Intracranial Stenting

Abstract

Prevention from stroke is the best treatment option as stroke is related with a relatively high rate of mortality and functional impairments with the survivors either having requirement for institutional care or being permanently disabled. Primary prevention is important because almost 70% are first events. However, patients who have a TIA or a stroke have a greater risk of a second stroke, which may be associated with mortality or morbidity. Extracranial carotid and vertebral artery occlusive disease is one of the leading causes of stroke. Years before, the value of carotid endarterectomy for patients having symptomatic 70% stenosis have clearly been documented by the results of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST). For patients with carotid stenosis <50%, these trials showed that there was no significant benefit of surgery. The Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial showed non-inferiority of carotid stenting with lower 30-day risk in terms of death, stroke or MI. In the past, therapeutic decisions were based on the occlusion degree of the artery lumen obtained at DSA in large series. Recent imaging interpretation of arterial occlusive disease not only includes evaluation of degree of the stenotic lumen but also includes atherosclerotic plaque type identification, which may have a predictive value on assessment of potential risk of procedural complications. Although DSA offers the highest spatial resolution and dynamic information of blood flow, with the recent advances on CT technology, CTA offer the advantage of imaging at multiple projections, 3D depiction of vessels and cross-sectional images for the exact measurement of the stenotic lumen. Doppler ultrasound may be used as first-line assessment due to its nature of easy and fast application. Additionally, markedly increased advent of the B-mode sonography results in increased quality of vessel wall detection, ulceration and dissection. MRA is also commonly used for detection and grading of carotidvertebral artery stenoses. Main limitation of MRA is the tendency to overestimate the degree of stenosis, which is tried to be overcome by the use of different imaging parameters and reconstruction techniques. On the other hand, better soft tissue imaging capability of cross-sectional MR imaging brings the superiority of assessment of the fibrous cap, the size of the necrotic core and hemorrhage, and the extent of inflammatory activity within the plaque, which may lead to potential complication. The usual approach for carotid-vertebral stenting is the femoral percutaneous introduction of preferably long vascular sheath to the related arterial site. Alternative routes offering potential advantages and disadvantages are the brachial, radial and direct puncture of the affected common arteries. The balloon expandable bare stents, which were used for carotid stenting in the last decade, is prone to an infrequent but serious complication of stent compression same as with balloon expandable covered stents. Recently, balloon-expandable stents are commonly used for treatment of extracranial vertebral artery occlusive disease. Innovated technology with introduction of nitinol self-expanding tapered stents has led to better anatomic compliance to carotid bifurcation. An important feature of self-expandable stents used for carotid stenting is the cell design. Existing stents may either have open-cell design which offer more conformability and closed-cell design with less conformability but believed to have higher resistance to particle penetration.