A person having symptoms of a stroke needs immediate emergency care, just as if he or she were having a heart attack. The sooner medical treatment begins, the fewer brain cells that are damaged.
The effects of a stroke may range from mild to severe and may be temporary or permanent. A stroke can affect vision, speech, behavior, the ability to think and the ability to move parts of the body. Sometimes it can cause a coma or death. The effects of a stroke depend on the specific brain cells that are damaged, how much of the brain is affected and how fast blood flow is restored to the affected area.
One or more mini-strokes (transient ischemic attacks or TIAs) may occur before a person has a full-blown stroke. Symptoms for both are similar. However, unlike stroke symptoms, TIA symptoms disappear within minutes (usually 10 to 20) up to 24 hours. A TIA is a warning signal that a stroke may soon occur, and the condition needs to be treated as an emergency.
There are two major types of strokes:
Ischemic stroke is caused by a blocked or narrowed artery.
Hemorrhagic stroke is caused by sudden bleeding from an artery.
General symptoms of a stroke include sudden onset of:
- Numbness, weakness or inability to move (paralysis) of the face, arm or leg, especially on one side of the body
- Trouble seeing in one or both eyes, such as dimness, blurring, double vision or loss of vision
- Confusion or trouble speaking
- Trouble walking, dizziness or loss of balance or coordination
- Severe headache with no known cause
Symptoms of a stroke may vary, depending on the type of stroke, as well as the location and degree of brain damage. If a stroke is caused by a large blood clot or bleeding, symptoms occur within seconds. When an artery that is already narrowed or blocked, stroke symptoms usually develop gradually within minutes to hours or, rarely, days. However, symptoms of a small stroke may be attributed to normal aging or confused with other conditions that cause similar symptoms.
Causes and Risk Factors
Ischemic stroke occurs when blood flow through a blood vessel (artery) that supplies blood to the brain is blocked.
Blockage may develop from a blood clot in an artery leading to the brain (thrombus) or one formed in another part of the body, usually the heart (embolus). The clot travels with the blood until it blocks an artery in the brain.
These blood clots can be caused by an irregular heart beat, heart valve problems, infection of the heart muscle, hardening of the arteries, blood-clotting disorders, inflammation of the blood vessels or heart attack. They may also be caused by a clot that breaks away from a ruptured cerebral aneurysm or a bleeding arteriovenous malformation.
A less common cause of ischemic stroke occurs when blood pressure becomes too low (hypotension), reducing blood flow to the brain. This usually occurs with narrowed or diseased arteries. Low blood pressure can result from a heart attack, large loss of blood or severe infection. Each of these conditions affects the flow of blood through the heart and blood vessels and increases the risk of stroke. Additionally, surgery to correct narrowed or blocked arteries in the neck may sometimes cause a stroke.
Hemorrhagic stroke is caused by sudden bleeding from a blood vessel inside the brain (cerebral hemorrhage) or in the spaces around the brain (subarachnoid hemorrhage). Sudden bleeding may result from the bursting of a blood vessel that has stretched and thinned (aneurysm). The most common cause of bleeding inside the brain is high blood pressure.
Uncommon causes of hemorrhagic stroke include inflamed blood vessels, which may develop from syphilis or tuberculosis, blood-clotting disorders, head or neck injuries, radiation treatment for cancer or cerebral amyloid angiopathy (a condition in which a protein substance builds up and weakens the blood vessels in the brain, causing bleeding and a stroke).