12/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Aortic arch injections alone are inadequate; suboptimal studies can lead to misinterpretations as an irregular stenosis can be either underestimated or overestimated in a single projection. Advantages Cerebral angiography permits an evaluation of the entire carotid artery system, providing information about tandem atherosclerotic disease, plaque morphology/ulceration, and collateral circulation that may affect management [61]. The presence of irregular or ulcerated plaque identified on catheter angiography is associated with a greater risk of recurrent stroke and greater benefit from carotid endarterectomy [62]. Disadvantages The disadvantages of catheter angiography include its invasive nature, high cost, and risk of morbidity and mortality. In a 1990 review of prospective studies using cerebral angiography, the risk of all neurologic complications was approximately 4 percent and the risk of serious neurologic complications or death was approximately 1 percent (range 0 to 6 percent) [59]. In a 2003 single-center prospective study of 986 patients undergoing angiography for diagnosis of carotid stenosis or ischemic stroke, an overall neurologic complication rate of 1.7 percent was reported, with a 0.6 percent rate of neurologic complications resulting in permanent sequelae [63]. The risk of morbidity is increased with cerebrovascular symptoms, advanced age, diabetes, hypertension, elevated serum creatinine, and peripheral vascular disease. The size of the catheter, amount of contrast, and procedure duration also affect the likelihood of complications [63,64]. One study found that embolic events following angiography occur more frequently than the apparent neurologic complication rate [65]; the clinical significance of this finding is unclear. Although often considered the "gold standard" of carotid neurovascular imaging methods, conventional DSA has the disadvantage of a limited number of projections, typically two or three, depicting the carotid artery and bifurcation. This limitation could lead to an underestimation of the degree of carotid stenosis in arteries that have asymmetrical rather than concentric stenotic lumens [66,67]. Rotational angiography provides 16 to 32 projections and is far less subject to this problem, but it is less often used in practice. Accuracy As already noted, catheter cerebral angiography has been considered the gold standard for the evaluation of internal carotid artery stenosis [8]. Noninvasive imaging versus catheter angiography In a 2006 meta-analysis of 41 studies and 2541 patients that assessed the accuracy of noninvasive imaging compared with catheter angiography, CDUS, magnetic resonance angiography (MRA), contrast-enhanced MRA (CEMRA), and CTA, all had high sensitivities and specificities for diagnosing 70 to 99 percent internal carotid artery stenosis in patients with ipsilateral carotid territory ischemic symptoms [25]. The https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 13/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate accuracy of the noninvasive tests for 50 to 69 percent carotid stenosis appeared to be substantially reduced compared with 70 to 99 percent stenosis. However, data were limited. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Stroke in adults" and "Society guideline links: Occlusive carotid, aortic, renal, mesenteric, and peripheral atherosclerotic disease".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topics (see "Patient education: Carotid artery disease (The Basics)" and "Patient education: Stroke (The Basics)" and "Patient education: Duplex ultrasound (The Basics)") Beyond the Basics topics (see "Patient education: Stroke symptoms and diagnosis (Beyond the Basics)") SUMMARY AND RECOMMENDATIONS Goals The main goal of carotid artery imaging is determining the presence and degree of atherosclerotic stenosis or complete occlusion. In addition, carotid imaging can identify other arteriopathies (eg, dissection) and evaluate carotid plaque characteristics. (See 'Goals of imaging' above.) https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 14/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Stenosis measurement The main methods of carotid stenosis measurement are the NASCET, ECST, and common carotid (CC) methods. The NASCET method is the most widely adopted. The NASCET and ECST methods were used in two major randomized clinical trials evaluating the utility of endarterectomy in symptomatic patients ( figure 1). The results of all three methods have a nearly linear relationship to each other and provide data of similar prognostic value. (See 'Measurement of stenosis' above.) Choice of imaging test Most patients are evaluated for carotid disease using one of the noninvasive tests (carotid duplex ultrasound [CDUS], time-of-flight magnetic resonance angiography [TOF MRA], contrast-enhanced MRA [CEMRA], or computed tomography angiography [CTA]). These noninvasive imaging modalities all have high sensitivities and specificities for diagnosing 70 to 99 percent internal carotid artery stenosis in patients with ipsilateral carotid territory ischemic symptoms. The accuracy of the noninvasive tests for 50 to 69 percent carotid stenosis is reduced compared with 79 to 99 percent stenosis. (See 'Choice of imaging test' above.) Symptomatic patients For patients with stroke or transient ischemic attack (TIA) potentially due to carotid stenosis, we generally perform CTA or MRA of the head and neck initially. If >50 percent carotid stenosis is identified, we then perform confirmatory CDUS. If discordant results are found, we then consider alternate angiographic imaging different than the initial modality (ie, CTA if MRA was done initially, and vice versa). (See 'Selection of initial test' above and 'Confirmation of stenosis' above.) The management of symptomatic carotid stenosis is reviewed elsewhere. (See "Management of symptomatic carotid atherosclerotic disease".) Asymptomatic patients For patients who have suspected asymptomatic carotid disease, we generally use CDUS as our initial imaging modality. If >50 percent stenosis is identified and carotid revascularization will not be pursued (eg, based on assessment of relative risks and benefits in the individual patient), patients with asymptomatic carotid stenosis can be followed with noninvasive vascular imaging of the carotid artery, typically with CDUS, particularly if they may be candidates for revascularization in the setting of stenosis progression. (See "Management of asymptomatic extracranial carotid atherosclerotic disease", section on 'Imaging surveillance'.) If >50 percent stenosis is identified and if carotid revascularization is being considered, we then proceed to CTA or MRA with a similar approach to concordant and discordant https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 15/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate results as described above. (See 'Selection of initial test' above and 'Confirmation of stenosis' above.) Importantly, all patients with carotid stenosis should receive intensive medical therapy including antiplatelet and statin therapy and other measures to address risk factors for atherosclerosis. Specific recommendations are discussed separately. (See "Management of asymptomatic extracranial carotid atherosclerotic disease", section on 'Intensive medical therapy and follow-up' and "Overview of primary prevention of cardiovascular disease".) The role of carotid revascularization for patients with asymptomatic carotid stenosis is also reviewed separately. (See "Management of asymptomatic extracranial carotid atherosclerotic disease", section on 'Role of carotid revascularization'.) CTA CTA provides an anatomic depiction of the carotid artery lumen and allows imaging of adjacent soft tissue and bony structures. Three-dimensional reconstruction allows accurate measurements of residual lumen diameter and degree of stenosis. (See 'Computed tomography angiography' above.) MRA The MRA techniques most often employed for evaluating the extracranial carotid arteries utilize either two- or three-dimensional TOF MRA or gadolinium-enhanced MRA (contrast-enhanced MRA [CEMRA]). MRA produces a reproducible three-dimensional image of the carotid bifurcation with good sensitivity for detecting high-grade carotid stenosis ( image 2). Both TOF MRA and CEMRA are accurate for the identification of high-grade carotid artery stenosis and occlusion. (See 'Magnetic resonance angiography' above.) Ultrasound CDUS uses B-mode ultrasound imaging and Doppler ultrasound to detect focal increases in blood flow velocity indicative of high-grade carotid stenosis ( image 1A). It is noninvasive, safe, and inexpensive, with good sensitivity and specificity for detecting high-grade carotid stenosis. (See 'Carotid duplex ultrasound' above.) TCD Transcranial Doppler (TCD) examines the major intracerebral arteries through the orbit and at the base of the brain. TCD is often used in conjunction with CDUS to evaluate the hemodynamic significance of internal carotid artery stenosis. TCD monitoring for microembolic signals is a powerful tool for risk-stratifying patients with asymptomatic carotid stenosis. (See 'Transcranial Doppler' above.) Catheter angiography Cerebral catheter angiography remains the gold standard for imaging the carotid arteries. 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Clin Radiol 1998; 53:682. 67. Elgersma OE, Buijs PC, W st AF, et al. Maximum internal carotid arterial stenosis: assessment with rotational angiography versus conventional intraarterial digital subtraction angiography. Radiology 1999; 213:777. Topic 1118 Version 24.0 https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 22/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate GRAPHICS Methods of measuring carotid stenosis in NASCET and ECST Modi ed from Donnan, GA, Davis, SM, Chambers, BR, Gates, PC, Lancet 1998; 351:1372. NASCET: North American Symptomatic Carotid Endarterectomy Trial; ECST: European Carotid Surgery Trial; CC: Common Carotid Method. Graphic 58353 Version 2.0 https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 23/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Carotid artery stenosis assessed by duplex ultrasonography Carotid duplex ultrasound demonstrating high-grade left carotid stenosis. Note the elevated peak systolic and end diastolic velocities (upper right) as well as large echolucent plaque visible in the bulb (arrow). Courtesy of Brett L Cucchiara, MD. https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 24/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Graphic 69525 Version 7.0 https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 25/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate CTA left carotid stenosis Corresponding CTA from the same patient demonstrating a long- segment focal high-grade stenosis in the left internal carotid artery just past the bifurcation (arrow). CTA: computed tomography angiography. Courtesy of Brett L Cucchiara, MD. https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 26/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Graphic 140388 Version 1.0 https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 27/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Carotid artery stenosis assessed by magnetic resonance angiography A magnetic resonance angiogram (MRA) shows marked narrowing and stenosis at the origin of the right internal carotid artery (arrow). Courtesy of Jonathan Kruskal, MD. Graphic 79993 Version 4.0 https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 28/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Consensus panel grayscale and Doppler US criteria for diagnosis of ICA stenosis Primary parameters Additional parameters Degree of stenosis (%) ICA PSV Plaque ICA/CCA PSV ICA EDV (cm/sec) estimate (%)* ratio (cm/sec) Normal <125 None <2.0 <40 <50 <125 <50 <2.0 <40 50 50 to 69 125 to 230 2.0 to 4.0 40 to 100 70 but less than near occlusion 50 >230 <4.0 >100 Near occlusion High, low, or Visible Variable Variable undetectable Total occlusion Undetectable Visible, no Not applicable Not applicable detectable lumen US: ultrasound; ICA: internal carotid artery; PSV: peak systolic velocity; CCA: common carotid artery; EDV: end diastolic velocity. Plaque estimate (diameter reduction) with grayscale and color Doppler US. Reproduced with permission from: Grant EG, Benson CB, Moneta GL, et al. Carotid artery stenosis: Grayscale and Doppler ultrasound diagnosis Society of Radiologists in Ultrasound Consensus Conference. Ultrasound Q 2003; 19(4):190-8. Copyright 2003 Wolters Kluwer Health, Inc. https://journals.lww.com/ultrasound-quarterly/pages/default.aspx. Graphic 140389 Version 1.0 https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 29/30 7/5/23, 11:40 AM Evaluation of carotid artery stenosis - UpToDate Contributor Disclosures Brett L Cucchiara, MD No relevant financial relationship(s) with ineligible companies to disclose. Scott E Kasner, MD Grant/Research/Clinical Trial Support: Bayer [Stroke]; Bristol Meyers Squibb [Stroke]; Medtronic [Stroke]; WL Gore and Associates [Stroke]. Consultant/Advisory Boards: Abbvie [Stroke]; AstraZeneca [Stroke]; BMS [Stroke]; Diamedica [Stroke]; Medtronic [Stroke]. All of the relevant financial relationships listed have been mitigated. John F Eidt, MD Grant/Research/Clinical Trial Support: Syntactx [Clinical events, data/safety monitoring for medical device trials]. All of the relevant financial relationships listed have been mitigated. Joseph L Mills, Sr, MD No relevant financial relationship(s) with ineligible companies to disclose. John F Dashe, MD, PhD No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/evaluation-of-carotid-artery-stenosis/print 30/30