This is the narrowing of the arteries in the neck (carotid artery) that form the main blood supply to the brain. Risk factors for such narrowing include high blood cholesterol levels, hypertension, the presence of atherosclerosis and heart disease and heavy smoking. Narrowing and blockage of the carotid arteries can result in a major stroke. Sometimes particles from the plaques that narrow the arteries can break off, causing an embolic stroke.
Patients are sometimes diagnosed after a medical checkup when the doctor hears an abnormal sound (a bruit) on using a stethescope over the carotid arteries. Patients can also present with mini-stroke episodes (transient ischaemic attacks), in which they can get slurred speech, blurred vision, upper limb weakness or a drooping mouth. These mini-strokes usually reverse within 24 hours. Sometimes the episodes of mini-strokes can increase in frequency, occurring many times within 24 hrs. If this happens, it is an indication for urgent treatment.
Sometimes diagnosis is made when the patient is asymptomatic but is worked up for other diseases.
The most commonly used imaging to detect CAS is a specialised and detailed ultrasound scan that can determine the percentage of narrowing or blockage. Other tests that can be used include CT or MRI scans.
The objective of treating CAS is to prevent a major paralysing stroke from occurring. Treatment is necessary in patients who have more than 70 % narrowing of the artery associated with reversible stroke symptoms or in patients who have more than 80% narrowing without symptoms.
Conventional surgery for CAS is the carotid endarterectomy. This procedure involves surgically exposing the carotid artery and physically removing the plaques that cause the narrowing of the artery. This procedure is usually done under anaesthesia and requires close neurological monitoring as strokes can occur during surgery. It is usually done for younger patients with few co-morbid diseases and good surgical risk.
For high-risk patients, the alternative is carotid artery stenting. This procedure involves making a puncture in the groin artery and using a guidewire to pass the narrowing, inflating a balloon to widen the artery before deploying a stent to keep the artery open. The stenting can be done under local anaesthesia and as such is reserved for patients who have high surgical risk. Strokes can also occur during stenting, so patients also require close monitoring during the procedure.