Strokes at a Glance
By Marina Lowell - Published on Saturday, 04 July 2009 19:26
A stroke is the sudden death of brain cells when they are deprived of oxygen. Strokes are caused by the rupture of an artery or blood flow to the brain being blocked. Symptoms of a stroke can include: sudden tingling, weakness, or paralysis on one side of the body or difficulty with balance, speaking, swallowing, or vision.Anyone suspected of having a stroke should go for emergency care right away.
Clot-busting drugs like TPA can be used to reverse a stroke, but there is only a short time period in which they can be used.
Minimizing risk factors can help prevent strokes; prevention methods include: controlling high blood pressure, elevated cholesterol, tobacco abuse, and diabetes.
What is a stroke? - A stroke happens when the blood supply to the brain is disrupted. When this happens, oxygen and glucose can't reach the brain; this causes brain cells to die. Blood flow can stop for a variety of reasons.
What causes a stroke?
* Blockage of an artery - The most common cause of a stroke is a blockage of an artery in the brain by a clot. When the part of the brain supplied by the clotted blood vessel is deprived of blood and oxygen, the cells of that part of the brain die. Clots usually form in small blood vessels within the brain which have narrowed due to things like high blood pressure (hypertension), high cholesterol, diabetes, and smoking.
* Embolic stroke - When blood clots form within the heart or in a large artery, it is possible for small clots to break off and travel to the arteries in the brain. and cause a stroke. When the clot lodges in an artery of the brain, the flow of oxygen-rich blood to the brain is blocked, causing a stroke.
* Cerebral hemorrhage - When a blood vessel in the brain ruptures and bleeds into the surrounding brain tissue, it can cause a stroke by depriving blood and oxygen to parts of the brain. Uncontrolled high blood pressure is the most common reason for a hemorrhage. Blood is also very irritating to the brain.
* Subarachnoid hemorrhage - When an abnormal blood vessel that leaks or ruptures, blood can accumulate in the space beneath the arachnoid membrane that lines the brain. Subarachnoid hemorrhages usually cause a sudden, severe headache and stiff neck. If not treated, it will lead to coma and brain death.
* Atherosclerosis (hardening of the arteries) - If the arteries leading to the brain become narrow because of atherosclerosis, plaque or cholesterol, debris can break off and float downstream, which can disrupt the blood supply to a part of the brain. Unlike lacunar strokes, bigger parts of the brain can lose blood supply, and this may produce more symptoms.
Vasculitis is a rare cause of stroke; it is a condition in which the blood vessels become inflamed.
What are the risk factors for stroke?
The most common risk factors 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.
In people under 50 years old, less common risk factors are also considered. These include illicit drugs, such as cocaine or amphetamines, ruptured aneurysms, and genetic predispositions to blood clotting.
What is a transient ischemic attack (TIA)?
A TIA is a short episode (less than 24 hours) of temporary impairment to the brain, caused by a loss of blood supply. It causes a loss of function in the part of the body that is controlled by the portion of the brain affected. The loss of blood supply to the brain is usually the result of a clot that spontaneously formed in a blood vessel within the brain, but it can also be caused by an embolism.
A TIA can develop slowly or rapidly, but all TIAs resolve within 24 hours. Strokes take longer to resolve than TIAs, and with strokes, complete function may never return. Most TIAs only last a few minutes, but they should be looked at with the same urgency as a stroke, to prevent recurrences and/or strokes. TIAs can occur once, multiple times, or precede a permanent stroke. A TIA should be considered an emergency; there is no guarantee that the situation will resolve and function will return.
A TIA from a clot to the eye can cause temporary visual loss. A TIA that involves the carotid artery (the largest blood vessel supplying the brain) can produce problems with movement or sensation on one side of the body. This can cause paralysis of the arm, leg, and face, all on one side. Double vision, dizziness, and loss of speech, understanding, and balance can also be symptoms depending on what part of the brain is affected.
What is the impact of strokes?
In the United States, stroke is the third largest cause of death. Strokes cost billions of dollars lost in work, hospitalization, and the care of survivors in nursing homes. However, the biggest cost of a stroke is the loss of independence in 30% of the survivors.
What are stroke symptoms?
When brain cells are deprived of oxygen, they stop doing their tasks. The symptoms following a stroke depend on the area of the brain affected and the amount of brain tissue damage. Small strokes may not cause any symptoms, but can still damage brain tissue. These are called silent strokes.
The five major signs of stroke are:
* Sudden numbness or weakness of the face, arm or leg, especially on one side of the body
* Sudden confusion or trouble speaking or understanding. Sometimes weakness in the muscles of the face can cause drooling
* Sudden trouble seeing in one or both eyes
* Sudden trouble walking, dizziness, loss of balance or coordination
* Sudden, severe headache with no known cause
What should be done if you suspect you or someone else is having a stroke?
If any signs of stroke suddenly appear, the first action should be calling 911. The family doctor and/or neurologist should also be called, but the first priority is to make sure that the ambulance arrives as soon as possible. Lying flat will promote an optimal blood flow to the brain, but 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.
Aspirin is useful in preventing strokes, but once the symptoms of a stroke begin, it is best not to take any more aspirin until the patient receives medical attention. If the stroke is of the bleeding type, aspirin could make it worse.
Cincinnati Prehospital Stroke Scale (CPSS)
There are three commands, known as the Cincinnati Prehospital Stroke Scale, that can be used to assess whether a person is experiencing a stroke. Anyone can command a potential stroke victim to: smile, raise both arms, or speak a simple sentence.
The three commands are used by doctors as a first step in the assessment process for signs of stroke. If someone has trouble with any of these simple commands, emergency services should be called immediately with a description of the situation, noting that you suspect the individual is having a stroke.
How is a stroke diagnosed?
If someone is suspected of having a stroke, they should be taken to a medical facility immediately. First the doctor takes a medical history from the patient or others familiar with the patient, and then performs a physical examination. A family doctor may be useful in the assessment; having previous knowledge of the patient can improve the accuracy of the evaluation. A neurologist will often help with the diagnosis and management of stroke patients.
Having slurred speech or weakness on one side of the body does not necessarily mean that the person is having a stroke. There are many other possibilities that can cause these symptoms. Other conditions that can mimic a stroke include: brain tumors, a brain abscess, migraine headache, bleeding in the brain either spontaneously or from trauma, meningitis or encephalitis, an overdose of certain medications, or an imbalance of sodium, calcium, or glucose in the body can also cause changes in the nervous system that can mimic a stroke.
In the acute stroke evaluation, many things will happen 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, getting blood tests, and performing an electrocardiogram. Part of the physical examination is the use of a stroke scale that helps care providers determine the severity of a stroke, and whether aggressive intervention is warranted.
With an acute stroke, there is a narrow time frame to intervene with medications to reverse the loss of blood supply to part of the brain. The patient needs to be properly evaluated and stabilized before any clot-busting drugs can be used.
Computerized tomography: To help find the cause of a suspected stroke, a special x-ray test called a CT scan of the brain is often performed. A CT scan looks for bleeding or masses within the brain; that is a very different situation from a stroke, and it's also treated differently.
MRI scan: Magnetic resonance imaging uses magnetic waves make an image of the brain. The MRI images are much more detailed than those from CT, but this 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 can be done later in the course of patient care if finer details are needed for further making medical decisions. People with metals in their body, like pacemakers, cannot be subjected to the powerful magnetic field of an MRI.
Conventional angiogram: An angiogram is a test that can be used to view the blood vessels. Dye is injected through a long catheter tube which is inserted into an artery. X-rays are taken simultaneously with the injection of the dye. Angiograms provide very detailed images of blood vessels, but it is used only when absolutely necessary since it is an invasive procedure.
Computerized tomography with angiography: A dye is injected into a vein in the arm; with the CT scan, this provides better images of the blood vessels in the brain. This procedure can give information about aneurysms or arteriovenous malformations.
Carotid Doppler ultrasound: A carotid Doppler ultrasound is a non-invasive method that uses sound waves to look for narrowings and decreased blood flow in the carotid artery, which is the major artery in the neck that supplies blood to the brain.
Heart tests: Tests that evaluate heart function may be used to search for the source of an embolism in stroke patients. An echocardiogram is a sound wave test that is done by putting a microphone on the chest or down the esophagus to see the heart chambers.
Blood tests: Blood tests can be done to look for signs of inflammation that can suggest inflamed arteries. Certain blood proteins are measured, because they can increase the chance of stroke by thickening the blood. These tests are done to find treatable causes of a stroke or to help prevent further injury.
What is the treatment of a stroke?
* Tissue plasminogen activator (TPA) - Alteplase (TPA) can be used to dissolve the blood clot that is causing the stroke. This drug has to be used within a short period of time. The earlier that it is given, the better the result and the less potential for the complication of bleeding into the brain. TPA must be given within three hours after the symptoms start. TPA is usually injected into a vein in he arm; if it is dripped directly into the blood vessel that is blocked, it may be given up to six hours after the symptoms start.
* Heparin and aspirin - Blood-thinning drugs are sometimes used to improve the stroke victim's recovery. However, it's not clear whether these drugs improve the outcome from the current stroke or if they just help to prevent subsequent strokes. Aspirin given after the onset of a stroke can have a small, but measurable effect on recovery in some patients.
* Managing other medical problems - Blood pressure and cholesterol must be carefully controlled to prevent future strokes. In an acute stroke, blood pressure will be tightly controlled to prevent further damage. In transient ischemic attacks, the patient may be given medications even if the blood pressure and cholesterol levels are acceptable. In people with diabetes, glucose levels might be high after a stroke. Controlling the glucose level may minimize the size of a stroke. Also, oxygen may be given to stroke patients when necessary.
* Rehabilitation - When a patient is no longer acutely ill, the healthcare staff helps them with rehabilitation. This may include some or all of the following: speech therapy to relearn talking and swallowing; occupational therapy to regain dexterity in the arms and hands; physical therapy to improve strength and walking; and family education to orient them in caring for their loved one at home and the challenges they will face.
The goal of rehabilitation is for the patient to resume their pre-stroke activities and functions as much as possible. Unfortunately, since a stroke involves the permanent loss of brain cells, it is not alway possible for the patient to return to their pre-stroke status.
When a patient goes home, a nurse might come to the home for a while, until the family gets used to caring for the patient. If needed, physical therapy may continue at home. Eventually, the patient is left at home with caregivers. Caring for the patient at home can be easy or almost impossible. Sometimes adequate care cannot be given at home, and it becomes necessary to place the patient in a board and care home or a skilled nursing facility.
What complications can occur after a stroke?
Swallowing can be affected; abnormal swallowing can occur independently of slurred speech, but a stroke that causes slurred speech seems to predispose the patient to abnormal swallowing. If food and saliva goes into the trachea instead of the esophagus, it can lead to pneumonia or a lung infection.
If a patient is immobile for a long time, blood clots can develop in a leg vein. When this happens, there is a risk that the clot might travel upwards and lodge in the lungs; this can be a life-threatening situation. Prolonged immobility can also cause pressure sores (a breakdown of the skin); frequently repositioning the patient can prevent this.
A stroke and a heart attack may occur at the same time or close to each other. Stroke patients often have problems with depression when they are recovering; this needs to be recognized and treated.
While some patients can return to a near-normal condition with minimal awkwardness or speech defects, most are left with permanent problems like weakness on one side of the body, difficulty or the inability to speak, or incontinence of the bowel and/or bladder. Also, a large number of people become unconscious and die after a major stroke.
After a massive stroke, the patient's ability to think or function may be severely reduced. In this case, the family has some very difficult decisions to make. It is sometimes better to limit further medical intervention. The doctor and the patient's family may discuss and implement orders to not resuscitate the patient in the case of a cardiac arrest, since the quality of life for the patient would be very poor. This decision can be made somewhat easier if the patient has made such a request while they were well.
What can be done to prevent a stroke?
Risk factor reduction - High blood pressure: Controlling the risk factors can decrease the chances of having a stroke. The most important risk factor for stroke is high blood pressure; this has to be controlled very carefully.
Smoking: Cigarettes cause the carotid arteries to develop severe atherosclerosis. If this happens, these arteries can close, and the blood flow to the brain can be blocked. Atherosclerosis in general is accelerated by smoking.
Diabetes: Diabetes causes small vessels to close prematurely. When these blood vessels close in the brain, small (lacunar) strokes can occur, so it is important to control blood sugar in diabetic patients. A high level of blood cholesterol is also a risk factor for a stroke, because it will eventually block blood vessels. A healthy diet and medications can help to decrease blood cholesterol levels.
Blood thinner/warfarin: An irregular heart beat can increase the risk of an embolic stroke, where the blood clot travels from the heart, through the bloodstream, and into the brain. Warfarin is a blood thinner that prevents the blood from clotting. Sometimes is also used to prevent the recurrence of a stroke with certain other heart conditions, and conditions in which the blood clots on its own. Patients on warfarin need to know that they are at increased risk for bleeding, and they need to have periodic blood checks to make sure the drug is working properly.
Aspirin and other antiplatelet therapy: These drugs reduce the tendency of the blood to clot in the arteries. People on these medicines have a higher chance of bleeding, but this risk is less than when taking an anticoagulant like warfarin.
Carotid endarterectomy: A TIA or a stroke may be caused by the narrowing of the carotid arteries (the major arteries in the neck that supply blood to the brain). There is an operation called carotid endarterectomy that cleans out the carotid artery and restores blood flow to normal. This procedure will reduce the incidence of a subsequent stroke; this operation may also be performed to prevent a first stroke.
What is in the future for stroke treatment? - There are studies being done on some more drugs that dissolve clots. These drugs are injected into the veins (like TPA) or directly into the clogged artery. There are also tests being done with new medications that help slow the degeneration of nerve cells that are deprived of oxygen.
Stem cells are also being used to try to replace brain cells damaged by a previous stroke; stem cells have the potential to develop into many different organs. There are new therapies being developed for the treatment of stroke victims, but they are not yet perfect and they may not restore complete function.