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STROKE


A stroke, known medically as a cerebrovascular accident (CVA), is the rapidly developing loss of brain function(s) due to disturbance in the blood supply to the brain. This can be due to ischemia (lack of blood flow) caused by blockage (thrombosis, arterial embolism), or a hemorrhage (leakage of blood).


As a result, the affected area of the brain is unable to function, leading to inability to move one or more limbs on one side of the body, inability to understand or formulate speech, or an inability to see one side of the visual field.


A stroke is a medical emergency and can cause permanent neurological damage, complications, and even death. It is the leading cause of adult disability in the United States and Europe and it is the number two cause of death worldwide.Risk factors for stroke include advanced age, hypertension (high blood pressure), previous stroke or transient ischemic attack (TIA), diabetes, high cholesterol, cigarette smoking and atrial fibrillation. High blood pressure is the most important modifiable risk factor of stroke.


A stroke is occasionally treated in a hospital with thrombolysis (also known as a “clot buster”). Post-stroke prevention may involve the administration of antiplatelet drugs such as aspirin and dipyridamole, control and reduction of hypertension, the use of statins, and in selected patients with carotid endarterectomy, the use of anticoagulants.


Treatment to recover any lost function is stroke rehabilitation, involving health professions such as speech and language therapy, physical therapy and occupational therapy. Stroke symptoms usually come on suddenly, and should always be treated as a medical emergency.


They include a sudden onset of any of the following:

  • Weakness of the face, arm, and/or leg on one side of body

  • Numbness in the face, arm, and/or leg one side of body

  • Inability to understand spoken language

  • Inability to speakInability to write

  • Vertigo and/or gait imbalance

  • Double vision

  • An unusually severe headache


Why do stroke symptoms start so suddenly?

The symptoms of stroke begin suddenly because they are caused by an abrupt interruption of blood flow to an area of the brain. When this happens it only takes a few seconds for that part of the brain to stop functioning.


What causes a stroke?

Blockage of an arteryThe 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

  • 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. An embolism can also originate in a large artery (for example, the carotid artery, a major artery in the neck that supplies blood to the brain) and then travel downstream to clog a small artery within the brain.


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 hemorrhageIn 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. Some migraine headache episodes can even mimic stroke with loss of function of one side of the body or vision or speech problems. Usually, the symptoms resolve as the headache resolves.


Causes and Risk Factors of Stroke

There are two broad categories of strokes, called ischemic stroke or hemorrhagic stroke. Ischemic stroke is caused by a blockage of a blood vessel in the brain or neck. This stroke can stem from three different conditions: thrombosis, embolism or stenosis: Thrombosis (cerebral thrombosis) is the formation of a clot within a blood vessel of the brain or neck and is usually caused by atherosclerotic plaque build-up.


Embolism (cerebral embolism) is the movement of a clot from another part of body to the brain or neck. These clots can form on artificial valves in the heart, on atherosclerotic plaques in aorta or caused from a condition called atrial fibrillation. Atrial fibrillation is an irregular heartbeat whereby the upper chamber of the heart quivers rapidly rather than beats. Because this quivering motion is not forceful enough to send all the blood to the heart’s lower chambers, the blood pools, thus allowing clots to develop.


Stenosis is a severe narrowing of an artery in or leading to the brain. Roughly 2/3 of all strokes are caused by clots.


Hemorrhagic stroke is the bleeding into the brain or the spaces surrounding the brain which is caused by a number of disorders that affect the blood vessels (i.e., high blood pressure and cerebral aneurysm).


There are two types of hemorrhagic stroke:subarachnoid intracerebral. Ubarachnoid hemorrhage is caused by the rupture of a blood vessel on the surface of the brain so that blood fills the space between the brain and the skull.


An intracerebral hemorrhage is caused by the rupture of a blood vessel within the brain itself. Some factors that increase the risk of stroke are genetically determined, others are simply a function of natural processes, and still others result from a person’s lifestyle. The factors resulting from heredity or natural processes can’t be changed, but those that are environmental can be modified with a doctor’s help.


There are five uncontrollable risk factors:

  • Age – your chances of having a stroke go up as you get older. Two-thirds of all strokes happen to people over age 65. Your stroke risk doubles with each decade past age 55.

  • Sex – males have a slightly higher risk than females.

  • Race – American blacks have a higher stroke risk than most other racial groups.Family history of diabetes.

  • Family history of stroke or TIA (transient ischemic attack).


There are two basic controllable risk factors:

Treatable medical disorders – includes diabetes, atrial fibrillation, heart attack, high blood pressure, high cholesterol, carotid artery disease, heart disease, personal history of stroke or TIA and patent foramen ovale (PFO). PFO is an abnormal opening between the right and left sides of the heart.


Lifestyle factors – includes smoking, drinking too much, obesity, drug abuse (especially cocaine), physical inactivity and low estrogen.


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. 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. TPA may reverse stroke symptoms in more than one-third of patients, but may also cause bleeding in 6% patients, potentially making the stroke worse.


For posterior circulation strokes that involve the vertebrobasilar system, the time frame for treatment with TPA may be extended even further to 18 hours. 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 (see below). In certain patients, aspirin given after the onset of a stroke does have a small, but measurable effect on recovery. The treating doctor will determine the medications to be used based upon a patient’s specific needs. 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; and4. 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. Depending upon the severity of the stroke, some patients are transferred from the acute care hospital setting to a skilled nursing facility to be monitored and continue physical and occupational therapy. Many times, home health providers can assess the home living situation and make recommendations to ease the transition home.


Unfortunately, some stroke patients have such significant nursing needs that they cannot be met by relatives and friends and long-term nursing home care may be required. Prevention of Stroke


Strokes may be prevented by lowering your blood pressure, quitting smoking, beginning or increasing exercise, controlling medical problems with medications (i.e., atrial fibrillation requires anticoagulants), maintaining optimal weight, and eating a diet high in fruits and vegetables.


If you have a blocked carotid artery your doctor may suggest a carotid endarterectomy to remove the fatty deposits.

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