The carotid arteries are located in the neck on each side of the windpipe.  They provide important blood flow to the head including the brain.  Normally, these arteries have a smooth lining but in diseased vessels due to the formation of cholesterol plaque a narrowing develops.  This results in deranged blood flow and dislodgement of plaque and other debris, a process called embolisation, that can travel to the brain causing a stroke or transient ischaemic attack (TIA). 

A stroke occurs when blood flow to a part of the brain is restricted causing brain cells to die.  This may be due to pressure from bleeding (cerebral haemorrhage) or blockage of an artery in the brain (cerebral infarction).  The latter can be caused by carotid artery disease from embolisation or severe restriction of blood flow to the brain.
Surgical treatment involves improving the blood flow in order to reduce the risk of stroke or TIA.  The options are:
  1. Carotid endarterectomy (CEA)
  2. Carotid angioplasty with stenting (CAS)
CEA in conjunction with best medical therapy has long been proven in the medical literature to be beneficial if performed by qualified surgeons.  CAS is still under research and is useful for specific circumstances of carotid artery disease.
 

Symptoms of carotid artery disease

 
Asymptomatic carotid stenosis
Narrowing of the carotid artery may be silent but the risk of stroke is still present.
 
Amaurosis fugax
Temporary blockage to the blood flow of the retina (back of the eye ball) results in transient blindness.  This appears as a dark curtain coming across the eye and may last for minutes to hours.  It is usually a sign of embolisation from the carotid artery.
 
TIA
Temporary blockage to the blood flow of a part of the brain can result in the following symptoms which resolve within 24 hours:
  • Speech difficulty
  • Visual loss
  • Weakness and/or numbness on one side of the body
  • Poor coordination
Stroke
Symptoms are similar to the above but last for more than 24 hours.
 

Diagnosis of carotid artery disease

 
The degree of arterial stenosis or narrowing is proportional to the risk of stroke for each patient, and has important implications on treatment.  The assessment is achieved using one or more of the following tests:
 
  1. Duplex ultrasound
  2. Computed tomography angiography
  3. Magnetic resonance angiography
  4. Catheter angiography 
 
Usually, duplex ultrasound is sufficient in accurately providing the degree of carotid stenosis, and no further imaging is required.
 

Treatment

 
Best medical therapy
Risk factor modification: optimisation of blood pressure, cholesterol, diabetes and cessation of smoking are mandatory in risk reduction of stroke.
 
Antiplatelet therapy: aspirin or clopidogrel slightly thins the blood and can reduce the risk of stroke or heart attack by ~25%.
 
Carotid endarterectomy
This procedure involves removal of the carotid plaque under a local or general anaesthetic.  It is similar to a “re-bore” of the artery, and takes approximately 2 hours to perform.
 
A neck incision is made, and the carotid arteries carefully exposed.  Heparin is given to thin the blood whilst clamps are applied to the arteries.  The artery is then opened and the diseased plaque meticulously resected.  Extreme care is exercised to ensure complete removal of any loose plaque.
 
Risks of surgery
Despite best surgical practice, specific complications may occur.
  1. Stroke
  2. Cranial nerve injury
  3. Bleeding
  4. Re-stenosis
  5. Heart attack
 
Carotid Artery Stenting
This procedure involves inserting a stent to expand the carotid artery.  First, a catheter containing a fine filter is passed through the groin artery, and deployed above the carotid plaque.  This will catch any debris during subsequent manipulation of the carotid artery.  Another catheter containing the stent is then passed to the level of the stenosis and deployed.
 
The patient is awake during surgery in order for the neurological status to be monitored.  The stent remains in the patient indefinitely but the filter is removed at the end of the procedure.
 
Risks of CAS
  1. Stroke
  2. Groin haematoma
  3. Allergy to dye
  4. Kidney dysfunction
  5. Re-stenosis
  6. Heart attack