What is a Stroke?

Warning Signs

Recognizing Stroke Signs and Symptoms


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Neurology Stroke Clinic: (608) 265-8899

Neurosurgery Clinic (including information about aneurysm, carotid stenosis and arteriovenous malformations (AVM)): (608) 263-7502

Stroke specialists at UW Health, University of Wisconsin Hospital and Clinics in Madison, Wisconsin know that education is a key component in recognizing stroke signs and symptoms and implementing the quick, decisive action required for proper treatment.


What is a stroke?


A stroke occurs when a blood clot blocks an artery (a blood vessel that carries blood from the heart to the body) or a blood vessel (a tube through which the blood moves through the body) breaks, interrupting blood flow to an area of the brain. When either of these things happen, brain cells begin to die and brain damage occurs.
When brain cells die during a stroke, abilities controlled by that area of the brain are lost. These abilities include speech, movement and memory. How a stroke patient is affected depends on where the stroke occurs in the brain and how much the brain is damaged.


Hemorrhagic Stroke


This type of stroke happens when a blood vessel leaks or ruptures in or near the brain. The ruptured vessel stops blood supply for the areas past the leak. Then blood floods the nearby tissues causing pressure and function changes.

  • Subarachnoid hemorrhage: This occurs when a blood vessel on the surface of the brain ruptures and bleeds into the space between the brain and skull. The most common cause is a ruptured aneurysm caused by high blood pressure. Other causes are rupture of an AVM (arteriovenous malformation), bleeding from an injury due to a blow to the head or venous or capillary problems.
  • Intracerebral hemorrhage: This is bleeding into the tissue deep within the brain. High blood pressure is often the cause of this type of stroke. Injury and rupture due to problem vessels can also be the cause.

Ischemic Stroke


This type of stroke occurs when a clot or piece of clot clogs a narrowed blood vessel, cutting off the blood flow to a part of the brain. A brain attack caused by too little blood reaching a part of the brain is called an ischemic stroke.

  • Thrombotic stroke: This is caused by a blood clot (thrombus) in an artery going to the brain. The clot blocks blood flow to part of the brain. Blood clots may form in arteries damaged by arteriosclerosis. This type of brain attack accounts for around 60 percent of all strokes.
  • Embolic stroke: This type of brain attack accounts for about 20 percent of all strokes. It is caused by a clot that formed somewhere else in the body and traveled to clog a vessel in or leading to the brain.
  • Systemic hypo perfusion: This occurs because of a low flow of blood to the brain. It happens when too little blood reaches the brain.