Introduction
Carotid artery dissection is a tear in the artery of the neck. It causes the blood from arterial pressure to enter the artery's vessel wall, resulting in its split. It can either lead to hematoma or dilatation of arteries. This acts as a source for thrombus formation. Recent advanced imaging techniques have enabled screening of this condition. CT (computed tomography) angiography is a commonly used tool for assessment in recent times. The test includes injecting contrast material into blood vessels and CT scan imaging.
What Is Carotid Artery Dissection?
It is a condition where the vessel layer is separated in the carotid artery. It disrupts blood flow to specific brain regions leading to stroke. The condition may occur intracranially or extracranially, causing subarachnoid hemorrhage (bleeding in the space between the brain and its membrane) or ischemia (reduced blood flow). It occurs predominantly in younger patients.
How Does Carotid Artery Dissection Develop?
A spontaneous tear of the inner layer of the carotid artery forms an intramural (situated in the walls of the organ) hematoma. The tear can be due to trauma or idiopathic (unknown) reasons. The hematoma progresses to form stenosis (narrowing) and a thrombus (blood clot). Carotid artery dissection caused by trauma can be blunt or penetrating.
Blunt trauma occurs in motor vehicle collisions or chiropractic (alternative medicine) manipulation. Rapid neck rotation and hyperextension (excessive neck movement in one direction) leads to this trauma.
A family history of the disease increases the risk in individuals with the idiopathic cause of carotid artery dissection development.
A few systemic disorders, such as Marfan syndrome (inherited disorder of connective tissue), Ehler- Danlos syndrome (inherited disorder of skin, bone, and vessels), fibromuscular disorder (twisting of blood vessels in the body), and other connective tissue diseases, may increase the risk of developing the disease.
What Is the Incidence of Carotid Artery Dissection Development?
The disease occurs with similar frequency in all age groups. Carotid artery dissection commonly causes stroke (brain damage due to interruption to blood supply) formation in individuals below 40 years of life. The complications of carotid artery dissection show a slight male predominance.
The frequency of carotid artery dissection formation exhibits seasonal variation. The peak incidence of disease development is in the autumn season. This phenomenon is attributed to weather-associated factors that cause changes in blood pressure, coagulation (clotting), blood flow, diet, physical activities, and air pollution. Migraine is a risk factor for disease occurrence.
What Is the Pathologic Process of Carotid Artery Dissection?
A tear formed in the internal vessel wall of the carotid artery causes a hematoma to form in the blood vessel wall. This feature is known as false lumen. When the blood enters the false lumen to form stenosis, it causes complete obstruction of the carotid artery.
Based on the location of the hematoma in the intima (innermost membrane) or adventitia (outermost membrane of the vessel wall), there may be stenosis or dilatation of the carotid artery. The condition gradually progresses to stroke formation at the tear site due to complete arterial obstruction. If there is thrombus formation at the injury site, it may migrate elsewhere in blood vessels leading to ischemia or stroke.
In a few instances, rupturing blood vessels within the cranium can cause subarachnoid hemorrhage. Rarely, pseudoaneurysms (false aneurysms due to arterial injury) can form due to carotid artery dissection.
What Are the Symptoms of Carotid Artery Dissection?
The symptoms of carotid artery dissection vary significantly among individuals. Some patients are asymptomatic, whereas others may exhibit symptoms of acute stroke. Some of the most common symptoms are
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Headache.
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Blurred vision or transient blindness is caused by decreased blood flow to the retina (nerve tissue at the back of the eye).
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Facial, eye, or neck pain.
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If the pain is present, it is on the ipsilateral side (on the same side of the body).
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Horner syndrome develops when cervical artery hematoma compresses adjacent sympathetic nerves. The feature is the appearance of ptosis (drooping eye) with miosis (excessive pupil constriction). The condition is often painful if it develops from internal carotid artery dissection.
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Neck swelling.
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Tinnitus is pulsatile (patients experience throbbing in the ear).
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Reduced sensation of taste.
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Symptoms that are similar to migraine.
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Stroke.
How to Diagnose Carotid Artery Dissection?
Young individuals with recent trauma must be examined for neurologic deficits. Neck trauma associated with anterior neck pain and tenderness can raise suspicion and requires further evaluation. A bruit sound (blood flowing) may be heard on a physical evaluation over the carotid artery. In a few patients with trauma expanding hematoma (pool of clotted blood) occurs.
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Imaging Studies - These diagnostic tests are helpful in disease confirmation.
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Carotid Ultrasound - This imaging technique is the least invasive but less sensitive. The imaging of intracranial vessels is not possible. The imaging detects a hematoma or thrombus intramurally as thickened hypoechoic (low echo) structure.
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CT Angiogram - This imaging technique can be combined with brain CT (computed tomography). The imaging technique helps diagnose intracranial bleeding or acute stroke. The test shows tapering of the carotid artery like a flame, a classic sign of disease confirmation.
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Magnetic Resonance Angiography - The test is performed on individuals contraindicated to undergo CT imaging study. The test is less sensitive for detecting carotid artery dissection and identifying affected vessels supplying the brain.
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Standard Digital Subtraction Angiography - In earlier times, it was a commonly used imaging technique. However, with the development of modern imaging techniques, the use of this technique has been reduced.
What Is the Role of CT Angiography in Carotid Artery Dissection Diagnosis?
CT angiography is the most commonly used technique for carotid artery dissection due to the inclusion of multidetector scans. This test is the first choice for diagnosing patients with trauma and disease symptoms. It is a fast and noninvasive procedure. There is an improvement in spatial and temporal resolution in this test.
Internal carotid artery dissection in non-contrast CT is identified with indirect findings and is not sensitive. However, contrast CT imaging reveals soft-tissue swelling and hematoma near the perivascular fat and internal carotid artery. The hematoma is a crescent-shaped hyperattenuating (occurs when the clot is formed in a vessel) focus.
The technique can also diagnose if there are any fractures in cervical bones. The enlargement of the dissected artery is visualized. The appearance of abnormalities in vessel contour is a sensitive feature for disease detection.
The lumen appears narrow, oval, irregular, or slit-like in a cross-section view. Pseudoaneurysm is imaged in a few patients. In addition, extravascular structures are visualized.
How Is Carotid Artery Dissection Treated?
The treatment for this condition depends on the cause of stroke development in patients. Intracranial or extracranial dissection occurrence can alter the course of treatment. If the cause is due to neck trauma, cervical spine immobilization must be performed. Antiplatelet or anticoagulants are used when thrombosis is detected or to minimize the risk of stroke. Anticoagulation therapy includes intravenous administration of Heparin followed by Warfarin. Endovascular stenting is recommended in patients with medical treatment failure or anticoagulation contraindications. Surgery does not play any beneficial role in treating carotid artery dissection.
Conclusion
Carotid artery dissection is a rare condition of the blood vessel, which has the potential to develop stroke. Hematoma is formed in carotid artery dissection due to trauma, accidents, or other factors. CT angiography is a preferred technique for diagnosis. The imaging and contrast agents can effectively detect hematoma and soft tissue swelling that develops close to the artery. The treatment depends on the patient's symptoms and the location of the tear.
