What Is a Stroke?
A stroke, also known as a brain attack, occurs when blood flow to the brain is blocked or a blood vessel inside or on the surface of the brain bursts. A stroke is a serious medical emergency and requires immediate medical attention, just like a heart attack. Stroke ranks as the fourth leading killer in the United States. It is the most common cause of adult disability.
With stroke, the sooner treatment begins, the better. Knowing the signs of stroke and calling 911 immediately can help save the person from death or disability. Timely treatment can save brain cells and greatly reduce or even reverse the damage.
Strokes can be prevented and treated. Making lifestyle changes and getting regular medical and prenatal care can help prevent stroke and significantly reduce the risk for other disorders such as dementia, heart disease, and diabetes. The stroke rate is rising in adults under the age of 49. While nearly three-quarters of strokes occur in people over 65, the risk about doubles each decade after age 55.
Common Effects of Stroke
The brain is nourished by a rich network of blood vessels. A blockage or bursting in one of these blood vessels can occur in any area of the brain. Since each brain region is responsible for different functions, the effects of stroke range from mild to severe depending on the type, severity, and location of the stroke. The effects of stroke may be temporary or permanent.
Problems with muscle movement (motor sensory impairment)
Damage to the part of the brain that controls balance and coordination can cause movement problems. A common problem after a stroke is weakness or paralysis (being unable to move). This may affect only the face, an arm, or a leg, or it may affect one entire side of the body. A person who has had a stroke may have problems with daily activities such as walking, dressing, eating, and using the bathroom. Slurred speech due to weakness or a lack of coordination of the muscles involved in speaking is called dysarthria and is a physical, not a language, problem. Dysarthria can arise from damage to either side of the brain. It is often associated with trouble swallowing (dysphagia).
Problems with cognition, thinking, or memory
Stroke may cause problems with thinking, awareness, attention, learning, judgment, and memory. Some people with stroke have a “neglect” syndrome, which means that they have no knowledge of one side of their body (usually the left side), or one side of the visual field, and are unaware of the problem. A person with stroke may be unaware of his or her surroundings, or may be unaware of the cognitive, emotional, and/or behavioral problems that resulted from the stroke. Some people will experience a permanent decline in cognitive function known as vascular cognitive impairment (VCI), which includes vascular dementia, but also refers to a gradual decline in mental function caused by multiple strokes over time. VCI appears to primarily affect the brain's executive function—the ability to plan activities. This could include anything from getting dressed in the morning to managing medications, finances, or negotiating a business deal. Controlling risk factors for stroke can reduce the risk of vascular cognitive impairment and dementia.
Problems with speaking or understanding speech
People who have had a stroke often have problems speaking or understanding spoken language. This is often accompanied by similar problems in reading and writing. In most people, language problems result from damage to the left hemisphere of the brain. Severe damage can result in a complete inability to speak or understand (called aphasia).
Problems with emotion
People with stroke may have difficulty controlling their emotions or may express inappropriate emotions in certain situations such as difficulty controlling crying or laughing. Post-stroke depression, which is common, is a serious medical problem that can hamper recovery and rehabilitation and may even lead to death by suicide. Post-stroke depression is treatable with medications and psychotherapy.
Problems with pain and sensation
After a stroke, some people may experience pain, uncomfortable numbness, or strange sensations. These sensations can be due to many factors, including damage to the sensory regions of the brain, stiff joints, spastic muscles, or a disabled limb. An uncommon type of pain resulting from stroke is called central stroke pain or central pain syndrome (CPS). CPS results from damage to an area of the brain called the thalamus, which is involved with sensory perception and movement. The pain is a mixture of sensations, including heat and cold, burning, tingling, numbness, sharp stabbing, and an underlying aching pain. It is intense in the area affected most by the stroke and is made worse by movement and temperature changes, especially cold temperatures. There are a few treatments or therapies to combat CPS that can be effective, but most pain medications provide little—if any--relief from these sensations.
Types of Stroke
There are two major kinds of stroke. About 80% of all strokes are ischemic strokes, which are caused by a blood clot that blocks a blood vessel or artery in the brain. About 20% are hemorrhagic strokes, which are caused by a blood vessel in the brain that breaks and bleeds into the brain.
Ischemic Stroke
An ischemic stroke occurs when the supply of blood to one or more regions of the brain is suddenly cut off or interrupted. Ischemic stroke is most commonly caused by a blood clot or debris (such as plaque—a mixture of fatty substances, including cholesterol) that blocks or plugs an artery in the brain. Arteries are the blood vessels that carry blood from the heart to the brain and body.
Blockages that cause ischemic strokes can come from three conditions:
- Thrombosis—A clot develops within a diseased blood vessel of the brain and grows large enough to impair blood flow.
- Embolism—A clot forms in another part of the body (such as the heart or a diseased artery in the chest or neck) and moves into a narrower artery in the neck or brain.
- Stenosis—An artery in the head or neck narrows. The most common cause of stenosis is atherosclerosis—a condition where deposits of plaque collect along the inside of arteries, causing a thickening and hardening and loss of elasticity in the walls of arteries. Atherosclerosis of heart vessels can also lead to a heart attack.
Ischemic stroke can also provoke inflammation, swelling (edema), and other processes that can continue to cause damage for hours to days after the initial stroke. In large ischemic strokes, the swelling can cause the pressure inside the skull to rise to dangerous levels.
Immediately after an ischemic stroke, the brain usually contains an irreversibly damaged core of tissue and an area of viable but at-risk tissue. Restoring normal blood flow—a process called reperfusion—is essential to rescuing the tissue that is still viable. The longer reperfusion is delayed, the more cells will die.
Hemorrhagic Stroke
In a healthy brain, neurons (brain cells) do not come into direct contact with blood. The blood-brain barrier, an elaborate meshwork of tightly fitting cells that form the inside layer of tiny blood vessels called capillaries, regulates which parts of the blood can pass through to the brain cells and what substances from neurons can pass into the bloodstream.
When an artery in the brain bursts, blood gushes into or around the brain, damaging the surrounding tissue. This is called a hemorrhagic stroke. The blood that enters the brain increases the pressure inside the skull (intracranial pressure), which can cause significant tissue damage. The mass of blood compresses the adjacent brain tissue, and toxic substances in the blood further injure the brain.
There are multiple types of hemorrhagic stroke, categorized by where the bleeding occurs:
- Subarachnoid hemorrhage involves rupture of a vessel on the surface of the brain and bleeding into the space between the brain and an envelope of tissue called the arachnoid layer.
- Intracerebral hemorrhage involves bleeding within the brain itself.
Transient Ischemic Attack (TIA)
A transient ischemic attack (TIA) is a temporary interruption of blood flow to the brain, often caused by a clot, which dissipates after a short time. After the blockage dissipates, stroke symptoms go away. Any stroke damage from a TIA is typically temporary and is not visible on brain imaging such as MRI. However, a TIA is an important warning sign that a larger, more serious stroke could come soon.
A TIA—sometimes incorrectly referred to as a mini-stroke—starts just like any other stroke. Generally, the symptoms or deficits begin to disappear in less than 20 minutes, and often go away within an hour. One type of TIA is caused by a narrowing of the carotid artery and causes occasional vision loss in one eye. People often describe this feeling “like a shade coming down over the eye” on the affected side.
TIAs often indicate a high risk for a more serious stroke and an underlying condition that requires medical help. About one in three people who have a TIA will have a stroke sometime in the future, with the majority of those occurring within a year of the TIA. Because TIAs last for only a few minutes, many people mistakenly ignore them. However, taking action can save a life. Calling 911 as soon as symptoms appear can make the difference in avoiding lifelong disability.
Stroke in Women
Some risk factors for stroke apply only to women, including pregnancy, childbirth, and menopause. These factors are tied to hormonal changes that affect women at different stages of life. In women of childbearing age, stroke risk is relatively low (with an annual incidence of one in 10,000). However, studies have shown that being pregnant increases that risk threefold.
Several factors contribute to the increased risk of stroke during pregnancy:
- Blood clotting proteins are naturally more active during pregnancy. In some cases, clots form in the brain's large draining veins, leading to stroke, headache, or seizure.
- Pregnancy-related stroke is more likely to occur in women who experience certain complications, such as infections or preeclampsia (high blood pressure with fluid retention), or who have other risk factors for stroke, such as high blood pressure or diabetes.
- Most strokes occur during the first few weeks after delivery. These strokes may be caused by a drop in blood volume or by the rapid hormonal changes that follow childbirth.
In the same way that hormonal changes during pregnancy and childbirth are associated with increased stroke risk, hormonal changes during menopause can also increase the risk of stroke. Although hormone replacement therapy (HRT) may help some symptoms of menopause, studies have shown that HRT may increase the risk of stroke, especially in women more than 10 years post-menopause. Estrogen patches used on the skin have not been found to increase the risk of stroke and may be a better option than estrogen pills for these women. More research is needed in this area. Women should talk with their doctor about their symptoms and risks to find appropriate treatments.
Children and Stroke
Children have several unique stroke risk factors. Children’s risk of stroke is highest during the perinatal period—which begins just before birth and ends a few weeks after. Boys and Black children are at a higher risk for stroke than other groups.
Infants and children who have a stroke usually experience the same symptoms of stroke as adults. But children are more likely to have other symptoms, including seizures, breathing problems, or loss of consciousness. It can be difficult to identify stroke in younger children.
Risk factors for childhood stroke include congenital (present at birth) heart problems, head trauma, and blood-clotting disorders. An important risk factor for Black children is sickle cell disease, which can cause narrowing of brain arteries.
The outcome of stroke in children is difficult to predict. Children who have a stroke generally recover better than adults with appropriate treatment and rehabilitation. Children’s brains have greater plasticity. Brain plasticity is the brain’s ability to reorganize, change, and adapt to deficits and injury, and to rewire itself to carry on necessary functions. Generally, outcomes are worse in children under age one and in those who lose consciousness or have seizures. A stroke that occurs during infancy or childhood can cause permanent disability.
Where can I find more information about stroke?
Information may be available from the following organizations and resources: