Intracranial–Intracranial Bypass for Treatment of Complex Vascular Lesions and Tumors

51 Intracranial–Intracranial Bypass for Treatment of Complex Vascular Lesions and Tumors

Gabriel Mauricio Longo-Calderón, Edgar Nathal, and Jorge Mura

Abstract

Complex neurovascular revascularization procedures have evolved in the last five decades, since the first superficial temporal artery to middle cerebral artery (STA-MCA) bypass described by Yasargil. Nowadays, bypass surgery, especially the intracranial-intracranial (IC-IC) bypass is used not only in aneurysm surgery but also in complex skull base tumors surgery.

The STA-MCA bypass is considered as “first-generation bypass.” It is a low-flow extracranial-intracranial (EC-IC) bypass. With the addition of autologous venous and arterial grafts came the “second-generation bypass” (high-flow EC-IC), which requires graft interposition and two anastomoses.

The evolution of bypass surgery continued with a “third-generation bypass” (IC-IC) bypass, in which donors and receptors are intracranial vessels. This kind of bypass is more complex because it usually requires a deep and narrow corridor and includes different techniques such as end-to-end anastomosis (reanastomosis), end-to-side anastomosis (reimplantation), side-to-side anastomosis (in situ bypass), and intracranial graft bypass.

Preoperative imaging workup is essential to select the right bypass in each case. Bypass patency can be assessed by intraoperative indocyanine green (ICG), fluorescein videoangiography, intraoperative Doppler, or intraoperative angiography.

In this chapter, we present a series of IC-IC bypass in different surgical scenarios, which were performed to preserve normal circulation through anastomoses of similar caliber vessels. The advantage of utilizing intracranial vessels as donors, instead of extracranial grafts, is that it allows using the technique in emergency surgeries.

Keywords: bypass, IC-IC, intracranial-intracranial, vascular, cerebral revascularization, brain tumors, brain aneurysm

51.1 Introduction

Cerebral revascularization procedures have presented an important development in the last 50 years showing three different evolution stages; Yasargil first introduced the superficial temporal artery–middle cerebral artery (STA-MCA) anastomosis in 1967,1 a low-flow (15–25 mL/min) extracranial-intracranial (EC-IC) bypass, considered as the first-generation bypass surgery.

Currently, bypass surgery can be useful for flow replacement or flow augmentation.² In the first type, a bypass is used to prevent infarction in the context of an arterial sacrifice. In the second type, cerebral blood flow is increased to meet the metabolic needs of an under-perfused parenchyma.

Evidence from studies, such as the Carotid Occlusion Surgery Study (COSS),³ has failed to demonstrate the utility of flow augmentation bypass in occlusive intracranial disease, contrary to the results of the Japanese EC-IC bypass surgery trial (JET) that focused on the efficacy of bypass for the stage II ischemia, showing a lower recurrence rate in the bypass-surgery group than the medical treatment group.⁴ On the other hand, flow replacement is critical in certain neurosurgical situations.⁵ Second-generation EC-IC bypass is based mainly on the use of radial artery or saphenous vein grafts, communicating the cervical carotid or vertebral arteries with large intracranial receptor arteries. Its main advantage is an immediate high flow, on average 70 to 140 mL/minute.

51.2 Intracranial-Intracranial (IC-IC) Bypass

This third-generation cerebral revascularization procedure is based on the use of purely intracranial donors and receptor vessels. Advantages over EC-IC bypass are: being more anatomical, shorter graft length, avoids cervical incisions, intracranial protection, and similar caliber between donor and receptor arteries.⁶ IC-IC can be divided according to anastomosis type as follows:

51.2.1 Single

When aneurysm is not amenable to direct clipping or multiple clip reconstruction without assuring distal flow or when distal branch is coming out of the aneurysm dome, a single IC-IC bypass can be performed. The advantage of this technique is that it can be life-saving in emergency cases, and the immediate availability of the donor saves time in order to harvest a graft.

a)End-to-end anastomosis: After trapping and sectioning the aneurysm (usually fusiform) an end-to-end anastomosis can be done to re-anastomose the vessel; before doing it, attention must be paid to the tension of the anastomosis. If the gap is too large a graft interposition should be considered (Fig. 51.1).

b)End-to-side anastomosis: Sometimes, a branch arises from the dome of an aneurysm. In order to completely exclude the aneurysm, the branch must be sacrificed. In these cases, the branch is cut from the aneurysm dome and can be re-implanted to the parent vessel or other proximal donor (Fig. 51.2).

c)Side-to-side anastomosis: When one vessel needs to be sacrificed proximally, and you have a donor and receptor vessels in close proximity and parallel to each other, a side-to-side reconstruction can be done. There are few favorable anatomical situations for these anastomoses: MCA with M2 and M3 parallel segments with anterior cerebral artery (ACA) A3–A3 segments, posterior inferior cerebellar artery (PICA): PICA-PICA, posterior cerebral artery–superior cerebellar artery (PCA-SCA) among others (Fig. 51.3).

Fig. 51.1Mycotic aneurysm (case 4). A 50-year-old male had a 1-week history of fever, headache, and right-sided brachial paresis. He presented with decreased mental status and Glasgow Coma Scale (GCS) 11 on admission. A CT scan revealed a right-sided parietal hematoma (a); a CT angiography (CTA) established an M3 mycotic aneurysm (arrow) with only one branch arising distally (b, c). Cardiologic evaluation was compatible with infectious endocarditis. (d) Schematic representation of the surgical procedure. The mycotic emboly was impacted in a small bifurcation, occluding one branch completely and the other partially. A resection of the compromised artery was achieved and reconstruction of the angular artery was possible. (e) Postoperative CTA confirmed bypass patency with preservation of the angular artery. The clip of the second occluded branch can be seen. (f) Postoperative CT reveals a small infarction of the occluded branch and the lesion secondary to the intracerebral hematoma. The patient had a favorable evolution with mild dysphasia.

Fig. 51.2Ruptured middle cerebral artery aneurysm (case 6). A 66-year-old female presented with thunderclap headache and left-side hemiparesis. The Glasgow Coma Scale at admission was 13. (a) CT scan was compatible with subarachnoid hemorrhage with a right-side sylvian hematoma. (b) CT angiography revealed a right-side MCA aneurysm. Surgery was performed 24 hours after onset. (c) The resected aneurysm specimen shows that the MCA and the two branches were originated in an atheroma part of the aneurysm neck, making a proper clipping of the lesion impossible; then, double IC-IC bypass was decided intraoperatively. (d) Postoperative CT scan. (e) Three-dimensional CTA showing the double IC-IC bypass between MCA early temporal branch–M2 frontal branch, and M1–M2 temporal branch reanastomosis (arrows). The patient had a favorable course, with Glasgow Outcome Scale (GOS) 5 at discharge.

Fig. 51.3Fusiform aneurysm (case 7). A 27-year-old man presented with headache. Neurological examination was normal. CT scan was negative for hemorrhage. CT angiography revealed a right unruptured middle cerebral artery aneurysm. (a) Angiography confirmed a right M3 fusiform aneurysm. (b) Three-dimensional angiography. Aneurysm anatomy was complex for conventional clipping because of the origin of two M3 branches at the dome. A double IC-IC bypass was performed. (c) Three-dimensional angiography. A superficial temporal artery to middle cerebral artery (STA-MCA) M3 branch bypass was used to reconstruct one branch (arrow). The clip used in the trapping of the aneurysm can be seen in color. (d) An M2-M3 bypass with STA interposition graft was used to reconstruct the second branch (arrow), and aneurysm trapping was made with two L aneurysm clips (Peter Lazic, Tuttlingen, Germany), which can be seen in color.

51.2.2 With Graft Interposition

Depending of the length of the graft, these can be classified in two types: Short graft and when the donor vessel is far from the receptor a long “jump” graft is needed (Fig. 51.4, Fig. 51.5, and Fig. 51.6).

Fig. 51.4Giant internal carotid artery aneurysm (case 14). A 64-year-old female presented with headache and right hemiparesis. She was diagnosed with a giant left carotid ophthalmic segment aneurysm of 34 × 19 mm with secondary hydrocephalus. A ventriculoperitoneal shunt was installed. (a) A T2-weighted MRI reveals an unruptured partially thrombosed giant paraclinoid aneurysm with brainstem compression. (b) Three-dimensional angiography showing a giant carotid ophthalmic segment aneurysm. (c) A left C2–C5 radial artery interposition graft bypass was performed plus trapping and aneurysm resection (arrow). At home she evolved with bypass occlusion at 28 days postoperative (secondary to aspirin suspension). (d) Bypass revision was indicated, and distal temporal M2 branch reanastomosis was performed (arrow).

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