Carotid stenosis is a narrowing or constriction of the inner surface of the
carotid artery, usually caused by atherosclerosis.
Pathophysiology The carotid artery is the large vertical
artery in red. The blood supply to the carotid artery starts at the arch of the
aorta. The carotid artery divides into the internal carotid artery and the
external carotid artery. The internal carotid artery supplies the brain.
Plaque often builds up at that division, and causes a narrowing. Pieces of plaque
can break off and block the small arteries above in the brain, which
causes a stroke. Plaque can also build up at the origin of the carotid artery
at the aorta. Signs and symptoms
The carotid artery is the large artery whose pulse can be felt on both sides of
the neck under the jaw. On the right side it starts from the brachiocephalic
trunk as the common carotid artery, and on the left side the common carotid
artery comes directly off the aortic arch. At the throat it forks into the
internal and external carotid arteries. The internal carotid artery supplies the
brain, and the external carotid artery supplies the face. This fork is a common
site for atherosclerosis, an inflammatory buildup of atheromatous
plaque that can narrow the lumen of the common or internal carotid arteries.
The plaque can be stable and asymptomatic, or it can be a source of
embolization. Emboli break off from the plaque and travel through the
circulation to blood vessels in the brain. As the vessel gets smaller, they
can lodge in the vessel wall and restrict blood flow to parts of the
brain which that vessel supplies. This ischemia can either be temporary,
yielding a transient ischemic attack, or permanent resulting in a thromboembolic
stroke. Clinically, risk of stroke from carotid
stenosis is evaluated by the presence or absence of symptoms and the degree of
stenosis on imaging. Transient ischemic attacks are a warning
sign, and are often followed by severe permanent strokes, particularly within
the first two days. TIAs by definition last less than 24 hours and frequently
take the form of a weakness or loss of sensation of a limb or the trunk on one
side of the body, or the loss of sight in one eye. Less common symptoms are
artery sounds, or ringing in the ears. Diagnosis
Carotid stenosis is usually diagnosed by color flow duplex ultrasound scan of the
carotid arteries in the neck. This involves no radiation, no needles and no
contrast agents that may cause allergic reactions. This test has moderate
sensitivity and specificity, and yields many false-positive results.
Typically duplex ultrasound scan is the only investigation required for decision
making in carotid stenosis as it is widely available and rapidly performed.
However, further imaging can be required if the stenosis is not near the
bifurcation of the carotid artery. One of several different imaging
modalities, such as angiogram, computed tomography angiogram or magnetic
resonance imaging angiogram may be useful. Each imaging modality has its
advantages and disadvantages - Magnetic resonance angiography and CT angiography
with contrast is contraindicated in patients with renal insufficiency,
catheter angioigraphy has a 0.5% to 1.0% risk of stroke, MI, arterial injury or
retoperitoneal bleeding. The investigation chosen will depend on the
clinical question and the imaging expertise, experience and equipment
available. Screening
The U.S. Preventive Services Task Force recommends against screening for carotid
artery stenosis in those without symptoms.
Management Options include:
Medications alone and control of risk factors for atherosclerosis).
Medical management plus carotid endarterectomy or carotid stenting,
which is preferred in patients at high surgical risk and in younger patients.
Control of smoking, hypertension, and hyperlipidemia.
The goal of treatment is to reduce the risk of stroke. Intervention can cause
stroke; however, where the risk of stroke from medical management alone is
high, intervention may be beneficial. In selected trial participants with
asymptomatic severe carotid artery stenosis, carotid endarterectomy reduces
the risk of stroke in the next 5 years by 50%, though this represents a
reduction in absolute incidence of all strokes or perioperative death of
approximately 6%. In most centres, carotid endarterectomy is associated
with a 30-day stroke or mortality rate of