How to prevent a stroke

How can I keep from having another stroke? — If you had an ischemic stroke—a stroke caused by a blocked artery in the brain—there are many things you can do to lower the chances of having another stroke.

If you had a transient ischemic attack, sometimes called a “mini-stroke” or TIA, you can also lower the chances that you will have a full-blown stroke.

To lower your risk of stroke, you should:

• Lower your blood pressure, if it is high
• Keep your blood sugar as close to normal as possible, if you have diabetes
• Lower your cholesterol, if it is high
• Stop smoking, if you smoke
• Do something active for at least 30 minutes a day on most days of the week
• Lose weight, if you are overweight
• Eat a diet rich in fruits, vegetables, and low-fat dairy products, and low in meats, sweets, and refined grains (such as white bread or white rice)
• Eat less salt (sodium)
• Limit the amount of alcohol you drink

• If you are a woman, do not drink more than 1 drink a day
• If you are a man, do not drink more than 2 drinks a day

Medicines and lifestyle changes work together to give the most benefit. It’s very important that you take all the medicines your doctor prescribes. It’s just as important to make the lifestyle changes your doctor recommends.

Take your medicines every day — If you had a stroke or TIA, your doctor or nurse will prescribe medicines to lower your risk of having another stroke. Some of these medicines work by “lowering your risk factors.” That means that they help lower blood pressure, blood sugar and cholesterol. Other medicines help by keeping blood clots from forming, which is what causes many strokes. 

Whatever medicines your doctor prescribes, make sure you take them every day as directed. If you cannot afford your medicines or if they cause side effects, talk to your doctor or nurse. There are often ways to deal with these problems.

Lifestyle changes — Lifestyle changes can do a lot to lower your risk of stroke. That’s partly because the right lifestyle choices can help control risk factors such as blood pressure, blood sugar, and cholesterol. To reduce your risk of stroke, make these lifestyle changes:

• Stop smoking, if you smoke (this is discussed in more detail below)
• Do something active for at least 30 minutes a day on most days of the week
• Lose weight, if you are overweight
• Eat a diet rich in fruits, vegetables, and low-fat dairy products, and low in meats, sweets, and refined grains (such as white bread or white rice)
• Eat less salt (sodium)
• Limit the amount of alcohol you drink

• If you are a woman, do not drink more than 1 drink a day
• If you are a man, do not drink more than 2 drinks a day

Stop smoking — If you smoke, ask your doctor or nurse about how to quit. There are strategies and medicines that can improve your chances of success. Studies show that people are most successful at quitting if they take medicines to help them quit and work with a counselor. You might also have a better chance at success if you combine nicotine replacement with one of the prescription medicines that help people quit.

You can also get help from a free phone line (1-800-QUIT-NOW) or online at www.smokefree.gov.

Subarachnoid Hemorrhage

We have covered many causes of stroke under the umbrella of cerebrovascular accidents. Now is the time for one of the  subtypes of brain bleeding, subarachnoid hemorrhage (SAH). This entity, and one type of hemorrhagic stroke, is the most dreadful for patients and physicians alike.This is because it carries the highest mortality rate of strokes and surgical management is imperative. As you will see in the discussion below the most common cause of SAH in the United States is trauma but more concerning are the non-traumatic SAH. This are commonly due to ruptured cerebral aneurysms that need to be repaired for the bleeding to stop. 

So here are the basics of subarachnoid hemorrhage, or SAH.


What is a subarachnoid hemorrhage? — A subarachnoid hemorrhage is a type of stroke bleeding that causes brain bleeding around your brain. “Hemorrhage” is the medical term for bleeding.

If you have a subarachnoid hemorrhage, the bleeding happens in a part of your head called the “subarachnoid space.” This is the area between your brain and the thin layer of tissue that covers it.

The most common cause of a subarachnoid hemorrhage is a bulging blood vessel that bursts. Doctors call this a “ruptured aneurysm.”

A subarachnoid hemorrhage is life threatening, especially when it is caused by a ruptured aneurysm. Many people who have a subarachnoid hemorrhage die from it.

What are the symptoms of a subarachnoid hemorrhage? — The main symptom is a sudden and very painful headache. It can feel like the worst headache you ever had.

Other symptoms include:

• Fainting (passing out)
• Having a seizure
• Nausea or vomiting
• Stiff neck
• Being bothered by bright light
• Low back pain 

 

Is there a test for subarachnoid hemorrhage? — Yes. If your doctor suspects you have had a subarachnoid hemorrhage, he or she can order one or more of these tests:

• CT scan of your head - This test uses a type of X-ray to take pictures of the inside of your head. If there is bleeding around your brain, a CT scan will likely show it.   

• Lumbar puncture (sometimes called a “spinal tap”) – During this procedure, a doctor puts a needle into your lower back and takes out a small sample of spinal fluid. Spinal fluid is the fluid that surrounds the brain and spinal cord. If this fluid has more red blood cells than usual, you could have a subarachnoid hemorrhage. This test is done if the CT scan does not show bleeding but your doctor still thinks you might have a subarachnoid hemorrhage.

• Other imaging tests – If the CT scan or lumbar puncture shows a subarachnoid hemorrhage, your doctor might do other tests to see if the cause is a ruptured aneurysm. These tests include:

• CT angiography (often called “CTA”) or magnetic resonance angiography (often called “MRA”) – These tests use special types of CT and MRI scans to create pictures of the blood vessels in the brain. Doctors use a dye injection in CTA, and sometimes in MRA. The dye is a chemical that makes blood vessels show up more clearly.  

• Catheter angiography – For this test, the doctor puts a thin tube into a large artery in your leg. Then the doctor moves the tube into the large blood vessels that carry blood to your head. Next the doctor injects a dye into the tube that shows up on an X-ray. The dye can show problems with the blood vessels in the brain. 

 

How is a subarachnoid hemorrhage treated? — Most people who have a subarachnoid hemorrhage go to the intensive care unit (ICU) of a hospital for treatment. In the hospital, the doctor might:

• Give medicines and other treatments to reduce the brain damage caused by the bleeding
• Give medicines such as labetalol (brand name: Trandate^®) to lower blood pressure if it is too high
• Stop medicines that thin the blood, such as aspirin or warfarin (brand names: Coumadin^®, Jantoven^®). If you take blood-thinning medicines, your doctor might give you treatments to help your blood clot. This can help stop bleeding.
• Do tests to figure out the cause of the bleeding
• Watch the pressure in the brain to make sure it does not get too high

 If an aneurysm caused the subarachnoid hemorrhage, doctors must do surgery or another procedure to keep the bleeding from happening again. Depending on the size and location of the aneurysm, they might:

• Do surgery to put a small clip on the aneurysm.
• Put tiny coils in the aneurysm. (This is done during a catheter angiography procedure.)

 

After a subarachnoid hemorrhage, most people stay in the ICU for a few days, weeks, or sometimes longer. Doctors and nurses watch for problems such as:

• Irregular heartbeat (atrial fibrillation)
• Seizures
• Blood clots in the legs
• Lung infections
• Electrolytes out of balance – Electrolytes are chemicals in the body that must be present in the right amounts for your body to work correctly   
 

What will my life be like? — A subarachnoid hemorrhage is very serious. Many people die from this type of stroke. Many people who survive – but not all – have long lasting health problems afterwards.

People who have severe subarachnoid hemorrhages can have certain health problems later, such as:

• Memory problems
• Mood changes or problems with emotions
• Thinking problems
• Trouble speaking, walking, or doing other activities

 

For some people, these problems can be disabling. For others, they may not exist or cause only mild problems. The important thing is to seek medical attention fast.

Transient Ischemic Attack (TIA)

Transient ischemic attack, or TIA, is the medical term for neurologic symptoms, such as weakness or numbness, which begin suddenly, resolve rapidly and completely, and are caused by a temporary lack of blood in an area of the brain. TIAs are common, affecting at least 240,000 people each year in the United States.

Some people call TIAs "warning spells" because anyone who has a TIA is at risk for stroke. As a result, it is important to be aware of the signs and symptoms of TIA and seek treatment as soon as possible.

This topic discusses the symptoms, diagnosis, and treatment of transient ischemic attacks. Topics that discuss strokes are available separately.

WHAT IS A TRANSIENT ISCHEMIC ATTACK? — A transient ischemic attack (TIA) is an episode in which a person has signs or symptoms of a stroke (eg, numbness; inability to speak) that last for a short time. 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 may be 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.

Most TIAs result from narrowing of the major arteries to the brain, such as the carotid arteries. These blood vessels provide oxygenated blood to brain cells. These arteries can become clogged with fatty deposits, called plaques. Plaques partially block the artery, and can lead to the formation of a blood clot. This blood clot (thrombus) can further or completely block the artery. More frequently, a blood clot will detach from the wall of the artery, travel along the bloodstream to smaller branches, and block blood flow to the area of brain fed by that artery.

In some cases, TIAs can be caused by blood clots that form in the heart and travel to the brain (called emboli). TIAs can also occur as a result of narrowing and closure of small blood vessels deep inside the brain.

If an artery remains blocked for more than a few minutes, the brain can become damaged or infarcted (that is, the tissue in that area dies).

• With a TIA, the symptoms resolve completely (usually within a few hours or less)
• With a stroke, the symptoms may not resolve completely

Many people do not have a TIA before a stroke. However, a TIA is a warning sign that a person is at risk for a stroke. It is important to recognize and treat the symptoms of TIA to reduce the risk of having a stroke.

Transient ischemic attack symptoms — Symptoms of TIA are typically short-lived, lasting only a few minutes to hours. A TIA may occur only once, or may be recurrent (several times per day or once per year).

The most common symptoms of TIA include the following:

• Hand, face, arm, or leg weakness or numbness
• Difficulty speaking (garbled speech), slurred speech, or inability to speak at all
• Blurred, doubled, or decreased vision in one or both eyes

These symptoms are identical to those of a stroke. When the symptoms first develop, it is not easy to tell if a person is having a stroke or TIA.

TRANSIENT ISCHEMIC ATTACK RISK FACTORS — A number of factors can increase a person's risk of TIA, including the following:

• Age greater than 40 years
• Heart disease (eg, atrial fibrillation, carotid stenosis)
• High blood pressure
• Smoking
• Diabetes
• High blood cholesterol levels
• Illegal drug use or heavy alcohol use
• Recent childbirth
• Previous history of transient ischemic attack
• Sedentary lifestyle and lack of exercise
• Obesity
• Current or past history of blood clots

Risk of stroke after TIA — The risk of stroke after a TIA is highest in the first few days to weeks after the TIA. For example, the risk of having a stroke in the first two days after TIA has been estimated to be 4 to 10 percent. People with certain characteristics are thought to have a higher risk (eg, closer to 10 percent) of stroke compared to people without these characteristics.

• Diabetes
• Older than 60 years
• Blood pressure (higher than 140/90), measured after the TIA
• Weakness on one side of the body (eg, face, arm, leg) during the TIA
• Speech problems during the TIA
• TIA symptoms for 60 minutes or longer

TRANSIENT ISCHEMIC ATTACK DIAGNOSIS — Despite the fact that the symptoms of TIA usually resolve quickly, TIA is a medical emergency that should be evaluated as soon as possible because there is a high risk of a stroke after TIA.

When to call for emergency medical assistance — Anyone who is concerned that they are having a TIA should call for emergency medical attention immediately. Emergency medical services are available in most areas of the United States by calling 911.

Emergency medical services (EMS) personnel will respond as rapidly as possible, and will take the person to a hospital equipped to care for people during and after a TIA. Most clinics and medical offices do not have the ability to diagnose and treat people with a TIA. For these people, every minute is important.

Anyone who may be having a TIA should not drive to the hospital and should not ask someone else to drive, but should call 911. In addition, it is not necessary to call a doctor or nurse to ask for advice because precious time will be lost waiting for a return call. Getting to the Emergency Department quickly is the best option. Calling 911 is safer than driving for two reasons:

• From the moment EMS personnel arrive, they can begin evaluating and treating the patient. If the patient drives to the hospital, treatment cannot begin until after arriving in the emergency department.
• If a dangerous complication of a TIA occurs on the way to the hospital, EMS personnel may be able to treat the problem immediately.

Brain imaging — Depending upon the results of the history and physical examination, the clinician will usually order blood tests and a brain imaging test (eg, CT scan or MRI). The imaging test allows the clinician to see the area of the brain affected by the TIA.

Blood vessel imaging — The larger blood vessels that supply the brain can also be imaged using CT or MRI; these scans are referred to as CTA (computed tomography arteriogram) and MRA (magnetic resonance arteriogram). Ultrasound can be used to determine if there are blockages in blood vessels.

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. This is called conventional arteriography.

Heart testing — Because a large number of people with TIA also have coronary artery disease, there is a risk of ischemia (lack of blood flow) in the heart during the TIA. In some cases, the person is not able to tell the clinician that he or she feels chest pain. An electrocardiogram (ECG) is usually performed to help the clinician diagnose and treat heart problems as quickly as possible.

In some people with TIA, the heart or the aorta can be the source of a TIA-causing blood clot. Other heart testing, such as an echocardiogram, may be needed. This test uses sound waves to examine the heart and the aorta (the large vessel that arises directly from the heart; blood vessels that supply blood to the brain originate in the aorta).

Heart monitors (also called Holter or loop monitors) may be used to monitor the heart's rhythm for an extended period of time to detect paroxysmal (intermittent) atrial fibrillation.

TRANSIENT ISCHEMIC ATTACK TREATMENT — The optimal treatment of a TIA depends upon the presumed cause of the TIA, the time since the first TIA symptoms occurred, and the person's underlying medical problems.

The goal of treatment is to reduce the risk of having a stroke. There are several types of treatment:

• Treating risk factors, such as high blood pressure
• Antiplatelet therapy
• Anticoagulant therapy
• Revascularization

Treating risk factors — Anyone who has had a TIA has an increased risk of having a TIA or stroke in the future, especially within the first 48 hours after the TIA. The treatments discussed above can significantly reduce this risk. In addition, lifestyle changes and careful management of underlying medical problems can help to reduce the risk of future strokes. These include the following:

• Treatment of high blood pressure
• Controlling diabetes 
• Stopping smoking 
• Treating high cholesterol and lipids 

Antiplatelet therapy — Platelets are a type of cell circulating in the blood that normally clump together to stop bleeding. In TIA, platelets clump together and form clots inside narrowed arteries. The platelets "plug" themselves and/or the clot that forms around the plug can temporarily block blood flow in the brain. Antiplatelet therapy is given to help prevent new clots from developing.

Current guidelines from the American Heart Association/American Stroke Association and the American College of Chest Physicians recommend that most patients with a TIA and no contraindication receive an antiplatelet agent to reduce the risk of subsequent stroke. These guidelines note that aspirin, clopidogrel, and the combination of aspirin plus extended-release dipyridamole (Aggrenox) are all acceptable options for treatment. An exception is that patients who have a TIA caused by embolism from the heart due to an irregular heart rhythm (atrial fibrillation) should be treated with anticoagulation.

Dipyridamole and aspirin — Dipyridamole is a medication that may be given after a TIA to reduce the risk of stroke. It is often given in an extended-release form, which combines dipyridamole with aspirin (called Aggrenox®, which contains 200 mg dipyridamole (ER-DP) and 25 mg aspirin). It is taken two times per day.

Side effects of dipyridamole include headache, upset stomach, and/or diarrhea. Headaches usually improve over the first week.

Aspirin — Aspirin can help to reduce the risk of a future stroke by approximately 25 percent. The recommended dose of aspirin is between 50 and 325 mg per day. Higher doses of aspirin have no additional benefit but do increase the risk of gastrointestinal bleeding.

In the United States, one advantage of aspirin compared to other antiplatelet medications is cost; a one-month supply of aspirin costs approximately $3 compared to at least $160 per month for combined dipyridamole and aspirin and at least $135 per month for clopidogrel.

Clopidogrel — Clopidogrel (Plavix®) is an antiplatelet medication that is also used in patients after TIA to reduce the risk of stroke.

Compared to aspirin, clopidogrel causes a slightly higher frequency of rash and diarrhea, but a slightly lower frequency of stomach upset or gastrointestinal bleeding.

Clopidogrel is not usually recommended in combination with aspirin because the combination is no more effective at preventing another stroke than clopidogrel alone.

Anticoagulant therapy — Anticoagulants are often, but incorrectly, referred to as blood thinners. They work by decreasing the formation of blood clots. Anticoagulant therapy is usually recommended for selected people with an irregular heart rhythm (atrial fibrillation) who have had a TIA or are at risk for a TIA or stroke. The oldest and the most commonly used anticoagulant in this situation is warfarin. Newer anticoagulants are now available that appear to have more a more favorable side effect profile (ie, fewer excessive bleeding events) compared with warfarin.

Warfarin (Coumadin®) — Warfarin is a pill that is taken by mouth. People who take warfarin must be closely monitored with blood tests to ensure that the correct dose is used and that the risk of excessive bleeding or developing blood clots is minimized.

Revascularization — Revascularization is the medical term for reestablishing blow flow to an area. In people who have had a TIA, revascularization usually refers to a surgical procedure (carotid endarterectomy) that opens a blocked artery in the neck (the carotid artery), which improves blood flow to the brain and reduces the risk of stroke. The amount of blockage in the carotid artery can be measured with a non-invasive test, such as ultrasound, CT, or MRI.

Carotid endarterectomy is most successful when it is performed by a vascular surgeon who has specialized training and experience with the procedure. However, even in experienced hands, the procedure has risks, including bleeding, brain injury, stroke, and even death.

Some people are likely to benefit from carotid endarterectomy. For others, the risks of the procedure are greater than the potential benefits. Placement of a stent in the carotid artery is an alternative if carotid endarterectomy is not an option or if the person prefers not to have surgery.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

Transient Ischemic Attack (TIA) - The Basics

So we have discussed what is a stroke and hemorrhagic stroke now is the time for transient ischemic attack (TIA) or mini stroke.

What is a transient ischemic attack? — A transient ischemic attack (TIA) is like a stroke in that it causes the same symptoms as a stroke, but it does not damage the brain. TIAs happen when an artery in the brain gets clogged, or closes off, and then reopens on its own. This can happen if a blood clot forms and then moves away or dissolves. 

The symptoms of a TIA are the same as the symptoms of a stroke and can include:

• Weakness or numbness of the hand, tongue, cheek, face, arm, or leg
• Trouble speaking normally or at all
• Trouble seeing clearly with one or both eyes

TIA is sometimes called a “mini-stroke.” This is because a TIA is just like a stroke, except that a stroke causes long-lasting symptoms, while a TIA goes away quickly.

What is the difference between TIA and stroke? — A TIA does not cause permanent damage to the brain like a stroke does. But the symptoms are the same. This can make it hard to tell if a person is having a TIA or a stroke.

What causes a TIA? — Just like a stroke, a TIA can happen when the blood supply to part of the brain is cut off for a short time. This can happen if a blood clot blocks the flow of blood through an artery in the brain and then dissolves or moves away. It can also happen if one of the small arteries in the brain begins to close off from the effects of high blood pressure.

How can you tell if someone is having a TIA? — The symptoms of a TIA are the same as the symptoms of a stroke. There is an easy way to remember the signs of a stroke. Just think of the word “FAST” (by now you know the picture). Each letter in the word stands for one of the signs you should watch for:

• Face — Does the person’s face look uneven or droop on one side?
• Arm — Does the person have weakness or numbness in one or both arms? Does one arm drift down if the person tries to hold both arms out?
• Speech — Is the person having trouble speaking? Does his or her speech sound strange?
• Time — If you notice any of these stroke signs, even if they go away, call 9-1-1. You need to act FAST. The sooner treatment begins, the better the chances of recovery.

In the hospital, doctors can do tests to look for problems in the brain, blood vessels, and heart. This can help them choose the right treatment.

What is the risk of stroke after TIA? — A person who has had a TIA is at high risk of having a stroke. This risk is highest in the first few days to weeks after the TIA. That is why it is so important to get medical attention right away if you think you (or someone else) might have had a TIA.

How is a TIA treated? — TIAs are not usually treated directly. Instead, treatments are directed at reducing the risk that a person will go on to have a full-blown stroke. 

To lower your risk of stroke, you should:

• Lower your blood pressure, if it is high
• Keep your blood sugar as close to normal as possible, if you have diabetes
• Lower your cholesterol, if it is high
• Stop smoking, if you smoke
• Do something active for at least 30 minutes a day on most days of the week
• Lose weight, if you are overweight
• Eat a diet rich in fruits, vegetables, and low-fat dairy products, and low in meats, sweets, and refined grains (such as white bread or white rice)
• Eat less salt (sodium)
• Limit the amount of alcohol you drink

• If you are a woman, do not drink more than 1 drink a day
• If you are a man, do not drink more than 2 drinks a day

• Take your medicines exactly as directed. Medicines that are especially important in preventing strokes include:

• Blood pressure medicines
• Medicines to prevent blood clots, such as daily aspirin, warfarin (Coumadin®), and dabigatran (Pradaxa®) or apixaban (Eliquis®)
• Medicines called statins, which lower cholesterol such as atorvastatin (Lipitor®), simvastatin (Zocor®), or rosuvastatin (Crestor®)

Another way to prevent strokes is to have surgery to reopen clogged arteries in the neck. This surgery is appropriate for only a small group of people.





See "Transient Ischemic Attack" for more details on this topic.

Hemorrhagic Stroke - The Basics

It is time to discuss hemorrhagic stroke.


What is a hemorrhagic stroke? — Stroke is the term doctors use when a part of the brain is damaged because it goes without blood for too long. The word “hemorrhage” means bleeding. In a hemorrhagic stroke, the blood supply to a part of the brain is cut off because a blood vessel in or on the brain starts bleeding. 

How can you tell if someone is having a stroke? — To tell if someone is having a stroke, just think of the word “FAST”. Each letter in the word stands for 1 of the things to watch for:

• Face — Does the person’s face look uneven or droop to 1 side?
• Arm — Does the person have weakness or numbness in 1 or both arms? Does 1 arm drift down if the person tries to hold both arms out?
• Speech — Is the person having trouble speaking? Does his or her speech sound strange?
• Time — If you see any of these signs, call 9-1-1. You need to act FAST and get to a hospital. The sooner treatment begins, the better the chances of recovery.

Sometimes, people get a severe headache that starts all of a sudden when they have a hemorrhagic stroke.

How are hemorrhagic strokes treated? — In the hospital, your doctor might:

• Give you medicines and other treatments to reduce the brain damage caused by the bleeding
• Give you medicines to lower your blood pressure, if your blood pressure is too high
• Stop any medicines you take that thin the blood. If you take blood-thinning medicines, he or she might give you treatments to help your blood get thicker and stop bleeding.
• Do tests to figure out the cause of the bleeding
• Watch the pressure in your brain to make sure that it doesn’t get too high

Some people are also treated with surgery, depending on their symptoms and other factors (See "Hemorrhagic Stroke Treatment" for more information on this topic). Doctors can do surgery to:

• Remove a collection of blood, if it is pressing down on the brain or causing the brain to swell
• Stop the bleeding in the brain and fix the blood vessel that was bleeding

Can hemorrhagic strokes be prevented? — Sometimes. You can lower your chance of having a hemorrhagic stroke by:

• Getting treated for high blood pressure – This is very important, because untreated high blood pressure is a common cause of hemorrhagic strokes. Treatment can involve lifestyle changes, diet changes, and medicines.
• Not smoking
• Not using illegal drugs

Having surgery to fix the abnormal blood vessel that caused the stroke can also prevent it from bleeding again.

What happens after a stroke? — Some people recover from a stroke without any long-term problems or with only minor problems. But many people have serious problems after a stroke. For example, they might be unable to speak or feed themselves, or they might be unable to move one side of their body.

After a stroke, people are also more likely to get other medical problems. These can include blood clots in the legs, heart problems, bed sores, or lung infections. Your doctor or nurse will try to prevent these problems from happening and will treat them if they do happen

Ischemic Stroke

As we have mentioned in prior posts the term ischemic stroke is used to describe a variety of conditions in which blood flow to part or all of the brain is reduced, resulting in tissue damage. Although in some cases this may be a chronic condition, most strokes occur acutely. Research over the last four decades has resulted in a significant expansion of our knowledge and understanding of the molecular and cellular processes that underlie ischemia-induced cellular injury.

The goal of this review is to provide an overview of the underlying factors, such as the hemodynamic changes and molecular and cellular pathways, which are involved in stroke-related brain injury.

STROKE SUBTYPES — Acute ischemic stroke subtypes are often classified in clinical studies using a system developed by investigators of the TOAST trial, based upon the underlying cause. Under this system, strokes are classified into the following categories:

• Large artery atherosclerosis
• Cardioembolism
• Small vessel occlusion
• Stroke of other, unusual, determined etiology
• Stroke of undetermined etiology

Ischemic strokes are due to a reduction or complete blockage of blood flow to some areas of the brain. This reduction can be due to decreased systemic perfusion, severe stenosis or occlusion of a blood vessel. Decreased systemic perfusion can be the result of low blood pressure, heart failure, or loss of blood. Determination of the type of stroke can influence treatment to be used. The main causes of ischemia are thrombosis, embolization, and lacunar stroke from small vessel disease. Ischemic strokes represent about 80 percent of all strokes. (See "Stroke Symptoms and Diagnosis")

• Thrombosis refers to obstruction of a blood vessel due to a localized occlusive process within a blood vessel. The obstruction may occur acutely or gradually. In many cases, underlying pathology such as atherosclerosis may cause narrowing of the diseased vessel. This may lead to restriction of blood flow gradually, or in some cases, platelets may adhere to the atherosclerotic plaque forming a clot leading to acute occlusion of the vessel. Atherosclerosis usually affects larger extracranial and intracranial vessels. In some cases, acute occlusion of a vessel unaffected by atherosclerosis may occur because of a hypercoagulable state.

• Embolism refers to clot or other material formed elsewhere within the vascular system that travels from the site of formation and lodges in distal vessels causing blockage of those vessel and ischemia. The heart is a common source of this material, although other arteries may also be sources of this embolic material (artery to artery embolism). In the heart, clots may form on valves or chambers. Tumors, venous clots, septic emboli, air and fat can also embolize and cause stroke. Embolic strokes tend to be cortical and are more likely to undergo hemorrhagic transformation, probably due to vessel damage caused by the embolus

• Lacunar stroke occurs as a result of small vessel disease. Smaller penetrating vessels are more commonly affected by chronic hypertension leading to hyperplasia of the tunica media of these vessels and deposition of fibrinoid material leading to lumen narrowing and occlusion. Lacunar strokes can occur anywhere in the brain but are typically seen in sub-cortical areas. Atheroma can also encroach on the orifices of smaller vessels leading to occlusion and stroke. (See "Lacunar Stroke".)

• Nonatherosclerotic abnormalities of the cerebral vasculature, whether inherited or acquired, predispose to ischemic stroke at all ages, but particularly in younger adults and children. These can be divided into noninflammatory and inflammatory etiologies. The following list, though not exhaustive, highlights the major nonatherosclerotic vasculopathies associated with ischemic stroke:

• Arterial dissection
  
• Fibromuscular dysplasia 
• Vasculitis 
• Moyamoya disease
• Sickle cell disease arteriopathy 
• Focal cerebral arteriopathy of childhood 

• Decreased systemic perfusion due to systemic hypotension may produce generalized ischemia to the brain. This is most critical in the borderzone (or watershed) areas, which are territories that occupy the boundary region of two adjacent arterial supply zones. The ischemia caused by hypotension may be asymmetric due to preexisting vascular lesions. Areas of the brain commonly affected include the hippocampal pyramidal cells, cerebellar Purkinje cells, and cortical laminar cells discussed below.

GENETICS OF STROKE — Many of the known risk factors for stroke are variable traits influenced by multiple genes, making it difficult to sort out the genetics behind them. The study of stroke genetics is also impaired by interactions between different risk factors that modulate their effects. It is widely accepted, however, that there is a genetic component to stroke that can lead to increased or decreased risk. Much of the evidence for this comes from studies of twins and from families with a history of stroke.

• Earlier studies of twins have been troubled by low sample numbers and poor classification of stroke type. However, these studies indicate that stroke-related death in one sibling is associated with a higher risk of stroke-related death in the other sibling among monozygotic (identical) twins versus dizygotic (fraternal) twins. This observation suggests that genetic factors shared by the monozygotic twins played a role in their strokes. 

• A family history of stroke is associated with an increased risk of stroke among the offspring. This has been observed for offspring with maternal and paternal histories of stroke, and among individuals having a sibling with a prior stroke.

Monogenic disorders — A number of monogenic syndromes are associated with an increased risk of ischemic stroke, including the following:

• Marfan syndrome and Ehlers-Danlos syndrome, which predispose to cervical artery dissection 
• Familial moyamoya disease 
• Fabry disease 
• Pseudoxanthoma elasticum
• Homocystinuria
• Menkes disease
• Cerebral autosomal dominant arteriopathy with subcortical infarctions and leukoencephalopathy
• Cerebral autosomal recessive arteriopathy with subcortical infarctions and leukoencephalopathy (CARASIL)
• Hereditary endotheliopathy with retinopathy, nephropathy, and stroke (HERNS)
• Sickle cell disease 
• Mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS)

It is important to note that all of these conditions together account for only a small percentage of ischemic strokes.

SUMMARY

• Under normal conditions, the rate of cerebral blood flow is primarily determined by the amount of resistance within cerebral blood vessels. Dilation of vessels leads to an increased volume of blood in the brain and increased cerebral blood flow, whereas constriction of vessels has the opposite effect. Cerebral blood flow is also determined by variation in the cerebral perfusion pressure.

• The brain is exquisitely sensitive to even short durations of ischemia. Multiple mechanisms are involved in tissue damage that results from brain ischemia. 

• Brain ischemia initiates a cascade of events that eventually lead to cell death, including depletion of ATP, changes in ionic concentrations of sodium, potassium, and calcium, increased lactate, acidosis, accumulation of oxygen free radicals, intracellular accumulation of water, and activation of proteolytic processes.

• Cell death following cerebral ischemia or stroke can occur by either necrosis or by apoptosis. Low levels of ATP within the core infarct are insufficient to support apoptosis, and cell death occurs by necrosis. In the ischemic penumbra, ATP levels are sufficiently high that cell death by apoptosis can occur. As the duration of ischemia increases, however, ATP levels are eventually depleted and the proportion of cells that undergo necrosis is increased.

What is a Stroke - In-depth Overview

I understand that the information contained here regarding ischemic and hemorrhagic stroke is somewhat elaborate but some of you out there will want to comprehend “what is a stroke” better. If you are like me, you would want all the nitty-gritty details of the condition that is afflicting you, your father, your mother, your friend… So here it is. I must warn you though, this may look to some of you (and me) like a textbook chapter.

There are two broad categories of stroke, hemorrhagic stroke and ischemic stroke; and these are diametrically opposite conditions: hemorrhagic stroke is characterized by too much blood within the closed cranial cavity, while ischemic stroke is characterized by too little blood to supply an adequate amount of oxygen and nutrients to a part of the brain.

Each of these categories can be divided into subtypes that have somewhat different causes, clinical pictures, clinical courses, outcomes, and treatment strategies. As an example, intracranial hemorrhage can be caused by intracerebral hemorrhage (ICH, also called parenchymal hemorrhage), which involves bleeding directly into brain tissue, and subarachnoid hemorrhage (SAH), which involves bleeding into the cerebrospinal fluid that surrounds the brain and spinal cord.

This entry will review the classification and causes of stroke. 

DEFINITIONS — Stroke is classified into two major types:

• Brain ischemia due to thrombosis, embolism, or systemic hypoperfusion
• Brain hemorrhage due to intracerebral hemorrhage or subarachnoid hemorrhage

A stroke is the acute neurologic injury that occurs as a result of one of these pathologic processes. Approximately 80 percent of strokes are due to ischemic cerebral infarction and 20 percent to brain hemorrhage.

An infarcted brain is pale initially. Within hours, the gray matter becomes congested with engorged, dilated blood vessels and minute petechial hemorrhages. When an embolus blocking a major vessel migrates, lyses, or disperses within minutes to days, recirculation into the infarcted area can cause a hemorrhagic infarction and may aggravate edema (swelling) formation due to disruption of the blood-brain barrier.

A primary intracerebral hemorrhage, or hemorrhagic stroke, damages the brain directly at the site of the hemorrhage by compressing the surrounding tissue. Physicians must initially consider whether the patient with suspected cerebrovascular accident is experiencing symptoms and signs suggestive of ischemia or hemorrhage.

The great majority of ischemic strokes are caused by a diminished supply of arterial blood, which carries sugar and oxygen to brain tissue. Another cause of stroke that is difficult to classify is stroke due to occlusion of veins that drain the brain of blood, cerebral venous sinus thrombosis. Venous occlusion causes a back-up of fluid resulting in brain edema, and in addition it may cause both brain ischemia and hemorrhage into the brain.

BRAIN ISCHEMIA — There are three main subtypes of brain ischemia:

• Thrombosis generally refers to local obstruction of an artery. The obstruction may be due to disease of the arterial wall, such as arteriosclerosis, dissection, or fibromuscular dysplasia; there may or may not be superimposed thrombosis.
• Embolism refers to particles of debris originating elsewhere that block arterial access to a particular brain region. Since the process is not local (as with thrombosis); further events may occur if the source of embolism is not identified and treated.
• Systemic hypoperfusion is a more general circulatory problem, manifesting itself in the brain and perhaps other organs.

Blood disorders are an uncommon primary cause of stroke. However, increased blood coagulability can result in thrombus formation and subsequent cerebral embolism in the presence of an endothelial lesion located in the heart, aorta, or large arteries that supply the brain.

Transient ischemic attack (TIA) is defined clinically by the temporary nature of the associated neurologic symptoms, which last less than 24 hours by the classic definition. The definition is changing with recognition that transient neurologic symptoms are frequently associated with brain damage.

BRAIN HEMORRHAGE — There are two main subtypes of hemorrhage stroke:

• Intracerebral hemorrhage refers to bleeding directly into the brain parenchyma
• Subarachnoid hemorrhage refers to bleeding into the cerebrospinal fluid within the subarachnoid space that surrounds the brain

Intracerebral hemorrhage — Bleeding in intracerebral hemorrhage (ICH) is usually derived from arterioles or small arteries. The brain bleeding is directly into the brain parenchyma, forming a localized hematoma (clot). Accumulation of blood occurs over minutes or hours; the hematoma gradually enlarges by adding blood at its periphery like a snowball rolling downhill. The hematoma continues to grow until the pressure surrounding it increases enough to limit its spread or until the hemorrhage decompresses itself by emptying into the ventricular system or into the cerebrospinal fluid (CSF) on the pial surface of the brain.

The most common causes of hemorrhagic stroke are hypertension, trauma, bleeding diatheses, amyloid angiopathy, illicit drug use (mostly amphetamines and cocaine), and vascular malformations. Less frequent causes include bleeding into tumors, aneurysmal rupture, and vasculitis.

The earliest symptoms of hemorrhagic stroke relate to dysfunction of the portion of the brain that contains the hemorrhage. As examples:

• Bleeding into the right putamen and internal capsule region causes left limb motor and/or sensory signs
• Bleeding into the cerebellum causes difficulty walking
• Bleeding into the left temporal lobe presents as aphasia

The neurologic symptoms usually increase gradually over minutes or a few hours. In contrast to brain embolism and SAH, the neurologic symptoms related to hemorrhagic stroke may not begin abruptly and are not maximal at onset.

Headache, vomiting, and a decreased level of consciousness develop if the hematoma becomes large enough to increase intracranial pressure or cause shifts in intracranial contents. These symptoms are absent with small hemorrhages; the clinical presentation in this setting is that of a gradually progressing stroke.

ICH destroys brain tissue as it enlarges. The pressure created by blood and surrounding brain edema is life-threatening; large hematomas have a high mortality and morbidity. The goal of treatment is to contain and limit the bleeding. Recurrences are unusual if the causative disorder is controlled (eg, hypertension or bleeding diathesis).

Subarachnoid hemorrhage — The two major causes of SAH are rupture of arterial aneurysms that lie at the base of the brain and bleeding from vascular malformations that lie near the pial surface. Bleeding diatheses, trauma, amyloid angiopathy, and illicit drug use are less common. 

Rupture of an aneurysm releases blood directly into the cerebrospinal fluid (CSF) under arterial pressure. The blood spreads quickly within the CSF, rapidly increasing intracranial pressure. Death or deep coma ensues if the bleeding continues. The bleeding usually lasts only a few seconds but rebleeding is very common. With causes of SAH other than aneurysm rupture, the bleeding is less abrupt and may continue over a longer period of time.

Symptoms of SAH begin abruptly in contrast to the more gradual onset of ICH. The sudden increase in pressure causes a cessation of activity (eg, loss of memory or focus or knees buckling). Headache is an invariable symptom and is typically instantly severe and widespread; the pain may radiate into the neck or even down the back into the legs. Vomiting occurs soon after onset. There are usually no important focal neurologic signs unless bleeding occurs into the brain and CSF at the same time (meningocerebral hemorrhage). Onset headache is more common than in ICH, and the combination of onset headache and vomiting is infrequent in ischemic stroke.

Approximately 30 percent of patients have a minor hemorrhage manifested only by sudden and severe headache (the so-called sentinel headache) that precedes a major SAH. The complaint of the sudden onset of severe headache is sufficiently characteristic that a minor SAH should always be considered. 

The goal of treatment of SAH is to identify the cause and quickly treat it to prevent rebleeding. The other goal of treatment is to prevent brain damage due to delayed ischemia related to vasoconstriction of intracranial arteries; blood within the CSF induces vasoconstriction, which can be intense and severe. The treatment of SAH will be discussed separately.

In the next articles I will try to go over each of the specific types of strokes, risk factors for stroke, stroke medications, stroke rehab, and, most importantly, prevention of stroke.