What Is a Stroke? What Causes a Stroke?

Editor's Choice
Main Category: Stroke
Also Included In: Neurology / Neuroscience
Article Date: 17 Aug 2009 - 0:00 PDT

email to a friend   printer friendly   view / write opinions   rate article

A stroke is a condition where a blood clot or ruptured artery or blood vessel interrupts blood flow to an area of the brain. A lack of oxygen and glucose (sugar) flowing to the brain leads to the death of brain cells and brain damage, often resulting in an impairment in speech, movement, and memory.

The two main types of stroke include ischemic stroke and hemorrhagic stroke. Ischemic stroke accounts for about 75% of all strokes and occurs when a blood clot, or thrombus, forms that blocks blood flow to part of the brain. If a blood clot forms somewhere in the body and breaks off to become free-floating, it is called an embolus. This wandering clot may be carried through the bloodstream to the brain where it can cause ischemic stroke. A hemorrhagic stroke occurs when a blood vessel on the brain's surface ruptures and fills the space between the brain and skull with blood (subarachnoid hemorrhage) or when a defective artery in the brain bursts and fills the surrounding tissue with blood (cerebral hemorrhage). Both result in a lack of blood flow to the brain and a buildup of blood that puts too much pressure on the brain.

The outcome after a stroke depends on where the stroke occurs and how much of the brain is affected. Smaller strokes may result in minor problems, such as weakness in an arm or leg. Larger strokes may lead to paralysis or death. Many stroke patients are left with weakness on one side of the body, difficulty speaking, incontinence, and bladder problems.

Who gets stroke?

Anyone can suffer from stroke. Although many risk factors for stroke are out of our control, several can be kept in line through proper nutrition and medical care. Risk factors for stroke include the following:

• Over age 55
• Male
• African American, Hispanic or Asian/Pacific Islander
• A family history of stroke
• High blood pressure
• High cholesterol
• Smoking cigarettes
• Diabetes
• Obesity and overweight
• Cardiovascular disease
• A previous stroke or transient ischemic attack (TIA)
• High levels of homocysteine (an amino acid in blood)
• Birth control use or other hormone therapy
• Cocaine use
• Heavy use of alcohol

What causes stroke?

Ischemic strokes are ultimately caused by a thrombus or embolus that blocks blood flow to the brain. Blood clots (thrombus clots) usually occur in areas of the arteries that have been damaged by atherosclerosis from a buildup of plaques. Embolus type blood clots are often caused by atrial fibrillation - an irregular pattern of heart beat that leads to blood clot formation and poor blood flow.

Hemorrhage strokes can be caused by uncontrolled high blood pressure, a head injury, or aneurysms. High blood pressure is the most common cause of cerebral hemorrhage, as it causes small arteries inside the brain to burst. This deprives brain cells of blood and dangerously increases pressure on the brain.

Aneurysms - abnormal blood-filled pouches that balloon out from weak spots in the wall of an artery - are the most common cause of subarachnoid hemorrhage. If an aneurysm ruptures, blood spills into the space between the surfaces of the brain and skull, and blood vessels in the brain may spasm. Aneurysms are often caused or made worse by high blood pressure.

A study found that a Single Gene Defect Can Lead To Stroke And Deadly Diseases Of The Aorta And Coronary Arteries.

A less common from of hemorrhage stroke is when an arteriovenous malformation (AVM) ruptures. AVM is an abnormal tangle of thin-walled blood vessels that is present at birth.

A study found that migraines increase stroke risk during pregnancy.

What are the symptoms of stroke?

Within a few minutes of having a stroke, brain cells begin to die and symptoms can become present. It is important to recognize symptoms, as prompt treatment is crucial to recovery. Common symptoms include:

• Dizziness, trouble walking, loss of balance and coordination
• Speech problems
• Numbness, weakness, or paralysis on one side of the body
• Blurred, blackened, or double vision
• Sudden severe headache

Smaller strokes (or silent strokes), however, may not cause any symptoms, but can still damage brain tissue.

A possible sign that a stroke is about to occur is called a transient ischemic attack (TIA) - a temporary interruption in blood flow to part of the brain. Symptoms of TIA are similar to stroke but last for a shorter time period and do not leave noticeable permanent damage.

A study found that women are more likely to experience non-traditional stroke symptoms.

How is stroke diagnosed?

A stroke is a medical emergency, and anyone suspected of having a stroke should be taken to a hospital immediately so that tests can be run and the correct treatment can be provided as quickly as possible.

Physicians have several tools available to screen for stroke risk and diagnose an active stroke. These include:

• Physical assessment - blood pressure tests and blood tests to see cholesterol levels, blood sugar levels, and amino acid levels


• Ultrasound - a wand waved over the carotid arteries in the neck can provide a picture that indicates any narrowing or clotting


• Arteriography - a catheter is inserted into the arteries to inject a dye that can be picked up by X-rays


• Computerized tomography (CT) scan - a scanning device that creates a 3-D image that can show aneurysms, bleeding, or abnormal vessels within the brain


• Magnetic resonance imaging (MRI) - a magnetic field generates a 3-D view of the brain to see tissue damaged by stroke


• CT and MRI with angiography - scans that are aided by a dye that is injected into the blood vessels in order to provide clearer and more detailed images


• Echocardiography - an ultrasound that makes images of the heart to check for embolus

How is stroke treated?

The primary goal in treating ischemic stroke is to restore blood flow to the brain. This will be attempted using blood clot-busting drugs such as aspirin, heparin, or tissue plasminogen activators that must be administered within three hours of the stroke. In addition, surgical procedures may be performed that can open up or widen arteries. These include carotid endarterectomy (removal of plaque and widening of the carotid artery) and angioplasty (a balloon that widens the cartoid artery and is held open with a metallic mesh tube called a stent).

A study found that cholesterol lowering drugs can prevent stroke recurrence.

Hemorrhagic stroke is treated differently than ischmic stroke. Surgical methods used to treat this stroke variant include aneurysm clipping, aneurysm embolisation, and arteriovenous malformation (AVM) removal. Aneurysm clipping consists of a small clamp placed at the base of the aneurysm that isolates it from the circulation of it's attached artery and keeps the aneurysm from bursting or re-bleeding. Aneurysm embolisation (coiling) uses a catheter inserted into the aneurysm to deposit a tiny coil that coil fills the aneurysm, causing clotting and sealing off the aneurysm off from arteries. AVM removal is a surgical procedure to remove usually smaller AVMs or AMVs that are in more accessible portion of the brain in order to eliminate the risk of rupture.

US researchers found that patients who had experienced strokes as long as six months earlier were able to regain brain function through the help of a novel robotic device that they squeezed with their hand.

Most stroke victims will require rehabilitation after the event. A person's condition is generally dependent on the area of the brain and the amount of tissue that was damaged. It is common for the rehabilitation process to include speech therapy, occupational therapy, physical therapy, and family education.

A study carried out by researchers at the University of Illinois, Chicago found that Tai Chi helped stroke victims regain balance.

A new study has found that the short window of time to treat stroke patients can be expanded.

A stroke patient was intravenously injected with his own bone marrow stem cells as part of a research trial at The University of Texas Medical School at Houston.

How can stroke be prevented?

One way to prevent a stroke is to notice a transient ischemic attack (TIA) - or mini stroke - that provides symptoms similar to stroke. Knowing the symptoms of stroke can lead to earlier treatment and better recovery.

Much of stroke prevention is based on living a healthy lifestyle. This includes:

• Knowing and controlling blood pressure
• Finding out if you have atrial fibrillation
• Not smoking
• Lowering cholesterol, sodium, and fat intake
• Following a healthy diet
• Drinking alcohol only in moderation
• Treating diabetes properly
• Exercising regularly. Moderate aerobic fitness can reduce stroke risk, a study found.
• Managing stress
• Not using drugs
• A study found that drinking three cups of tea per day reduces the risk of stroke
• Taking preventive medications such as anti-platelet and anticoagulant drugs to prevent blood clots
• Cholesterol lowering drugs can prevent stroke recurrence

Written by Peter Crosta M.A.
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today