Carotid Artery Disease

There are two large arteries called carotid arteries situated in either side of the neck. They are responsible for the majority of the blood supply to the brain. On each side, the common carotid artery (left and right common carotid arteries) branches into two arteries:

• The internal carotid artery that goes into the brain
• The external carotid artery that supplies the head and face

Atherosclerotic disease commonly affects the area where the common carotid arteries branch out (carotid bifurcation). These atherosclerotic plaques deposited over the inner surface of the artery causes narrowing (stenosis) of the vessel.

• Small fragments of the atherosclerotic plaque may break off and pass along the artery into the smaller vessels inside the brain.
• This causes the blood flow to the brain to reduce or stop completely (transient ischaemic attack or stroke).
• Studies show around 80% of all strokes is related to a lack of blood supply to the brain and these are related to the narrowing of the carotid artery.
• The possibility of fragments released from the plaque depends on a few factors such as:
  • The severity of the atherosclerotic disease (i.e. the degree of narrowing (stenosis) in the carotid artery).
  • The composition of the plaque.

Transient ischaemic attack (TIA) and stroke

1. Transient ischaemic attack (TIA)

TIA occurs when there is an occlusion (closure or blockage) of the blood vessels supplying the brain with oxygen.

Due to the lack of blood supply and therefore oxygen reaching the brain, ischaemia occurs to the brain cells for a short period of time.

When a blood vessel gets obstructed, the body will try to correct it through one of the following methods:

• Dissolving the obstruction with innately present blood components
• Dilating other blood vessels that supply the same region of the brain so as to prevent permanent brain cell death

If the salvage is successful, the neurological symptoms experienced by the patient will be temporary. These symptoms can include:

• Numbness
• Tingling sensation
• Weakness of one side of the body
• Loss of vision over one eye
• One sided facial weakness
• Speech difficulty (slurring of speech)

In a TIA, these symptoms usually resolve within 24 hours.

2. Stroke (ischaemia)

Stroke is the third most common cause of death and the leading cause of disability in many developed countries.

In a stroke, the body is unable to correct the occlusion (closure or blockage).

This results in permanent brain cell death over the region of the brain where the occluded blood vessel supplies.

The symptoms of a stroke are similar to a TIA but they persist beyond 24 hours.

Occlusion of a major blood vessel in the brain will result in a large area of brain cell death and could be fatal or severely disabling.

Patients' disability after stroke can be improved by rehabilitation exercises as the surrounding viable brain will take over part of the work of the affected brain cells.

1. Duplex ultrasound

A duplex ultrasound is able to measure the velocity of blood flow in a vessel.

It is a painless and non-invasive test that effectively:

• Detects the presence of carotid artery disease
• Assesses the severity of the occlusion (narrowing/stenosis)

2. Computed tomography angiogram and magnetic resonance angiogram

Both these tests serve as "second line tests" particularly for planning treatment.

Computed tomography angiogram uses a CT scan to obtain detailed images of the blood vessels once a contrast medium (dye) is injected through a thin, long tube (catheter) placed in a vein in the arm. As the dye flows through the blood vessels, the CT scan takes images.

Magnetic resonance angiogram uses the same concept except that in this case, a magnetic resonance imaging (MRI) machine is used instead of a CT scan.

3. Carotid angiogram

Carotid angiogram is considered the standard test to diagnose and measure the severity of carotid artery disease.

This is an invasive procedure that requires an artery in the groin area to be punctured.

A long thin tube (catheter) is inserted into the punctured groin artery and guided into the carotid artery by using X-ray imaging.

Generally, people who are at risk of developing atherosclerotic disease have a higher chance of developing carotid artery disease.

The following people are prone to have atherosclerotic disease:

• Diabetic
• Hypertension
• Hyperlipidaemia
• Morbid obesity
• Cigarette smoking
• Patients suffering coronary artery disease or peripheral artery disease

The treatment for carotid artery disease cannot reverse the stroke event if it has already happened. However, it is aimed at preventing stroke by means of:

Control atherosclerosis - an essential for all carotid artery disease patients

• Screening for risk factors
• Optimal treatment of the medical diseases
• Serum lipid lowering
• Quit smoking
• Weight reduction

Control local diseased carotid artery

• Carotid endarterectomy.
• Surgical procedure performed under general anaethesia or regional nerve block.
• Diseased carotid artery is exposed through an incision over the neck. Artery is clamped temporarily and the diseased part is opened.
• Plaque together with the most inner lining of the vessel is removed.
• Vessel is repaired when blood flow to the brain can be restored, which can be done using a shunt, if necessary.
• Atherosclerotic or without additional synthetic patch after plaque is removed.

Carotid angioplasty and stenting

Internationally, carotid surgery is still superior to carotid endarterectomy.

Carotid angioplasty is usually performed when it is not possible to do carotid surgery.

This includes previous surgery or radiotherapy in the neck.

The procedure is usually done under sedation and/or local anaesthesia and sometimes general anaesthesia. It involves the insertion and inflation of a small balloon in the occluded artery to widen the area, as well as putting a stroke-protection device during the procedure to minimise complication.