Etiology
The most important causes are atherosclerosis, aortitis, trauma and radiation injury.
Pathogenesis.
The most frequent site is the bifurcation of the common carotid artery, followed by the beginning segment of the common carotid artery, in addition to the siphon of the internal carotid artery, the middle cerebral artery and the anterior cerebral artery.
It is generally believed that carotid plaque causes cerebral ischemia mainly through the following two pathways: one pathway is the alteration of hemodynamics caused by severely narrowed carotid artery, resulting in hypoperfusion of the corresponding parts of the brain; the other pathway is the dislodgement of microemboli in the plaque or microthrombi on the surface of the plaque, causing cerebral embolism. There is no consensus as to which of these two mechanisms is more predominant, but most believe that there is a close relationship between plaque stenosis, plaque morphological characteristics and cerebral ischemic symptoms, and that the two together induce neurological symptoms, while the relationship between stenosis and symptoms may be even closer.
Carotid artery stenosis due to atherosclerosis is most often seen in middle-aged and elderly people, and is often associated with multiple cardiovascular risk factors. Carotid stenosis due to cephalothoracic aortitis is most often seen in adolescents, especially in young women. Carotid artery stenosis due to injury or radiation has a history of corresponding injury or radiation exposure prior to the onset of the disease.
Clinically, carotid stenosis is divided into two categories: symptomatic and asymptomatic, depending on whether the stenosis produces symptoms of cerebral ischemia.
Symptomatic carotid stenosis
Cerebral ischemic symptoms: tinnitus, vertigo, blackness, blurred vision, dizziness, headache, insomnia, memory loss, drowsiness, and dreaminess may be present. Ocular ischemia manifests as vision loss, hemianopia, diplopia, etc.
Localized transient loss of neurological function in TIA is clinically manifested by transient impairment of sensory or motor function of one limb, transient monocular blindness or aphasia, etc., which usually lasts only a few minutes and fully recovers within 24h after the onset. There are no focal lesions on imaging.
Ischemic stroke: common clinical symptoms include sensory impairment of one limb, hemiparesis, aphasia, cerebral nerve damage, and in severe cases, coma, with corresponding neurological signs and imaging features.
Asymptomatic carotid stenosis Many patients with carotid stenosis do not have any clinical signs and symptoms of the nervous system. Sometimes, only a weakened or absent carotid pulsation is detected during physical examination, and a vascular murmur is heard at the root of the neck or at the carotid artery meridian. Asymptomatic carotid artery stenosis, especially severe stenosis or plaque ulceration, is recognized as a “high-risk lesion” and is receiving increasing attention.
Laboratory tests
No relevant data have been identified.
Other ancillary tests
Doppler-ultrasound is the preferred non-invasive carotid artery examination that combines Doppler flowmetry and ultrasound imaging in real time, and is simple, safe and inexpensive. It can not only display the anatomical image of carotid artery and perform morphological examination of plaque, such as distinguishing intraplaque bleeding from plaque ulceration, but also display the arterial blood flow, flow rate, flow direction and intra-arterial thrombus. With an accuracy of over 95% in diagnosing the degree of carotid stenosis, Doppler-ultrasound has been widely used in the screening and follow-up of carotid stenotic lesions.
The shortcomings of ultrasonography include the inability to examine lesions in the intracranial internal carotid arteries; the results are easily influenced by the skill level of the operator.
Magnetic resonance angiography (MRA) is a noninvasive vascular imaging technique that clearly displays the three-dimensional morphology and structure of the carotid arteries and their branches and can reconstruct intracranial arterial images. The carotid vessels have a linear profile and are particularly suitable for MRA, which can accurately visualize thrombotic plaques, the presence or absence of clotted aneurysms and intracranial arteries, and is extremely helpful for diagnosis and protocol determination.
The prominent disadvantage of MRA is that slow or complex flow often results in signal loss and exaggerated stenosis. It also has limitations in showing sclerotic plaques. MRA is contraindicated in patients with metal retention (e.g., metal stents, pacemakers, or metal prostheses).”
CT angiography CT angiography (CTA) is a non-invasive angiographic technique developed on the basis of spiral CT. The method involves transvascular injection of contrast, volumetric scanning during peak contrast concentration in the circulating blood or in the target vessel, and subsequent processing to obtain a digital stereoscopic image. The carotid artery in the extracranial segment is suitable for CTA examination, mainly because the carotid artery course is perpendicular to the CT section, thus avoiding the disadvantage of relatively insufficient resolution for vessels with horizontal course in spiral CT scanning. the advantage of CTA can directly display calcified plaque. At present, 3D revascularization is generally performed by surfacehadeddisplay (SSD) and maximumintensityprojection (MIP). However, SDD cannot directly show the density difference CTA technique has been used more often in the diagnosis of carotid artery stenosis, but the technique is not mature enough and needs to be improved by further accumulation of experience.
Digital subtraction angiography Currently, although non-invasive imaging methods have been increasingly used for the diagnosis of carotid artery lesions, each method has definite advantages and disadvantages. High-resolution MRA, CTA, and Doppler-ultrasound imaging are of great value for primary diagnosis and follow-up. Although angiography is no longer used for screening, primary diagnosis and follow-up, digital subtraction angiography (DSA) remains the “gold standard” for the diagnosis of carotid artery stenosis in terms of accurate evaluation of lesions and determination of treatment options. DSA for carotid stenosis should include aortic arch angiography, bilateral common carotid artery selective angiography, intracranial segmental carotid artery selective angiography, bilateral vertebral artery selective angiography, and basilar artery selective angiography, which can provide a detailed understanding of the location, extent, and degree of the lesion as well as the formation of side branches; help determine the nature of the lesion such as ulcers, calcified lesions, and thrombosis; and understand coexisting vascular lesions such as aneurysms and vascular malformations. Aneurysms, vascular malformations, etc. Arteriography can provide the most valuable imaging basis for surgical and interventional treatment.
Arteriography is an invasive and expensive test, and the literature reports a complication rate of 0.3% to 7%. The main complications are cerebral vasospasm, dislodgement of plaque causing stroke, cerebral embolism and contrast allergy. Renal impairment, vascular injury and hematoma at the puncture site, and pseudoaneurysm.