UNDERSTANDING GENETICS AND STROKES

GENETICS
From the Blueprint to You

Created in April 2003 for 50 years of DNA: A Celebration of the Genome, From the Blueprint to You explores the world of genetics, DNA, the Human Genome Project, the ethical, legal and social implications of genetic research and the future of genomics.

Follow the links below to each chapter: All chapters are in

• From the Blueprint to You: A Brief Guide to Genetics
• DNA as the Instruction Book
  • The Genetic Code: Figure A
  • Making a Protein: Figure B
• Human Genome Project
• Implications for the Future
• Glossary of Terms

ISCHEMIC STROKE-ischemia in the tissues of the brain.
LACUNAR INFARCTION-occlusion of a small artery in the brain resulting in a small area of dead brain tissue, called a lacunar infarct; often caused by stenosis of the small arteries, called small vessel disease.
TRANSIENT ISCHEMIC ATTACK (TIA)-a short-lived stroke that lasts from a few minutes up to 24 hours; often called a mini-stroke.
INFARCT-an area of tissue that is dead or dying because of a loss of blood supply.
ISCHEMIA-a loss of blood flow to tissue, caused by an obstruction of the blood vessel, usually in the form of plaque stenosis or a blood clot.
CEREBRAL BLOOD FLOW (CBF)-the flow of blood through the arteries that lead to the brain, called the cerebrovascular system
ACUTE STROKE-a stage of stroke starting at the onset of symptoms and last for a few hours thereafter.

WHAT IS STROKE?
A stroke occurs when the blood supply to part of the brain is suddenly interrupted or when a blood vessel in the brain bursts, spilling blood into the spaces surrounding brain cells. In the same way that a person suffering a loss of blood flow to the heart is said to be having a heart attack, a person with a loss of blood flow to the brain or sudden bleeding in the brain can be said to be having a "brain attack."

Brain cells die when they no longer receive oxygen and nutrients from the blood or when they are damaged by sudden bleeding into or around the brain. Ischemia is the term used to describe the loss of oxygen and nutrients for brain cells when there is inadequate blood flow. Ischemia ultimately leads to infarction, the death of brain cells which are eventually replaced by a fluid-filled cavity (or infarct) in the injured brain.

When blood flow to the brain is interrupted, some brain cells die immediately, while others remain at risk for death. These damaged cells make up the ischemic penumbra and can linger in a compromised state for several hours. With timely treatment these cells can be saved.

Even though a stroke occurs in the unseen reaches of the brain, the symptoms of a stroke are easy to spot. They include sudden numbness or weakness, especially on one side of the body; sudden confusion or trouble speaking or understanding speech; sudden trouble seeing in one or both eyes; sudden trouble walking, dizziness, or loss of balance or coordination; or sudden severe headache with no known cause. All of the symptoms of stroke appear suddenly, and often there is more than one symptom at the same time. Therefore stroke can usually be distinguished from other causes of dizziness or headache. These symptoms may indicate that a stroke has occurred and that medical attention is needed immediately.

There are two forms of stroke: ischemic - blockage of a blood vessel supplying the brain, and hemorrhagic - bleeding into or around the brain. The following sections describe these forms in detail.

ISCHEMIC STROKE
An ischemic stroke occurs when an artery supplying the brain with blood becomes blocked, suddenly decreasing or stopping blood flow and ultimately causing a brain infarction. This type of stroke accounts for approximately 80 percent of all strokes. Blood clots are the most common cause of artery blockage and brain infarction. The process of clotting is necessary and beneficial throughout the body because it stops bleeding and allows repair of damaged areas of arteries or veins. However, when blood clots develop in the wrong place within an artery they can cause devastating injury by interfering with the normal flow of blood. Problems with clotting become more frequent as people age.

Blood clots can cause ischemia and infarction in two ways. A clot that forms in a part of the body other than the brain can travel through blood vessels and become wedged in a brain artery. This free-roaming clot is called an embolus and often forms in the heart. A stroke caused by an embolus is called an embolic stroke. The second kind of ischemic stroke, called a thrombotic stroke, is caused by thrombosis, the formation of a blood clot in one of the cerebral arteries that stays attached to the artery wall until it grows large enough to block blood flow.

Ischemic strokes can also be caused by stenosis, or a narrowing of the artery due to the buildup of plaque (a mixture of fatty substances, including cholesterol and other lipids) and blood clots along the artery wall. Stenosis can occur in large arteries and small arteries and is therefore called large vessel disease or small vessel disease, respectively. When a stroke occurs due to small vessel disease, a very small infarction results, sometimes called a lacunar infarction, from the French word "lacune" meaning "gap" or "cavity."

The most common blood vessel disease that causes stenosis is atherosclerosis. In atherosclerosis, deposits of plaque build up along the inner walls of large and medium-sized arteries, causing thickening, hardening, and loss of elasticity of artery walls and decreased blood flow.

TRANSIENT ISCHEMIC ATTACKS
A transient ischemic attack (TIA), sometimes called a mini-stroke, starts just like a stroke but then resolves leaving no noticeable symptoms or deficits. The occurrence of a TIA is a warning that the person is at risk for a more serious and debilitating stroke. Of the approximately 50,000 Americans who have a TIA each year, about one-third will have an acute stroke sometime in the future. The addition of other risk factors compounds a person's risk for a recurrent stroke. The average duration of a TIA is a few minutes. For almost all TIAs, the symptoms go away within an hour. There is no way to tell whether symptoms will be just a TIA or persist and lead to death or disability. The patient should assume that all stroke symptoms signal an emergency and should not wait to see if they go away.

HOW DO YOU RECOGNIZE STROKE?
Symptoms of stroke appear suddenly. Watch for these symptoms and be prepared to act quickly for yourself or on behalf of someone you are with:

§       Sudden numbness or weakness of the face, arm, or leg, especially on one side of the body.

§       Sudden confusion, trouble talking, or understanding speech.

§       Sudden trouble seeing in one or both eyes.

§       Sudden trouble walking, dizziness, or loss of balance or coordination.

§       Sudden severe headache with no known cause.

http://www.ninds.nih.gov/disorders/stroke/detail_stroke.htm#appendixhttp://
www.ninds.nih.gov/disorders/stroke/detail_stroke.htm#appendix

 IMPORTANT: Please inform the emergency room or your doctors do not treat a patient who has CADASIL with Thrombolyisis and anticoagulant treatments, Arteriography, Vasoconstricting medicines (issued from rye ergot or from Tripoptan) and products aimed at unblocking blood vessels as they increase the risk of a hemorrhage.

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