The term “stroke” refers to a sudden stoppage of blood flow to a part of the brain. It can happen either due to a block in a supply route (artery) or a blast (rupture) in a supply route.
Experts classify these into different types of strokes.
The block to a supply route occurs due to a blood clot that lodges within a blood-supplying vessel, an artery, or one of its smaller branches.
Following are the common medical terms used to identify the main two types of strokes.
|Cerebrovascular event (CVA)||stroke|
|Ischemic stroke||A stroke as a result of a blockage by a blood clot in an artery|
|Hemorrhagic stroke||A stroke as a result of bleeding due to damage to an artery in the brain|
Types of stroke
Of the two types, “ischaemic strokes” are much more commoner than “hemorrhagic strokes”. In the US, as much as 80 per cent of strokes are ischemic strokes according to the US government website.
Ischemic stroke often occurs in certain places. One place is the junction where the main supply route (common carotid artery) divides into two smaller branches: internal and external. (Read the brain’s blood supply routes). These clots usually travel higher up and block a smaller artery. The extent of the damage depends on the size of the clot and the part of the brain it blocks. See Figure 1.
Sometimes, a clot can originate within the heart itself too.
In a hemorrhagic stroke, blood seeps through from an arterial branch due to a leak or a rupture of that vessel. Brain damage occurs due to pressure due to blood collection (Figure 2).
Transient Ischemic Attack (TIA): “mini-stroke”
This term is used as its name implies a very brief attack due to a temporary blockage of a blood vessel. The block is caused by a very small blood clot that will dislodge by itself. This is considered a warning. However, it is a medical emergency meaning that we need to call 911 immediately.
The “mini-stroke” typically resolves within 24 hours; however, it can become a full-blown stroke if not attended.