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1) Carotid arteries
The common carotid artery is paired and located on the left and right side of the neck, supplying the head with blood. At the so-called carotid bifurication point, the common carotid artery divides into the internal carotid artery and the external carotid artery. The external carotid artery is responsible for the supply of blood to the facial muscles and the tissue outside the interior of the skull. The right and left internal carotid arteries, together with the two vertebral arteries (these are lateral to the vertebral column, a.k.a. the spine), are responsible for the blood supply of the brain.
2) Carotid artery stenosis
Narrowings of the brain-supplying carotid arteries can lead to a stroke in the brain. These narrowings are called stenoses and are caused by what is commonly known as plaques. As a result of the narrowing, immidiate blood flow becomes turbulent, causing the rate of blood flow to rise. Correspondingly, small particles from vessel depositions (from the arterosclerotic plaque) can be entrained and carried into the brain. Such small particles are also referred to as microemboli. This can cause a stroke.
The aim of the treatment is to prevent the occurrence of a stroke.
A) Carotid artery stenosis risk factors
As is true for all vascular diseases, smoking, high blood pressure (hypertension) and increased blood lipids (hypercholesterolaemia) are considered as risk factors for the development of carotid stenosis.
B) Anzeichen/Beschwerden einer Carotisstenose
In most cases, narrowings of carotid arteries do not show any symptoms. The diagnosis is therefore made by chance due to a distinctive sound from the stethoscope and a subsequent ultrasound examination.
In some cases, however, the carotid stenoses may lead to symptoms. These are caused by poor blood circulation of certain brain regions, triggered by microembolisms. The microembolisms are small plaque-related particles protracted by the blood stream. Those affected suffer from specific neurological symptoms. These may, for instance, be movement or sensory disturbances in the arms or legs or in the facial area. Another possibility of occurrence may be a temporary blindness or a gray veil-like cover over the field of vision of the eye (Amaurosis fugax). Other than that, speech- and word-finding impediments can be signs of symptomatic carotid stenosis. On the basis of the severity and the duration of the disturbance of the blood circulation, the precursor of the stroke, the so-called “mini-stroke”, which is medically referred to as TIA (transient ischemic attack), is distinguished from the actual stroke, which causes a permanent deficit due to a definite brain damage. In the case of the TIA, treatment must be carried out immediately.
C) Carotid artery stenosis diagnosis
Clinical signs of carotid stenosis with symptoms has been mentioned previously. The actual identification of carotid artery narrowings is achieved by means of an ultrasound (duplex sonography), whereby the degree of carotid stenosis (%ST), according to specific criteria and the rate of blood flow, is indicated. Depending on the findings, complemental medical imaging such as magnetic resonance imaging (MRI) or computed tomography (CT angiography) may be of need.
D) Treatment of carotid artery stenosis
a) Drug treatment
The treatment of carotid artery narrowings will definitely be done medicinally. It includes the patelet function inhibition (antiplatelet drug) as well as the dispense of statins, lowering the LDL cholesterol in the blood (the “bad” cholesterol), which by means of such, solidify the arterosclerotic, lipid-containing vascular plaque (plaque stabilization).
b) Invasive treatment
According to current data, carotid surgery is only effective if symptoms of stenosis are present, with the degree of stenosis being at least 70%, or if carotid stenoses with no symptoms despite optimal drug therapy remain at an advanced degree or are progressive. An operation is performed or a carotid stent is deployed. This is done to prevent the transfer of small particles from the arterosclerotic plaque (microemboli). An operative procedure is also necessary in the rare case of a lack of blood circulation within the brain, caused by carotid artery stenosis. This deficiency indicates unusual symptoms for blood pressure reductions, such as dizziness and disorders of consciousness. A special magnetic resonance examination of the brain, which also measures the blood distribution inside the brain, shows a decrease in blood flow to one side of the brain.
Carotid surgery or carotid stent?
In extensive international studies, research has been carried out in order to determine whether a carotid stent is of any particular benefit to the elderly, who tolerate anesthesia poorly. However, it was found that elderly in specific, have a higher risk of a stroke upon the placement of a stent. The reason for this is the possible portraction of microthroms during stent placement – so long as no protective mechanism has been pushed behind the carotid stenosis. Therefore, the initial enthusiasm for the carotis stent has partially elapsed, nevertheless does the stent remain valuable as an additional part of the treatment of carotid stenosis.
The operation is performed under general anesthesia. General anesthesia slows the metabolism of the brain, thereby reducing the sensitivity of the brain in response to a decrease of oxygen content during the carotid constriction. The carotid artery is unloaded using a Non-Touch technique. With that, the artery is temporarily clamped in front of and behind the narrowing, next opened for the removal of the plaque.
In the event that the brain receives too little oxygen, which is measured with a special device, a temporary bypass circuit, a shunt, must be installed in order to supply the brain with sufficient oxygen during the clamping phase. The occlusion of the vessel is done with a patch of body-borne veins, of heterologous material (denatured, specially prepared animal material, e.g. bovine heart tisue – bovine pericardium) or plastic, to prevent the vessel from narrowing through with the seam. Suitable as venous material, is a piece of the saphenous or facial vein crossing the carotid is suitable.
Alternatively, the operation can also be performed under local anesthesia. Then however, a different surgical technique, the so-called eversion endarterectomy, is generally used. In this surgical method, the plaque is protruded from the internal carotid artery and the internal carotid artery resected into the common carotid artery. For that no patch needs to be sewn, with the operating time hence being shorter.
The main complication, with medical literature reporting estimates of up to 3%, is a stroke, which can be caused by a protraction of plaquematerial into the brain during surgery. Our institutional experience as well as my own personal experience reveal a stroke rate of less than one percent.
During the course of aftercare, it is necessary to counteract the risk factors of vessel calcification (arterosclerosis) in order to prevent possible narrowings in other body arteries. Every year, an ultrasonic check-up of blood vessels must be done as well an analyzis of blood lipid and vitamin D3 level. Lastly, the absence of nicotine remains absolutely indispensable.[/vc_column_text][/vc_column][/vc_row]