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Interventional Neuroradiology is a minimally invasive approach in the treatment of vascular diseases of the central nervous system. Conditions in the past that would have required surgical intervention such as aneurysms, vascular malformations, and tumors of the brain, spine, head and neck can be considered for treatment by using an endovascular approach to reach the lesion.
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[Functional and Stereotactic Neurosurgery][Cerebrovascular Surgery Center] Carotid Angioplasty and Stenting
From: Neurovascular Newsletter June 1998
Ronald Budzik, M. D., Christopher M. Putman, M. D., Alexander Norbash, MD
The Interventional Neuroradiology service at Massachusetts General Hospital
and the MGH Brain Aneurysm & AVM Center. 

Stroke is the third leading cause of death in the United States, and represents a major cause of morbidity in the adult population. Although there are many causes of acute stroke including emboli from the heart, blood vessel dissection, and small perforator vessel occlusion, a common treatable cause of acute stroke is atheromatous narrowing at the carotid bifurcation. It is generally believed that in this situation ischemic stroke most commonly occurs from local thrombus formation that develops as a consequence of both ulceration and laminar flow disturbances in and around the stenotic lesion. This local thrombus formation serves as a source for eventual arterial to arterial thrombo-embolism into the intracranial circulation, most commonly to the middle cerebral artery territory. Less frequently, ischemic stroke may be due to low flow from a critical stenosis resulting in a hemodynamic insufficiency to a region of the brain.

Carotid endarterectomy is currently the treatment of choice for atheromatous carotid artery stenosis at the bifurcation. Recent large series demonstrate a benefit of surgical therapy for symptomatic carotid stenoses of greater than 70% lumenal narrowing, and for asymptomatic stenoses greater than 60% compared with conservative medical management. This conclusion is based on large studies in which the procedural complication rates are weighed against the reduction in stroke rates from the intervention. According to actuarial analysis, by two years the risk of ipsilateral stroke was 9% for surgical patients and 26% for medically treated patients, a 17% reduction in absolute risk with surgery (reference 1). Because stroke rates on medical management are low, the periprocedural complication rate (stroke rate) must be minimized in order to obtain a benefit for patients. However, the risk of perioperative stroke or death is highly dependent on the experience and technical expertise of those performing the procedures and is highly variable. The North American Symptomatic Carotid Endarterectomy Trial reported 0.6% mortality, 5.5% perioperative cerebrovascular events, and 2.1% major stroke (reference 1). A more recent review of the published literature reported a 5.6% risk of perioperative stroke and/or death (reference 2). However, complication rates as high as 18-19% have been reported. Patients with higher risk of procedural complications from carotid endarterectomy often have confounding medical problems, such as coexistent angina, vascular anomalies (high carotid bifurcation), prior radiation treatment or are undergoing repeat surgery for restenosis. In an effort to reduce the treatment complications in these patients, new innovative treatments such as angioplasty and stenting are being developed.

In the past several years, multiple centers in the United States and abroad have begun evaluating balloon angioplasty and vascular stenting as an alternative to surgical carotid endarterectomy for carotid stenosis in high risk patients. The procedure is relatively straightforward, simple, and minimally invasive. The use of metallic vascular stents for the carotid arteries, similar to those that have been used to treat stenoses in the coronary, renal, and iliac arteries, has become widespread. Balloon angioplasty alone, by design, causes a controlled dissection of the vessel wall, widening the vessel lumen. Stenting following or during angioplasty is thought to assist in covering the region of dissection induced with angioplasty, potentially reducing the risk of procedure related thrombo-embolism to the brain. The use of a stent is also thought to reduce the risk of acute restenosis seen following angioplasty in other vascular systems, which could be disastrous in the carotid system. Long term restenosis is a problem with endarterectomy as well as with angioplasty alone. The use of stents in conjunction with angioplasty for the carotid system may also reduce the long term risk of restenosis as has been show in other vascular systems.

After a patient has been referred for treatment and has had an appropriate neurological and vascular work up suggesting that treatment may be indicated, diagnostic angiography and potential angioplasty and stenting can be performed. In most cases the procedure can be performed via a standard percutaneous transfemoral approach with the patient anesthetized using light intravenous sedation. Standard diagnostic carotid and cerebral angiography is first performed to confirm the suspected lesion and to evaluate the cerebral circulation for collaterals. Prior to treating the stenosis the patient is anticoagulated and an antiplatelet agent given. To treat a typical stenosis in the proximal internal carotid artery, a guiding catheter is placed from the groin into the common carotid artery. A microwire is used through the guiding catheter to gently cross the stenotic lesion in the internal carotid artery. If the stenosis is too tight to pass a stent primarily, an angioplasty balloon is passed over the microwire to predilate the stenosis in preparation for stent placement. Leaving the microwire across the dilated segment, the balloon is removed and exchanged for the stent delivery device. Once in position, the stent is deployed across the region of the stenosis. If needed, an additional balloon can be placed inside the deployed stent for post-dilation to make sure the struts of the stent are pressed firmly against the inner surface of the vessel wall.

Angioplasty and stenting of carotid stenosis has several potential advantages when compared with surgical endarterectomy. Since no surgical incision needs be to be made in the neck, scarring of the neck related to previous surgery, radiation or trauma do not interfere with the ability to safely reach the lesion for treatment. Also, stenoses that are out of the reach of the usual surgical exposure such as high carotid bifurcations (above the mandible) or those at the skull base do not pose any additional technical challenges. Less importantly, no scar in the neck is made and local complications from surgery such as infection, cranial nerve deficits, and hematomas are for the most part not seen with angioplasty and stenting. Finally, re-treatment of restenosis is a technically simple procedure with angioglasty and stenting compared with a technically challenging procedure with re-do endarterectomy. Angioplasty and stenting does not have an advantage compared to carotid endarterectomy in several important areas. A local anesthesic can be used for either procedure CEA or angioplasty and stenting in most patients. Expense, length of hospital stay and recovery times are similar for both procedures. As of yet, angioplasty and stenting cannot claim equal safety compared with CEA and no studies have addressed long term outcomes of patients following stenting.

Published data evaluating the use of carotid angioplasty and stenting is somewhat sparse compared to the relatively widespread use of the new technique. Initial results are encouraging, but complication rates are difficult to define as with any new procedure. Patients with multiple medical problems or with difficult lesions were often the majority of patients included in the published series making direct comparison with the results of endarterectomy difficult. Initial reports suggest complication rates for minor stroke, major stroke, and death in the 2-10% range (reference 3). Most patients treated with the new technique have been symptomatic; many have had other medical problems which were thought to elevate the risks of endarterectomy. However, some centers are treating asymptomatic patients with high grade stenosis of the internal carotid artery.

We have performed carotid angioplasty and stenting in selected cases of symptomatic lesions, and believe patients should be selected carefully for treatment with this new procedure. We reserve the use of the procedure for patients who would otherwise benefit from carotid endarterectomy but have features of their condition which place them at a high surgical risk. These include: 1) re-operation for progressive stenosis following one or more CEAs, 2) excessive scarring following previous surgery, or radiation (i.e. following treatment of head and neck cancer), 3) high carotid bifurcations, 4) tandem stenotic lesion of the carotid, 5) intra-petrous carotid stenosis. Close pre and post treatment evaluation should be performed, if possible by a neurologist specializing in cerebrovascular disease and stroke. Patients should be treated in a center with expertise in managing the complications related to the procedure such as cerebral emboli.

References:

1. North American Symptomatic Carotid Endarterectomy Trial Collaboration. Beneficial effect of carotid endarterectomy in symptomatic patients with high grade carotid stenosis. N Engl J Med. 1991;325:445-453.

2. Rothwell PW, Slattery J, Warlow CP. A systematic review of the risks of stroke and deathe due to endarterectomy for symptomatic carotid stenosis. Stroke. 1996;27:260-265.

3. Balousek PA, Smith WS, Gress DR, Halbach VV, et al. Angioplasty and stenting for carotid occlusive disease: Current status and recommendations. Journal of Neurovascular Disease 1997;2(2):52-58.

4. Bettman MA, Katzen BT, Whisnant J, et al. Carotid Stenting and Angioplasty: A Statement for Healthcare Professionals From the Councils on Cardiovascular Radiology, Stroke, Cardio-Thoracic and Vascular Surgery, Epidemiology and Prevention, and Clinical Cardiology, American Heart Association. Circulation 1998;97:121-123.

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