Stroke

What is a stroke?

Brain cell function requires a constant delivery of oxygen and glucose from the bloodstream. A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. Blood flow can be compromised by a variety of mechanisms.

Blockage of an artery

• Narrowing of the small arteries within the brain can cause a lacunar stroke, (lacune means "empty space"). Blockage of a single arteriole can affect a tiny area of brain causing that tissue to die (infarct).
  
  
• Hardening of the arteries (atherosclerosis) leading to the brain. There are four major blood vessels that supply the brain with blood. The anterior circulation of the brain that controls most motor activity, sensation, thought, speech, and emotion is supplied by the carotid arteries. The posterior circulation, which supplies the brainstem and the cerebellum, controlling the automatic parts of brain function and coordination, is supplied by the vertebrobasilar arteries.

• Embolism to the brain from the heart. In some instances blood clots can form within the heart and the potential exists for them to break off and travel (embolize) to the arteries in the brain and cause a stroke.

Rupture of an artery (hemorrhage)

• Cerebral hemorrhage (bleeding within the brain substance). The most common reason to have bleeding within the brain is uncontrolled high blood pressure. Other situations include aneurysms that leak or rupture or arteriovenous malformations (AVM) in which there is an abnormal collection of blood vessels that are fragile and can bleed.

What causes a stroke?

Blockage of an artery

The blockage of an artery in the brain by a clot (thrombosis) is the most common cause of a stroke. The part of the brain that is supplied by the clotted blood vessel is then deprived of blood and oxygen. As a result of the deprived blood and oxygen, the cells of that part of the brain die and the part of the body that it controls stops working. Typically, a cholesterol plaque in a small blood vessel within the brain that has gradually caused blood vessel narrowing ruptures and starts the process of forming a small blood clot.

Risk factors for narrowed blood vessels in the brain are the same as those that cause narrowing blood vessels in the heart and heart attack (myocardial infarction). These risk factors include:

• high blood pressure (hypertension),
  
• high cholesterol,
  
• diabetes, and
  
• smoking.

Embolic stroke

Another type of stroke may occur when a blood clot or a piece of atherosclerotic plaque (cholesterol and calcium deposits on the wall of the inside of the heart or artery) breaks loose, travels through the bloodstream and lodges in an artery in the brain. When blood flow stops, brain cells do not receive the oxygen and glucose they require to function and a stroke occurs. This type of stroke is referred to as an embolic stroke. For example, a blood clot might originally form in the heart chamber as a result of an irregular heart rhythm, such as occurs in atrial fibrillation. Usually, these clots remain attached to the inner lining of the heart, but occasionally they can break off, travel through the blood stream, form a plug (embolism) in a brain artery, and cause a stroke.

Cerebral hemorrhage

A cerebral hemorrhage occurs when a blood vessel in the brain ruptures and bleeds into the surrounding brain tissue. A cerebral hemorrhage (bleeding in the brain) causes stroke symptoms by depriving blood and oxygen to parts of the brain in a variety of ways. Blood flow is lost to some cells. As well, blood is very irritating and can cause swelling of brain tissue (cerebral edema). Edema and the accumulation of blood from a cerebral hemorrhage increases pressure within the skull and causes further damage by squeezing the brain against the bony skull further decreasing blood flow to brain tissue and cells.

Subarachnoid hemorrhage

In a subarachnoid hemorrhage, blood accumulates in the space beneath the arachnoid membrane that lines the brain. The blood originates from an abnormal blood vessel that leaks or ruptures. Often this is from an aneurysm (an abnormal ballooning out of the wall of the vessel). Subarachnoid hemorrhages usually cause a sudden, severe headache, nausea, vomiting, light intolerance, and a stiff neck. If not recognized and treated, major neurological consequences, such as coma, and brain death may occur.

Vasculitis

Another rare cause of stroke is vasculitis, a condition in which the blood vessels become inflamed causing decreased blood flow to brain tissue.

Migraine headache

There appears to be a very slight increased occurrence of stroke in people with migraine headache. The mechanism for migraine or vascular headaches includes narrowing of the brain blood vessels.

What are the risk factors for stroke?

Overall, the most common risk factors for stroke are:

• high blood pressure,
  
• high cholesterol,
  
• smoking,
  
• diabetes and
  
• increasing age.

Heart rhythm disturbances like atrial fibrillation, patent foramen ovale, and heart valve disease can also be the cause.

An example of a genetic predisposition to stroke occurs in a rare condition called homocystinuria, in which there are excessive levels of the chemical homocystine in the body. Scientists are trying to determine whether the non-hereditary occurrence of high levels of homocystine at any age can predispose to stroke.

What are stroke symptoms?

When brain cells are deprived of oxygen, they cease to perform their usual tasks. The symptoms that follow a stroke depend on the area of the brain that has been affected and the amount of brain tissue damage.

Small strokes may not cause any symptoms, but can still damage brain tissue. These strokes that do not cause symptoms are referred to as silent strokes. According to The U.S. National Institute of Neurological Disorders and Stroke (NINDS), these are the five major signs of stroke:

1. Sudden numbness or weakness of the face, arm or leg, especially on one side of the body. The loss of voluntary movement and/or sensation may be complete or partial. There may an associated tingling sensation in the affected area.
   
2. Sudden confusion or trouble speaking or understanding. Sometimes weakness in the muscles of the face can cause drooling.
   
3. Sudden trouble seeing in one or both eyes
   
4. Sudden trouble walking, dizziness, loss of balance or coordination
   
5. Sudden, severe headache with no known cause
   

What should be done if you suspect you or someone else is having a stroke?

If any of the symptoms mentioned above suddenly appear, immediate emergency medical attention should be sought. The first action should be to activate the emergency medical system in your area . The goal is to get the stroke victim to a hospital as quickly as possible to confirm the diagnosis.

The first priority is ensuring that the ambulance arrives as soon as possible since first responders, EMTs and paramedics may be able to help make the diagnosis and alert the hospital about the stoke victim's situation.

While waiting for the ambulance, the following first aid suggestions may be helpful:

• The affected person should lie flat to promote an optimal blood flow to the brain.
  
  
• If drowsiness, unresponsiveness, or nausea are present, the person should be placed in the rescue position on their side to prevent choking should vomiting occur.
  
  
• Although aspirin plays a major role in stroke prevention (see below), once the symptoms of a stroke begin, it is generally recommended that additional aspirin not be taken until the patient receives medical attention. If stroke is of the bleeding type, aspirin could theoretically make matters worse. Moreover, patients with stroke may have swallowing difficulties and may choke on the pill.

Three commands, known as the Cincinnati Prehospital Stroke Scale (CPSS), may help to determine if the potential for stroke exists. Ask the patient to do the following:

1. Smile: the face should move symmetrically
2. Raise both arms: looking for weakness on one side of the body
3. Speak a simple sentence

How is a stroke diagnosed?

A stroke is a medical emergency. Anyone suspected of having a stroke should be taken to a medical facility immediately for evaluation and treatment. Initially, the doctor takes a medical history from the patient if possible or from others familiar with the patient if they are available. Important questions include what the symptoms were, when they began, if they were getting better, worse or staying the same. Past medical history adds important information looking for risk factors for stroke and for medications that can cause bleeding (for example, warfarin [Coumadin], clopidogrel [Plavix], prasugrel [Effient]).

Physical examination is key in confirming the parts of the body that have stopped functioning and may help determine what part of the brain has lost its blood supply. If available, a neurologist, a doctor specializing in disorders of the nervous system and diseases of the brain, can assist in the diagnosis and management of stroke patients.

Just because a person has slurred speech or weakness on one side of the body does not necessarily signal the occurrence of a stroke. There are many other possibilities that can be responsible for these symptoms. Other conditions that can mimic a stroke include:

• brain tumors,
  
• brain abscess (a collection of pus in the brain caused by bacteria or a fungus),
  
• migraine headache,
  
• bleeding in the brain either spontaneously or from trauma,
  
• meningitis or encephalitis,
  
• an overdose of certain medications, or
  
• an electrolyte imbalance in the body. Abnormal concentrations (too high or too low) of sodium, calcium, or glucose in the body may also cause changes in the nervous system that can mimic a stroke.

In the acute stroke evaluation, many things will occur at the same time. As the physician is taking the history and performing the physical examination, nursing staff will begin monitoring the patient's vital signs, performing blood tests, and performing an electrocardiogram (EKG or ECG).

Computerized tomography: In order to help determine the cause of a suspected stroke, a special X-ray test called a CT scan of the brain is often performed. A CT scan is used to look for bleeding or masses within the brain that may cause symptoms that mimic a stroke, but are not treated with thrombolytic therapy with TPA.

MRI scan: Magnetic resonance imaging(MRI) uses magnetic waves rather than X-rays to image the brain. The MRI images are much more detailed than those from CT, but due to the length of time to do the test and lack of availability of the machines in many hospitals, is not a first line test in stroke. While a CT scan may be completed within a few minutes, an MRI may take more than an hour to complete. An MRI may be performed later in the course of patient care if finer details are required for further medical decision making. People with certain medical devices (for example, pacemakers) or other metals within their body, cannot be subjected to the powerful magnetic field of an MRI.

Computerized tomography with angiography: Using dye that is injected into a vein in the arm, images of the blood vessels in the brain can give information regarding aneurysms or arteriovenous malformations. Moreover, other abnormalities of brain blood flow may be evaluated. With faster machines and better technology, CT angiography may be done at the same time as the initial CT scan to look for a blood clot within an artery in the brain.

CT and MRI images often require a radiologist to interpret their results.

Conventional angiogram: An angiogram is another test that is sometimes used to view the blood vessels. A long catheter tube is inserted into an artery in the groin or arm and threaded into the arteries of the brain. Dye is injected while X-rays are taken and information can be obtained about blood flow in the brain. The decision to perform CT angiography versus conventional angiography depends upon a patient's specific situation and the technical capabilities of the hospital.

Carotid Doppler ultrasound: A carotid Doppler ultrasound is a non-invasive test that uses sound waves to look for narrowing or stenosis and decreased blood flow in the carotid arteries (the major arteries in the front of the neck that supply blood to the brain).

Heart tests: Certain tests to evaluate heart function are often performed in stroke patients to search for the source of an embolism. Electrocardiograms (EKG or ECG) may be used to detect abnormal heart rhythms like atrial fibrillation that are associated with embolic stroke.

Ambulatory rhythm monitoring may be considered if the patient complains of palpitations or passing out episodes (syncope) and the doctor cannot find reason for it on the EKG. The patient can wear a Holter monitor for 1-2 days and sometimes longer looking fro a potential electrical conduction problem with the heart.

Echocardiograms or ultrasounds of the heart can help evaluate the structure and function of the heart including the heart muscle, valves and the motion of the heart chamber when the heart beats. As well, specifically for stroke patients, this test may be able to find blood clots within the heart and the presence of a patent foramen ovale, both potential causes of stroke.

Blood tests: In the acute situation, when the patient is in the midst of a stroke, blood tests are done to check for anemia, kidney and liver function, electrolyte abnormalities and blood clotting function.

What is the treatment of a stroke?

Tissue plasminogen activator (TPA)

There is opportunity to use alteplase (TPA) as a clot-buster drug to dissolve the blood clot that is causing the stroke. There is a narrow window of opportunity to use this drug. The earlier that it is given, the better the result and the less potential for the complication of bleeding into the brain.

Present American Heart Association guidelines recommend that if used, TPA must be given within 4 1/2 hours after the onset of symptoms. for patients who waken from sleep with symptoms of stroke, the clock starts when they were last seen in a normal state.

TPA is injected into a vein in the arm but, the time frame for its use may be extended to six hours if it is dripped directly into the blood vessel that is blocked requiring angiography, which is performed by an interventional radiologist. Not all hospitals have access to this technology.

Heparin and aspirin

Drugs to thin the blood (anticoagulation; for example, heparin) are also sometimes used in treating stroke patients in the hopes of improving the patient's recovery. It is unclear, however, whether the use of anticoagulation improves the outcome from the current stroke or simply helps to prevent subsequent strokes.

Managing other Medical Problems

Blood pressure will be tightly controlled often using intravenous medication to prevent stroke symptoms from progressing. This is true whether the stroke is ischemic or hemorrhagic.

Supplemental oxygen is often provided.

In patients with diabetes, the blood sugar (glucose) level is often elevated after a stroke. Controlling the glucose level in these patients may minimize the size of a stroke.

Patients who have suffered a transient ischemic attacks, the patient may be discharged with blood pressure and cholesterol medications even if the blood pressure and cholesterol levels are within acceptable levels. Smoking cessation is mandatory.

Rehabilitation

When a patient is no longer acutely ill after a stroke, the health care staff focuses on maximizing the individuals functional abilities. This is most often done in an inpatient rehabilitation hospital or in a special area of a general hospital. Rehabilitation can also take place at a nursing facility.

The rehabilitation process can include some or all of the following:

1. speech therapy to relearn talking and swallowing;
   
2. occupational therapy to regain as much function dexterity in the arms and hands as possible;
   
3. physical therapy to improve strength and walking; and
   
4. family education to orient them in caring for their loved one at home and the challenges they will face.

The goal is for the patient to resume as many, if not all, of their pre-stroke activities and functions. Since a stroke involves the permanent loss of brain cells, a total return to the patient's pre-stroke status is not necessarily a realistic goal in many cases. However, many stroke patients can return to vibrant independent lives.

Stroke At A Glance

• Stroke is the sudden death of brain cells due to lack of oxygen.
  
• Stroke is caused by the blockage of blood flow or rupture of an artery to the brain.
  
• Sudden tingling, weakness, or paralysis on one side of the body or difficulty with balance, speaking, swallowing, or vision can be a symptom of a stroke.
  
• Any person suspected of having a stroke or TIA should present for emergency care immediately
  
• Clot-busting drugs like TPA can be used to reverse a stroke, but the time frame for their use is very narrow. Patients need to present for care as soon as possible so that TPA therapy can be considered.
  
• Stroke prevention involves minimizing risk factors, such as controlling high blood pressure, elevated cholesterol, tobacco abuse, and diabetes.