Stroke is the term doctors use when a part of the brain dies because it goes without blood for too long. There are two main types of stroke: ischemic stroke, which caused by a blockage in a blood vessel in the brain, and hemorrhagic stroke, which is caused by bleeding in the brain or surrounding area.
In the United States, approximately 750,000 strokes happen each year, most of which are caused by a blockage in a blood vessel. Strokes can cause long-lasting disability or even death. However, early treatment and preventive measures can reduce the brain damage that occurs because of stroke.
The symptoms of a stroke usually begin suddenly but sometimes develop over hours or days, depending upon the type of stroke. In both ischemic and hemorrhagic stroke, one or more areas of the brain can be damaged. Depending upon the area affected, a person may lose the ability to move one side of the body, the ability to speak, or a number of other functions.
The damage from a stroke may be temporary or permanent. A person’s long term outcome depends upon how much of the brain is damaged, how quickly treatment begins, and several other factors.
TYPES OF STROKE
There are two main types of stroke: ischemic and hemorrhagic
Ischemic stroke — Ischemic strokes are caused by a blockage (clog) in one of the blood vessels that supply oxygen and other important nutrients to the brain. If the artery remains blocked for more than a few minutes, and enough blood can’t get through, the brain can become damaged. The majority of strokes are ischemic.
There are two main subtypes of ischemic stroke, thrombotic and embolic.
Thrombotic stroke — A thrombotic stroke results from a problem within an artery (blood vessel) that supplies blood to the brain. This is most likely to occur in arteries that are clogged with fatty deposits, called plaques. Plaques partially block the artery, and can rupture and bleed, forming a blood clot. This blood clot (“thrombus”) can further clog or completely block the artery, which then slows or prevents blood flow to the area of brain fed by that artery. Blood clotting disorders can also cause clots to form within arteries in some people.
Embolic stroke — An embolic stroke occurs when a blood clot or other particle breaks loose from another part of the body, often the heart or a large artery in the neck, and travels through the bloodstream to the brain where it lodges in a smaller blood vessel. The blood clot or particle, called an “embolus,” then blocks blood flow to that area of the brain, reducing the amount of oxygen and nutrients that reach that area. One of the most common causes of embolic strokes is an irregular heart rhythm called “atrial fibrillation.” Emboli can also originate in the aorta and in the arteries within the neck and head and travel further along within arteries within the brain.
Transient ischemic attack (TIA) — Transient ischemic attacks are episodes in which a person has signs or symptoms of a stroke (eg, weakness; inability to speak) that last for a short time, but without any sign of stroke on brain scans such as MRI or CT. Symptoms of a TIA usually last between a few minutes and a few hours. A person may have one or many TIAs. People recover completely from the symptoms of a TIA.
A TIA is a warning sign that a person is at high risk for a stroke; immediate treatment can decrease or eliminate this risk. It is important to get help right away if you think you may be having a TIA or a stroke.
Hemorrhagic stroke — Hemorrhagic strokes occur when blood vessels in the brain leak or rupture (break), causing bleeding in or around the brain. “Hemorrhage” is the medical term for bleeding. This can lead to pressure within the head, which can cause damage to the brain. Also, blood is irritating to the brain tissue, and can cause it to swell.
There are two main subtypes of hemorrhagic stroke, intracerebral and subarachnoid.
Intracerebral hemorrhage — In an intracerebral hemorrhage (ICH), bleeding occurs within the brain. This damages the brain as blood collects and puts pressure on the surrounding tissue. Some common causes of ICH include:
●High blood pressure
●Deformities in blood vessels, such as an aneurysm (a weakening in the lining of the blood vessel)
Subarachnoid hemorrhage — Subarachnoid hemorrhage occurs when a blood vessel on the surface of the brain ruptures. The blood builds up and causes pressure in the “subarachnoid” space, which is between two layers of the tissue covering the brain. The most common early symptom of a subarachnoid hemorrhage is a severe headache called “thunderclap headache,” which many patients describe as the worst headache of their life.
STROKE RISK FACTORS
There are a number of risk factors for stroke; some of these factors increase the risk of one type of stroke (hemorrhagic or ischemic), while others increase the risk of both types.
Ischemic stroke risk factors include the following:
●Age older than 40 years
●High blood pressure
●High blood cholesterol levels
●Illegal drug use
●Previous history of transient ischemic attack
●Inactive lifestyle and lack of exercise
●Current or past history of blood clots
●Family history of cardiac disease and/or stroke
Hemorrhagic stroke risk factors include the following:
●High blood pressure
●Illegal drug use (especially cocaine and “crystal meth”)
●Use of warfarin or other blood thinning medicines
Risk factors can increase the risk of stroke, but strokes can happen in people who don’t know that they are at risk. In some cases, the stroke may be due to problems with the blood vessels in the brain or the blood itself. For example:
●A hemorrhagic stroke can occur if a person has an aneurysm (a weakness in a blood vessel wall), even if this has never caused symptoms in the past.
●An ischemic stroke may occur in a healthy person who takes certain medications (for example, estrogen replacement therapy increases the risk of blood clots).
Occasionally, strokes occur in people who have no risk factors.
Signs and symptoms of stroke often develop suddenly and then may temporarily improve or slowly worsen, depending upon the type of stroke and area of the brain affected.
Classic symptoms — Knowing the signs and symptoms of a stroke can be lifesaving. Classic stroke symptoms can be recalled with the acronym FAST. Each letter in the word stands for one of the things you should watch for:
●Face – Sudden weakness or droopiness of the face, or problems with vision
●Arm – Sudden weakness or numbness of one or both arms
●Speech – Difficulty speaking, slurred speech, or garbled speech
●Time – Time is very important in stroke treatment. The sooner treatment begins, the better the chances are for recovery. Therefore, call an ambulance (dial 9-1-1 in the US and Canada) right away.
Signs and symptoms of a stroke may be similar to other conditions; the only way to know for sure is to be seen as soon as possible by an experienced doctor or nurse.
When to call for emergency medical assistance — A stroke is a medical emergency. If you think you or someone around you may be having a stroke, call 9-1-1 immediately. Do not try to drive yourself to the hospital.
Emergency medical services (EMS) workers will respond as quickly as possible, and will take you to a hospital that can care for people during and after a stroke. For a person having a stroke, every minute is important. It is important to call 9-1-1 in this situation because:
●From the moment EMS workers arrive, they can begin evaluating and treating you. If you drive yourself to the hospital or have someone else drive you, treatment cannot begin until after you arrive in the emergency department.
●If a dangerous complication of a stroke (eg, a seizure or loss of consciousness) occurs on the way to the hospital, EMS workers may be able to treat the problem immediately.
Anyone who has signs or symptoms of a stroke needs immediate medical attention in an emergency department or hospital. Most clinics and medical offices do not have the ability to perform the tests needed to diagnose stroke, or the ability to provide the specialized treatment(s) needed to limit damage to the brain.
Brain and blood vessel imaging — After doing a quick physical exam, the doctor or nurse usually sends the patient right away for an imaging test of the brain (eg, CT scan or MRI scan) and an imaging test of the blood vessels in the neck and head (eg, CT angiography or MR angiography) that supply the brain with blood. The imaging allows the doctor or nurse to see the area of the brain affected by the stroke, as well as to confirm the type of stroke (ischemic or hemorrhagic). Other tests may be done as well.
Occasionally, a catheter must be inserted through a blood vessel in the groin and threaded up to the blood vessels of the neck, where dye is injected to highlight any areas of blockage.
Heart testing — An electrocardiogram (ECG) is performed in most people who are thought to be having a stroke. Because many people with ischemic strokes also have coronary artery disease, there may be a lack of blood flow (called “ischemia”) in the heart during the stroke. In some cases, the person may not be able to tell the clinician that he or she feels chest pain. The ECG will help the clinician to diagnose and treat any heart problems as quickly as possible.
Other heart testing may also be recommended, such as an echocardiogram. This test uses sound waves to examine the heart and the aorta (the main artery that supplies the whole body). In some people with embolic strokes, the heart or the aorta is the source of the blood clot that led to the stroke. As an example, a heart rhythm problem called atrial fibrillation is a high-risk condition for blood clot formation and ischemic stroke. Some people have occasional episodes of atrial fibrillation but are not aware of it, and it may not show up on routine heart tests such as the ECG. Therefore, doctors often use continuous cardiac monitoring to look for atrial fibrillation and other heart rhythm problems for the first day or two when patients are in the hospital for a stroke. In some cases, patients will need to wear a small portable cardiac monitor for a period of time after the stroke to see if they have episodes of atrial fibrillation.
The treatment of a stroke depends upon the type of stroke, the time that has passed since the first symptoms occurred, and the patient’s other medical problems.
OUTCOME AFTER STROKE
The effects of a stroke can be temporary or permanent, and a person may lose function partially or completely. The medical team caring for the patient can give guidance to family members regarding the risk of long term disability or death. However, the outcome can vary greatly from person to person, and it is not always possible to predict what will happen.