Stroke overview

Thought I would post a brief review about the various types and causes of stroke before the upcoming week.

There are 2 types of stroke: Ischemic and Hemorrhagic, each with several subtypes. At this point in time we believe that inflammation plays a larger role in Ischemic rather than hemorrhagic stroke.

In an Ischemic stroke blood clots form, block arteries and cut off blood flow. An ischemic stroke can occur in one of two ways. The first is an Embolic stroke during which a blood clot forms somewhere in the body (most commonly the heart) and travels through the blood stream to the brain. The clot eventually travels in the brain to blood vessels small enough to block its passage. Once lodged, the clot causes a stroke known as an embolus. The second type of ischemic stroke is a Thrombotic stroke. In a thrombotic stroke blood flow is impaired due to a blockage in one or more of the arteries supplying blood to the brain. The process that leads to the blockage is known as thrombosis and the subsequent clot that is formed is known as a thrombus.

Strokes that are caused by blood clots can happen as a result of blood vessels that are clogged with build up of cholesterol. The body reacts to these build ups as multiple, tiny and repeated injuries to the vessel wall; responding as it would to any other wound in the body and forms a clot. Two types of thrombosis can cause stroke: large vessel thrombosis and small vessel disease (or lacunar infarction). Large vessel thrombosis is the most common and best understood type of thrombotic stroke. Large vessel thrombosis is most often caused by a combination of long-term atherosclerosis that is followed by rapid clot formation. Patients that suffer a thrombotic stroke are also likely to have coronary artery disease and a heart attack is frequently the cause of death in patients who have suffered this type of brain attack. The second cause of thrombosis is small vessel disease or a lacunar infarction. This type of disease occurs when the blood flow is blocked to a very small arterial vessel. The term lacunar infarction comes from the Latin word lacuna which means hole and describes the small cavity remaining after the product of deep infarction have been resolved by other cells in the body. Small vessel disease is most likely linked to hypertension, however we know the least about this disease.

The second major type of stroke is a hemorrhagic stroke, caused by the breakage or "blow out" of a blood vessel in the brain. A hemorrhage can be caused by a number of disorders that affect the blood vessels, including long term hypertension and cerebral aneurysm. An aneurysm is a very weak or thin spot on a blood vessel wall that is usually present at birth. Aneurisms develop over a number of years and usually do not cause any detectable problems until they break. There are two types of hemorrhagic stroke: subarachnoid and intracerebral. An intracerebral hemorrhage causes bleeding from within the brain itself with hypertension usually being the primary cause of this hemorrhage. In a subarachnoid hemorrhage an aneurysm bursts in a large artery or near the thin, delicate membrane surrounding the brain. Blood spills into the area around the brain, causing the protective fluid to become contaminated with blood.

Information taken adapted from http://www.stroke.org 9/28/08