Revascularization with saphenous vein bypasses for complex intracranial aneurysms

Abstract

Most intracranial aneurysms can be managed with either microsurgical clipping or endovascular coiling. A subset of complex aneurysms with aberrant anatomy or fusiform/dolichoectatic morphology may require revascularization as part of a strategy that occludes the aneurysm or parent artery or both. Bypass techniques have been invented to revascularize nearly every intracranial artery. An aneurysm that will require a saphenous vein bypass is one that cannot be treated with conventional microsurgical clipping or endovascular coiling and also requires deliberate sacrifice of a major intracranial artery as part of the alternative treatment strategy. In the past 7 years the senior author (MTL) has performed a total of 110 bypasses, of which 46 were for aneurysms. Twenty-two of these patients received high-flow extracranial-to-intracranial bypasses using saphenous vein grafts, of which 16 had aneurysms that were giant in size. We review the indications for saphenous vein bypasses for complex intracranial aneurysms, surgical techniques, and clinical management strategies.

Figure 1

Surgical technique illustration. (A) Harvest of saphenous vein graft. The patient's thigh is positioned by bending the leg slightly at the knee and externally rotating the leg. The skin incision is extended to the knee as the dissection progresses, following the course of the vein. (B) Extracranial anastomosis. The proximal anastomotic site is exposed through a standard carotid endarterectomy approach. For end-to-side anastomoses, a 4- or 5-mm aortic punch is used to cut a circular hole in the carotid artery (white arrow). A suction drain is also used for this anastomosis to keep the field clean (black arrow). (C) Intracranial anastomosis. Background yellow material is placed under the artery not only to create a stage for the anastomosis, but also to protect the underlying brain and provide contrast to better visualize the often transparent arterial walls. (D) A drain is placed under this background material and secured by running it underneath a retractor blade (arrow). When connected to continuous suction, this drain keeps the anastomotic site clear and allows the assistant to irrigate the stage liberally. Monofilament 9–0 nylon suture is used for this anastomosis, with the first suture placed to approximate the vein graft and one end of the arteriotomy. Running continuous stitches are placed loosely from one end of the arteriotomy to the other. Leaving the suture loose until all stitches are placed facilitates visualization of the delicate tissues during the suturing and insures that the suture is tied tightly at the end. (E) A continuous field from the cranial exposure to the cervical exposure is draped. The vein graft is tunneled from the cranial field to the cervical field using a #28-French chest tube. (F) Notches in the bone flap are created to prevent obstruction of flow in the bypass (black arrow).

Figure 2

Tandem bypass. Preoperative axial computed tomography scan (A) reveals subarachnoid hemorrhage in the left sylvian and ambient cisterns from rupture of the ICA aneurysm. (B) Preoperative digital subtraction angiography shows Dacron graft from the subclavian artery to the ICA on the left. (C) Selective ICA injections show a dolichoectatic ICA aneurysm in the anteroposterior view. (D) Intraoperative photographs show that about a 1-cm length of Dacron graft was opened for the proximal anastomosis site. (E) The completed back wall of the proximal anastomosis can be seen as the front wall is being sutured. (F) The completed distal end-to-side anastomosis between the saphenous vein and the MCA is shown, using a running suture. (G) Postoperative distal subtraction angiography of the proximal anastomosis are seen in the anteroposterior view shows the contoured occlusion of the distal Dacron graft. (H) Anteroposterior views show the distal anastomosis and the filling from the tandem bypass is both anterograde in the distal MCA territory and retrograde to supply the distal ICA and anterior cerebral artery. The aneurysm has been trapped with clips and no longer fills. Modified from Auguste et al. ICA, internal carotid artery; MCA, middle cerebral artery.

Figure 3

ECA-SCA Bypass. (A,B) A 60-year-old woman presented with a giant basilar artery trunk aneurysm and brainstem compression syndrome. She underwent a right orbitozygomatic-pterional craniotomy, cervical carotid artery exposure, harvest of saphenous vein graft, and ECA-to-SCA saphenous vein bypass graft. (C) Small temporary clips are placed on the SCA, which is then arteriotomized with a beveled #27-gauge needle and microscissors. The arteriotomy is lengthened until it is approximately three times the vessel's diameter. The contrast material is under the vessel. (D) Monofilament 9–0 nylon suture was used for this anastomosis. (E) Temporary clips were removed to re-establish flow in the recipient artery and back flow is appreciated into the saphenous vein graft. (F,G) The extracranial anastomosis is appreciated through a standard carotid endarterectomy approach. A suction drain is also used for this anastomosis to keep the field clean in (G). Postoperative angiogram (H) proximally and (I) distally revealed a patent bypass graft with excellent flow. (J) On postoperative day 3, the nondominant right vertebral artery was occluded endovascularly with coils. ECA, external carotid artery; SCA, superior cerebellar artery.