Generality
Carotid stenosis is a disease that affects the carotid arterial system.
The term stenosis, in this case, indicates a reduction in the vascular caliber, as a result of which the blood flow downstream of the narrowing is decreased; the result is a state of suffering of the organs it reaches, due to a lack of oxygen and nutrients carried by the blood.
The main cause of carotid stenosis is atherosclerosis, a particular form of arteriosclerosis that affects the great vessels.
What is carotid stenosis. Pathological anatomy
Stricture (from the Greek στενόω, narrow) of the carotid is the narrowing of the carotid vessel lumen. Before proceeding with the detailed description of the pathology, it is useful to briefly recall the "anatomy of the carotid system. This last" is composed of:
- Two common carotid arteries, right and left.
- Two branches for a single common carotid: the internal and external carotid.
- Collateral branches, which arise from the internal and external carotids.
The carotid system, through its various ramifications, supplies the cerebral districts and the areas of the head corresponding to the face and eyes. The partial or total occlusion of the carotid artery results in an ischemic phenomenon affecting the perfused tissues, since the flow rate of the blood pumped by the heart is compromised. The outcome of a carotid occlusion is clearly dramatic. , as the non-oxygenated tissues undergo necrosis (cell death). The necrosis of the tissues can be followed by a cerebral stroke and, when the carotid stenosis is severe, the death of the sick individual.
From the studies of pathological anatomy (i.e. on how a tissue or organ affected by a disease looks like), conducted on the carotids affected by stenosis, the following characteristics emerged:
- Occlusions are more frequent in the left carotid, which arises directly from the aortic arch, in the thorax. The reason is as follows. Atherosclerosis preferably affects the great vessels, and, in the case of the left carotid, the connection direct with a larger vessel predisposes it to risks of stenosis, of atheromatous origin, higher than the right carotid; the latter, in fact, arises from the anonymous artery, which in turn originates from the aortic arch.
- Brain lesions, due to ischemia, are more or less marked according to the extent of the narrowing of the carotids. There is a direct proportionality: a greater occlusion of the vessel, therefore, means more serious damage and a progressive worsening of the symptoms.
- Occlusions usually occur at the level of the bifurcations and at the origin of the collateral branches of the carotids.
Carotid stenosis is a typically male pathology, since atherosclerosis, the main cause of stenosis, affects men more than women. Furthermore, it is a pathology that spares no one, given that atherosclerosis is a condition that, sooner or later, afflicts every individual.
Causes of carotid stenosis. Pathophysiology
The main cause of carotid stenosis is atherosclerosis, a particular form of arteriosclerosis, which preferably affects large-caliber arterial vessels. Atherosclerosis is characterized by the appearance of medium tunic of the arterial vessel, of a raised plaque with precise contours. This focus is called atheroma. Atheroma has a fibrolipid consistency: the fibrous component is due to a proliferation of the fibrous connective tissue ("scar" tissue); the lipid component, on the other hand, comes from the blood plasma and consists of cholesterol crystals, triglycerides and fatty acids.
The onset of an atheroma is due to various factors, all equally important. The best known are:
- Hypertension
- Obesity
- Smoke
- Hypercholesterolemia
- Sedentary life
- Diabetes
- Aging
The atheroma, which develops at the level of the intimate tunic of the vessel, arises as a result of an imbalance between the vessel wall and the blood circulating in the lumen of the artery. In other words, the factors that induce atherosclerosis cause the blood flow in the vessel to be altered to the point of causing a lesion in the vessel wall, ie in the endothelium. The lesion creates an inflammatory situation and attracts blood plasma cells, such as red blood cells and white blood cells, whose intervention generates the first small plaque. Hypertension, for example, creates a swirling flow within the arteries. This explains why atheromas develop electively where there are bifurcations of the carotid: here the stresses to which the vessel is subjected are higher. Another example of instability in the relationship between the internal wall of the carotid and the blood concerns aging, an event that affects every individual. It reduces the elasticity and contractility of the arteries, thus modifying their blood flow.
The picture is enriched, moreover, with the formation, at the level of the atheroma, of a thrombus. The thrombus is a solid mass of blood cells. The consequence is natural, since, where a lesion is created, there is also the recall of platelets, or thrombocytes, and factors that deal with the coagulation process. These actors contribute to increase the thickening of the atheroma. At this point, the lumen of the arterial vessel of the carotid narrows further.
Making the situation even worse is the possibility that the thrombus will break apart into smaller particles, which are lost in the bloodstream. These free particles, called emboli, can reach the brain, accelerating the processes of ischemia and stroke.
Other causes of carotid stenosis are:
- Aneurysms
- Fibromuscular dysplasias
- Arteritis
- Kinking
- Coiling
Symptoms and signs
A clinical sign of a carotid stenosis is the absence of pulsations in the affected vessel. The verification is carried out by palpation and has a certain degree of uncertainty. In fact, pulsation may also be present in conjunction with a narrowing of the carotid.
The main sign that characterizes a carotid stenosis is the so-called transient ischemic attack, also known as TIA. It is defined as transitory, since it has a duration limit: no more than 24 hours. The ischemic attack occurs at the cerebral, facial and ocular level, that is the areas not sufficiently supplied by the occluded carotid artery. The clinical signs, due to TIA, are manifested by:
- Loss of limb control: hemiplegia of the side opposite to that of the occluded carotid. This is explained because - for example - the right hemisphere of the brain, supplied by the right carotid, controls the limbs of the left side of the body.
- Difficulty in speaking: language sometimes becomes incomprehensible.
- Vision problems: double or blurred vision. Possible blindness, which initially presents with a black or gray veil that falls in front of the eye. In this case, the affected eye is on the same side as the occluded carotid.
- Lack of coordination in walking.
- Paresis of the face.
If the stenosis involves ischemic damage of a greater extent, which lasts up to 3 days, it is called RIND, that is reversible ischemic neurological deficits. Symptoms are similar to those of TIA.
Finally, if the "occlusion of the carotid artery is severe and almost, if at all, complete, the resulting symptom is"ischemic stroke, or stroke. The consequences are evident and no longer transitory: the individual, who is affected by it, totally loses sensitivity, the faculty of movement and the various functions controlled by the areas no longer oxygenated by the blood flow. In most cases, this situation leads to death.
Diagnosis
An initial diagnosis of carotid stenosis can be based on monitoring, by simple palpation, the pulsations of the carotid artery. The absence of pulsation at the level of one of the two carotids could mean that there is an occlusion.
An important test is the so-called carotid sign, useful to determine not only the presence of stenosis, but also which of the two carotid pathways is occluded. It consists in alternately compressing one of the two carotids, interrupting the blood flow that flows through the carotid vessel.If the compressed carotid artery is the healthy one, after a time ranging from 10 to 30 seconds, the patient shows signs of malaise, pallor and loss of consciousness. If the compressed carotid artery is already occluded, the patient does not show symptoms, since the opposite way, patent, compensates for the lower inflow, due to stenosis, to the cerebral districts.
Instrumental diagnostic tests consist of:
- Doppler ultrasound
- Digital angiography
- Angioscanner
- Angio
Doppler ultrasound. This is a non-invasive examination, useful for the doctor to identify the position of the atheromatous plaque and the degree of stenosis, i.e. how much the lumen has narrowed. In fact, it is a method that allows, through an "ultrasound, to observe the morphology of the vessel walls and identify any anomalies thereof; by means of a Doppler, however, it is possible to evaluate, with an" ultrasound analysis, the hemodynamic situation, that is the blood flow velocity, in the "carotid area affected by the plaque. This last datum, that is how far the blood travels at the occlusion point, reveals the degree of stenosis of the atheromatous plaque.
Digital angiography. It is the most accurate investigation and is useful for assessing the degree of stenosis. It consists in injecting an iodinated contrast medium into the arterial circulation, by means of a catheter. The catheter is conducted in the area to be investigated. In this area, the path of the catheter is followed by means of radiographic instrumentation, which shows the internal structure of the carotid.
Computed tomography angiography, or CT angiography. It is based on the scan of the carotid area. The images, obtained by radiographic instrumentation, show the three-dimensional structure of the carotid vascular cavities. It requires the injection of an iodized contrast medium.
Magnetic resonance angiography, or angiography. The examination uses a paramagnetic contrast medium, which is injected into the patient. It allows to evaluate the location and extent of the alterations in the carotid vessel lumen.
Therapy
Pharmacological therapy is useful to improve the patient's symptoms or to prevent their worsening, but it does not "fix" a lesion, such as atheroma, present on the arteries. It involves the administration of:
- Medicines that thin the blood. They are used to avoid the formation, or worsening, of thrombi present in the areas affected by atheromas. Worsening of a thrombus can degenerate, as previously mentioned, into an embolus. To thin the blood, the patient can be given:
- The antiplatelet agents. They decrease platelet aggregation and lump formation. One of the most used is aspirin.
- Anticoagulants. They act on coagulation factors. They should be used with caution, before surgery or if the patient is suffering from other diseases that require anticoagulant treatment. One of the most used is coumadin.
- Drugs that limit the evolution of atheromatous plaque
- The lipid-lowering agents. They decrease the level of cholesterol and triglycerides in the blood, that is the lipids that act in the formation of plaque.
- The antidiabetics. They are indicated for diabetics. Diabetes is a condition that predisposes to carotid stenosis.
- Antihypertensives. They serve to normalize blood pressure. The whirling blood flow, generated by hypertension, favors the lesion of the intima of the vessels and the consequent formation of atheromatous plaques.
Surgery, on the other hand, is the only therapeutic approach useful for restoring normal blood flow within the occluded carotid artery.
Two types of intervention are possible:
- Endoarterectomy. With this surgery the atheromatous plaque and any lumps and residues, linked respectively to thrombi and emboli, are eliminated.
This technique involves the removal of the intimate tunic and part of the middle one, in which the atheroma is present. It is practiced under local anesthesia, therefore the patient remains conscious, by direct incision along the anterior part of the neck. requires the surgeon to first cut off the flow of blood through the carotid artery. At that point, the doctor can incise the carotid artery, open it, and remove the plaque. The incision area is clearly identified thanks to diagnostic instruments. Once the plaque has been removed, the eliminated vascular tissue is replaced with artificial tissue, or of venous origin. At this point, the carotid artery is closed.
- Carotid angioplasty and stenting. The operation serves to "reject" the atheromatous plaque, restoring the normal size of the carotid vessel lumen. It is performed under local anesthesia. The vascular surgeon operates using two catheters: one is provided with a metal mesh (stent) and the other with a balloon. By introducing them into the arterial circulation and reaching the area affected by the atheroma, the doctor ensures that, by means of the balloon, the normal diameter of the occluded carotid artery is re-established, and, by means of the metal mesh, the enlargement is maintained. it is inflated only once the catheter has been guided into the area affected by the plaque. It will later be removed.
Surgery is necessary when carotid occlusion affects more than 70% of the vessel lumen. The same applies in cases where, despite the shrinkage is lower in terms of percentage, the symptomatology foresees the possibility of critical situations, such as TIA, RIND or stroke. In the absence of these serious symptomatic conditions and at percentages of stenosis lower than 70%, the intervention is not a priority. The reason is due to the extreme delicacy of the surgical operations involving the carotid artery. When the patient has an advanced stage of carotid stenosis, the risks associated with the intervention do not exceed those that could create a stroke. Therefore, the plaque is eliminated.
