Causes of Stroke

There are three causes of a stroke:

  • A blocked artery (ischemic stroke)
  • A leaking or bursting of a blood vessel (hemorrhagic stroke, aneurysm, arteriovenous malformation)
  • A temporary disturbance of blood flow to the brain (transient ischemic attack)

Ischemic Stroke

  • An ischemic stroke happens when blood flow through the artery that supplies oxygen-rich blood to the brain becomes blocked.
  • The underlying condition for this type of obstruction is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis 
  • Source: American Heart Association (2020)

Hemorrhagic Stroke

  •  A hemorrhagic stroke is caused by a weakened vessel that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue.
  • The two types of hemorrhagic strokes are intracerebral (within the brain) hemorrhage or subarachnoid hemorrhage.
  • Intracerebral hemorrhage is the most common type of hemorrhagic stroke. It occurs when an artery in the brain bursts, flooding the surrounding tissue with blood.
  • Subarachnoid hemorrhage is a less common type of hemorrhagic stroke. It refers to bleeding in the area between the brain and the thin tissues that cover it.
  • A hemorrhagic stroke occurs when a weakened blood vessel ruptures. Two types of weakened blood vessels usually cause hemorrhagic stroke: aneurysms and arteriovenous malformations (AVMs).
  • Source: American Heart Association (2020) 


  • Aneurysms usually develop at branching points of arteries and are caused by constant pressure from blood flow. They often enlarge slowly and become weaker as they grow, just as a balloon becomes weaker as it stretches. One the balloon pops, it causes a hemorrhage. 
  • Source: American Heart Association (2020) 

Arteriovenous Malformation

  • A tangle of blood vessels in the brain bypasses normal brain tissue and directly diverts blood from the arteries to the veins 
  • People are born with brain AVM's, but they're not hereditary. 
  • More than 50% of patients with an AVM have an intracranial hemorrhage.
  • Among AVM patients, 20 to 25% have seizures.
  • Patients may have headaches due to increased blood flow around an AVM.
  • 15% may have difficulty with movement, speech and vision.
  • Source: American Heart Association (2020) 

Transient Ischemic Attack

  • TIAs are sometimes called "mini-strokes," because their symptoms last only for a few minutes up to 24 hours before disappearing . But "warning stroke" is a better label, because a TIA often foreshadows a full-blown stroke and needs to be taken seriously.
  • TIAs are caused by a clot or blockage in the brain. The blockage is short term. The clot usually dissolves on its own or gets dislodged, and symptoms usually last for a short time. 
  • Source: American Heart Association (2020) 

Page last updated 10/2020