Stroke is a leading cause of disability in both sexes, but it's not an equal-opportunity health crisis.
Most of the 700,000 people who have strokes each year in the United States are women, and more women die of strokes than men do. Among stroke survivors, women are more disabled and more likely to enter a nursing home. For years, it's been thought this disparity exists mainly because women live longer and tend to have strokes later in life, when they also have other health problems and less support for remaining at home.
But research shows a worrisome gender difference even in midlife. According to a study, women ages 45 to 54 are more than twice as likely as men to suffer a stroke (Neurology, published online, June 20, 2007). This finding comes from data on more than 17,000 adults collected between 1999 and 2004 as part of the U.S. Department of Health and Human Services' National Health and Nutrition Examination Survey.
When a stroke occurs, brain cells die quickly, so it's critical to get help immediately. It's a medical emergency similar to a heart attack (many health organizations now prefer the term "brain attack"). The severity of the impact depends on factors such as the location of the stroke, the extent of tissue damage, and how quickly symptoms are treated.
Types of strokes
Brain cells require a constant supply of oxygen- and nutrient-carrying blood. A stroke suddenly interrupts that supply. In ischemic strokes, which make up more than 80% of all cases, the cause is a blood clot blocking an artery supplying the brain. The clot may form in a blood vessel within the brain (thrombotic stroke), or it may form elsewhere and travel to the brain, where it lodges in a narrow vessel (embolic stroke).
If the blood supply is interrupted only temporarily, so that symptoms go away in less than a day, it's called a transient ischemic attack (TIA), or a warning stroke. A TIA must be taken seriously and treated as an emergency, because at the start, there's no way to distinguish it from a full-blown stroke, and because about one-third of those who experience a TIA will go on to have a full stroke, often within a year.
Slightly less than 20% of strokes are hemorrhagic strokes, in which a blood vessel in the brain bursts. Brain cells are deprived of the blood supplied by the vessel, and surrounding tissue is damaged because the leaking blood irritates neurons and creates pressure on the brain. There are two types of hemorrhagic strokes. In a subarachnoid hemorrhage, the burst blood vessel is on the surface of the brain and blood accumulates in the space between the brain and the skull; in an intracerebral hemorrhage, an artery bursts in the interior of the brain.
Every stroke is a medical emergency. With each minute that passes, an estimated two million brain cells die. In ischemic stroke, nearby cells may die quickly, but a larger surrounding area, only partially deprived of blood, may recover if circulation is rapidly restored. Likewise, in hemorrhagic strokes, slow but almost complete recovery is sometimes possible as blood is reabsorbed and swelling subsides.
Anatomy of a stroke
In ischemic stroke, a blood clot blocks an artery that supplies the brain, damaging nearby brain tissue. The clot may get stuck in an artery in the brain or in a carotid artery narrowed by fatty deposits (plaque). In hemorrhagic stroke, a blood vessel ruptures within the brain or at its surface. When blood spills into the space between the skull and the brain, it's called a subarachnoid hemorrhage.
What are the symptoms?
Because the brain controls all the body's functions, stroke symptoms can take many forms, including these:
Numbness or weakness in the face, arm, or leg. The symptoms may include a drooping face, slurred speech, or paralysis of a limb. Often only one side is affected.
Confusion. A stroke can make it difficult to speak or understand words (aphasia).
Vision problems. Vision may dim or be lost entirely in one or both eyes. It may also become difficult to move the eyes.
Trouble walking. Stroke can cause staggering, poor balance, and a sense of dizziness, clumsiness, or impaired coordination.
Severe headache. A stroke may cause a sudden, violent headache.
If you have any of these symptoms, or observe them in someone else, call 911. Note the time when the symptoms began, and, if possible, bring a list of medications (or the prescription bottles themselves) to the hospital with you.
Unlike a person having a possible heart attack, a person who might be having a stroke should not take an aspirin, because aspirin might worsen the bleeding caused by a hemorrhagic stroke.
Could you recognize stroke in someone else?
If you suspect someone is having a stroke, think FAST:
At the hospital
A physician will assess your symptoms and take your medical history. The symptoms may have another cause, such as severe migraine, a seizure, or a brain tumor. If the doctor believes it's a stroke, she or he will perform brain imaging to determine whether it is ischemic or hemorrhagic. A computed tomography (CT) scan of the head is usually performed first to detect hemorrhaging. If none is found, treatment can begin immediately for ischemic stroke. That kind of stroke may not show up on a CT scan, especially when it is small, in its early stages, or located deep within the brain. You may be given a test called CT angiography, in which contrast material is injected to highlight clots or narrowed blood vessels in the brain.
Your physician may also recommend screening with magnetic resonance imaging (MRI). A specific MRI technique called diffusion-weighted imaging can detect a stroke shortly after it occurs and earlier than in CT. It takes longer than CT and is not always available in an emergency, but in some academic centers, it's the first imaging technique used.
The chief FDA-approved medical treatment for people experiencing an ischemic stroke is tissue plasminogen activator (tPA), or alteplase, an enzyme that dissolves blood clots. In clinical trials, patients taking tPA (brand name Activase), compared to controls, were 33% to 55% more likely to have little or no disability three months later. For best effects, tPA must be delivered intravenously within three hours of the onset of symptoms (see "Treatment delayed is treatment denied"). The physician must be sure the person is actually having a stroke and that there is no bleeding in the brain.
Although this treatment has been available since 1996, many smaller community hospitals remain wary of it, fearing they lack the experience needed to make it safe and effective. But in 2007, reassuring results from an international study of tPA published in the journal Lancet showed that rates of cerebral hemorrhage and death were no higher in less-experienced hospitals than in controlled clinical trials at academic centers.
The most serious potential complication is bleeding in the brain, which occurs in roughly 6% of people treated with tPA and is fatal for about half of them. Because of this risk, tPA can't be given to a person with current or recent bleeding, recent surgery or head trauma, a previous stroke, uncontrolled high blood pressure, or clotting problems.
Treatment delayed is treatment denied
Patients must start to take tissue plasminogen activator, or tPA, within three hours after the symptoms begin. Unfortunately, most of them are not evaluated in time. The American Stroke Association has set as a goal that evaluation and treatment decisions should be made within one hour of arrival in a hospital's emergency department. In May 2007, the Centers for Disease Control and Prevention reported that only 48% of stroke patients get to the emergency room within two hours after the onset of symptoms, and only 65% receive brain imaging within one hour of their arrival. For reasons that aren't completely clear, women are less likely than men to receive prompt imaging.
The report emphasizes the importance of calling an ambulance. Patients transported to the hospital by ambulance arrive more than an hour earlier on average, and they don't wait as long for imaging. In some states, ambulances carrying likely stroke victims can bypass the nearest hospital in favor of the nearest primary stroke center — a facility with round-the-clock access to imaging and physicians who deliver tPA. A list of primary stroke centers is available at the National Stroke Association Web site, www.stroke.org.
Other ways to address clots
According to guidelines from the American Stroke Association, physicians may consider two other therapies when tPA can't be used or the clot does not respond to it.
One approach is to deliver a clot-dissolving drug directly to the site of the clot through a catheter. The other is to remove the clot by means of a catheter device called the Merci retriever. The physician makes an incision in the groin and threads the device up to the carotid artery, which feeds the brain. Once it reaches the clot, the retriever snares and removes it. The procedure takes about an hour and a half and is covered by insurance. It's been used in selected patients at more than 200 hospitals in the United States, and a registry has been established to track the outcome. A study showed that the Merci device restored blood flow to the brain in more than two-thirds of stroke patients, but so far, the long-term results aren't clear, and surgical clot retrieval has not been tested in a randomized clinical trial.
When the diagnosis is TIA rather than a full stroke, evaluation and treatment focus on identifying and addressing possible causes of artery blockage. A clinician may use ultrasound to check the carotid arteries in the neck for narrowing or clotting. The carotid artery may be surgically opened to remove a clot (carotid endarterectomy), or a stent may be inserted through a catheter to hold the artery open. Medication to reduce clotting may be prescribed.
American Stroke Association888-478-7653 (toll free)www.strokeassociation.org
Massachusetts General Hospital Stroke Service617-726-8459www.massgeneral.org/stopstroke/forpublic.aspx
National Stroke Association800-787-6537 (toll free)www.stroke.org
Stopping a brain bleed
Hemorrhagic stroke is less common but more often lethal than ischemic stroke. During a hemorrhagic stroke, physicians will aid breathing and use medications to control seizures, reduce brain swelling, maintain normal blood pressure, and ease pain. Depending on the source of the bleeding, surgery may also be necessary. A surgeon might clip off an aneurysm (a bulge in a weakened arterial wall) or insert particles of a glue-like substance near the aneurysm to halt bleeding.
Routine surgery is not recommended for intracranial bleeding. Surgery is most likely to be performed on people who have an accumulation of blood near the surface of the brain, or bleeding in the cerebellum (the lower back of the brain) that puts pressure on areas that control breathing. As a new way to treat hemorrhagic stroke, researchers are studying drugs that promote clotting.
Neurologists are also investigating neuroprotective drugs, which would shield brain cells from the damage caused by interrupted blood flow in both ischemic and hemorrhagic stroke. Researchers at Massachusetts General Hospital and Brigham and Women's Hospital are testing whether breathing a high concentration of oxygen while awaiting treatment might protect brain cells.