Causes and types of strokes

A stroke may occur if an artery bursts or is blocked. This may prevent blood flow to the brain.

Your brain gets blood mainly through:

• two arteries in your neck (carotid arteries)
• two arteries near your spine (vertebral arteries)

These four arteries branch into other blood vessels that supply your brain with blood.

If blood cannot flow to your brain, your brain cells will start to die. Stroke symptoms will start to appear.

There are two types of stroke: ischemic and hemorrhagic.

Ischemic strokes

This type of stroke happens when a blood vessel in the brain is blocked. This may be caused by a blood clotting disorder. There are two types of ischemic stroke:

• Thrombotic
  Over time, fatty deposits (plaque) attach inside the artery walls. The plaque may narrow or close the artery. This may reduce blood flow to the brain.
  
  A thrombotic stroke is caused by plaque build up and the sudden formation of a blood clot.
• • Large vessel: This is the most common type of stroke. This stroke occurs when a larger artery in the brain is blocked.
  • Small vessel (lacunar): This type of stroke occurs deep in the brain when a smaller artery in the brain is blocked.
• Embolic
  This occurs when a small blood clot forms in any part your body and travels in the bloodstream to the brain. This clot becomes stuck and blocks a blood vessel.
  
  The blood clot often travels from the heart. A common cause of an embolic stroke is atrial fibrillation.

In more severe strokes, the large arteries in your brain or neck may be blocked. This blockage may cause permanent injury to a large part of the brain.

Ischemic strokes may lead to widespread brain injury. This injury can cause swelling in the brain. This swelling may lead to severe disability or death.

A thrombotic stroke occurs when plaque narrows artery walls and reduces blood flow to the brain.

An embolic stroke occurs when a small blood clot blocks a blood vessel.

Transient ischemic attacks (TIAs)

A thrombotic or embolic ischemic stroke may be called a TIA.

TIAs have the same symptoms as a stroke but they do not cause brain injury. They are sometimes called mini-strokes. If you had a TIA, your stroke risk is higher.

Important: TIAs require the same immediate attention as a stroke.

Hemorrhagic strokes

This type of stroke happens when a blood vessel in the brain ruptures and bleeds. This may be caused by a blood clotting disorder. There are two types of hemorrhagic stroke:

• Subarachnoid hemorrhage
  It happens when blood leaks into the space between the brain and middle membrane that covers it. This is called the subarachnoid space.
  
  Common causes include:
  • Aneurysm
    This happens when an artery or blood vessel becomes weak and bulges. A brain aneurysm is found on the arteries that supply blood to the brain. The aneurysm may become large and break (rupture).
  • Arteriovenous malformation (AVM)
    This occurs when blood flows directly from the arteries to veins, rather than passing through the capillaries first.
• Intracerebral hemorrhage
  This occurs when a small blood vessel in the brain bursts and leaks. This causes bleeding in the brain. This is often caused by high blood pressure.