Types of Stroke

About 80 percent of strokes are ischemic. An ischemic stroke is most frequently caused by a blood clot that lodges in an artery and blocks the flow of blood to a part of the brain. High blood pressure is the most important risk factor for ischemic stroke.

Ischemic strokes are typically preceded by symptoms or warning signs that may include:

• Loss of strength or sensation on one side of the body
• Problems with speech and language
• Changes in vision or balance.

They usually occur at night or first thing in the morning. Symptoms develop over a few minutes or worsen over hours. Often a TIA (transient ischemic attack) or “mini-stroke” may offer some warning of a major ischemic stroke.

There are three types of Ischemic strokes:

• Thrombotic strokes are caused by a blood clot (thrombus) in an artery going to the brain.
• Embolic strokes occur when a clot that’s formed elsewhere (usually in the heart or neck arteries) travels in the bloodstream and clogs a blood vessel in or leading to the brain.
• Systemic hypoperfusion (low blood flow) is caused by circulatory failure of the heart.

A hemorrhagic stroke occurs when a blood vessel ruptures within the brain. About 15 to 20 percent of strokes are hemorrhagic. There are two kinds of stroke due to ruptured blood vessels:

• Subarachnoid hemorrhage is bleeding between the brain and the surrounding membrane.  This bleeding usually happens when an irregular bulge (aneurysm) in a blood vessel bursts.  This is frequently caused by high blood pressure.  Sometimes subarachnoid hemorrhage can be caused by trauma to the head or abnormal blood vessel formation in the head (arteriovenous malformation).
• Intracerebral hemorrhage due to ruptured blood vessels. Intracerebral hemorrhage occurs when a blood vessel bleeds into the tissue deep within the brain. The main causes are chronically high blood pressure and aging blood vessels. Arteriovenous Malformations (AVMs) are also congenital malformations of blood vessels in the brain which can rupture into brain tissue as they get larger.

In both types of hemorrhagic stroke, blood flow is disrupted to part of the brain.

Victims of hemorrhagic strokes are often younger and the fatality rate is higher than for ischemic stroke. Overall prognosis is also poorer for those who have hemorrhagic strokes.

The symptoms of a hemorrhagic stroke usually appear suddenly and often include:

• Severe headache
• Nausea and vomiting.
• Partial or total loss of consciousness

About 10 percent of strokes follow incidents called transient ischemic attacks, or TIAs. A TIA is a “mini-stroke” that occurs when a blood clot blocks an artery for a short time. TIAs may occur days, weeks or months before the onset of a stroke. The symptoms of a TIA are like the warning signs of a stroke, but they usually last only a few minutes.

TIAs are strong predictors of stroke risk. Don’t ignore them. Call 9-1-1 or seek emergency medical attention immediately.