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Updated 04 August 2011

Stroke

A stroke, also known as a cerebrovascular accident (CVA), occurs when an artery that supplies oxygen-rich blood to the brain bursts or becomes blocked by a blood clot.

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Summary

  • A stroke or brain attack occurs when the blood flow to a certain part of the brain is interrupted or disturbed and brain tissues are starved of oxygen. That part of brain tissue dies and can no longer function.
  • High blood pressure is the leading cause of strokes.
  • About 70% of people who have a stroke remain independent and 10% recover completely.
  • The brain uses 70% of the body’s oxygen, but cannot store it like muscles can. This is why the brain needs a constant supply of blood to work properly.
  • A stroke may occur suddenly or take several hours, and in some cases a few days, to develop.
  • In experienced hands, selected patients will benefit from thrombolytic therapy, if given early.

Description

A stroke, also known as a cerebrovascular accident (CVA), occurs when an artery that supplies oxygen-rich blood to the brain bursts or becomes blocked by a blood clot. Blood clots cause destruction and swelling and often cause immediate severe neurological deficits which, if the patient survives, may substantially improve with time as the blood clot is absorbed. More commonly, if a blood vesel is blocked, cells are deprived of oxygen and die. This is known as an infarction. As a result, the part of the body controlled by those cells can no longer function properly.

Like a heart attack, a stroke requires immediate medical treatment when symptoms are noticed. In some cases, spesific treatment can reduce the number of brain cells that are permanently damaged by the stroke.

The effects of a stroke depend on the extent of the brain damage. The damage may be mild or severe, temporary or permanent. The patient may recover within several days or weeks after the stroke, or may never recover fully. Recovery may continue to occur for months or even years after the stroke. If limb paralysis has not disappeared by five to six months after the stroke, it will probably be permanent. The effects of a stroke also depend on which area of the brain is damaged, the number of cells or size of the area involved and how quickly the blood supply is restored to the region.

Many patients have transient ischaemic attacks (TIAs) well before the actual stroke occurs. These are short periods of reduced blood flow in an artery to the brain, which cause spells of loss of function of the region of brain supplied by that artery, but which are reversible. This temporary neurological change, for example weakness or loss of co-ordination, lasts about 5 to 30 minutes and leaves no permanent damage. However, TIAs are warnings of an impending stroke and must be taken seriously.

Type of strokes

  • Ischaemic, thrombotic or clot stroke: An ischaemic stroke usually affects the cerebral hemispheres, the area of the brain that governs movement, language and the senses. Only 20% of people who have this type of stroke will die.
  • Haemorrhagic or bleeding stroke: This type of stroke is less common than an ischaemic stroke, but more deadly – it accounts for about 50% of deaths from strokes.

Cause

  • Ischaemic stroke (infarction)
  • Haemmorrhagic stroke (bleed)

Ischaemic stroke

  • Atherosclerosis or hardening and narrowing of the arteries causes an ischaemic stroke. A blood clot (thrombus) forms in such a narrowed artery and obstructs the flow of blood to a part of the brain. However, unlike disease of the vessels of the heart (the coronary arteries), atherosclerosis of vessels of the brain itself is not very common.
  • The commonest cause of ischaemic stroke (infarction) is a blood clot formed in another part of the body, usually the large blood vessel in the neck (the carotids), the aortic arch, or the heart. This clot (embolus) breaks loose and travels in the blood stream until it blocks an artery that supplies blood to the brain. This is probably the commonest cause of major stroke
  • Very commonly, chronic hypertension leads to changes in the walls of small blood vessels which supply the deep parts of the cerebral hemispheres. These may sometimes block and cause small strokes, with variable results (may clear rapidly or there may be permanent weakness).

Haemorrhagic stroke

  • A haemorrhagic stroke occurs when an artery inside the brain suddenly starts bleeding (cerebral haemorrhage).
  • This type of stroke can also occur when an artery in the surrounding tissues on the surface of the brain starts to bleed (subarachnoid haemorrhage).
  • The usual cause of subarachnoid haemorrhage is that an artery with a weak point in its wall blows this out to form a balloon- or bubble-like swelling (an aneurysm), which eventually ruptures.
  • However, high blood pressure or hypertension (over 140/90 mm Hg) is the most common cause of the bleeding into the brain. The constant force of uncontrolled raised blood pressure weakens the walls of blood vessels to a point when the artery is torn open and bleeds.

Symptoms

In some cases almost the only recognisable sign of an oncoming stroke is a transient ischaemic attack (TIA).
Symptoms may develop suddenly or progress over time. Typically, bleeds into the brain may cause a very severe deficity, with immediate decrease in level of consciousness. Ischaemic strokes (infarctions) tend to be less severe, but there is considerable overlap in the nature of the neurological deficit between.

The symptoms may include the following:

  • Sudden numbness and tingling of the face or limbs
  • Weakness or paralysis of one side of the body (face, arm and leg)
  • Drooling as a result of weakened facial muscles
  • Sudden changes in vision, such as double vision, dimness, blurring or blindness in one or both eyes (usually the result of a stroke affecting the base of the brain)
  • Difficulty with walking or standing, or inability to do either
  • Difficulty with speaking or with speech comprehension, or inability to speak or understand speech
  • Loss of balance, clumsiness
  • Confusion and personality changes, problems with judgement
  • Difficulty with performing everyday tasks, such as eating and getting dressed
  • Sudden nausea or vomiting
  • A severe headache with any of the above symptoms, quickly followed by loss of consciousness with weakness of one side of the body (bleeding or haemorrhagic stroke)
  • A sudden, severe headache and stiff neck occurring out of the blue, often followed by change in consciousness or unconsciousness (subarachnoid haemorrhage)

Prevalence

  • About one percent of the population is affected by stroke.
  • About 75% of people who have a stroke are older than 65 years. It seldom occurs below 40 years.
  • Up to the age of 55 years, men are more at risk of a stroke than women. After this age, both sexes have the same risk. Black men are more at risk than men of other races.

Course

Brain cells become damaged after just over four minutes without oxygen. Damaged and dying cells surround the stroke area and more cells may become damaged and die during the hours that follow.

The body tries to restore oxygen supply to damaged cells by enlarging other arteries close to the stroke area. This is easier if a large artery has been blocked, but if the blockage occurred in a smaller artery of the brain, the body may not be able to restore oxygen supply to the affected area in time. If the blood supply to the damaged cells is not restored within four to six hours, brain cells will die.

The body parts that the damaged cells control will no longer be able to function. Depending on the location and extent of the damage, and the delay before the blood supply could be restored, the loss of function may be mild or severe, temporary or permanent.

A person’s recovery from a stroke also depends on these factors. The chances of regaining your abilities are best in the first few months after a stroke. Many people who have had a stroke have permanent neurological problems, such as hemiplegia (weakness on one side of the body), aphasia (difficulty with speaking or inability to speak) or incontinence (inability to control the bowel and bladder). Approximately 50% of people who have suffered a stroke will have long-term problems with functions such as talking, understanding and making decisions. Some may also have behavioural problems. Such long-term effects of a stroke may be visible immediately after the stroke or only months or years afterwards.

Risk factors

Some risk factors can be controlled and managed, others not.

Controllable risk factors

  • High blood pressure: It is estimated that approximately 40% of strokes can be attributed to high blood pressure (hypertension). Apart from the increased risk of bleeding, the walls of arteries that have been weakened by continuous high blood pressure are more susceptible to atherosclerosis. This is the build-up of a plaque of fatty deposits in the arteries. Diet, exercise and weight loss are the first steps in controlling high blood pressure.
  • Smoking: A smoker has a 50% greater chance of suffering a stroke, because smoking encourages the build-up of a plaque of fatty deposits in the arteries. Smoking also makes the blood clot faster and, because the nicotine in tobacco constricts arteries, it increases the heart rate and blood pressure, making the smoker’s heart work much harder than non-smokers’ hearts do. Only after smokers have stopped smoking for 10 years does their risk of having a stroke become reduced to equal that of non-smokers.
  • Cardiovascular disease: Several heart conditions increase a person’s risk of having a stroke, because the heart does not pump blood efficiently enough, which leads to pooling and clotting of the blood. These conditions include a previous heart attack causing congestive heart failure, heart-valve disease and irregular, rapid heartbeat (such as atrial fibrillation).
  • Transient ischaemic attack: Although a TIA lasts only a few minutes and leaves no permanent damage, between 15 and 20% of people who have a stroke previously had one or more TIAs.
  • Diabetes: This chronic disease doubles a sufferer’s risk of having a stroke because it increases the severity of atherosclerosis. Diabetes also interferes with the breakdown of a blood protein called fibrin, which forms and holds blood clots together.
  • Obesity
  • Use of stimulant drugs (amphetamines and cocaine)
  • High levels of low-density lipoprotein (LDL) cholesterol: High LDL cholesterol levels increase the risk of atherosclerosis.
  • Polycythaemia (high levels of red blood cells)
  • Other causes: Damage to arteries, blood conditions such as sickle cell anaemia and migraines increase stroke risk. Women who get migraines, smoke and take oral contraceptives have an increased risk of having a stroke, although stroke caused by migraine is extremely rare.

Uncontrollable risk factors

  • Age: The older you get, the greater the risk of having a stroke. About 75% of all people who have a stroke are older than 65 years.
  • Family history is another factor that cannot be changed; the risk of having a stroke is greater if a family member has had a stroke or TIA of any cause.

When to see a doctor

  • If any stroke symptoms appear.
  • If you think that you have previously had a transient ischaemic attack, but did not consult your doctor at the time.
  • If a TIA occurs – this requires immediate medical attention because, when symptoms begin, it is difficult to determine whether they are due to such an attack or to a developing full stroke.

Diagnosis

A stroke is often a medical emergency, as immediate medical care and treatment may be necessary to prevent life-threatening complications.

A doctor should confirm that the person has had a stroke, where it is located and to what extent the brain was damaged. These tests must be done as soon as possible, as immediate treatment can limit the extent of the neurological damage in a few patients. The diagnosis of stroke is not difficult: particularly in the setting of a patient with multiple risk factors such as diabetes or hypertension, sudden onset of weakness of one side of the body or sudden change in sensation of one side of the body are highly likely to be due to a stroke.

The practitioner first takes a medical history (if possible). The initial physical examination includes checking the blood vessels in the eyes for signs of atherosclerosis, and listening for unusual noises in the heart and in the prominent neck arteries. The doctor or specialist also measures the patient’s blood pressure and tests for strength, sensation and neurological reflexes.

To help determine the cause of the stroke, the doctor will have several other tests done, including a chest X-ray, an electrocardiogram, and a magnetic resonance imaging (MRI) scan or computerised axial tomography (CAT) scan. MRI uses magnetic fields to produce an image that provides information about the structure and biochemistry of the brain. CAT produces images of the brain by computer-analysed X-rays, which show structures or variations in the density of different types of tissue. These investigations help determine whether symptoms are the result of a stroke or some other brain disorder. CAT scan is cheaper and is usually the most appropriate test: intravenous contrast material should usually not be administered

The doctor may also ask for other laboratory tests to be done, to determine whether other conditions are present. Other diagnostic tests may include:

  • Sonar of carotid arteries in the neck
  • In highly selected cases, arteriography of the arteries supplying the brain, namely the carotid and vertebral arteries
  • Other blood tests, such as full blood count, electrolytes, serum cholesterol

Treatment

Hospitalisation

  • Many patients who have suffered a stroke may need to be hospitalised immediately.
  • Fluids are administered intravenously to prevent dehydration.
  • Patients undergo physiotherapy to prevent pneumonia.
  • Patients are turned regularly and repositioned in bed, and given skin care to prevent bedsores.
  • Rehabilitation is started in hospital.
  • Sometimes emergency neurosurgery is necessary to remove blood clots or to repair a ruptured aneurysm.

Specialised treatment

  • The time of the onset of a stroke to entry into an assessment and treatment protocol should be reduced. Avoid wasting time.
  • Cardiac valvular lesions, epilepsy, meningitis, encephalitis, bacterial endocarditis, cerebral abscess, vasculitis, alcoholism, drug abuse, neurofibromatosis and tuberous sclerosis need to be excluded.
  • By means of neurological investigation, identification of either a carotid artery or vertebral-basilar stroke pattern needs to be determined as management is different. Prognostication is possible by this approach.
  • Selected patients with non-haemorrhagic ischaemic infarcts respond to r-TPA (intravenous thrombolytic therapy) given by experts in the field. Hypertension must be carefully managed to prevent hemorrhagic transformation in the stroke region. Ask your health caregiver about this option. Only about 10% of patients with stroke will be able to receive such a treatment, which should be given in a dedicated stroke unit. Major contra-indications to giving TPA include uncontrolled hypertension, large strokes and drowsiness.
  • Modern transthoracic echocardiography (ultrasound) is effective in identifying intracardiac thrombi, valve vegetations, valvular stenosis or insufficiency. Trans-oesophageal echocardiography may also be needed to evaluate the left atrium (heart chamber) for the presence of clots. These conditions need separate specialised heart treatment to prevent recurrent stroke due to thrombi that dislodge from the heart into the cerebral circulation.
  • Aspirin in pharmacological dosis reduces the incidence of stroke and death in susceptible persons. Ticlopidine is a new alternative to aspirin for stroke prophylaxis (prevention). Side-effects, such as bleeding, need consideration. In general use of anticoagulants such as warfarin is not useful unless there is a clear indication such as atrial fibrillation associated with risk factors for stroke.
  • Atherosclerotic narrowing of the carotid (neck) arteries is an important cause of stroke. Narrowing may be graded as mild, moderate or severe. The degree is determined by duplex doppler ultrasound testing. Patients with a high-grade stenosis (narrowing) of between 70-99% are at risk of stroke. One or both carotid arteries (i.e. on both sides of the neck) may be partially or completely occluded (shut by clot). There is no affective surgical treatment if the carotid artery is completely blocked. Patients with symptomatic high-grade stenosis or recent transient ischaemic attacks (TIA) will benefit from vascular surgery. This means that the narrowed segment is widened surgically by an operation termed carotid endarterectomy. This procedure, in selected patients, is effective in reducing the risk of further strokes, but the procedure itself is associated with risk of death and stroke, although both are relatively rare. This aspect must be considered when giving informed consent for the operative intervention. In specialised units, carotid stent angioplasty, may be an alternative treatment to carotid endarterectomy. However, the precise role for stenting is unclear, and research trials are underway to obtain more information
  • Patients with cerebral ischaemia due to recurrent cardiogenic and embolic strokes (originating from the heart) need anticoagulation, in the form of warfarin.
  • Oral contaceptives: estrogen increases the risk of clotting, and estrogen-containing oral contraceptives should be discontinued in women who have had a stroke.
  • Consideration to modifiable stroke risk factors is important. Special care should de directed at diabetes (control), hypertension (pressure levels), atrial fibrillation and hyperlipidaemia (need cholesterol lowering statins and Mediterranean-type diet). Statins act independantly to reduce the risk of stroke, and patients with TIAs or strokes should receive a statin and 150 mg of aspirin daily unless contraindicated.
  • Stroke following aneurysmal subarachnoidal haemorrhage, has an acute mortality rate of 50%, and a recurrence rate of 50% in the first six months. Identification and treatment of cerebral aneurysms are important.

Rehabilitation

  • When the patient leaves the hospital, recovery and prevention of further strokes are discussed. This includes changes in diet and lifestyle, ongoing drug treatment and possible surgery.
  • People who are at risk of bleeding strokes will be advised to keep a check on their blood pressure. If high blood pressure caused the stroke, the patient will have to continue taking medication to control high blood pressure.
  • Rehabilitation is an important aspect of stroke treatment. It is aimed at enhancing the brain’s efforts to recover and helping people resume as many as possible of their pre-stroke activities. Rehabilitation may involve physical, occupational and speech therapy. The success of rehabilitation depends on the support of family and caregivers. Although rehabilitation has a lot to offer stroke victims, it should not raise unrealistic expectations of a full return to the state of health they had before.
  • A factor that enhances the success of rehabilitation is gentle but regular aerobic exercise, such as swimming.
  • Stroke victims often feel depressed and angry. Psychological care can help them cope and increase their tolerance to disability.

Prevention

Controlling the risk factors that can be managed is the first step in preventing a stroke. These precautionary measures include those that should be followed to prevent a heart attack:

  • Follow a healthy diet low in salt, fat and cholesterol.
  • Don't smoke.
  • Control your weight, so it is normal for your height and build.
  • Exercise regularly.
  • Monitor your blood pressure regularly and have regular blood tests for cholesterol.
  • Women who are at high risk should not use birth-control pills.
  • Patients who have had a stroke should drink moderately – in other words, have no more than one alcoholic drink a day.
  • Maintain strict control of blood sugar in persons with diabetes mellitus.
  • Daily intake of low-dose aspirin and statins can prevent strokes.
  • High risk patients with hyperlipidaemia need cholesterol-lowering statin therapy in conjunction with a low fat diet.

Reviewed by Dr J. Carr, FCP(SA) Neurology, MSc(Med)

 
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