In a “stroke”, neurons die as a result of sudden stop of receiving oxygen and nutrients 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;

• Ischemic stroke
• Hemorrhagic stroke

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.

Medical terms

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 common 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

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 clot size and the part of the brain it blocks. See Figure 1. 

Sometimes, a clot can originate within the heart itself too.

Hemorrhagic stroke 

In a hemorrhagic stroke, blood seeps through from an arterial branch due to a leak or a vessel rupture. Brain damage occurs due to pressure due to blood collection (Figure 2). 

What is Transient Ischemic Attack (TIA): “mini-stroke”?

 This term is used as its name implies a very brief attack due to a temporary passage block. The block is caused by a small blood clot that will dislodge by itself. This is considered a warning. However, it is a medical emergency. 

The “mini-stroke” typically resolves within 24 hours; however, it can become a full-blown stroke if not attended.