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Causes of Stroke

Ischemic strokes and transient ischemic attacks (TIAs) are caused by a blocked artery that supplies oxygen-rich blood to the brain. Many medical conditions, such as atherosclerosis (when plaque builds up in the artery) and carotid artery disease (when plaque builds up in the carotid arteries), can increase a person’s risk of ischemic stroke or TIA.

Another type of ischemic stroke, called an embolic stroke, occurs when a blood clot or piece of plaque breaks away from the arterial wall, traveling through the bloodstream and getting stuck in one of the brain’s arteries. This can be caused by blood disorders or heart conditions, such as atrial fibrillation, in which the upper chambers of the heart contract in a fast or irregular way, causing blood to pool in the heart and forming blood clots in heart chambers. Ischemic stroke or TIA can also be caused by atherosclerosis, a condition in which lesions form in the small arteries of the brain and can block blood flow to the brain.

What causes hemorrhagic stroke?

Hemorrhagic stroke is caused by sudden bleeding brain, which causes the brain to swell and puts increased pressure on the skull, damaging brain cells and tissues. Conditions that can cause a hemorrhagic stroke include high blood pressure, aneurysms or arteriovenous malformation.

An aneurysm is a balloon-like bulge in an artery that can burst. When it ruptures, this burst blood vessel or leaking blood vessel carries a high risk of death. An arteriovenous malformation is a tangle of faulty arteries and veins that can also rupture within the brain.

Risks for stroke

Risk factors for a stroke or transient ischemic attack include:

  • High blood pressure: High blood pressure is defined as staying at or above 140/90 mmHg, or 130/80 mmHg for a person who has diabetes or chronic kidney disease.
  • Smoking: Smoking can damage blood vessels and increase blood pressure, and may also reduce the amount of oxygen reaching the body’s tissues.
  • Diabetes: Individuals with diabetes have a high blood sugar level because the body doesn’t make enough insulin or doesn’t use insulin properly.
  • Heart disease: Conditions such as coronary heart disease, cardiomyopathy, heart failure and atrial fibrillation can lead to the blood clots that in turn lead to a stroke.
  • Brain aneurysms: Aneurysms are balloon-like bulges that can stretch and burst.
  • Arteriovenous malformations (AVMs): AVMs are tangles of malformed arteries and veins that can rupture within the brain. AVMs are often present at birth, but in many cases aren’t diagnosed until they rupture.  
  • Age and gender: The risk of stroke increases with age; for younger people, men are more likely to have strokes than women, though women who are more likely to die from stroke than men. Women who take birth control pills have a slightly higher risk of stroke.
  • Race and ethnicity: Strokes are more common among African Americans, Alaska Natives and American Indians than among Caucasians, Hispanics or Asian Americans
  • Personal or family history: Individuals who have had a stroke or TIA or have a family history of stroke are at higher risk of having a stroke.
  • Certain medical conditions: Conditions such as sickle cell anemia, vasculitis (inflammation of the blood vessels) and bleeding disorders can increase a person’s risk of stroke.
  • Alcohol and illegal drug use: The use of drugs such as cocaine, amphetamines or other drugs may increase the risk of stroke.
  • Unhealthy cholesterol levels
  • Lack of physical activity
  • Unhealthy diet
  • Obesity
  • Stress and depression

Locations for Stroke