右偏90°，矢中线平行于地面，床头抬高45°（侧颈前屈位）（图12.2A,B）。这种体位可以借助重力牵拉右侧大脑半球，开放纵裂。
A “trapdoor” incision is used instead of a bicoronal incision, with the anterior limb placed along the hairline (not on the forehead), the posterior limb behind the coronal suture, and the connecting limbs parasagittally just across the midline (Fig. 12.2B). This incision accommodates a craniotomy flap that is two thirds anterior and one third posterior to the coronal suture, and crosses the SSS to expose the opposite side. The dural flap is a semicircular flap based against the SSS. Gravity pulls the hemisphere down away from the falx to open the interhemispheric fissure without a retractor (Fig. 12.2C). A retractor may be needed on the inferior free edge of falx to better expose the PcaA and corpus callosum.
使用“门”状切口代替双侧冠状切口，前方切口沿发际（不要在额部），后方切口在冠状缝后方，侧方切口在过中线的旁正中（图12.2B）。切口的设计应与骨瓣相适应，使得骨瓣的2/3位于冠状缝前、1/3在冠状缝后，并过上矢状窦以显露对侧。硬膜瓣是基底位于上矢状窦侧的半圆形瓣。重力牵拉半球离开大脑镰，开放纵裂，无需牵开器（图12.2C）。大脑镰下方游离缘需要牵开器牵开以更好的显露胼周动脉和胼胝体。
Fig. 12.1 (A) Patient position for proximal pericallosal artery (PcaA) aneurysms, with the nose up, slight head extension, and the midline oriented vertically. (B) A bicoronal skin incision mobilizes the scalp flap inferiorly enough for a craniotomy cut across the anterior cranial fossa floor. The skin incision begins at the right zygoma and ends at the contralateral superior temporal line because the craniotomy is eccentric to the right side. (C) The craniotomy is usually made with a single bur hole. The craniotomy crosses the midline and exposes the superior sagittal sinus (SSS), eliminating any bony ledge that might obscure access to the interhemispheric fissure. The craniotomy flap extends inferiorly to the anterior cranial fossa floor, and laterally to the superior temporal line, leaving the temporalis muscle undisturbed. The posterior cut extends to the coronal suture. (D) The inner table of the inferior frontal bone is drilled until flat, in a manner analogous to drilling the sphenoid bone for a pterional approach. This additional bone removal increases visualization along the anterior cranial fossa floor for proximal control of low-lying PcaA aneurysms.
图12.1（A）近端胼周动脉（PcaA）动脉瘤病人体位，头部向上，轻微后伸，中线垂直。（B）行双侧冠状切口，尽量向下分离皮瓣，开颅显露前颅窝底。头皮切口从右侧颧弓到对侧颞上线，开颅偏向右侧。（C）通常单孔钻颅。开颅过中线并暴露上矢状窦（SSS），磨除任何可能影响进入纵裂的骨性突起。开颅瓣向下至前颅窝底，外侧至颞上线，颞肌予以保留。向后至冠状缝。（D）额下部颅骨内板打磨平整，某种程度上类似于翼点入路打磨蝶骨。这种额外的骨质磨除增加了前颅窝底的可视性，用于进行低位PcaA动脉瘤的近端控制。
Fig. 12.2 (A) Patient position for distal PcaA aneurysms, with the head turned 90 degrees to the right, and the head and neck angled up 45 degrees. This position orients the midline horizontally, allowing gravity to retract the right frontal lobe and open the anterior interhemispheric fissure. (B) A “trapdoor” skin incision is used instead of a bicoronal incision, with the anterior limb placed along the hairline (not on the forehead), the posterior limb behind the coronal suture, and the connecting limbs parasagittally just across the midline. The craniotomy is two thirds anterior and one third posterior to the coronal suture, and crosses the SSS to expose the left side. (C) The dural flap is the same as with the “nose up” approach: a semicircular flap based against the SSS. Gravity pulls the right hemisphere down away from the falx to open the interhemispheric fissure without a retractor. A retractor may be needed on the inferior free edge of the falx to better expose the PcaA and corpus callosum (CC).
图12.2（A）远端胼周动脉动脉瘤病人体位，头部右偏90°，头颈部倾斜45°。该体位中线水平位，使重力牵拉右侧额叶，开放前纵裂。（B）使用“门”状切口代替双侧冠状切口，前缘沿发际（不要在额部），后缘在冠状缝后方，侧缘在旁矢状面过中线。开颅瓣2/3位于冠状缝前、1/3在冠状缝后，并过上矢状窦以显露左侧。（C）硬脑膜瓣同仰卧位入路：基于上矢状窦的半圆形。重力牵拉右侧大脑半球离开大脑镰，开放纵裂，无需牵开器。大脑镰下方游离缘需要使用牵开器更好的显露PcaA和胼胝体（CC）。
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