A patient with cervical carotid artery disease may be completely asymptomatic or may present with symptoms of TIA, amaurosis fugax or a stroke. Physical findings may include decreased carotid pulses or a cervical bruit. However, a bruit may be present without significant disease in the carotid artery, and the absence of a bruit does not rule out carotid artery atherosclerosis. Clinical evaluation should be considered in patients who have risk factors for carotid artery disease, including hyperlipidemia, hypertension, diabetes, metabolic syndrome (MS), tobacco abuse and other predisposing factors.
Diagnostic tests for extracranial CAS have changed. The conventional contrast angiogram, once considered to be the gold standard for diagnosis, is rarely used today. The current first line of evaluation is a duplex ultrasound examination. This is a combination of B-mode imaging and pulsed Doppler velocity spectrum analysis. Duplex examination is very reliable, painless, noninvasive and relatively inexpensive. Initially, cardiologists were reluctant to use a duplex examination as a definitive diagnostic test before any surgical intervention. However, years of experience have shown that complex carotid duplex ultrasound evaluation, along with quantitative Doppler spectral analysis, offers excellent imaging resolution to assess the presence and degree of flow restriction (4
). One limitation of ultrasound study is the difficulty with differentiating total occlusion versus preocclusive disease or very tight stenosis of the internal carotid artery. Duplex ultrasound () has an added advantage of not only showing the lumen of the vessel but also characteristics of the plaque; this is often invaluable in deciding the appropriate form of treatment.
Ultrasound study showing severe stenosis of the right internal carotid artery (RT ICA)
Alternative diagnostic tests for extracranial CAS include magnetic resonance (MR) angiography and computed tomography (CT) angiography. MR angiography is noninvasive and does not require an iodinated contrast medium. However, it overestimates the degree of stenosis, is inappropriate for people who are claustrophobic or unable to remain still on the examination table, and is often technically inadequate. MR angiography with gadolinium has been used in the past, but it is known that gadolinium is not innocuous; it can cause significant skin lesions, particularly in patients with abnormal kidney function, and may cause nephrogenic systemic fibrosis or nephrogenic fibrosing dermopathy (5
). CT angiography is frequently used, often to delineate the extent of the disease including the intracranial component. However, CT angiography is expensive and has risks related to contrast media.