Stroke

Brain Attack/Stroke Triggers

As previously mentioned, brain attack occurs when blood flow to the brain is interrupted. Blood carries oxygen to the brain, and brain cells can die from the lack of oxygen resulting from the decreased blood flow. There are two common causes for this interruption:

Blood clots obstructing blood vessels
Bleeding into the brain

Blood clots cause what are known as ischemic strokes. Here's how: the clots act as a dam on the wall of the artery, obstructing the natural flow of blood to the brain. This clotting is often caused by a medical condition known as atherosclerosis, a hardening of the arteries that arises when the walls of the arteries get "gummed up" by fatty deposits and blood platelets. This gummy mess, called plaque, can eventually interrupt blood flow until the brain cells become oxygen starved. Brain attacks are the end result.

Heart disorders, such as an arrhythmia known as atrial fibrillation, or infections of the heart known as endocarditis can also cause blood clots. Another cause of blood clots can be the use of a mechanical heart valve (which is why blood thinners are prescribed for patients with mechanical heart valves). Some people have a flap-like hole in the heart from birth, a condition known as patent foramen ovale (PFO). An untreated PFO can elevate the risk of brain attack.

There are two different types of blood clots:

Thrombus- This is a clot that forms over time and stays at the site of the blockage, rather than traveling elsewhere on the artery highway.
Embolism- This is a traveling blood clot. It forms in one place, then gets carried along in the bloodstream until it wedges into a smaller vessel, blocking blood flow from that vessel. Brain attacks from embolisms are most frequently caused by heart disorders.

Bleeding in the brain, also known as hemorrhagic stroke, is the less frequent major cause of brain attack. This happens when small blood vessels in the brain weaken and finally burst, thereby damaging brain cells. The most common cause is hypertension. In some people, this rupture is caused by undiagnosed defects in the blood vessels called amyloidosis. Recreational drugs or alcohol abuse can also weaken these arteries.

For more information:

Go to the Stroke health topic, where you can:

Read articles on this topic
Browse the previously asked questions
Ask your own question.

This article is a NetWellness exclusive. NetWellness Article

Last Reviewed: Oct 12, 2007

Pooja Khatri, MD
Assistant Professor
Department of Neurology
College of Medicine
University of Cincinnati

Joseph P Broderick, MD
Professor and Chairman
Director, Greater Cincinnati/Northern Kentucky Stroke Team
Department of Neurology
College of Medicine
University of Cincinnati

Dennis Landis, MD
Professor
Department of Neurology
School of Medicine
Case Western Reserve University