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  • Updated 08.21.2018
  • Released 12.05.2001
  • Expires For CME 08.21.2021

Cerebral revascularization: surgical and endovascular approaches

Introduction

Overview

Cerebral vascular insufficiency, typically caused by extra- or intracranial steno-occlusive pathology, is a major determining factor in the development of cerebral infarction. The realization of such a cause-and-effect relationship prompted interest in developing techniques geared at correcting pathologic flow reductions of the cerebral circulation. During the latter half of the twentieth century, introduction of the operating microscope propelled development of microvascular neurosurgery, leading to the clinical application of endarterectomy, embolectomy, and bypass procedures. More recently, the availability of endovascular techniques, angioplasty, stenting, and embolectomy amplified the dimensions of care for many patients whose therapeutic options were previously limited. In this article, the authors review cerebral revascularization, from its inception to its current status.

Key points

• Cerebral vascular insufficiency, with its inherent risk of cerebral infarction, continues to be a prevalent cause of neurologic morbidity and mortality worldwide.

• The last 50 to 60 years have witnessed an explosive evolution of techniques geared at restoring blood flow to compromised regions of the brain.

• Presently, steno-occlusive lesions in the carotid and vertebrobasilar circulations can be effectively managed by either surgical or endovascular techniques.

• Although the use of these techniques has been consistently shown to be effective in certain subpopulations, others still require additional study.

• Increasingly sophisticated cerebrovascular bypass procedures have expanded the therapeutic options previously considered inoperable.

• Urgent endovascular rescue has become the standard of care for patients with acute ischemia secondary to large arterial cerebral occlusions.

Historical note and terminology

The problem of cerebral vascular insufficiency, in its various clinical presentations, has been recognized as a major topic of interest in neurology and neurosurgery for many years. In fact, cases of urgent embolectomy of the middle cerebral artery for the treatment of brain ischemia appeared in the literature as early as the 1950s (155; 34). However, the introduction of the operating microscope in 1953 was pivotal to the advances to come. Originally embraced by ENT and ophthalmic surgeons, its application to vascular surgery by Jacobson and Suarez caught the attention of Donaghy, Khodadad, Lougheed, and Sundt, all of whom championed its incorporation into the practice of vascular neurosurgery (145; 84; 99; 147; 89; 90; 91; 92; 103; 93; 77). The 1960s to 1970s witnessed the earliest application of microvascular techniques for the reconstruction of brain arteries. The influence of Senning, the Swiss cardiovascular surgeon who pioneered coronary endarterectomy, stemmed from the frequency of cerebral embolism following cardiac surgery (136; 135). As a result, he commissioned Yasargil to travel to the United States to work under Donaghy. On his return to Switzerland, having completed approximately 200 experimental bypass procedures in dogs, Yasargil began the application of microvascular techniques to neurosurgical patients, completing the first intracranial-intracranial and extracranial-intracranial bypasses by 1967 (163). The latter, primarily involving superficial temporal artery-middle cerebral artery anastomosis was quickly adopted as a surgical option for patients with symptomatic extra- and intracranial atherosclerotic stenosis or occlusion. Multiple small retrospective reports began to document its safety and efficacy, estimating graft patency rates of 90% to 96% and perioperative stroke and mortality rates of 2% to 3.6% and 1.2% to 3%, respectively (162; 28; 146). Since then, cerebrovascular bypass procedures have become increasingly sophisticated.

The association between extracranial carotid pathology and ipsilateral stroke was recognized and reported in the literature in the early 1900s by notable clinicians such as Chiari and Hunt (32; 82). Still, the introduction of carotid endarterectomy as a procedure to prevent stroke followed a similar timetable than that described for bypass, and was intimately ligated to C. Miller Fisher's insightful anatomoclinical reports of 1951 (Fisher1951; 60). Until then, "cerebral vasospasm" was the prevalent theory regarding the mechanism of cerebral infarction. Undoubtedly, the first successful carotid endarterectomy must be credited to DeBakey in 1953 (47; 62), although surgical reconstruction of the carotid artery had already been carried out by Carrea and Eastcott (53; 53; 25). The ensuing 2 decades witnessed an exponential growth in the application of carotid endarterectomy for the treatment of carotid atherosclerotic pathology; by the late early 1980s, there were over 30,000 carotid endarterectomies being carried out annually in the United States, making it the third most common surgical procedure (52). Despite its popularity, a pivotal retrospective study reported very troublesome results, with an overall stroke-mortality rate of 21.1% (54). The concern that this and other datasets generated became the underpinning for the organization of prospective clinical trials that eventually defined the role of carotid endarterectomy for stroke prevention (12).

The history of application of endovascular techniques for cerebral revascularization is more recent and rooted on the introduction of percutaneous dilating angioplasty (ie, "Dottering") in 1964 by Dotter and Judkins (51). This was followed a decade later by the dilating balloon catheter designed by Grüntzig who, a few years later and also working with Senning, pioneered the use of percutaneous transluminal angioplasty for the treatment of coronary arteries (Gruntzig and Hopff 1974; 72; 151). Not much later, multiple groups began reporting on the application of percutaneous transluminal angioplasty to the treatment of supra-aortic vessels, specifically the subclavian artery (11; 105; 149). Still, translating this approach from the peripheral to the cerebral circulation was tempered by concerns of distal embolization and acute closure; yet, the first successful percutaneous transluminal angioplasty of the extracranial carotid artery was published in the early 1980s (17). As experience continued to be gained with percutaneous transluminal angioplasty in different vascular territories, its inherent hurdles became widely known: (a) lesion and arterial wall recoil, (b) intimal dissection and acute closure, and (c) plaque dislodgement and distal embolization (141). These became the incentive for development of the first stents: metal scaffolding devices designed to maintain patency following balloon deflation. Once the first stents were successfully implanted in coronary arteries, the field exploded, bringing with it the opportunity for the utilization of these devices in the cerebral circulation (139; 148). The first reports of carotid artery stenting date back to the mid-1990s (50; 130; 150); since then, stents have been used in nearly every segment of the cerebral circulation, for a variety of indications.

Application of endovascular techniques for the urgent revascularization of patients suffering acute ischemic stroke due to a large artery occlusion (ie, Rescue) began in the 1980s, at first by intraarterial instillation of thrombolytic drugs directly into the occluding thrombus (170; 171; 48; 66; 65; 87; 68; 124). The interest in using this approach blossomed briskly, to the point that by the turn of the twentieth century, there had been 26 major series reported in the literature, encompassing over 500 patients and showing encouraging results. Despite advances in drug development and with new thrombolytic agents becoming available, there continued to be a system-wide interest in finding better methods for quickly restoring flow to the acute ischemic brain. Mechanical removal of the occluding particle (ie, thrombectomy) began to catch the attention of several groups, particularly because of the possibility of a more rapid intervention and the avoidance of potential hemorrhagic complications from the use of thrombolytic drugs. The technically challenging use of snares paved the way for successive introduction of increasingly trackable and efficient devices, culminating with the development, testing, and validation of the use of stent retrievers (ie, "stentrievers") for acute ischemic stroke intervention (66; 65; 87; 68; 124).

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