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 Carotid Artery, Stenosis
 Author: Lennard A Nadalo, MD, Clinical Professor, Department of Radiology, University of
 Texas Southwestern Medical School; Consulting Staff, Envision Imaging of Allen and Radiological
 Consultants Association.

 Lennard A Nadalo is a member of the following medical societies: American College of Radiology,
 American Society of Neuroradiology, American Society of Pediatric Neuroradiology, Radiological
 Society of North America, and Texas Radiological Society.

 Coauthor(s): Michelle C Walters, DO, Consulting Staff, Radiological Consultants Association

 Editors: Robert A Koenigsberg, DO, MSc, FAOCR, Professor, Director of Neuroradiology,
 Program Director, Diagnostic Radiology and Neuroradiology Training Programs, Department of
 Radiology, Hahnemann University Hospital, Drexel University College of Medicine; Bernard D
 Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services,
 Hutt Valley District Health Board, New Zealand; Douglas M Coldwell, MD, PhD, Professor of
 Radiology, Director, Division of Vascular and Interventional Radiology, University of Louisville
 School of Medicine; Robert M Krasny, MD, Resolution Imaging Medical Corporation; Kyung J
 Cho, MD, FACR, William Martel Professor of Radiology, Interventional Radiology Fellowship
 Director, University of Michigan Health System.



 Synonyms, Key Words, and Related Terms
 carotid artery stenosis, carotid plaque, ulcerated carotid plaque, carotid artery stenosis, carotid
 arterial stenosis, stroke, brain attack, CVA, cerebrovascular accident, carotid stenosis, carotid
 bruit, extra cranial carotid occlusive disease

 Introduction
 Background

 Stroke (brain attack) represents one of the most serious causes of mortality and morbidity in the
 United States and throughout the world. Each year, 150,000 patients die as a direct result of a
 cerebrovascular accident (CVA), while 600,000 patients experience the morbidity of aphasia,
 blindness, or paralysis. Among patients with stroke, extracranial carotid disease represents the
 cause of approximately one half of cases. The goals of carotid imaging can be described as early
 detection, clinical staging, surgical road mapping, and postoperative therapeutic surveillance
 (see Image 1).




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 Four of the most common methods of imaging the carotid artery are compared. Angio
 = angiography, CTA = CT angiography, Duplex = duplex ultrasonography, Gd =
 gadolinium enhancement, ICA = internal carotid artery, MRA = magnetic resonance
 angiography, TOF = time of flight.




 Surface-rendered 3-dimensional volume CT angiogram demonstrates a complete
 occlusion of the right common carotid artery (CCA).


 Imaging helps in detecting associated conditions early. Coronary artery disease, peripheral
 arterial stenosis, and hypertension are associated with an increased incidence of carotid arterial
 stenosis. Carotid arterial screening remains controversial. Good evidence supports evaluation for
 carotid stenosis prior to coronary arterial bypass surgery.1, 2, 3

 Detection of a carotid bruit is a common physical examination finding that may lead to a referral
 for carotid duplex sonography. The correlation between a carotid bruit and a hemodynamically
 important carotid stenosis is reported to be between 10-20%. A cardiac murmur may be
 transmitted to the neck. Stiff, calcified, or torturous vessels may generate a bruit in the absence
 of stenosis.

 Recent study

 The use of intravenous tissue plasminogen activator (t-PA) for stroke 3-4.5 hours after symptom
 onset has been endorsed by the American Heart Association, although time to treatment remains
 of extreme importance and should not be delayed. The European Cooperative Acute Stroke
 Study 3 (ECASS 3) showed benefit from t-PA in patients treated 3-4.5 hours after onset of
                     4, 5, 6, 7
 symptoms of stroke.

 For excellent patient education resources, visit eMedicine's Stroke Center and Dementia Center.
 Also, see eMedicine's patient education articles Stroke, Transient Ischemic Attack (Mini-stroke),
 and Stroke-Related Dementia.

 Pathophysiology

 Transient ischemic attack (TIA) is the result of a brief interruption of blood flow to the brain. In
 80% of cases, the interruption occurs as a result of blockage in the arterial circulation to the




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 brain due to an embolus, an obstructing arterial thrombus, or the stenotic effects of
 atherosclerosis. In the other 20%, the interruption is caused by minor hemorrhage in the brain.

 In both types of TIA, the lack of oxygen to the brain produces symptoms similar to those
 produced during a full stroke. Symptoms can affect vision, behavior, movement, speech, and
 thought processes. However, the symptoms of a TIA are temporary, generally lasting only 8-14
 minutes with most clearing within an hour, although they can continue for as long as 24 hours.
 Permanent damage is unlikely because the oxygen supply to the brain is restored fairly quickly.

 Thrombus causes 25-50% of all TIAs, and embolism causes 11-30%. A lacunar infarction occurs
 in 11-14% of patients with TIA. Less common causes of a TIA involve minor bleeding or sentinel
 leaks from a cerebral blood vessel (approximately 10% of cases). Mini strokes caused by
 bleeding are usually due to high blood pressure (hypertension). Since the underlying cause of
 this type of TIA is bleeding rather than blockage, the patient must receive an immediate and
 accurate medical evaluation. Treatment should not include thrombolytic drugs or aspirin because
 these agents increase bleeding.

 Once blockage or bleeding occurs, whether the person is about to have a TIA or a full stroke
 depends greatly on host factors, eg, the person's age and general health status and the location
 and size of the blockage or bleed. Other blood vessels in the area may enlarge to improve blood
 flow to the affected area, thus ending the TIA. Although a TIA is characterized by a brief
 interruption of blood flow, symptoms of a TIA (eg, weakness on 1 side of the body) may last
 much longer than the time needed to dissolve the blockage completely or to absorb the bleed.
 For most people, symptoms last approximately 8-14 minutes and usually clear within an hour,
 but they can last as long as 24 hours.

 Patients with symptoms of a TIA that persist for more than 24 hours usually are treated as
 though they have had a full stroke. More than 50,000 Americans have TIAs every year. In
 persons older than 65 years, 8.5% have been diagnosed with at least 1 mini stroke. The risk of
 stroke is highest soon after a TIA, and the risk continues to be approximately 5% during the first
 month following the TIA. Of patients with TIAs, 20-25% are estimated to develop a stroke within
 2 years.

 If the degree of carotid stenosis is severe, in the absence of adequate collateral circulation the
 ipsilateral cerebral hemisphere may become underperfused. When the arterial circulation falls,
 there is an increased risk of thrombosis within the middle cerebral artery (MCA), the anterior
 cerebral artery, and the more peripheral branches of the intracranial arterial circulation. Focal
 thrombosis may occur in areas of pre-existing atherosclerotic disease.

 Other general medical issues which may exacerbate symptoms related to carotid stenosis include
 chronic lung disease, cardiac disease with restricted cardiac function, and attempts to low
 systemic hypertension. Any adverse physiological change which further limits oxygenation to the
 brain may result in cerebral ischemia in patients who otherwise tolerated even high-grade
 carotid stenosis.

 The presence of 2 or more tandem arterial stenoses may result in symptomatic cerebral
 ischemia, even if any one of the narrowed arterial inflow circulation pathways was not critically
 narrowed.

 Frequency

 United States

 The prevalence of hemodynamically significant carotid stenosis varies with age and other risk
 factors. Estimates indicate that 5 per 1000 persons aged 50-60 years and approximately 10% of
 persons older than 80 years have carotid stenosis greater than 50%.




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 Strokes were responsible for more than 150,000 deaths in 1998. Stroke is the third leading
 cause of death in the United States after heart disease and cancer. Each year, approximately
 600,000 people have a stroke, and in 100,000 people, strokes recur annually. Approximately one
 half of all strokes result from significant extracranial arterial disease.

 International

 Carotid stenosis and CVA follow a similar pattern of occurrence within the developed world. A
 direct relationship exists between cigarette smoking and a diet rich in fat. The occurrence of
 carotid vascular disease probably is lower in underdeveloped countries; however, absolute
 incidence is difficult to measure.

 Mortality/Morbidity

 Patients with carotid artery stenosis are at increased risk for subsequent stroke, myocardial
 infarction (MI), and death. The risk of stroke is greatest for persons with neurologic symptoms
 such as TIAs, but it also is increased in patients with asymptomatic lesions. The proportion of all
 strokes attributable to previously asymptomatic carotid stenosis is small; however in patients
 older than 60 years who have cerebral infarction, approximately 15% have ipsilateral carotid
 stenosis of 70% or greater. The frequency of hemodynamically significant carotid artery stenosis
 is higher in symptomatic patients than in asymptomatic patients. In 40-50% of those with a
 complete stroke, the primary etiology of the stroke is related to extracranial carotid disease
 (stenosis).

 Morbidity of a true transient CVA is nil. Without a completed infarction, the ischemic brain should
 return to a normal functional state. However, if the period of cerebral ischemia persists beyond
 12-24 hours, even a seemingly full neurologic recovery is commonly associated with imaging
 findings of focal cerebral infarction. Beyond 24 hours and up to 48 hours following the initial
 CVA, neurologic recovery may be nearly complete, with small areas of infarction best
 demonstrated on T1-weighted diffusion cerebral MRIs.

 The completed infarct syndromes involve neurologic defects that persist beyond the period of
 active medical treatment in patients with acute stroke. The specific morbidity related to a stroke
 is a reflection of the portions of the brain that have become ischemic and is related closely to the
 cerebral vessels that are stenotic or thrombosed.

 Common stroke syndromes that may result from carotid stenosis, ulceration, or occlusion include
 the following:

     •   Regarding common and internal carotid artery (ICA) occlusion syndromes, young people
         with occlusion of the main trunk may be asymptomatic. Other manifestations of ICA
         occlusion include transient hemiplegia, persistent hemiparesis, unilateral loss of vision if
         the ophthalmic artery is involved, and aphasia when the dominant side is thrombosed.

     •   Embolization to the anterior cerebral artery or critical stenosis of carotid artery may
         affect the major branches of the anterior cerebral artery (medial striate artery,
         recurrent artery of Heubner, orbitofrontal artery, frontopolar artery, anterior internal
         frontal artery, middle internal frontal artery, posterior internal frontal artery,
         callosomarginal artery, pericallosal artery, and parieto-occipital artery).

     •   Anterior cerebral occlusion syndrome involving the main trunk results in contralateral
         hemiplegia (lower extremity), mild sensory deficits of the contralateral lower limb, and
         mental confusion or clouding of consciousness.




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    •   The middle cerebral artery, including the major branches (striate arteries, anterior
        cerebral head of caudate septum pellucidum, middle cerebral globus pallidus, anterior
        temporal branch, and orbitofrontal, operculofrontal, central sulcus, posterior parietal,
        angular, and posterior temporal branches) may be directly affected by embolization, or
        a thrombosis may result due to proximal stenosis of the ipsilateral ICA.

    •   Middle cerebral occlusion syndrome of the main trunk results in coma, contralateral
        flaccid hemiplegia, hemianesthesia hemianopia, and motor and sensory aphasia
        (dominant hemisphere).

    •   Middle cerebral occlusion syndromes of the posterior parietal, angular, or posterior
        temporal branches result in contralateral hemiparesis, contralateral astereognosis,
        contralateral homonymous hemianopia, sensory aphasia, agnosia, apraxia, and alexia if
        on dominant side.

    •   Embolization to perforation branches results in contralateral hemiplegia, contralateral
        rigidity, and tremor.

    •   Posterior cerebral branches, including major branches (anterior temporal artery,
        posterior temporal artery, posterior occipital artery, calcarine artery, and collateral
        arteries), may be involved. The primary blood flow pattern to the posterior cerebral
        artery may arise from the ICA. The stroke pattern resulting from embolization or
        stenosis affects the related cerebral structures, ie, the anterior temporal artery (inferior
        temporal lobe), posterior temporal artery (inferior temporal lobe), posterior occipital
        artery (inferior and medial occipital lobe, posterior corpus callosum), calcarine artery
        (calcarine cortex occipital lobe), and collateral arteries (thalamogeniculate
        thalamoperforating branches).

    •   Posterior cerebral occlusion syndrome of the main trunk includes contralateral
        hemianesthesia, contralateral homonymous hemianopia, sensory aphasia if on the
        dominant side, ipsilateral cerebellar signs, contralateral rigidity, tremors, and
        choreiform movements.

    •   Retrolenticular capsule includes hemiplegia hemihypalgesia, hemianesthesia, and
        contralateral homonymous hemianopia.

    •   Involvement of the calcarine artery includes contralateral homonymous hemianopia,
        loss of half of the person's macular vision, visual agnosia if on the dominant side,
        thalamic syndrome, contralateral hemianalgesia, contralateral dysesthesia, and pain.


 Race

 Strokes are more common among blacks and Hispanics than others. The incidence of CVA tends
 mirror the incidence of hypertension and diabetes. The rate of diabetes among Hispanics is
 greater than in the population as a whole. Hypertension is both more severe and more common
 among blacks than among others. The factors of diet, obesity and family history interact to
 result in a greater risk of carotid stenosis in both blacks and Hispanics.

 Treatment of patients who are asymptomatic for carotid stenosis and the overall management of
 hypertension tend to be less successful among patients of lower socioeconomic status, resulting
 in more frequent and more severe strokes. To the extent that blacks and Hispanics represent a
 greater percentage of the population in poverty, the medical treatment of strokes in minority
 patients has a worse outcome.




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 The complex interassociation of genetics, diet, and lifestyle is reflected by the relatively low rates
 of vascular disease reported among elderly persons living in remote areas of Italy and China.

 Sex

 Carotid stenosis requiring surgical treatment tends to occur in almost equal frequency in men
 and women. In general, women are more likely to seek and receive treatment for both benign
 and symptomatic carotid stenosis.

 Age

 Extracranial carotid disease tends to occur more frequently in elderly persons. In patients with
 increased risk factors, the age at first presentation tends to be younger.

 Anatomy

 Anatomy and variants

 The aortic arch presents many anatomic variations that may affect the treatment of patients with
 carotid stenosis. The most common aortic arch variant has 3 primary branches, ie, the
 innominate artery, the left common carotid artery (CCA), and the left subclavian artery. The
 right CCA arises from the innominate artery. The most common variant has a single (bovine)
 origin of the innominate artery and the left CCA (see Image 2).




 Thoracic arch angiography demonstrates one of the common variants of normal aortic
 arch (AA) development in which both the innominate artery (IA) and the left carotid
 artery share a common origin. The right common carotid artery (RCA) and the right
 internal carotid artery are irregular and narrowed. The long, multisegment areas of
 stenosis are believed to result from the effects of radiation therapy to the right side of
 the neck in this patient. Effects of radiation therapy are related to adverse effects on
 the vascular supply to the carotid or vertebral artery in the radiation field.


 The right subclavian artery may take its origin from the aortic arch distal to the left subclavian
 artery, in which case, the first aortic arch branch usually is the right CCA. Stenosis of the
 proximal origin of the CCA or the innominate artery may result in clinical cerebral ischemia and
 must be differentiated from carotid stenosis because the surgical approach is entirely different.
 The CCA bifurcates in the cervical region to form the external carotid artery (ECA) and the ICA.
 The level in the cervical region at which the bifurcation occurs is highly variable.

 Occasionally, the origin of the ICA occurs at or above the angle of the mandible. Four primitive
 connections that normally regress occur between the anterior and the posterior circulations. The
 persistent trigeminal artery is the most common anomaly. The persistent hypoglossal artery
 occurs at a rate of approximately 0.2%. Clinically, significant stenosis may occur at the origins of




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 both normal and anomalous vessels. The normal internal diameter of the ICA is highly variable.
 Within the same normal vessel, the diameter of the ICA varies and is larger in the proximal
 carotid bulb. As a result of normal variations, the absolute internal diameter is less significant
 than the ratio of the diameter of a stenotic vessel to the normal diameter of the distal ICA.

 Vascular causes of stroke

 The cervical portion of the CCAs and ICAs form the primary basis for diagnosis and treatment of
 carotid stenosis (see Image 5). Surgical treatment and prevention of stroke is directed toward
 the detection of extracranial carotid vascular disease because effective surgical treatment is
 limited to the cervical carotid artery and the brachiocephalic branches of the aorta. Extracranial
 carotid occlusive disease accounts for more than one half of strokes. While stenosis, thrombosis,
 and anomalies of the aortic arch may contribute to unusual collateral blood flow, stenosis and
 plaque ulceration within the common carotid bulb and proximal ICA indicate the primary
 anatomic structures found in the surgical treatment of stroke.




 Common carotid angiogram shows normal findings. Note the slightly dilated shape of
 the distal common carotid artery and the proximal internal carotid artery (carotid
 bulb). ec = external carotid artery; f = facial artery; l = lingual artery; ic = internal
 carotid artery; im = internal maxillary artery; o = occipital artery; p cer = posterior
 cerebral artery; p com = posterior communicating artery


 The ECA and its branches provide important collateral pathways, which may reduce the ischemic
 effects of an ICA stenosis (see Image 19). The primary external carotid arterial pathways involve
 branches of the ophthalmic artery, the internal maxillary artery, and the occipital artery. Plaque
 in the proximal ECA may result in a bruit, which can result in diagnostic confusion. Rarely, the
 ECA may become the source of distal embolization through enlarged collateral pathways. The
 ICA can be divided into a cervical portion, an intrapetrosal portion to the cavernous sinus, an
 intracavernous segment, and a supraclinoid segment with major distal branches including the
 anterior cerebral and MCAs. Major branches of the ICA include the ophthalmic,
 meningohypophyseal, posterior communicating, anterior choroidal, anterior cerebral, and MCAs.




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 Carotid Artery, Stenosis. Sagittal MPR image from a carotid CTA in a patient with
 sudden onset of aphasia. The proximal left ICA demonstrates a short segment of
 complete occlusion with flow preserved in the more distal left ICA. The common
 carotid artery (CCA) has a normal diameter.


 Decreased cerebral arterial perfusion can result in symptomatic cerebral ischemia if a significant
 degree of stenosis occurs at most points along the blood pathway from the aortic arch to the end
 intracranial vessels. Atherosclerotic stenosis tends to occur near the origins of major branch
 arteries and within the area of vascular turbulence. This is most likely related to intimal trauma,
 which tends to occur near the origins of arterial branches.

 Assessment of a patient who presents with cerebral vascular disease should include a search for
 an inflow stenosis near the origin of the right innominate artery or the proximal left CCA. In the
 most common anatomic presentation, the right CCA and the right subclavian artery arise from
 the innominate artery. Stenosis of the innominate artery may result in right-sided vertebral
 arterial steal as well as symptomatic reduction of right carotid arterial blood flow. Because of the
 larger diameter of the innominate artery, symptomatically significant stenosis of the innominate
 artery is less common than stenosis of the proximal left common artery.

 Clinical Details

 Risk factors for carotid artery disease are similar to those for coronary artery disease, ie,
 atherosclerosis of the main arteries that carry the oxygen-rich blood to the heart (coronary
 arteries). Therefore, people with one condition often also have the other. Risk factors for both
 (as shown by a coronary risk profile) that can be modified include smoking, lack of regular
 exercise, eating a high-fat high-cholesterol diet, obesity (>20% over an individual's ideal
 weight), uncontrolled diabetes, uncontrolled hypertension, uncontrolled stress and anger, high
 low-density lipoprotein (bad cholesterol) levels, and low high-density lipoprotein (good
 cholesterol) levels.

 Risk factors that cannot be modified include (1) sex, ie, men are more likely to have a stroke
 and survive, women are more likely to die as a result of stroke; (2) advanced age, ie,
 cardiovascular diseases tend to affect older people more than younger people; and (3) ethnicity,
 ie, African Americans have a higher risk of high blood pressure than others.

 TIA is a warning sign of a future stroke. An estimated 25% of patients with TIA develop a stroke
 within the next 2 years. Symptoms of a TIA include weakness, numbness or tingling on one side
 of the body, confusion, trouble with speaking, difficulty understanding speech, vertigo, and
 severe headache. TIAs also may cause a variety of visual symptoms that include partial loss of
 vision or complete blindness, double vision, abnormal eye movements, blurred vision, and a gray
 shading or fogging within the field of vision.




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 Medical treatment for mild to moderate carotid stenosis is most appropriate. Treatment is
 directed toward reducing the progression of the atherosclerotic disease process by lowering
 serum cholesterol levels, controlling hypertension, and by the administration of a medication
 such as aspirin, which decreases the likelihood of platelet or small clot embolization.

 Carotid endarterectomy of asymptomatic carotid stenosis is most commonly limited to lesions
 with a 70% or greater degree of stenosis.8 Asymptomatic carotid stenosis may be detected by
 the auscultation of a cervical (neck) bruit or other screening method. Symptomatic carotid
 stenosis (SCS) is characterized by an associated stroke, TIA, transient monocular (1 eye)
 blindness, or other objective symptom or sign of an ipsilateral cerebral vascular event.
 Treatment for most SCS is surgical.

 More recently, carotid stenosis has been successfully managed by means of endovascular carotid
 stent placement. The selection of a specific clinical treatment is based upon the degree of
 stenosis, the condition of the arterial vessels proximal to the carotid stenosis, and the availability
 of specific treatment options.

 Preferred Examination

 A complete medical history should be taken first. On the basis of risk factors and the family
 history and current symptoms, selecting a screening examination such as duplex carotid
 sonography, CT angiography (CTA), or magnetic resonance angiography (MRA) of the carotid
                                                          9
 artery may be appropriate (see Image 1, Images 13-15).




 Four of the most common methods of imaging the carotid artery are compared. Angio
 = angiography, CTA = CT angiography, Duplex = duplex ultrasonography, Gd =
 gadolinium enhancement, ICA = internal carotid artery, MRA = magnetic resonance
 angiography, TOF = time of flight.




 Oblique 3-dimensional contrast-enhanced magnetic resonance (MR) angiogram of the
 aortic arch and brachiocephalic vessels shows high-grade stenosis of the proximal left
 subclavian artery (white arrow). By using such a model, full depiction of the arch,
 brachiocephalic vessels, and carotid bulbs is possible. Because of superimposed
 structures, full rotation of the arterial model is necessary. Note the left common
 carotid artery (LCCA) behind the left jugular vein. The left subclavian artery (LSCA) is
 seen well (blue arrow).




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 Carotid Artery, Stenosis. Axial CT of the brain in a patient with the sudden onset of
 aphasia.




 Carotid Artery, Stenosis. Duplex carotid sonography in a patient with sudden onset of
 aphasia. The images are taken from the common carotid artery.



 After obtaining the medical history, carotid duplex imaging is performed most commonly in
 patients with moderate risk factors. In the author's practice, duplex sonography is the initial
 triage examination for patients with an asymptomatic bruit, known asymptomatic carotid
 vascular disease, and in patients with a complete stroke without prior history of carotid stenosis.

 In symptomatic patients and in most who present with abnormal carotid sonographic findings,
 another imaging test is performed. MRA or CTA offer full depiction of the cervical and cerebral
 portions of the CCA and ICA. In most cases, a diagnostic evaluation for cerebral vascular disease
 can be performed by using either MRA or CTA. The immediate availability of CTA in many critical
 hospitals on a 24-hour basis makes CTA attractive in the care of patients who present after
 hours in the emergency department.

 In the selection of patients for acute treatment for cerebral ischemia, axial CT images should be
 reviewed by using the criteria of less than one-third involvement of the middle cerebral
 distribution or by using the Alberta Stroke Program Early CT Score (ASPECTS). The role of
 cervical-cerebral angiography is evolving as less invasive alternative tests have become
 available. Many experienced vascular surgeons are more comfortable with cervical-cerebral
 catheter angiography than with other studies. In the author's practice, clinicians perform carotid
 angiography routinely, and cerebral angiography or digital subtraction angiography (DSA) is
 reserved for patients who are likely candidates for surgery or for patients who may benefit from
 angiographically based carotid intervention.

 Limitations of Techniques

 Although carotid duplex imaging offers an excellent means of initial evaluation of the extracranial
 cerebral vessels, the presence of dense calcifications in the carotid plaque tends to make the




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 study less accurate (see Image 20). Because carotid duplex imaging does not help in assessing
 the intracranial portion of the carotid artery, tandem lesions of the ICA may be missed. In a
 similar manner, proximal stenosis of the innominate artery and the left carotid artery cannot be
 evaluated near the origins from the aortic arch.




 Carotid Artery, Stenosis. The anterior communicating artery (AComA) represents an
 important collateral circulation which preserves blood flow to the left middle cerebral
 artery (L MCA) in this patient with sudden onset of aphasia. The proximal left ICA was
 noted to be occluded on the CTA of the cervical carotid arteries.



 MRA is contraindicated in patients who have cardiac pacemakers or cerebral aneurysm clips or in
 those who have undergone certain other medical procedures. In addition, MRA is highly motion
 sensitive. Many patients require sedation. Because of artifacts related to the MRA image, the
 degree of stenosis may be overestimated.

 CTA requires iodinated contrast agents to be injected at a relatively high flow rate. Patients with
 renal disease may not tolerate intravenous contrast agents. Motion artifacts remain a problem if
 the examination is performed by using older CT equipment (see Images 20-21).




 Carotid Artery, Stenosis. Duplex sonography of the external carotid artery in a patient
 who presented with the sudden onset of aphasia.




 Lateral selective right common carotid arteriogram. Only the proximal few centimeters
 of the internal carotid artery are patent (arrow). Selective catheterizations in the
 performance of carotid angiography provide higher resolution (smaller field of view),




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 high concentrations of intraluminal contrast agent, and extended angiographic
 imaging (longer runs of images). The almost occluded internal carotid artery is
 evaluated better by using selective common carotid angiography.




 Lateral common carotid arteriogram in a patient with a neck bruit. Note the focal
 narrowing of the proximal internal carotid artery (arrow). In severe cases, the kink
 may require carotid artery reconstruction.




 Anterior left common carotid arteriogram in a patient who presented with a loud left
 neck bruit. Note the horizontal line (arrow) in the proximal internal carotid artery,
 which represents a focal folding of the carotid artery. This configuration has been
 termed a kink. The bruit results from the turbulent blood flow through the focal
 narrowing.




 Lateral common carotid arteriogram in a patient with transient ischemic attacks. A
 small filling defect is noted in the common carotid bulb (arrow). A small blood clot was
 found at surgery, with intimal ulceration at the base of the clot.




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 Carotid Artery, Stenosis. Proximal duplex sonography of the left ICA in a patient who
 presented with the sudden onset of aphasia.


 Cerebral angiography also involves the injection of iodinated contrast agents. The overall
 contrast dose is similar to that required for CTA. The performance of catheter-based cervical-
 cerebral angiography depends on the skill and experience of the angiographer. Overall major
 morbidity rates are 0.1-1%. Injury may occur in the form of iatrogenic stroke or bleeding around
 the catheter introduction site. Angiograms do not provide much information concerning the
 nature of the plaque lesion. Cerebral angiography is the most costly means of carotid stenosis
 evaluation. If cases are selected carefully, the overall risk of diagnostic angiography together
 with the morbidity related to carotid surgery is less than the risk of stroke for the untreated
 patient (see Images 6-9, Image 11, Image 17).

 Differentials
 Alzheimer Disease
 Aorta, Dissection
 Arteritis, Giant Cell
 Brain, Aneurysm
 Brain, Arteriovenous Malformation
 Brain, Capillary Telangiectasia
 Brain, Cavernous Angiomas
 Brain, Hypertensive Hemorrhage
 Brain, MRI Appearance of Hemorrhage
 Brain, Stroke
 Brain, Venous Sinus Thrombosis
 Coronary Artery Disease
 Embolization, Hemorrhage

 Other Problems to Be Considered

 Radiograph
 Findings

 Standard radiographs may demonstrate calcification in the carotid vessels in the neck; however,
 only large calcified plaques are demonstrated on radiographs. In general, the information
 provided by radiographs of the neck or skull is not clinically helpful except to alert the clinical
 physician that the patient may be at risk for carotid stenosis.

 Degree of Confidence

 In general, calcification in a plaque indicates a chronic disease pattern. The absence of
 calcification on radiographs of the neck or lateral aspect of the skull does not exclude significant
 extracranial carotid disease.




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 False Positives/Negatives

 Calcification in the carotid bulb is not fully correlated with significant carotid arterial stenosis.
 High-grade stenosis of the proximal carotid artery may occur in the absence of calcifications, and
 dense carotid calcification may be seen in the absence of a high-grade carotid stenosis.

 CT SCAN




 Carotid Artery, Stenosis. Axial CT of the brain in a patient with the sudden onset of
 aphasia.




 CT and CT angiography in a patient with a load left neck bruit and symptoms of a
 transient ischemic attack. A, CT scan demonstrates that the left jugular vein (LJV) is
 superimposed on the left common carotid artery (LCCA). B, After electronic removal of
 the superficial left jugular vein, a high-grade stenosis of the origin of the left external
 carotid artery (LECA) is demonstrated clearly. Dense calcifications are seen (red
 arrows) near the origins of both the left external carotid artery and the carotid bulb.
 The left internal carotid artery is not significantly stenotic.




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 Oblique multiplanar reformatted CT angiogram demonstrates a mild degree of stenosis
 in the proximal right internal carotid artery (RICA). RJV = right jugular vein.




 Maximum intensity CT angiogram demonstrates mild bilateral carotid stenosis. L = left,
 R = right.




 Surface-rendered 3-dimensional volume CT angiogram demonstrates a complete
 occlusion of the right common carotid artery (CCA).




 Axial CT angiograms (A and B) demonstrate bilateral occlusions of the right and left
 common carotid arteries (arrows).




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 Intracranial CT angiogram in a patient with bilateral common carotid occlusion shows
 an absence of flow in the right and left internal carotid arteries (ICAs). ACA = anterior
 cerebral artery, MCA = middle cerebral artery, PCA = posterior cerebral artery, PCCA =
 posterior communicating cerebral artery.




 Axial CT image of a patient with a focal stenosis of the internal carotid artery. The
 cavernous sinus (CS) is distended, with an abscess (arrowheads). Stenosis of the
 intracavernous internal carotid artery was a response to the abscess in this patient.

 Findings

 Axial CT images of the cerebral circulation provide both an accurate means of assessing stenosis
 and carotid plaque. Although early attempts to apply CT in the evaluation of the carotid artery
 were limited by movement artifacts and thick scanning sections, current multisection CT
 scanners allow for the acquisition of thin (eg, 1.0-2.0 mm) axial images within a brief time (a
 single breath hold). Intravenous contrast material must be injected rapidly enough (3-4 mL/s for
 a total volume of 120-150 mL of 300-320 mg/mL nonionic contrast agent) to achieve a contrast
 density of at least 150 HU or in the innominate and carotid inflow to continuing distally into the
 intracranial carotid artery. Imaging begins just before the contrast density peaks in the carotid
        10
 artery.


 Initially, all images should be reviewed in the axial plane (see Image 34).
 Multiplanar and curved multiplanar reformatted images are often helpful (see Image 21, Image
 24). The intraluminal diameter should be measured by using an electronic workstation with
 electronic calipers. If the image of the carotid artery is enlarged before measurement, error is
 reduced. Measurements are made across the lumen through the narrowest portion of the
 proximal ICA and across the area of the ICA that is above the stenosis and is believed to be
 normal. The degree of stenosis is calculated according to criteria developed by the North
 American Symptomatic Carotid Endarterectomy Trial (NASCET) and is reported as a percentage
 of stenosis (see Image22, Images 24-25).

 Carotid ulceration




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 Another mechanism related to cerebral infarction is embolization from the heart or great vessels.
 Except to acknowledge the need to evaluate some patients after MI by using echocardiography,
 the heart as a source of cerebral emboli is beyond the scope of consideration for this article. The
 carotid arteries may be a source of cerebral emboli via release of the contents of the plaque, via
 turbulence or clot formation on the ulcerated surface. Carotid ulcers are best demonstrated by
 using the higher resolution of catheter angiography; however, the use of multisection CTA
 increases the likelihood of carotid ulcer identification. Larger deeper ulcers are successfully
 depicted with most CTA techniques (see Image 29).

 Carotid plaque

 Dense calcifications in the carotid artery limit the accuracy of measurements of the degree of
 stenosis across the plaque if maximum intensity projection (MIP) or shaded-surface display
 imaging is used. After first attempting to measure the degree of stenosis by using axial images,
 curved multiplanar reformatted images obtained through the lumen help show the stenosis.
 Certain workstation techniques can be applied that can image reverse the pixels above 300 HU.
 Image inversion subtracts calcified plaque from the image, which tends to result in a clearer
 image of the contrast agent–filled carotid lumen. Occasionally, contrast may be seen entering
 the subintimal area of the plaque. Complex and dissected carotid plaques may be detected in
 this manner (see Image 20).

 Carotid thrombosis

 Care must be exercised in cases of carotid thrombosis. Very slow flow rates may be missed if the
 timing of the intravenous contrast agent bolus or the peak density of the contrast material is less
 than optimal. Comparison of 3-dimensional (3D) volume images should always be made to axial
 images (Images 33-34). The intracranial collateralization pattern helps make the diagnosis of
 thrombosis and offers important clinical information (see Images 35-38).

 Tumors of the cervical region may surround the CCA or the ICAs. One of the advantages of cross
 -sectional imaging, such as CTA, is the identification of the tissues that surround the carotid and
 vertebral arteries.

 Degree of Confidence

 Carotid CTA represents a reliable means of estimating the degree of stenosis in both extracranial
 and intracranial vessels. Limitations in the degree of confidence are related to technical factors.
 Current multisection CT scanners allow for the acquisition of up to 16 sections for each gantry
 rotation. Each rotation may require as little as 0.4 seconds. Axial collimation for cervical-cerebral
 CTA is performed by using a collimation of 0.75 mm with a reconstruction of 1.5 mm for each
 axial image.

 Axial images, multiplanar reformatted images, and 3D volume MIP and volume-model images
 contribute to the sensitivity and accuracy of multisection CTA. By using available multisection CT
 scanners, extracranial carotid stenosis can be diagnosed to a degree of accuracy equal to or
 exceeding that of catheter-based angiography. CT offers an excellent means of detecting a
 tumor that might surround the carotid artery in the neck.

 When the carotid artery is imaged by using CTA, artifacts include motion, poor cardiac function,
 and dense carotid calcification. Overall accuracy for carotid CTA exceeds 95%. Intracranial CTA
 with a multisection scanner reportedly helps in identifying intracranial carotid stenosis with a
 sensitivity of greater than 98%, a specificity of 99%, and an accuracy of greater than 98%.
 Multisection CT scanners have been introduced that acquire 8 scans with each gantry rotation.
 With this newest technology, CTA represents the best overall means with which to investigate
 carotid stenosis in a less invasive and more cost-effective manner.




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 False Positives/Negatives

 False-positive results of carotid CTA are related to motion artifacts. Sudden movement,
 breathing, or swallowing by the patient during scanning may result in a misregistration of the
 axial images on 3D or multiplanar reformatted images. In such cases, only measurements taken
 from the axial images should be considered.

 False-negative results may occur if the vessels of the carotid bulb are very dilated and torturous.
 Superimposed jugular veins and arteries may hide a stenosis (see Image 21). A careful review of
 axial images, together with carefully performed curved multiplanar reformatted images through
 the carotid lumen, demonstrate the stenotic area in most patients.

 MRI




 Oblique 3-dimensional contrast-enhanced magnetic resonance (MR) angiogram of the
 aortic arch and brachiocephalic vessels shows high-grade stenosis of the proximal left
 subclavian artery (white arrow). By using such a model, full depiction of the arch,
 brachiocephalic vessels, and carotid bulbs is possible. Because of superimposed
 structures, full rotation of the arterial model is necessary. Note the left common
 carotid artery (LCCA) behind the left jugular vein. The left subclavian artery (LSCA) is
 seen well (blue arrow).




 Axial T1-weighted echo-planar diffusion image in a patient with high-grade internal
 carotid stenosis. Arrows point to multiple, small, subacute cerebral infarcts that have
 resulted from left internal carotid artery stenosis.




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 Carotid MR angiogram demonstrates very high-grade stenosis (arrow) in the proximal
 internal carotid artery in a patient with a recent onset of stroke.




 Axial T1-weighted diffusion MRI demonstrates 3 subacute infarcts (arrows) in the
 medial parietal aspect of the brain in a patient known to have a very high-grade
 proximal stenosis of the right internal carotid artery.




 Magnetic resonance (MR) angiograms of the cervical vessels and the circle of Willis
 show marked narrowing of the internal carotid artery (arrow). Flow is nearly absent in
 the right intracranial internal carotid artery and in the M1 segment of the right middle
 cerebral artery.




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 Carotid artery stenosis. Axial 3-dimensional maximum intensity magnetic resonance
 (MR) angiogram in a patient with bilateral carotid artery occlusion. Note the absence
 of flow in the intracranial internal carotid arteries (yellow arrows). The remaining
 blood flow to the cerebral hemispheres is the result of collateral branches of the
 vertebral arteries, including the posterior communicating arteries (white arrows).

 Findings

 MRA usually is performed by using 2 primary methods, ie, time-of-flight and ultrashort T1-
 weighted imaging. Time-of-flight imaging is performed without intravenous contrast agent by
 using a spoiled gradient-echo sequence. The images are displayed with a MIP protocol in multiple
 projections. Contrast-enhanced MRA is performed by using a timed and rapid injection of a
 gadolinium-based contrast, such as gadolinium dimeglumine. Because the volume of contrast
 agent is limited to 15-20 mL in most cases, timing of the contrast agent bolus and good venous
 access are essential. The images are obtained by using a short recovery time (TR), short echo
 time (TE), and T1-weighted technique (TR/TE/flip angle, 4.9/2.4/35°). The images are displayed
                                                   11
 in multiple projections by using an MIP technique.

 A 3D time-of-flight image of the carotid artery or a contrast-enhanced short-TE short-TR image
 is interpreted in much the same manner as CTAs or carotid angiograms of the same area. The
 stenotic area of the ICA should be evaluated according to the NASCET criteria. Because of the
 effects of turbulence, 3D time-of-flight imaging tends to cause overestimation of high-grade
 stenoses. In some cases, an area of discontinuity may be generated in the area of the stenosis.
 This results from turbulent blood flow patterns at the point of a high-grade stenosis and within
 very stenotic longer stenoses.

 The results of contrast-enhanced MRA are closely correlated with angiographic and operative
 findings. Gadolinium-based contrast agent has the effect of shortening the T1 qualities of the
 blood flowing through the stenosis (see Images 12-13, Image 27). Residual lumen is displayed
 with high signal intensity. High-grade stenosis tends to remain an attenuated but visible
        12
 lumen. Results of contrast-enhanced MRA are usually better than those of 3D time-of-flight
 imaging.

 Recent advances in contrast-enhanced MRA allow for improved imaging speed without the need
 for temporal interpolation. Time-resolved contrast-enhanced carotid MRA with a sensitivity-
 encoding (SENSE) reconstruction technique enables visualization of the carotid artery without
 superimposed venous structures.

 The early identification of stroke in the vascular distribution of a related carotid stenosis helps in
 focusing on an ipsilateral carotid lesion. T1-weighted diffusion-based imaging effectively depicts
 focal cerebral ischemia (see Image 28), and the finding is often correlated with a proximal
 carotid stenosis (see Image 27, Image 30). In other cases, intracranial MRA demonstrates no
 flow pattern, confirming carotid thrombosis (see Image 36).




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 Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate
 dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol
 [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or
 nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic
 Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-
 stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA
 scans.

 NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark
 patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow
 spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms,
 hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more
 information, see the FDA Public Health Advisory or Medscape.

 Degree of Confidence

 Both systematic and random errors affect the results of cerebrovascular MRA. Systematic errors
 are primarily the result of artifacts and are related to 3D time-of-flight imaging. Areas within the
 carotid artery that generate turbulence may develop a recirculating pattern of blood flow. In the
 returning blood flow, the lumen is recorded as artifactually narrowed. Short-segment occlusions
 may be suggested in patients with very high-grade stenosis (>85% stenosis). Time-of-flight MRA
 results should be reported in a manner similar to those of carotid duplex sonography. Although
 measurements obtained by using the NASCET criteria should be attempted, the significance of
 the recorded stenosis should be reported with caution.

 Random errors may occur when measurements of the internal lumen are made mechanically.
 Measuring from enlarged images reduces the relative degree of random error. MRA results
 obtained by using a very short-TR, short-TE, gadolinium-enhanced, timed bolus technique can be
 interpreted in much the same manner as those of carotid angiography and CTA. Intracranial MRA
 has a sensitivity of 92-95%, a specificity of 91%, and an overall accuracy of 91% in the
 detection of intracranial carotid stenosis.

 False Positives/Negatives

 Certain variations of the CCA may be difficult to interpret by using MRA findings. Narrow bands
 of intimal thickening may result in a high degree of stenosis; however, the central luminal
 narrowing is difficult to demonstrate on MRA examination. The proximal ICA may become folded
 or kinked. Such a kink generates turbulence just beyond the fold. A short-segment pseudo-
 occlusion may be seen on a time-of-flight study. The ectatic appearance of fibromuscular
 hyperplasia may be difficult to resolve by using time-of-flight imaging alone.

 The spasm of migraine can simulate carotid dissection on MRA studies performed during an
 acute migraine event. Assessment of the proximal carotid artery near its origin from the aortic
 arch requires a good contrast bolus, breath-holding and, in general, good cooperation on the
 part of the patient.

 False-negative carotid MRA results are primarily the result of limitations of resolution. Small
 surface ulcers may not be resolved on MRA images. At other times, deeper ulcers may contain
 blood clots, which reduce the apparent size of some ulcers.

 Ultrasound
 Findings

 B-mode ultrasonography




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 The earliest manifestation of carotid vascular disease is characterized by increased arterial
 intimal-medial thickness. The normal range for combined intimal-medial thickness of the CCA
 has been reported to vary with age, up to a maximum thickness of 0.8 mm. Incremental
 increased thickening of the carotid intima is associated with increased risk of cerebral ischemic
 events, coronary ischemia, and first-time MI. Treatment with lipid-lowering drugs has been
 shown to decrease the intimal thickness of the carotid artery. Decrease in the thickness of the
 intima of the CCA has been correlated directly with successful treatment with drugs that lower
 serum low-density lipoprotein levels.

 The sonographic characteristics of symptomatic and asymptomatic carotid plaques are different.
 Symptomatic plaques are more likely to be hypoechoic and highly stenotic while asymptomatic
 plaques are hyperechoic and moderately stenotic. Evaluation of the surface of the plaque has not
 been demonstrated to be a satisfactory index of plaque instability.

 After carotid endarterectomy, intimal thickness varies in the surgical site. The thickness of the
 neointima has been correlated with carotid wall stiffness and restenosis after carotid surgery.
 Comparison of current carotid sonographic velocities to those obtained before carotid
 endarterectomy is important. In general, the velocity of flow should become reduced with
 successful surgery. However, velocities may remain elevated after surgery due to scar formation,
 which results in carotid wall stiffness. Restenosis may occur as a result of surgery or generalized
 atherosclerotic vascular disease.

 Doppler ultrasonography
                                                                                          13
 Doppler ultrasonography is the primary noninvasive test for evaluating carotid stenosis.
 Primary examination of the carotid plaque is somewhat subjective because terms such as soft
 plaque or irregular surface are often used to describe the primary sonographic images. The
 degree of stenosis is better measured on the basis of the waveform and spectral analysis of the
 CCA and its major branches, especially the ICA.

 As an example, consider the following case history. A 70-year-old man presented with a
 suspected stroke. Symptoms included right-sided hemiparesis and dysphasia. Duplex ultrasound
 findings revealed a significant stenosis of the proximal left ICA (see Images 14-15). The image
 showed mostly soft echogenic plaque protruding from the posterior aspect of the bulb and origin
 of the ICA. A fairly narrow residual lumen remained. Spectral Doppler imaging confirmed the
 high-grade stenosis, with peak systolic velocity of 325 cm/s and diastolic velocity of 105 cm/s. In
 the author's laboratory, a diastolic cutoff of 90cm/s is used to distinguish 60-79% from 80-99%
 lesions in patients such as this man.




 Carotid Artery, Stenosis. Duplex carotid sonography in a patient with sudden onset of
 aphasia. The images are taken from the common carotid artery.




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 Carotid Artery, Stenosis. Duplex sonographic image take from the common carotid
 bulb several hours following the sudden onset of aphasia.

 Note the blunted flow in the distal ICA compatible with the high-grade proximal obstruction. The
 CCA shows narrowing of approximately 40%. The opposite ICA was only mildly narrowed and
 demonstrated normal findings on spectral Doppler examination. The patient underwent carotid
 angiography. Angiographic findings helped confirm an 80% ICA stenosis. The patient was
 eventually treated with carotid endarterectomy. Follow-up studies in the author's laboratory (not
 shown) demonstrated a fully patent ICA. Some residual hemiparesis has remained on the right
 side, but the patient is much improved from his status after the initial stroke.

 Many published lists exist of carotid flow velocities, which are associated with a graduated
 degree of stenosis. A listing of flow velocity/carotid stenosis criteria used in the author's
 department is shown in the Table below.

 Carotid Stenosis Criteria

                  Peak Systolic               Peak End Diastolic               Peak Systolic
 Stenosis
                 Velocity (cm/s)               Velocity (cm/s)                 Velocity Ratio
     <50                <150                           <50                            <2.0
    50-59             150-200                         50-70                          2.0-2.5
    60-69             200-250                         50-70                          2.5-3.0
    70-79             250-325                         70-90                          3.0-3.5
    80-89             325-400                         70-100                         3.5-4.0
    90-99               >400                           >100                           >4.0
  Occlusion        Not applicable                 Not applicable                Not applicable

 Doppler ultrasonographic findings associated with stenosis include the following:

    •   Ipsilateral CCA-to-ICA flow ratios may not be valid in the setting of contralateral ICA
        occlusion.

    •   CCA waveforms may have a high-resistance configuration in ipsilateral ICA lesions.

    •   ICA waveforms may have a high-resistance configuration in ipsilateral distal ICA lesions.

    •   ICA waveforms may be dampened in ipsilateral CCA lesions.

    •   Long-segment ICA stenosis may not have high end-diastolic velocity.

    •   Velocities supersede imaging in grading stenosis.




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    •   Imaging can be used to downgrade stenosis in the setting of turbulence caused by
        kinking.

 In addition to the typical evaluation of the flow rate in the proximal ICA, it has been shown that
 the flow directly within the ophthalmic artery is highly specific for severe carotid stenosis.

 Transcranial Doppler ultrasonography

 Transcranial Doppler imaging is both sensitive and specific in the detection of intracranial ICA
 stenosis that is hemodynamically significant. By using a mean flow velocity of 100 cm/s,
 transcranial Doppler images help in identifying most intracranial stenotic lesions, with good
 specificity.

 Degree of Confidence

 The success of duplex sonography depends on careful technique. Results vary somewhat among
 laboratories. The author's practice has chosen to base its results on a composite mix of the
 published results comparing the degree of proven stenosis versus flow velocity and ICA-to-CCA
 velocity ratios. Results should be reported in the context of established criteria as a percentage
 of stenosis. The Table, above, represents the criteria used in the author's practice. The results
 should be confirmed with carotid CTA or carotid MRA before surgery.

 Discovery of a reversed direction of flow in the ophthalmic artery is closely associated with high-
 grade ipsilateral ICA stenosis, with a sensitivity of 55%, a specificity of 100%, a negative
 predictive value of 82%, and a positive predictive value of 100%.

 Transcranial duplex sonography with a threshold of 100 cm/s helps in identifying
 hemodynamically significant lesions, with a sensitivity of 93.9% and a specificity of 91.2%.

 False Positives/Negatives

 Use of duplex sonography is not valid in the setting of contralateral ICA occlusion. CCA
 waveforms may have a high-resistance configuration with ipsilateral ICA lesions. ICA waveforms
 may have a high-resistance configuration with ipsilateral distal ICA lesions. ICA waveforms may
 be dampened with ipsilateral CCA lesions. Long-segment ICA stenosis may not have high end-
 diastolic velocity. Velocities supersede imaging in grading stenosis. Imaging can be used to
 downgrade stenosis in the setting of turbulence caused by kinking.

 After carotid surgery, recorded flow velocities may be elevated more than those recorded during
 preoperative examinations. Comparison of the results of the current examination to those of a
 prior study is essential.

 Nuclear Medicine
 Findings

 Single photon emission CT (SPECT) and positron emission tomography (PET) of the brain may
                                                                                         14, 15
 demonstrate areas of cerebral ischemia versus areas of complete cerebral infarction.
 However, these studies provide only indirect imaging information related to carotid stenosis. By
 using a dynamic imaging method, an assessment of the inflow of technetium Tc 99m
 hexamethylpropylamine oxime (HMPAO) can be used to estimate the hemispheric cerebral blood
 flow. If such an assay is combined with a provocative challenge with acetazolamide, it is possible
 to differentiate patients with migraine from patients with an irreversible cerebral ischemia.




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 Degree of Confidence

 SPECT and PET of the brain both demonstrate cerebral infarction, which may indicate a related
 carotid stenosis. An acetazolamide challenge can successfully differentiate certain subclasses of
 cerebral ischemic syndromes, but all such studies provide indirect evidence of carotid stenosis.

 False Positives/Negatives

 False-positive results may occur as a result of confusion in the findings between an infarct of the
 brain and a low-grade brain neoplasm or abscess. In the evaluation of stroke, false-negative
 findings may occur in small areas of infarction, which may be below the resolution of a nuclear
 examination. Comparison with other studies (such as CT or MRI), which have higher resolution,
 is recommended.

 Angiography




 Thoracic arch angiography demonstrates one of the common variants of normal aortic
 arch (AA) development in which both the innominate artery (IA) and the left carotid
 artery share a common origin. The right common carotid artery (RCA) and the right
 internal carotid artery are irregular and narrowed. The long, multisegment areas of
 stenosis are believed to result from the effects of radiation therapy to the right side of
 the neck in this patient. Effects of radiation therapy are related to adverse effects on
 the vascular supply to the carotid or vertebral artery in the radiation field.




 Oblique lateral cervical arteriogram displayed by using a subtraction technique.
 Although the contrast agent was injected into the arch, both the carotid stenosis
 (arrows) and the carotid ulcerations (arrowheads) are demonstrated. ICA = internal
 carotid artery




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 Oblique lateral cervical angiogram obtained by using an injection into the aortic arch.
 Although a very high-grade right internal carotid stenosis is depicted (rc),
 superimposition of the jugular vein (v) makes its evaluation difficult. Selective
 common carotid angiography has the advantage of fewer superimposed vessels. lc =
 left carotid.




 Common carotid angiogram shows normal findings. Note the slightly dilated shape of
 the distal common carotid artery and the proximal internal carotid artery (carotid
 bulb). ec = external carotid artery; f = facial artery; l = lingual artery; ic = internal
 carotid artery; im = internal maxillary artery; o = occipital artery; p cer = posterior
 cerebral artery; p com = posterior communicating artery




 Lateral selective right common carotid arteriogram. Only the proximal few centimeters
 of the internal carotid artery are patent (arrow). Selective catheterizations in the
 performance of carotid angiography provide higher resolution (smaller field of view),
 high concentrations of intraluminal contrast agent, and extended angiographic
 imaging (longer runs of images). The almost occluded internal carotid artery is
 evaluated better by using selective common carotid angiography.




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 Lateral common carotid arteriogram in a patient with a neck bruit. Note the focal
 narrowing of the proximal internal carotid artery (arrow). In severe cases, the kink
 may require carotid artery reconstruction.




 Anterior left common carotid arteriogram in a patient who presented with a loud left
 neck bruit. Note the horizontal line (arrow) in the proximal internal carotid artery,
 which represents a focal folding of the carotid artery. This configuration has been
 termed a kink. The bruit results from the turbulent blood flow through the focal
 narrowing.




 Lateral common carotid arteriogram in a patient with transient ischemic attacks. A
 small filling defect is noted in the common carotid bulb (arrow). A small blood clot was
 found at surgery, with intimal ulceration at the base of the clot.




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 Lateral angiogram of the internal carotid artery (ICA) in a patient with a prior
 complete occlusion of the internal carotid artery. The irregular lumen (arrows) is
 consistent with recanalization of the thrombosis.




 Lateral carotid angiogram in a patient who had a recent transient ischemic attack.
 Note the multiple areas of deep ulceration in the proximal internal carotid artery and
 carotid bulb (arrows).




 Lateral common carotid angiography demonstrates collateral vessels that form after a
 long-standing complete occlusion of the internal carotid artery.




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 CT and CT angiography in a patient with a load left neck bruit and symptoms of a
 transient ischemic attack. A, CT scan demonstrates that the left jugular vein (LJV) is
 superimposed on the left common carotid artery (LCCA). B, After electronic removal of
 the superficial left jugular vein, a high-grade stenosis of the origin of the left external
 carotid artery (LECA) is demonstrated clearly. Dense calcifications are seen (red
 arrows) near the origins of both the left external carotid artery and the carotid bulb.
 The left internal carotid artery is not significantly stenotic.




 Lateral common carotid angiogram shows appropriate measurements (arrows) for
 calculating the degree of stenosis by using the North American Symptomatic Carotid
 Endarterectomy Trial (NASCET) criteria.




 Oblique multiplanar reformatted CT angiogram demonstrates a mild degree of stenosis
 in the proximal right internal carotid artery (RICA). RJV = right jugular vein.




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 Maximum intensity CT angiogram demonstrates mild bilateral carotid stenosis. L = left,
 R = right.




 Common carotid arteriogram demonstrates dilatation (black double arrow) of the
 internal carotid artery beyond the high-grade stenosis (white arrow). This poststenotic
 dilatation is associated with hemodynamically significant stenosis.




 Lateral carotid angiogram shows that the cervical carotid artery (CCA) is narrowed,
 but it has a smooth outline. The supraclinoid internal carotid artery (ICA) is occluded.
 Note the enlarged ophthalmic artery (Opthal A.), which functions as a major collateral.




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 Anteroposterior intracranial carotid angiogram shows absence of the normal middle
 cerebral arterial branches. Image also shows incomplete occlusion of the suprasellar
 internal carotid artery near the origin of the M1 segment of the right middle cerebral
 artery.




 Angiogram of the carotid artery near the skull base in a patient with a significant
 fracture of the skull base. Internal carotid artery compression and focal spasm is due
 to hemorrhage resulting from a pseudoaneurysm (arrow) of the upper cervical internal
 carotid artery. Treatment of this stenosis requires vascular control of the proximal and
 distal carotid artery. In this case, the stenosis is primary spasm, which might be
 considered a protective response to direct carotid artery injury.

 Findings

 Carotid angiography via a catheter injection of contrast agent is considered the standard of
 diagnostic imaging of the cervical and intracranial carotid arteries against which other techniques
 are often judged (see Image 5). The NASCET study was based on images created during
 catheter angiography. The diameters of stenosis can be measured directly. Luminal diameter
 ratios can be expressed. All contrast-enhanced angiographic studies depend on the radiographic
 density of iodinated contrast agent compared with normal blood and the density of the wall of
 the carotid artery (see Image 2-4, Image 6). Lesions may be smooth, irregular, or focal, or they
 may involve a long segment (see Image 2).

 Angiographic technique

 In the author's institution, all cervical-cerebral angiography is performed by using the Seldinger
 technique. The procedure initially involves entering the lumen of the artery of access with a
 needle. The femoral artery is used as access in most cases, while the axillary arteries may be
 entered as an alternative. A heparin-coated guide wire is passed through the hub of the needle
 into the lumen of the artery. Often a J-shaped guide wire is used initially to avoid intimal trauma.
 A 4F pigtail catheter is generally introduced over the guidewire into the ascending aortic arch.




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 Nonionic contrast (320 mg/mL of organically bound iodine) is injected at a rate of 20-25 mL for a
 total volume of 40-50 mL. The left anterior oblique projection is most common. If imaging is
 performed by using a digitally subtracted technique, less contrast material is needed.

 After the shape, smoothness, and patency of the proximal right CCA, the right subclavian artery,
 the left CCA, and the left subclavian artery are inspected, a catheter is selected to assist in the
 selective catheterization of the right CCA, the left CCA, and either or both of the vertebral
 arteries. A 0.035-in guidewire with a soft, straight tip is used to exchange the pigtail catheter for
 either a simple angle-tip catheter (eg, one with an HN1 shape) or one with a more complex hook
 or short-radius, curved shape.

 The guidewire chosen for the exchange may have a variable degree of flexibility in the distal
 several centimeters near the tip. With the guidewire leading into the proximal right and left CCA
 origins, the cerebral-shaped catheter is positioned in the CCAs below the carotid bulb. Vertebral
 injections are performed with the catheter in the vertebral artery near the origin of the vertebral
 artery to avoid spasm. After a small test injection is disinterred to verify the location and security
 of the catheter tip position, each of the carotid arterial circulations is studied. Images in a 30°
 ipsilateral left anterior oblique or right anterior oblique projection are obtained to clearly outline
 the carotid bifurcations. In some cases, the lateral and the anterior projections are needed.

 DSA performed by using a C-arm imager permits an optimal degree of rotation based on the
 patient's anatomic form. Imaging should include the intracranial carotid circulation in most
 cases. Selective catheterization of 1 or both vertebral arteries should be performed if clinically
 indicated in patients with vertebral basilar symptoms.

 Each injection of contrast agent into the CCA is given at a rate of 6-7 mL/s for a total volume of
 10-12 mL depending on the estimated flow rate in the CCA. Selective vertebral artery
 angiography is generally performed by using an injection rate of 4-5 mL/s for a total volume of 6
 -8 mL. Somewhat less contrast agent is needed if DSA imaging techniques are applied.

 The degree to which intracranial arteries beyond the ICA-MCA trifurcation must be studied
 should be based on an understanding of the patient's clinical presentation and symptoms.
 Collateral circulation is best understood by having full visualization of the intracranial circulation
 as well as the aortic arch and cervical carotid circulations.

 Measurements and other findings

 The most common method used to express measurements of the carotid artery is the NASCET
 criteria, which state that a percentage of stenosis is expressed as a factor of 100, ie, the
 diameter of the normal ICA located above the carotid bulb divided by the diameter of the
 proximal ICA at the narrowest point (see Images 22-23).

 Special consideration must be given for critical degrees of stenosis, often termed the string sign
 (see Image 4Image 6). The presence of contrast agent in a markedly restricted lumen may be
 an indication of a critical proximal focal stenosis or longer segmental narrowing. Depiction of
 residual intracranial arterial flow helps establish patency (see Images 31-32).

 Other findings noted on carotid angiography include calcification, ulceration (see Image 11),
 fibromuscular hyperplasia, carotid kinking or folding (see Images 7-8), focal thrombus formation
 (see Image 9), and intimal dissection. The plaque may become complicated by marked intimal
 thickening or subintimal hemorrhage (see Images 17-18).

 After a carotid thrombosis form, extensive collateralization patterns may be demonstrated (see
 Image 19), or partial recanalization may occur, resulting in a complex pattern of alternating
 narrowing and dilatation (see Image 10).




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 Degree of Confidence

 Findings on catheter-contrast angiography of the carotid artery are accurate if measurements
 and calculation of the degree of stenosis are made carefully by using an enlarged image. Both
 systematic and random errors may occur during stenosis measurement. The calculation of the
 degree of stenosis should be based on the NASCET criteria if possible. Catheter-based
 angiographic studies remain the most accurate means of assessment of the degree of carotid
 stenosis.

 False Positives/Negatives

 False-positive examinations may occur if injection of the contrast agent is not timed properly,
 resulting in a washed-out appearance on the image. If subtracted images are developed,
 overlying metal or dense calcifications result in shadowing of some of the plaque-artery lumen,
 making an accurate measurement of the residual lumen difficult. Movement, coughing, and the
 presence of metal artifacts may prevent an accurate examination. Rapid injection may cause a
 standing wave to form, which may appear similar to fibromuscular hyperplasia.

 False-negative results may occur if a nonselective angiographic technique is used (see Images 3-
 4). Superimposition of other arterial and venous structures may prevent adequate depiction or
 measurement of the stenosis. Despite technical limitations, catheter-based angiography remains
 the criterion standard against which other imaging techniques are compared.

 Intervention

 Intervention in patients with acute CVA is usually based on an attempt to relieve the intracranial
 thrombosis or an embolization by using thrombolytic agents. The success of such treatment
 depends on early intervention (during the first 4 h) after the onset of the ischemic event.

 With the demonstration of a thrombosis by using perfusion CT or perfusion-diffusion MRI
 techniques, catheter-directed thrombolytic therapy may be administered by using recombinant
 tissue-type plasminogen activator (rTPA) or another thrombolytic agent. The success of this
 therapy remains controversial and is the subject of ongoing research.

 Another important area of primary intervention is the treatment of ICA stenosis by using an
 endovascular stent across the stenotic vessel segment. This treatment results in improved
 vascular flow rates across the stenotic segment. Suboptimal anatomic results have been
 reported with the use of the self-expanding Wallstent in this application. Restenosis and
 recurrent cerebral embolization have been reported following endovascular treatment of carotid
 stenosis. The increased application of carotid stent placement can be expected to preserve the
 role of catheter-based cervical-cerebral carotid catheter angiography.

 Recent study

 The use of intravenous tissue plasminogen activator (t-PA) for stroke 3-4.5 hours after
 symptoms has been recommended by the American Heart Association, although time to
 treatment remains of extreme importance and should not be delayed. The European Cooperative
 Acute Stroke Study 3 (ECASS 3) showed benefit from t-PA in patients treated 3-4.5 hours after
 onset of symptoms of stroke.31, 32, 33, 34


 Medical/Legal Pitfalls




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      •    Use of interventional therapies in the treatment of acute CVA and carotid stenosis
           represents complex clinical decision making, which is subject to alternative
           interpretations of what constitutes a good standard of care.
              ◦   Patients with acute cerebral infarct may have significant morbidity if a large
                  infarction is not corrected on an emergency basis, whereas thrombolytic therapy
                  (intra-arterial or intravenous) may result in fatal intracerebral hemorrhage.

              ◦   The benefits of interventional treatment of patients with carotid stenosis must
                  compare favorably with those of conventional surgery of the carotid artery to
                  avoid medical/legal challenges.

              ◦   Interventional therapies, including angioplasty and angioplasty with stent
                  placement, may result in a hyperperfusion syndrome.

              ◦   Hemorrhage can occur within the zone of hyperperfusion.

              ◦   Preoperative CT scans and MRIs of the brain must be used to exclude focal
                  hemorrhage.

              ◦   Hyperperfusion syndrome has also been described after angioplasty of an MCA
                  stenosis.

 See also the Medscape topic Medical Malpractice and Legal Issues.



 Special Concerns

 Test Questions
 Question 1:

 Which of the following statements regarding time-of-flight magnetic resonance angiography
 (MRA) of the carotid artery is true?

 A.       The findings tend to underestimate the degree of stenosis.
 B.       The findings are somewhat less accurate than those of conventional angiography.
          Calcification of the carotid arterial bulb adversely affects the results in the same way that
 C.
          dense calcifications degrade carotid duplex sonography.
 D.       Time-of-flight MRA requires the use of intravenous contrast agent.
          Compared with contrast-enhanced MRA, time-of-flight MRA provides more accurate results
 E.       in the proximal neck and near the origins of the innominate, subclavian, and common
          carotid arteries.

 The correct answer is B: Although 3-dimensional time-of-flight MRA is often successful, the
 degree of stenosis tends to be overestimated in high-grade stenosis and carotid lesions that
 generate significant turbulence. These limitations may result in an apparent vascular thrombosis
 in areas of extreme narrowing. Time-of-flight images are obtained without the use of intravenous
 gadolinium-based contrast agent. As a result of the higher resolution of the angiogram, catheter-
 based angiography improves imaging in most patients; however, CT angiography and MRA
 findings are fully diagnostic in most clinical settings.




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 Question 2:

 Which of the following risk factors in not found in patients with carotid artery stenosis?

 A. Poorly managed hypertension
 B. A diet rich in saturated fat
 C. High doses of radiation to the neck, as in cancer therapy
 D. Poorly managed diabetes
 E. High levels of high-density lipoprotein

 The correct answer is E: In addition to the common risk factors for carotid artery and coronary
 arterial stenosis (eg, poorly managed hypertension and diabetes and saturated fat in the diet),
 radiation to the neck causes severe and premature vascular disease to develop within the
 irradiated vessels. Levels of high-density lipoprotein (good cholesterol) are usually low.


 Question 1 (T/F):

 The degree of stenosis that requires surgery is 60% in young patients, as measured according to
 the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria.

 The correct answer is False: The results of the NASCET studies have supported
 endarterectomy for asymptomatic patients with a stenosis greater than 70%. Surgery is
 indicated for symptomatic patients with a stenosis of 60% or greater.


 Question 2 (T/F):

 Densely calcified carotid stenosis makes it difficult to accurately measure the lumen with CT
 angiography (CTA); therefore, magnetic resonance angiographic (MRA) findings are interpreted
 more easily in patients with this condition.

 The correct answer is True: Time-of-flight MRA findings are less affected by dense
 calcifications than those of angiography or CTA.


 Question 3 (T/F):

 Carotid duplex sonography is more accurate in patients with severe stenosis of the internal
 carotid artery than in those with less stenosis.

 The correct answer is False: Very high-grade stenosis may appear as a complete occlusion.
 The results of duplex sonography are reported in ranges of stenosis based primarily on peak
 velocity of flowing blood measured in the proximal internal carotid artery during systole.


 Question 4 (T/F):

 After carotid surgery, the peak systolic velocity may remain slightly elevated in the absence of
 recurrent stenosis.

 The correct answer is True: After otherwise successful carotid endarterectomy, peak systolic
 velocities may remain above normal values.




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 Further Reading
 Clinical guidelines

 Acute stroke management. Carotid artery imaging. In: Canadian best practice recommendations
 for stroke care: 2006.
 Canadian Stroke Network - Disease Specific Society
 Heart and Stroke Foundation of Canada - Disease Specific Society. 2006. 2 pages. [NGC Update
 Pending] NGC:006262

 Screening for carotid artery stenosis: U.S. Preventive Services Task Force recommendation
 statement.
 United States Preventive Services Task Force - Independent Expert Panel. 1996 (revised 2007).
 6 pages. NGC:005970

 Antithrombotic therapy for peripheral artery occlusive disease. American College of Chest
 Physicians evidence-based clinical practice guidelines (8th edition).
 American College of Chest Physicians - Medical Specialty Society. 2001 Jan (revised 2008 Jun).
 29 pages. NGC:006669

 Clinical trials


 Comparing Carotid Stenting With Endarterectomy in Severe Asymptomatic Carotid Stenosis

 Stenting Versus Best Medical Treatment of Asymptomatic High Grade Carotid Artery Stenosis

 Cost-Effectiveness of a Specialized Ultrasound Instrument to Diagnose Carotid Stenosis as a Way
 to Reduce the Risk of Stroke


 Related eMedicine topics

 Carotid Ultrasound

 Atherosclerotic Disease of the Carotid Artery

 Stroke, Ischemic

 Aortoiliac Occlusive Disease

 MULTIMEDIA
 Media file 1: Four of the most common methods of imaging the carotid artery are
 compared. Angio = angiography, CTA = CT angiography, Duplex = duplex
 ultrasonography, Gd = gadolinium enhancement, ICA = internal carotid artery, MRA =
 magnetic resonance angiography, TOF = time of flight.




 Media type: Image




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 Media file 2: Thoracic arch angiography demonstrates one of the common variants of
 normal aortic arch (AA) development in which both the innominate artery (IA) and the
 left carotid artery share a common origin. The right common carotid artery (RCA) and
 the right internal carotid artery are irregular and narrowed. The long, multisegment
 areas of stenosis are believed to result from the effects of radiation therapy to the
 right side of the neck in this patient. Effects of radiation therapy are related to adverse
 effects on the vascular supply to the carotid or vertebral artery in the radiation field.




 Media type: X-RAY

 Media file 3: Oblique lateral cervical arteriogram displayed by using a subtraction
 technique. Although the contrast agent was injected into the arch, both the carotid
 stenosis (arrows) and the carotid ulcerations (arrowheads) are demonstrated. ICA =
 internal carotid artery




 Media type: X-RAY

 Media file 4: Oblique lateral cervical angiogram obtained by using an injection into the
 aortic arch. Although a very high-grade right internal carotid stenosis is depicted (rc),
 superimposition of the jugular vein (v) makes its evaluation difficult. Selective
 common carotid angiography has the advantage of fewer superimposed vessels. lc =
 left carotid.




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 Media type: X-RAY

 Media file 5: Common carotid angiogram shows normal findings. Note the slightly
 dilated shape of the distal common carotid artery and the proximal internal carotid
 artery (carotid bulb). ec = external carotid artery; f = facial artery; l = lingual artery;
 ic = internal carotid artery; im = internal maxillary artery; o = occipital artery; p cer =
 posterior cerebral artery; p com = posterior communicating artery




 Media type: X-RAY

 Media file 6: Lateral selective right common carotid arteriogram. Only the proximal few
 centimeters of the internal carotid artery are patent (arrow). Selective
 catheterizations in the performance of carotid angiography provide higher resolution
 (smaller field of view), high concentrations of intraluminal contrast agent, and
 extended angiographic imaging (longer runs of images). The almost occluded internal
 carotid artery is evaluated better by using selective common carotid angiography.




 Media type: X-RAY

 Media file 7: Lateral common carotid arteriogram in a patient with a neck bruit. Note
 the focal narrowing of the proximal internal carotid artery (arrow). In severe cases,




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 the kink may require carotid artery reconstruction.




 Media type: X-RAY

 Media file 8: Anterior left common carotid arteriogram in a patient who presented with
 a loud left neck bruit. Note the horizontal line (arrow) in the proximal internal carotid
 artery, which represents a focal folding of the carotid artery. This configuration has
 been termed a kink. The bruit results from the turbulent blood flow through the focal
 narrowing.




 Media type: X-RAY

 Media file 9: Lateral common carotid arteriogram in a patient with transient ischemic
 attacks. A small filling defect is noted in the common carotid bulb (arrow). A small
 blood clot was found at surgery, with intimal ulceration at the base of the clot.




 Media type: X-RAY

 Media file 10: Lateral angiogram of the internal carotid artery (ICA) in a patient with a
 prior complete occlusion of the internal carotid artery. The irregular lumen (arrows) is
 consistent with recanalization of the thrombosis.




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 Media type: X-RAY

 Media file 11: Lateral carotid angiogram in a patient who had a recent transient
 ischemic attack. Note the multiple areas of deep ulceration in the proximal internal
 carotid artery and carotid bulb (arrows).




 Media type: X-RAY

 Media file 12: Oblique magnetic resonance angiogram of the aortic arch and proximal
 subclavian and common carotid arteries in a patient who presented with dizziness,
 which was worsened by exercise. Blood pressure readings from each arm were of
 different in value, with the left arm blood pressure more than 20 mm Hg lower than
 that on the right side. High-grade stenosis of the proximal left subclavian artery is
 demonstrated (arrow).




 Media type: MRI

 Media file 13: Oblique 3-dimensional contrast-enhanced magnetic resonance (MR)
 angiogram of the aortic arch and brachiocephalic vessels shows high-grade stenosis of
 the proximal left subclavian artery (white arrow). By using such a model, full depiction
 of the arch, brachiocephalic vessels, and carotid bulbs is possible. Because of




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 superimposed structures, full rotation of the arterial model is necessary. Note the left
 common carotid artery (LCCA) behind the left jugular vein. The left subclavian artery
 (LSCA) is seen well (blue arrow).




 Media type: MRI

 Media file 14: Carotid Artery, Stenosis. Axial CT of the brain in a patient with the
 sudden onset of aphasia.




 Media type: CT

 Media file 15: Carotid Artery, Stenosis. Duplex carotid sonography in a patient with
 sudden onset of aphasia. The images are taken from the common carotid artery.




 Media type: X-RAY

 Media file 16: Carotid Artery, Stenosis. Duplex sonographic image take from the
 common carotid bulb several hours following the sudden onset of aphasia.




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 Media type: X-RAY

 Media file 17: Carotid Artery, Stenosis. Proximal duplex sonography of the left ICA in a
 patient who presented with the sudden onset of aphasia.




 Media type: X-RAY

 Media file 18: Carotid Artery, Stenosis. Axial image of a carotid CTA in a patient with
 right sided weakness and sudden onset of aphasia. The left ICA (yellow arrow) is
 occluded.




 Media type: CT

 Media file 19: Carotid Artery, Stenosis. Sagittal MPR image from a carotid CTA in a
 patient with sudden onset of aphasia. The proximal left ICA demonstrates a short
 segment of complete occlusion with flow preserved in the more distal left ICA. The
 common carotid artery (CCA) has a normal diameter.




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 Media type: CT

 Media file 20: Carotid Artery, Stenosis. The anterior communicating artery (AComA)
 represents an important collateral circulation which preserves blood flow to the left
 middle cerebral artery (L MCA) in this patient with sudden onset of aphasia. The
 proximal left ICA was noted to be occluded on the CTA of the cervical carotid arteries.




 Media type: CT

 Media file 21: Carotid Artery, Stenosis. Duplex sonography of the external carotid
 artery in a patient who presented with the sudden onset of aphasia.




 Media type: X-RAY

 Media file 22: Longitudinal sonogram of a left internal carotid stenosis of the proximal
 internal carotid artery (Prox. ICA). The peak systolic velocity (PV) recorded from
 within the lumen of the proximal internal carotid artery was greater than 325 cm/s.




 Media type: Image

 Media file 23: Cross-sectional sonogram of a moderately high-grade stenosis of the left
 internal carotid artery (ICA). Longitudinal and axial images are helpful in identification




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 of the branches of the internal carotid artery (I) versus those of the external carotid
 artery (E).




 Media type: CT

 Media file 24: Axial T1-weighted echo-planar diffusion image in a patient with high-
 grade internal carotid stenosis. Arrows point to multiple, small, subacute cerebral
 infarcts that have resulted from left internal carotid artery stenosis.




 Media type: MRI

 Media file 25: Lateral carotid angiogram shows a high-grade stenosis of the proximal
 internal carotid artery in comparison with a photograph of the plaque after
 endarterectomy.




 Media type: Image

 Media file 26: Intraoperative image obtained during carotid endarterectomy shows
 dissection of the plaque (black arrow). A bypass shunt (yellow arrow) allows blood to
 flow around the operative site, creating a bloodless surgical field without cross-
 clamping of the carotid artery.




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 Media type: Photo

 Media file 27: Lateral common carotid angiography demonstrates collateral vessels
 that form after a long-standing complete occlusion of the internal carotid artery.




 Media type: X-RAY

 Media file 28: Dense calcifications (arrows) of the common carotid bulb and proximal
 internal carotid artery. Calcifications such as these complicate assessment of the
 degree of internal carotid artery stenosis.




 Media type: CT

 Media file 29: CT and CT angiography in a patient with a load left neck bruit and
 symptoms of a transient ischemic attack. A, CT scan demonstrates that the left jugular
 vein (LJV) is superimposed on the left common carotid artery (LCCA). B, After
 electronic removal of the superficial left jugular vein, a high-grade stenosis of the
 origin of the left external carotid artery (LECA) is demonstrated clearly. Dense
 calcifications are seen (red arrows) near the origins of both the left external carotid
 artery and the carotid bulb. The left internal carotid artery is not significantly stenotic.




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 Media type: CT

 Media file 30: North American Symptomatic Carotid Endarterectomy Trial (NASCET)
 stenosis measurement. CCA = common carotid artery, D = narrowed diameter, ECA =
 external carotid artery, ICA = internal carotid artery, and N = normal diameter.




 Media type: Image

 Media file 31: Lateral common carotid angiogram shows appropriate measurements
 (arrows) for calculating the degree of stenosis by using the North American
 Symptomatic Carotid Endarterectomy Trial (NASCET) criteria.




 Media type: X-RAY

 Media file 32: Oblique multiplanar reformatted CT angiogram demonstrates a mild
 degree of stenosis in the proximal right internal carotid artery (RICA). RJV = right
 jugular vein.




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 Media type: CT

 Media file 33: Maximum intensity CT angiogram demonstrates mild bilateral carotid
 stenosis. L = left, R = right.




 Media type: CT

 Media file 34: Common carotid arteriogram demonstrates dilatation (black double
 arrow) of the internal carotid artery beyond the high-grade stenosis (white arrow).
 This poststenotic dilatation is associated with hemodynamically significant stenosis.




 Media type: X-RAY

 Media file 35: Carotid MR angiogram demonstrates very high-grade stenosis (arrow) in
 the proximal internal carotid artery in a patient with a recent onset of stroke.




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 Media type: MRI

 Media file 36: Axial T1-weighted diffusion MRI demonstrates 3 subacute infarcts
 (arrows) in the medial parietal aspect of the brain in a patient known to have a very
 high-grade proximal stenosis of the right internal carotid artery.




 Media type: MRI

 Media file 37: Even in the absence of a high-grade stenosis, carotid ulceration may
 result in cerebral infarct. Note the deep ulceration (arrow) demonstrated on this 3-
 dimensional volume image of the right carotid artery. The large vessel shown to the
 right is the right jugular vein (RJV). CCA = common carotid artery.




 Media type: CT

 Media file 38: Magnetic resonance (MR) angiograms of the cervical vessels and the
 circle of Willis show marked narrowing of the internal carotid artery (arrow). Flow is
 nearly absent in the right intracranial internal carotid artery and in the M1 segment of
 the right middle cerebral artery.




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 Media type: MRI

 Media file 39: Lateral carotid angiogram shows that the cervical carotid artery (CCA) is
 narrowed, but it has a smooth outline. The supraclinoid internal carotid artery (ICA) is
 occluded. Note the enlarged ophthalmic artery (Opthal A.), which functions as a major
 collateral.




 Media type: X-RAY

 Media file 40: Anteroposterior intracranial carotid angiogram shows absence of the
 normal middle cerebral arterial branches. Image also shows incomplete occlusion of
 the suprasellar internal carotid artery near the origin of the M1 segment of the right
 middle cerebral artery.




 Media type: X-RAY

 Media file 41: Surface-rendered 3-dimensional volume CT angiogram demonstrates a
 complete occlusion of the right common carotid artery (CCA).




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 Media type: CT

 Media file 42: Axial CT angiograms (A and B) demonstrate bilateral occlusions of the
 right and left common carotid arteries (arrows).




 Media type: CT

 Media file 43: Intracranial CT angiogram in a patient with bilateral common carotid
 occlusion shows an absence of flow in the right and left internal carotid arteries
 (ICAs). ACA = anterior cerebral artery, MCA = middle cerebral artery, PCA = posterior
 cerebral artery, PCCA = posterior communicating cerebral artery.




 Media type: CT

 Media file 44: Carotid artery stenosis. Axial 3-dimensional maximum intensity
 magnetic resonance (MR) angiogram in a patient with bilateral carotid artery
 occlusion. Note the absence of flow in the intracranial internal carotid arteries (yellow
 arrows). The remaining blood flow to the cerebral hemispheres is the result of
 collateral branches of the vertebral arteries, including the posterior communicating
 arteries (white arrows).




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 Media type: MRI

 Media file 45: Axial CT image of a patient with a focal stenosis of the internal carotid
 artery. The cavernous sinus (CS) is distended, with an abscess (arrowheads). Stenosis
 of the intracavernous internal carotid artery was a response to the abscess in this
 patient.




 Media type: CT

 Media file 46: Lateral view of internal carotid artery near the level of the cavernous
 sinus demonstrates a focal stenosis (arrows).




 Media type: X-RAY

 Media file 47: Angiogram of the carotid artery near the skull base in a patient with a
 significant fracture of the skull base. Internal carotid artery compression and focal
 spasm is due to hemorrhage resulting from a pseudoaneurysm (arrow) of the upper
 cervical internal carotid artery. Treatment of this stenosis requires vascular control of
 the proximal and distal carotid artery. In this case, the stenosis is primary spasm,
 which might be considered a protective response to direct carotid artery injury.




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 Media type: X-RAY

 Media file 48: Carotid Artery, Stenosis. Intraoperative angiography during the
 placement of a carotid stent. The proximal right ICA and the common carotid blub are
 significantly narrowed prior to the placement of a carotid stent.




 Media type: X-RAY

 Media file 49: Carotid Artery, Stenosis. The lumen of the proximal right ICA and right
 carotid bulb has been restored following the placement of a carotid stent.




 Media type: X-RAY



 REFERENCES
 1. Chappell FM, Wardlaw JM, Young GR, Gillard JH, Roditi GH, Yip B, et al. Carotid artery
 stenosis: accuracy of noninvasive tests--individual patient data meta-
 analysis. Radiology. May 2009;251(2):493-502. [Medline].
 2. Screening for carotid artery stenosis: U.S. Preventive Services Task Force recommendation




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 statement. Ann Intern Med. Dec 18 2007;147(12):854-9. [Medline].
 3. Waaijer A, van Leeuwen MS, van Osch MJ, van der Worp BH, Moll FL, Lo RT, et al. Changes in
 cerebral perfusion after revascularization of symptomatic carotid artery stenosis: CT
 measurement. Radiology. Nov 2007;245(2):541-8. [Medline].
 4. Saver JL, Gornbein J, Grotta J, Liebeskind D, Lutsep H, Schwamm L, et al. Number needed to
 treat to benefit and to harm for intravenous tissue plasminogen activator therapy in the 3- to 4.5
 -hour window: joint outcome table analysis of the ECASS 3 trial. Stroke. Jul 2009;40(7):2433-
 7. [Medline].
 5. Davis S, Donnan G. The ECASS III results and the tPA paradox. Int J Stroke. Feb 2009;4
 (1):17-8. [Medline].
 6. Saver JL, Gornbein J, Grotta J, et al. Saver JL, Gornbein J, Grotta J et al. Number Needed to
 Treat to Benefit and to Harm for Intravenous Tissue Plasminogen Activator Therapy in the 3- to
 4.5-Hour WindowJoint Outcome Table Analysis of the ECASS 3 Trial. Stroke. Stroke. Available at
 http://stroke.ahajournals.org/cgi/content/full/40/7/2433. Accessed July 21, 2009.
 7. Susan Jeffrey. AHA/ASA Science Advisory Recommends Use of tPA Between 3 and 4.5 Hours
 After Stroke. Medscape Today from WebMD. Available at
 http://www.medscape.com/viewarticle/703524. Accessed July 21, 2009.
 8. Warlow C. Endarterectomy for asymptomatic carotid stenosis?. Lancet. May 20 1995;345
 (8960):1254-5. [Medline].
 9. Lohan DG, Tomasian A, Saleh RS, Singhal A, Krishnam MS, Finn JP. Ultra-low-dose, time-
 resolved contrast-enhanced magnetic resonance angiography of the carotid arteries at 3.0
 tesla. Invest Radiol. Apr 2009;44(4):207-17. [Medline].
 10. Wyers MC, Powell RJ, Fillinger MF, Nolan BW, Cronenwett JL. The value of 3D-CT
 angiographic assessment prior to carotid stenting. J Vasc Surg. Mar 2009;49(3):614-
 22. [Medline].
 11. Blasel S, Hattingen E, Berkefeld J, Kurre W, Morawe G, Zanella F, et al. Evaluation of
 Angiographic and Technical Aspects of Carotid Stenting with Diffusion-Weighted Magnetic
 Resonance Imaging. Cardiovasc Intervent Radiol. Mar 14 2009;[Medline].
 12. Ryu CW, Jahng GH, Kim EJ, Choi WS, Yang DM. High Resolution Wall and Lumen MRI of the
 Middle Cerebral Arteries at 3 Tesla. Cerebrovasc Dis. Mar 19 2009;27(5):433-442. [Medline].
 13. Gerediaga GD, Elizagaray E, Canto-Morereira N, Albuquerque C, Branco R, Beirao I, et
 al. [Contralateral occlusion of the internal carotid artery in the study of carotid stenosis using
 Doppler ultrasonography.]. Rev Neurol. Apr 16-30 2009;48(8):406-11. [Medline].
 14. Matsubara S, Moroi J, Suzuki A, Sasaki M, Nagata K, Kanno I, et al. Analysis of cerebral
 perfusion and metabolism assessed with positron emission tomography before and after carotid
 artery stenting. J Neurosurg. Mar 20 2009;[Medline].
 15. Font MA, Fernandez A, Carvajal A, Gamez C, Badimon L, Slevin M, et al. Imaging of early
 inflammation in low-to-moderate carotid stenosis by 18-FDG-PET. Front Biosci. Jan
 1 2009;14:3352-60. [Medline].
 16. Schoenberg BS. Epidemiology of cerebrovascular disease. South Med J. Mar 1979;72(3):331
 -6, 334. [Medline].
 17. Tegos TJ, Kalomiris KJ, Sabetai MM, et al. Significance of sonographic tissue and surface
 characteristics of carotid plaques. AJNR Am J Neuroradiol. Sep 2001;22(8):1605-12. [Medline].
 18. Ubels FL, Terpstra WF, Smit AJ. Carotid intima-media thickness: influence of drug treatment
 and clinical implications. Neth J Med. Oct 1999;55(4):188-95. [Medline].
 19. Wagner AL. Isolated stenosis of a persistent hypoglossal artery visualized at 3D CT
 angiography. AJNR Am J Neuroradiol. Sep 2001;22(8):1613-4. [Medline].
 20. Angelini A, Reimers B, Della Barbera M, et al. Cerebral protection during carotid artery
 stenting: collection and histopathologic analysis of embolized debris. Stroke. Feb 2002;33
 (2):456-61. [Medline].
 21. Benade MM, Warlow CP. Costs and benefits of carotid endarterectomy and associated
 preoperative arterial imaging: a systematic review of health economic
 literature. Stroke. Feb 2002;33(2):629-38. [Medline].
 22. Benes V, Mohapl M. Alternative surgery for the kinked internal carotid artery. Acta Neurochir
 (Wien). Dec 2001;143(12):1267-72. [Medline].
 23. Berkefeld J, Turowski B, Dietz A, et al. Recanalization results after carotid stent




http://progps1.emedicine.com/gps/displaytopic.gps?view=plain&docid=417524                  5/4/2010
View Carotid Artery, Stenosis                                                           Page 54 of 54



 placement. AJNR Am J Neuroradiol. Jan 2002;23(1):113-20. [Medline].
 24. Blaser T, Hofmann K, Buerger T, et al. Risk of stroke, transient ischemic attack, and vessel
 occlusion before endarterectomy in patients with symptomatic severe carotid
 stenosis. Stroke. Apr 2002;33(4):1057-62. [Medline].
 25. Chambless LE, Folsom AR, Clegg LX, et al. Carotid wall thickness is predictive of incident
 clinical stroke: the Atherosclerosis Risk in Communities (ARIC) study. Am J Epidemiol. 2000;Mar
 1;151(5):478-87. [Medline].
 26. Felberg RA, Christou I, Demchuk AM, et al. Screening for intracranial stenosis with
 transcranial Doppler: the accuracy of mean flow velocity thresholds. J
 Neuroimaging. Jan 2002;12(1):9-14. [Medline].
 27. Garai I, Varga J, Szomjak E, et al. Quantitative assessment of blood flow reserve using
 (99m)Tc-HMPAO in carotid stenosis. Eur J Nucl Med. Feb 2002;29(2):216-220.
 28. Golay X, Brown SJ, Itoh R, Melhem ER. Time-resolved contrast-enhanced carotid MR
 angiography using sensitivity encoding (SENSE). AJNR Am J Neuroradiol. Sep 2001;22(8):1615-
 9. [Medline].
 29. Hallerstam S, Carlstrom C, Zetterling M, et al. Carotid atherosclerosis in relation to
 symptoms from the territory supplied by the carotid artery. Eur J Vasc Endovasc
 Surg. Apr 2000;19(4):356-61. [Medline].
 30. Hirai T, Korogi Y, Ono K, et al. Prospective Evaluation of Suspected Stenoocclusive Disease of
 the Intracranial Artery: Combined MR Angiography and CT Angiography Compared with Digital
 Subtraction Angiography. AJNR Am J Neuroradiol. Jan 2002;23(1):93-101. [Medline].
 31. Hodis HN, Mack WJ, LaBree L, et al. The role of carotid arterial intima-media thickness in
 predicting clinical coronary events. Ann Intern Med. Feb 15 1998;128(4):262-9. [Medline].
 32. Iu PP, Lam HS. Migrainous spasm simulating carotid dissection: a pitfall in MR arteriographic
 findings. AJNR Am J Neuroradiol. Sep 2001;22(8):1550-2. [Medline].
 33. Liu AY, Do HM, Albers GW, et al. Hyperperfusion syndrome with hemorrhage after
 angioplasty for middle cerebral artery stenosis. AJNR Am J Neuroradiol. Sep 2001;22(8):1597-
 601. [Medline].
 34. Macchi C, Molino Lova R, Miniati B, et al. Is the percentage of stenosis of the internal carotid
 artery a reliable measure of the risk of ischemic stroke? A morphometric study by duplex
 ultrasound of aortic arch branches in 500 normal adults. J Cardiovasc Surg
 (Torino). Feb 2002;43(1):71-6. [Medline].
 35. NCHS. Annual summary of births, marriages, divorces, and deaths: United States. In:
 Monthly Vital Statistics Report. Vol 42. National Center for Health Statistics;1994:13.
 36. Persson J, Formgren J, Israelsson B, Berglund G. Ultrasound-determined intima-media
 thickness and atherosclerosis. Direct and indirect validation. Arterioscler Thromb. Feb 1994;14
 (2):261-4. [Medline].
 37. Pexman JH, Barber PA, Hill MD, et al. Use of the Alberta Stroke Program Early CT Score
 (ASPECTS) for assessing CT scans in patients with acute stroke. AJNR Am J
 Neuroradiol. Sep 2001;22(8):1534-42. [Medline].

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