There is evidence that well-executed surgery or stenting in appropriately chosen cases arrests the TIAs and diminishes the risk of future strokes. These views initially received strong affirmation from two often-cited randomized studies—the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST). The conclusion reached in each of these studies was that carotid endarterectomy for symptomatic lesions causing degrees of stenosis greater than 70 to 80 percent in diameter reduces the incidence of ipsilateral hemispheral strokes and shows greater benefit with increasing degrees of stenosis. The results apply generally only if surgical complication rates are below 3 percent. These two trials differed in the method of estimating the degree of stenosis, but when adjustments are made, the results are comparable (Donnan et al, 1998). Further analysis of the North American trial by Gasecki and colleagues indicated that the risk of cerebral infarction on the side of the symptomatic stenosis is increased if there is a contralateral carotid stenosis but that operated patients (on the side of symptomatic stenosis) still had fewer strokes than those treated with medication alone. In those with bilateral carotid disease, the risk of stroke after 2 years was 69 percent, and if operated, 22 percent. As to the timing of endarterectomy, opinions have diverged but a meta-analysis reported by Rothwell and colleagues (2004) has suggested that the maximum benefit is accrued if surgery is performed within 2 weeks of a TIA or minor stroke.
Carotid angioplasty and stenting offer an alternative to carotid endarterectomy. Direct comparisons have been made in several organized trials, initially in patients who were too ill to undergo endarterectomy but subsequently, in a larger population of symptomatic patients. In one early trial reported by the CAVATAS investigators (Carotid and Vertebral Artery Transluminal Angioplasty Study), the incidence of minor (nonstroke) complications was lower in patients who had angioplasty and stenting than for surgery. Otherwise, the recurrent stroke rates were similar, 10 percent for both groups. A useful comparison between angioplasty and surgical endarterectomy has been made in the trial reported by Mas and associates (2006) and in the “SPACE” trial. While the first of these favored a surgical approach for severe symptomatic stenosis, the second gave equivalent results of approximately 6 percent combined stroke and death rates with either procedure. Subsequent trials, such as CREST (Brott et al, 2010), and SAPPHIRE (Yadav et al), both of which had approximately half of patients with asymptomatic carotid stenosis, gave similar results, namely that recurrent stroke rates are alike for endarterectomy and stenting. Longer term follow of the CREST trial patients indicated that the stroke rates between the two groups remained similar up to 10 years (approximately 7 percent of patients in each group had a stroke ipsilateral to the affected side of carotid disease).
In the final analysis, the relative benefits of surgery or medical treatment (anticoagulation or aspirin) depend mainly on the surgical risk—including on the record of the individual surgeon. If there is an established operative complication rate of less than 3 percent, then surgery can be recommended in symptomatic patients with carotid stenosis greater than 70 percent. This benefit extends to elderly patients and, indeed, it has been shown on a statistical basis to be most evident in patients older than age 75 (see the post hoc analysis of NASCET data by Alamowitch et al).
A trial in patients with complete atherosclerotic occlusion of the cervical internal, using extracranial to intracranial arterial bypass (COSS, reported by Powers and associates), failed to demonstrate an advantage of surgery over medical therapy. Bypass of this type is discussed further below and the section on Moyamoya disease.