Types of strokes: Journeys to the brain-5

blood clot in an ischaemic stroke

Ischemic stroke : source: National Heart, Lung, and Blood Institute; National Institutes of Health; U.S. Department of Health and Human Services.

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 to a supply route (artery) or a blast (rupture) in a supply route.

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

  • In the medical field, “stroke” is called “cerebrovascular accident” (in short, CVA).
  • A stroke due to blockage due to a blood clot is called “ischemic stroke”.
  • A stroke due to a broken supply route is called “hemorrhagic stroke”.

From the two types, the “ischaemic strokes” are much commoner than the “hemorrhagic strokes”. In the US, as much as 80 percent strokes are ischemic strokes according to the US government website.

Ischemic stroke

There are common places where ischemic stroke strikes. One place is the junction where the main supply route (common carotid artery) divides into two smaller branches: internal and external. (Read the blood flow: Journeys to the brain-4.). These clots usually travel higher up and block a smaller artery. The extent of the damage depends on the size of the clot and part of the brain it blocks. See Figure 1. 

Figure 1: Ischaemic stroke (image source: National Heart, Lung, and Blood Institute; National Institutes of Health; U.S. Department of Health and Human Services.

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

Hemorrhagic stroke 

Figure 2: Hemorrhagic stroke: source: National Heart, Lung, and Blood Institute; National Institutes of Health; U.S. Department of Health and Human Services:https://www.nhlbi.nih.gov/health-topics/stroke

In a hemorrhagic stroke, blood seeps through from an arterial branch either due to a leak or a rupture of that vessel. The brain damage occurs as a result of pressure due to blood collection (Figure 2). 

Transient Ischaemic 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 which 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 resolve within 24 hours; however, it can become a full-blown stroke if not attended.

Author: Prasantha De Silva

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