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 are 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
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:
- 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.
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.