Carotid artery dissection is a condition whereby the layers of the carotid artery are spontaneously separated. This potentially compromises blood flow to certain areas of the brain and can lead to a stroke. Furthermore, it can occur extracranially or intracranially and can lead to subarachnoid hemorrhage or brain ischemia. It is the most common cause of strokes in younger patients, and the importance of making a timely diagnosis is paramount to minimize potential morbidity and mortality of the disease.  There is a huge variation in the presenting signs and symptoms of this disease which makes it extremely difficult to diagnose on initial presentation.
Carotid artery dissection occurs spontaneously when a tear occurs in the intimal layer of the carotid artery creating an intramural hematoma. This tear can be spontaneous or caused by trauma.  The intramural hematoma causes the stenosis and eventual thrombus formation. Traumatic dissection can either be by blunt or penetrating trauma. Blunt trauma can be significant (e.g., motor vehicle collision), or it can seem minimal (e.g., chiropractic manipulation being the most classic example). A motor vehicle accident where there is rapid deceleration with simultaneous neck hyperextension and rotation may lead to an intimal tear of the carotid artery. "Idiopathic" is the most common cause of spontaneous carotid dissections in which a family history of dissection significantly increases one's risk.  Marfan syndrome, Ehlers-Danlos Syndrome, fibromuscular dysplasia and other connective tissue disorders also increase the risk of this disease. An elongated styloid process, which is called Eagle Syndrome, can also cause a spontaneous internal carotid artery dissection.
Carotid artery dissections occur in all age groups. They account for 2.5% of all strokes.  It is a common cause of stroke in patients younger than 40 years old. In all young patients, 20% of cerebrovascular accidents (CVAs) are caused by carotid artery dissection. The median age is in the mid-40s, and there seems to be a slightly higher incidence in males versus females.
A sudden tear in the intimal layer of the carotid artery occurs due to the factors listed above. These may be due to trauma or they can be spontaneous. This tear allows blood to flow into this intimal layer of the vessel and allows a hematoma to form within the blood vessel wall. This is commonly known as a false lumen. As blood enters this false lumen, it causes stenosis which may lead to complete occlusion of the carotid artery. This is a dynamic process which may lead to stenosis of the vessel or dilatation of the artery. This depends on where the hematoma develops, either toward the intima or adventitia. This process may lead to a stroke from a complete vascular occlusion at the site of the dissection. It may also be a nidus for thrombus formation that may later migrate distally, causing a stroke or transient ischemic attack. If the vessel ruptures intracranially, it may lead to a subarachnoid hemorrhage. Also, a pseudoaneurysm may result from a carotid dissection.
There is a tremendous amount of variation in the presentation of carotid dissection, hence making the diagnosis a challenge.  The presentation can range from an asymptomatic patient to one who presents with an acute stroke. Classic teaching describes a headache, facial or eye pain, and neck pain. The pain when present is usually on the ipsilateral side. A Horner's Syndrome may be present if a hematoma of the cervical artery compresses the adjacent sympathetic nerve fibers. When stroke-like symptoms are present with these symptoms, it can make the diagnosis somewhat less difficult. The family history of carotid dissection or connective tissue disorders may heighten one's suspicion. The presence of blunt or penetrating trauma is helpful to make the diagnosis. Blunt trauma makes it more challenging to make the correct diagnosis as some can occur from minor trauma such as a chiropractic neck manipulation. Unfortunately, many patients may not present with pain nor a mechanical trigger which further increases the challenge of making an accurate diagnosis.
As is common with many disease entities that are rare and can present with minor to more severe symptoms, one must have a higher index of suspicion to make this diagnosis. Unfortunately, having a too high index of suspicion in search of this disease may lead to overtesting in a vast array of patients that ultimately do not have a carotid artery dissection. A good history and physical is essential. Neurologic deficits should prompt one to consider this diagnosis especially if the patient is young and there is recent trauma. Getting a good medical and family history may aid in the diagnosis. Recent trauma to the neck with anterior neck pain is a clue. Neck pain and tenderness may be present. A bruit over the carotid artery may be heard in some patients with this disease. An expanding hematoma may be present if trauma has occurred.
If a cervical dissection is suspected, many diagnostic modalities may confirm the diagnosis. The initial and least invasive screening tool is a carotid ultrasound. Its sensitivity is not as good as a computed tomogram (CT) angiogram, and it does not allow for imaging of the intracranial vessels. A CT angiogram is more commonly ordered these days as it can be done concurrently with a brain CT that is looking for an acute stroke or intracranial bleed. A flame sign is classic that is tapering of the carotid artery can be seen. Magnetic resonance imaging and magnetic resonance angiography are reasonable alternatives if the patient has contraindications to a CT angiogram, but it is not as sensitive. Standard digital subtraction angiography was the most common means of making this diagnosis, but with the evolution of CT angiography, this imaging modality has become much less common from a diagnostic standpoint.
Treatment of a cervical dissection depends on many factors such as the cause (traumatic vs. spontaneous), and whether the patient has had a stroke. Also, whether this dissection is intracranial or extracranial will alter the treatment plan. Active bleeding with hematoma expansion will also be a factor in deciding treatment.
If there are no contraindications, antiplatelets may be used, or more commonly, systemic anticoagulation may be used to minimize the risk of a stroke. Also, endovascular stenting may be performed on some of these patients, especially if there are contraindications to anticoagulation or if medical management fails. The one-year recurrence rate is 0-10%.
Carotid dissection can lead to minor symptoms or more commonly, to severe neurologic deficits and/or death. Prognosis is variable and depends on whether the diagnosis is made before the onset of stroke symptoms. All patients have a very high risk of stroke, intracranial bleeding, and are subjected to anticoagulation which has its set of risks.
Carotid dissection is a rare disease, and it is an extremely difficult diagnosis to make. The presentation can vary from minor symptoms to more severe life-threatening symptoms, as discussed above. Treatment is aimed at minimizing the risk of stroke and the worsening of symptoms.
Carotid artery dissection is a rare vascular disorder that has the potential to cause a severe stroke. Thus, it is best managed by an interprofessional team that includes a neurologist, emergency department physician, radiologist, vascular surgeon and an internist. The diagnosis is made by CT scan but the management depends on patient symptoms and whether the disease in extra or intracranial. Asymptomatic patients may be treated with systemic anticoagulation but if there is a risk of bleeding or rupture, the patient may require surgery. Today a viable option is stenting. These patients should be monitored in a neuro ICU by nurses until they are hemodynamically stable and have no evidence of any neurological deficit. Patients need to be educated about blood pressure control as the recurrence of dissection has been reported in up to 10% of cases. (Level V)
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