Illinois Neurological Institute

What is a Stroke?

A stroke, sometimes called a “brain attack,” occurs when there is a sudden interruption of the blood supply to the brain. When this happens, the part of the brain not receiving the flow of blood is deprived of oxygen and begins to die. A stroke requires immediate medical attention.

There are two types of strokes that can occur, hemorrhagic and ischemic.  A hemorrhagic stroke occurs when a blood vessel breaks, causing blood to seep into brain tissue. Hemorrhagic strokes can be intracerebral or subarachnoid. An intracerebral hemorrhage occurs when a blood vessel within the brain tissue ruptures. A subarachnoid hemorrhage occurs when a weakened area of a blood vessel, called an aneurysm, breaks and blood is spilled around the surface of the brain, under the protective arachnoid layer of connective tissue. The second type of stroke is ischemic. This type of stroke occurs when blood flow to the brain’s cells is blocked.  This can be caused by a clot or piece of plaque getting wedged inside a blood vessel.  Ischemic strokes are more common than hemorrhagic, accounting for 85% of all strokes. However, hemorrhagic types of strokes are responsible for more than 30% of stroke deaths.

Transient Ischemic Attack (TIA) is also known as a “mini stroke.”  It is caused by blockage of blood flow to a tiny artery which causes stroke symptoms, but the symptoms resolve usually in 20 minutes or less and almost always within one hour.  Even though the symptoms go away, anyone experiencing this should call 911 immediately to be evaluated and closely monitored.  Fifteen percent of people who experience a TIA suffer an ischemic stroke, usually within a few days.