Carotid artery dissection
Encyclopedia
Carotid artery dissection is a separation of the layers of the artery wall supplying oxygen-bearing blood to the head and brain, and is the most common cause of stroke
in young adults. (While generic dissection can imply any kind of tear, cut or other breach in a tissue, in this context of vascular medicine, dissection is a blister-like de-lamination between the outer and inner walls of a vessel, generally originating with a partial leak in the inner lining.)
Non-ischaemic signs and symptoms
Ischaemic signs and symptoms
The incidence of spontaneous carotid artery dissection is low, and incidence rates for internal carotid artery dissection have been reported to be 2.6 to 2.9 per 100,000.
Observational studies and case reports published since the early 1980s show that patients with spontaneous internal carotid artery dissection may also have a history of stroke in their family and/or hereditary connective tissue disorders, such as Marfan syndrome
, Ehlers-Danlos syndrome
, autosomal dominant polycystic kidney disease, pseudoxanthoma elasticum, fibromuscular dysplasia
, and osteogenesis imperfecta
type I.
However, although an association with connective tissue disorders does exist, most people with spontaneous arterial dissections do not have associated connective tissue disorders. Also, the reports on the prevalence of hereditary connective tissue diseases in people with spontaneous dissections are highly variable, ranging from 0% to 0.6% in one study to 5% to 18% in another study.
The probable mechanism of injury for most internal carotid injuries is rapid deceleration, with resultant hyperextension and rotation of the neck, which stretches the internal carotid artery over the upper cervical vertebrae, producing an intimal tear. After such an injury, the patient may remain asymptomatic, have a hemispheric transient ischemic event, or suffer a stroke.
occurs when a small tear forms in the innermost lining of the arterial wall (known as the tunica intima
). Blood is then able to enter the space between the inner and outer layers of the vessel, causing narrowing (stenosis
) or complete occlusion
. The stenosis that occurs in the early stages of arterial dissection is a dynamic process and some occlusions can return to stenosis very quickly. When complete occlusion occurs, it may lead to ischaemia. Often, even a complete occlusion is totally asymptomatic
because bilateral circulation keeps the brain well perfused. However, when blood clots form and break off from the site of the tear, they form emboli, which can travel through the arteries to the brain and block the blood supply to the brain, resulting in an ischaemic stroke
, otherwise known as an cerebral infarction
. Blood clots, or emboli, originating from the dissection are thought to be the cause of infarction in the majority of cases of stroke in the presence of carotid artery dissection. Cerebral infarction causes irreversible damage to the brain. In one study of patients with carotid artery dissection, 60% had infarcts documented on neuroimaging.
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
in young adults. (While generic dissection can imply any kind of tear, cut or other breach in a tissue, in this context of vascular medicine, dissection is a blister-like de-lamination between the outer and inner walls of a vessel, generally originating with a partial leak in the inner lining.)
Signs and symptoms
The signs and symptoms of carotid artery dissection may be divided into ischaemic and non-ischaemic categories:Non-ischaemic signs and symptoms
- Headache or neck pain
Ischaemic signs and symptoms
- Decreased pupil size with drooping of the upper eyelid (Horner syndrome)
- Transient vision loss
- Ischaemic stroke
Causes
The causes of internal carotid artery dissection can be broadly categorised into two classes: spontaneous or traumatic.Spontaneous
Once considered uncommon, spontaneous carotid artery dissection is an increasingly recognised cause of stroke that preferentially affects the middle-aged.The incidence of spontaneous carotid artery dissection is low, and incidence rates for internal carotid artery dissection have been reported to be 2.6 to 2.9 per 100,000.
Observational studies and case reports published since the early 1980s show that patients with spontaneous internal carotid artery dissection may also have a history of stroke in their family and/or hereditary connective tissue disorders, such as Marfan syndrome
Marfan syndrome
Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers....
, Ehlers-Danlos syndrome
Ehlers-Danlos syndrome
Ehlers–Danlos syndrome is a group of inherited connective tissue disorders, caused by a defect in the synthesis of collagen . The collagen in connective tissue helps tissues to resist deformation...
, autosomal dominant polycystic kidney disease, pseudoxanthoma elasticum, fibromuscular dysplasia
Fibromuscular dysplasia
Fibromuscular dysplasia, or fibromuscular dysplasia of arteries, often abbreviated as FMD, is a disease that can cause narrowing of arteries in the kidneys, the carotid arteries supplying the brain, and, less commonly, the arteries of the abdomen...
, and osteogenesis imperfecta
Osteogenesis imperfecta
Osteogenesis imperfecta is a genetic bone disorder. People with OI are born with defective connective tissue, or without the ability to make it, usually because of a deficiency of Type-I collagen...
type I.
However, although an association with connective tissue disorders does exist, most people with spontaneous arterial dissections do not have associated connective tissue disorders. Also, the reports on the prevalence of hereditary connective tissue diseases in people with spontaneous dissections are highly variable, ranging from 0% to 0.6% in one study to 5% to 18% in another study.
Traumatic
Carotid artery dissection is thought to be more commonly caused by severe violent trauma to the head and/or neck. An estimated 0.67% of patients admitted to the hospital after major motor vehicle accidents were found to have blunt carotid injury, including intimal dissections, pseudoaneurysms, thromboses, or fistulas. Of these, 76% had intimal dissections, pseudoaneurysms, or a combination of the two.The probable mechanism of injury for most internal carotid injuries is rapid deceleration, with resultant hyperextension and rotation of the neck, which stretches the internal carotid artery over the upper cervical vertebrae, producing an intimal tear. After such an injury, the patient may remain asymptomatic, have a hemispheric transient ischemic event, or suffer a stroke.
Pathophysiology
Arterial dissection of the carotid arteriesCarotid artery
Carotid artery can refer to:* Common carotid artery* External carotid artery* Internal carotid artery...
occurs when a small tear forms in the innermost lining of the arterial wall (known as the tunica intima
Tunica intima
The tunica intima is the innermost layer of an artery or vein. It is made up of one layer of endothelial cells and is supported by an internal elastic lamina...
). Blood is then able to enter the space between the inner and outer layers of the vessel, causing narrowing (stenosis
Stenosis
A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....
) or complete occlusion
Vascular occlusion
Vascular occlusion is a sudden blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is...
. The stenosis that occurs in the early stages of arterial dissection is a dynamic process and some occlusions can return to stenosis very quickly. When complete occlusion occurs, it may lead to ischaemia. Often, even a complete occlusion is totally asymptomatic
Asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
because bilateral circulation keeps the brain well perfused. However, when blood clots form and break off from the site of the tear, they form emboli, which can travel through the arteries to the brain and block the blood supply to the brain, resulting in an ischaemic stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, otherwise known as an cerebral infarction
Infarction
In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...
. Blood clots, or emboli, originating from the dissection are thought to be the cause of infarction in the majority of cases of stroke in the presence of carotid artery dissection. Cerebral infarction causes irreversible damage to the brain. In one study of patients with carotid artery dissection, 60% had infarcts documented on neuroimaging.