Atherosclerosis is the most common cause of carotid artery stenosis, accounting for more than 90% of cases. In addition, there are rare causes such as aortitis, trauma and radiation injury. Carotid artery stenosis due to different causes varies greatly in terms of clinical manifestations, diagnostic methods, treatment and relationship with stroke. Carotid stenosis due to atherosclerosis, especially at the bifurcation of the common carotid artery, is directly related to ischemic stroke, and its treatment is important for stroke prevention.
1. Etiology
The most important causes are atherosclerosis, aortitis, trauma and radiation injury.
Pathogenesis: The best site is the bifurcation of the common carotid artery, followed by the beginning of the common carotid artery, 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 through two main pathways.
One pathway is the altered hemodynamics caused by a severely stenosed carotid artery, resulting in hypoperfusion of the corresponding parts of the brain
The other pathway is the detachment of microemboli in the plaque or microthrombi on the plaque surface causing cerebral embolism.
There is no consensus on which of the above 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 the two together induce neurological symptoms, while the relationship between stenosis and symptoms may be closer.
2. Epidemiology
Stroke is the leading cause of disability in adults today and the third leading cause of mortality after cardiovascular disease and tumors. Stroke imposes a huge economic and psychological burden on families and society, and its prevention and treatment is a major public health problem.
Epidemiological studies have shown that the annual incidence of stroke in Europe and the United States is 200/100,000, of which 80% are ischemic strokes and 20% are hemorrhagic strokes. About half of the patients with ischemic stroke have ipsilateral extracranial segment carotid artery stenosis. In more than 20% to 25% of all stroke patients, the occurrence of stroke is directly related to atherosclerotic lesions at the bifurcation of the common carotid artery. The annual incidence of stroke with symptomatic carotid stenosis is 12%, and the 5-year incidence is 30% to 50%.
A study of the natural course of asymptomatic carotid stenosis found that 83% of patients had no symptoms of cerebral ischemia before stroke occurred, but about 3/4 of stroke patients had severe carotid stenosis ipsilateral to the intracranial lesion.
Although there is no large-scale epidemiological survey in China, a group of domestic data shows that a certain percentage of patients with cerebral ischemia also have carotid artery stenosis, and there is a close relationship between carotid artery lesions and cerebral ischemic symptoms.
3.Clinical manifestations
Carotid artery stenosis caused by atherosclerosis is mostly seen in middle-aged and elderly people, and is often accompanied by a variety of cardiovascular risk factors. Carotid artery stenosis caused by cephalothoracic aortitis is mostly 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 classified into two categories: symptomatic and asymptomatic, depending on whether it produces symptoms of cerebral ischemia.
(1) Symptomatic carotid stenosis
(1) Cerebral ischemic symptoms: tinnitus, vertigo, blackness, blurred vision, dizziness, headache, insomnia, memory loss, drowsiness, and dreaminess. Eye ischemia manifests as vision loss, hemianopia, diplopia, etc.
(2) Ischemic stroke: common clinical symptoms include sensory impairment of one limb, hemiparesis, aphasia, cerebral nerve damage, and coma in severe cases with corresponding neurological signs and imaging features.
(2) Asymptomatic carotid artery 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 artery 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 stenosis, especially severe stenosis or plaque ulceration, is recognized as a “high-risk lesion” and is receiving increasing attention.
4. Complications
Large-scale clinical data show that 50% carotid artery stenosis increases the risk of transient ischemic attack and stroke by 4%.
5.Examination
(1) Doppler-ultrasound examination
Doppler-ultrasound examination is the preferred non-invasive carotid artery examination method that combines Doppler flow measurement and real-time imaging of ultrasound, 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 hemorrhage from plaque ulcer, but also display arterial blood flow, flow rate, flow direction and intra-arterial thrombus. The accuracy of diagnosing the degree of carotid stenosis is over 95%, and Doppler-ultrasound examination has been widely used in screening and follow-up of carotid stenotic lesions.
(2) Magnetic resonance angiography
Magnetic resonance angiography is a noninvasive vascular imaging technique that clearly shows the three-dimensional morphology and structure of the carotid artery and its branches, and is capable of reconstructing intracranial arterial images. The carotid vessels have a linear profile and are particularly suitable for MRA, which can accurately show thrombotic plaques, the presence or absence of clotted aneurysms and intracranial arteries, and is extremely helpful in diagnosing and determining options.
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 trapped objects (such as metal stents, pacemakers or metal prostheses).
(3) CT angiography
CT angiography is a non-invasive angiographic technique developed on the basis of spiral CT. The method is to inject contrast into the blood vessels and perform a volumetric scan when the concentration of contrast in the circulating blood or target vessels reaches its peak, and then process it to obtain a digital stereoscopic image. CTA is suitable for carotid arteries in the extracranial segment, 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 during spiral CT scanning. the advantage of CTA can directly show calcified plaques.
MIP reconstructed images are similar to angiography and can show calcification and attached thrombus, but the 3D spatial relationship is not as good as SDD. Further experience is needed to improve it.
(4) Digital subtraction angiography
Although non-invasive imaging methods have been more and more widely 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 is still the “gold standard” for the diagnosis of carotid artery stenosis in terms of accurate evaluation of lesions and determination of treatment options.
6. Diagnosis
Men older than 60 years of age with a history of long-term smoking, obesity, hypertension, diabetes and hyperlipidemia, and other risk factors for cardiovascular disease. Carotid artery vascular murmur is found during physical examination. The diagnosis can be made through the comprehensive analysis of the results of non-invasive auxiliary tests.
7.Differential diagnosis
Carotid artery stenosis risk factors and high-risk groups Atherosclerosis is a systemic disease, and various cardiovascular and cerebrovascular disease risk factors such as age (>60 years old), gender (male), long-term smoking, obesity, hypertension, diabetes and hyperlipidemia are also applicable to the screening of carotid artery stenosis due to atherosclerosis.
High-risk groups include patients with TIA and ischemic stroke, patients with lower extremity atherosclerotic occlusive disease, patients with coronary artery disease (especially those requiring coronary artery bypass or intervention) and those with carotid artery vascular murmurs detected during physical examination.
8.Treatment
The treatment of carotid stenosis aims to improve cerebral blood supply, correct or alleviate the symptoms of cerebral ischemia; prevent the occurrence of TIA and ischemic stroke. Treatment is based on the degree of carotid stenosis and the patient’s symptoms, including medical treatment, surgical treatment and interventional treatment.
(1) Internal treatment
The purpose of conservative medical treatment is to reduce the symptoms of cerebral ischemia, reduce the risk of stroke, and control the existing diseases such as hypertension, diabetes, hyperlipidemia and coronary heart disease. Internal conservative treatment includes the following.
① Reducing body weight.
(ii) Smoking cessation.
(3) Limiting alcohol consumption.
(2) Anti-platelet aggregation therapy
Many large randomized, prospective multicenter clinical trials have confirmed that anti-platelet aggregation drugs can significantly reduce the incidence of cerebral ischemic disease, the commonly used drugs in clinical practice are aspirin, ticlopidine (trade name of Ralliadex), etc.
(3) Surgical treatment
The aim of surgical treatment of carotid stenosis is to prevent the occurrence of stroke and, to a lesser extent, to prevent and slow down the onset of TIA. The standard surgical procedure is carotid endarterectomy. Complications of CE include perioperative stroke and death; also cerebral nerve injury, wound hematoma infection, postoperative hypertension, and postoperative hyperperfusion syndrome; the incidence of myocardial infarction and hypotension is low.
9.Prognosis
According to foreign studies, the risk of stroke within 1 year for asymptomatic severe carotid stenosis (>70%) is 2% to 5%, and the annual stroke rate for those with ulcerated plaque is 7.5%. In Europe and the United States, about 35% of ischemic cerebrovascular disease is caused by carotid artery stenosis.
10. Prevention
Because the most important causes of this disease are atherosclerosis, aortitis, trauma and radiation injury, active treatment and prevention of the primary cause is the key to prevent this disease. Carotid percutaneous transluminal angioplasty or carotid stenting implantation can be done to eliminate potential sources of emboli and prevent the occurrence of stroke if significant carotid stenosis is found.