Interventional Neurology—Recent Advances and New Applications


is necessary. Fifteen per cent of patients with a large vessel occlusion, without intra-arterial thrombolysis, may have a favorable functional outcome.7


Recent data on


the nuances of the technique highlight the unique needs of an acute ischemic stroke patient. In general, most anterior circulation strokes should perhaps be done without general anesthesia but with careful titration of sedatives with the help of the anesthesia team.13


Risks of the procedure primarily concern symptomatic intracerebral hemorrhage, and consistently average around 10 %.9,10,11 Recanalization rates consistently average around 75 %.11,12


The first-line approach to


recanalize a large vessel occlusion is mechanical thrombolysis. The Merci® Retrieval system (Concentric Medical, Mountain View) was the first FDA approved treatment option for embolectomy in cerebral arteries. This prospective, multicenter single-arm study with 177 patients demonstrated a combined 68 % recanalization rate, symptomatic hemorrhage rate of 9.8 %, with 36 % of patients achieving functional independence.11


The


Analogous to recanalization of acute coronary occlusions, intracranial stent placement provides for rapid recanalization by entrapping the thrombus between the stent and vessel wall. The Solitaire flow restoration device with intention for thrombectomy (SWIFT) study aims to compare this closed cell, stent attached to a wire against the Merci Retrieval device with outcome measures evaluating both clinical outcomes and angiographic recanalization rates.14


Many technical iterations have


subsequently been reported using parts of the available tools in varying techniques tailored to the location and putative type of clot.15,16


Endovascular Aspects of Secondary Stroke Prevention


Although less bold, the benefits of effective medical management strategies for secondary stroke prevention likely outweigh the benefits associated with interventional strategies. Such medical strategies include antiplatelet agents and medications to treat the risk factors associated with atherosclerosis, including hypertension, diabetes, and elevated lipids. Lifestyle changes, particularly smoking cessation, are equally important.17


Carotid Artery Stenosis in the Neck


The North American carotid endarterectomy (NASCET) trial reported a 26 % risk of stroke at two years for patients with hemodynamically significant atherosclerosis at the origin of the internal carotid artery.18 It is important to remember that the protocol for this often-referenced trial was created over 20 years ago, in 1987. Therefore, with current medical management, particularly with improvements in cholesterol and hypertension management strategies, the risk of recurrent stroke with such a lesion may in fact be less. Current surgical interventions to lower the risk of stroke among people with carotid artery stenosis include carotid endarterectomy (CEA) as well as carotid angioplasty and stent placement (CAS). A number of randomized clinical trials in Europe and North America have addressed the effectiveness of these procedures, which, when combined together, have mixed results. The two most recent large, randomized, sufficiently powered trials that addressed the clinically relevant safety and efficacy measures between CEA and CAS include the International carotid stenting study (ICSS) and the Carotid


US NEUROLOGY


Penumbra Stroke System (Penumbra, Alameda) was FDA approved in 2008 and is the most widely used thromboaspiration device in the US. This prospective, multicenter single-arm study with 125 patients demonstrated a combined 82 % recanalization rate, an 11 % symptomatic hemorrhage rate, but only 25 % of patients achieved functional independence at 90 days.12


revascularization endarterectomy versus stenting (CREST) trial. In ICSS, 1,713 patients from 50 mostly European academic centers showed a primary outcome of stroke, death, or procedural myocardial infarction (MI) at 120 days to be 8.5 and 5.2 % for CAS and CEA, respectively. There was a remarkably low 1.7 % rate of disabling stroke in both groups.19 CREST is currently the largest trial to date comparing outcomes of both procedures in patients with >50 % carotid artery stenosis. In the trial, 2,502 patients from North America were randomized from 117 centers. Nearly all CAS procedures were done with embolic protection devices, a first.20


Both procedures entail considerable risk (for example, potentially disabling stroke), and the desired efficacy of the operations will not be achieved unless the perioperative morbidity and mortality are kept low.


Intracranial Stenosis


Proof of clinical efficacy in using endovascular techniques, including angioplasty, balloon-mounted stents, and self-expanding stents alone or in combination is underway via randomized clinical trials. Both the Vitesse intracranial stent study for ischemic therapy (VISSIT) and Stenting and aggressive medical management for preventing recurrent stroke in intracranial stenosis (SAMMPRIS) trials may provide helpful data on whether endovascular revascularization confers any additional clinical benefit in secondary stroke prevention. The current literature has raised concerns for stent restenosis, as well as the significant variability in techniques, imaging protocols, and patient selection that current practice reflects. As a result, angioplasty and stent placement for the treatment of symptomatic ICAD should be performed on carefully selected patients at high-volume centers. Despite these concerns, use of angioplasty and stent placement for intracranial atherosclerosis has increased dramatically since FDA approval of Wingspan in 2005. The Wingspan Stent system involves the use of a noncompliant Gateway balloon for submaximal angioplasty followed by deployment of a self-expanding open cell nitinol stent that aims to sustain continuous outward radial force. Nearly 10,000 patients have undergone this procedure worldwide. Some of these concerns include the appropriateness and safety of a stent in the intracranial vessels, concurrent need for antiplatelet therapy, the costs, and the true impact in reducing the risk of recurrent stroke. In the extracranial carotid artery, stent-assisted angioplasty has been shown to have superior safety and efficacy compared with balloon angioplasty alone.22


For symptomatic intracranial stenosis, Marks et al. published a series of over 120 patients treated with intracranial angioplasty alone. At


39


Mean follow-up of 2.5 years showed for the primary endpoint of any stroke, MI, death, or post-procedure ipsilateral stroke to be 7.2 % for CAS and 6.8 % for CEA p=0.51. At 30 days, the incidence of stroke or death was 4.4 and 2.3 % for CAS and CEA, respectively. MI was significantly higher in the CEA group. No significant difference existed with subgroup analyses of either the symptomatic or asymptomatic groups. Therefore, the primary considerations in deciding the best management approach for secondary stroke prevention in a patient with carotid artery disease include several factors. The patient’s age, the presence or absence of related cerebral ischemic symptoms; the presence, location, and morphology of the carotid artery lesions, the presence of intracranial occlusive lesions; the presence and severity of accompanying coronary artery disease; how well medical risk factors are controlled; and the experience and track record of the surgeons and interventionalists who would be chosen to perform the surgery or stenting. Also important is the patient’s and family’s preferences for open surgery or a radiologically monitored procedure that has no neck incision.21


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