A stroke, also known as a CerbroVascular Accident (CVA), is an acute injury to brain tissue, resulting from an interruption of blood flow to an area of the brain. If the blood flow can be restored in time, the damage may be completely or partly reversible, or at least limited in extent. The crucial factor here is rapid diagnosis and appropriate treatment,
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The visible effects of a stroke, regardless of the cause, will depend on the area of the brain damaged – both where in the brain, and how large and area – and again, on how quickly blood flow is restored. There may be some immediate improvement of symptoms, with further slow improvement in the months following the stroke.
For some, however, the damage may be permanent: the parts of the body controlled by the damaged cells can no longer function.
A special mention must be made of the “temporary” warning stroke, properly called a Transient Ischaemic Attack, or TIA. Any stroke whose effects are 100% totally reversed within 24 hours, is defined as a TIA. Any TIA is considered a medical emergency. Not only must it be managed as a stroke at that time, but the implications of a TIA are serious : unless correctly managed, there is up to 20% chance that it will recur within 90 days, the next time not as another TIA, but as a full stroke.
Causes
The fundamental cause in any type of stroke is the interruption of blood supply to a part of the brain. However, it is useful to categorise the basic types of stroke, because this helps to identify the underlying cause of the interruption, and thus decide on appropriate treatment.
The basic classification of stroke is:
Ischaemic stroke
(80% of all strokes) are usually due to some form of blockage:
(a) Cerebral artery thrombosis – clots forming in the brain artery
(b) Cerebral artery embolus – a clot or other particle from elsewhere in the body lodges in a brain artery. More than 85% of particles blocking arteries are clots, the rest are usually bits of atheromatous plaque. This is relevant because the treatment for this is highly specialised and must be started quickly to be effective.
(c) Systemic hypoperfusion – this is a general circulatory problem (not common) whose main effects happen to be seen in the brain.
A further classification specifies whether the arteries involved are located inside or outside of the brain, and whether they are large or small vessels. An overview of all these shows that by far the commonest cause of ischaemic stroke is a blood clot of some kind (85%) either forming in the brain artery, or coming from somewhere else.
Very often, there is underlying atherosclerosis of either the brain arteries, or of the other arteries providing the source of the clots. It follows, thus, that the underlying causes contributing to the formation of atherosclerosis will be relevant here too. Often, the source of clots is the heart itself, when clots form inside the heart due to chronic rhythm disturbances such as Atrial Fibrillation. (AF) AF can occur alone or associated with Coronary Artery Disease, or Valve problems.
Heamhorrhagic stroke
A bleed causing a stroke can be:
(a) Intracerebral - inside the brain tissue itself. Here the blood gradually accumulates and compresses surrounding brain tissue more and more until the brain cells actually die. The immediate need here is to stop the bleeding, and identify and treat the cause. Uncontrolled hypertension is a common cause, but bleeding into a tumour, vasculitis, or a bleeding disorder may be involved.
(b) Subarachnoid – here the bleeding is into one of the membranes surrounding the brain. The commonest cause is rupture of an aneurysm ( a blowout) of a brain artery, or a bleed from an abnormal artery.
Symptoms
In some cases almost the only recognisable sign of an oncoming stroke is a transient ischaemic attack (TIA). As described, this is a medical emergency, and prompt treatment can avoid the onset of a severe, permanent stroke.
Stroke symptoms may develop suddenly or progress over time. Ischeamic strokes due to an embolus suddenly blocking an artery produce symptoms with sudden onset, and with maximal defecit at the start.
Bleeds into the brain are a little slower : it may take minutes or hours for the accumulation of blood to compress nearby brain tissue, and cause more and more detectable problems.
A subarachnoid bleed typically has a sudden onset, with (usually) an instant, severe headache, with widespread pain and vomiting. There may be few localising signs, such as arm or leg paralysis.
The symptoms of stroke 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)
Risk factors
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. There is also an increased risk of lipohyalinosis with advancing age.
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.
Controllable risk factors
Hypertension
This is probably the single most important factor in stroke development. Hypertension affects the walls of arteries in several ways:
The wall can become thickened, narrowing the space available for blood flow
The function of the cells lining the artery is compromised
Although thickened, the wall becomes weaker, and can form blowouts – these are called aneurysms
The development of atheroma with cholesterol plaques is hastened
The risk of clot formation within the artery is much increased
Lipohyalinosis can occur – this condition is a buildup of a lipid plus a form of degeneration of the artery. It often affects the small arteries deep inside the brain. Strokes due to this are called “Lacunar infarcts”.
It is clear thus, that strict control of hypertension is an extremely important factor, especially in persons known to be at risk of developing strokes. Managementof hypertension may include lifestyle changes such as weight loss and exercise, plus medical therapy.
Cardiovascular disease
The development of atheroma affects cerebral arteries as well, but it also contributes in other ways.
Atheromatous plaque is the commonest cause of localised narrowing of arteries, especially the larger arteries, which are often the source of emboli blocking brain arteries. High LDL is thus a recognised risk factor.
Atheromatous Coronary Artery Disease (CAD) is the commonest cause of heart attacks, which can also contribute to hypoperfusion at the time of an infarct.
Heart failure as a result of atheromatous disease can lead to sluggish blood flow, with an increased risk of clots forming and lodging in the brain arteries.
Heart rhythm disturbances, notably Atrial Fibrillation (AF), often result from atheromatous disease. This AF is the commonest source of clots in the heart, and a very common cause of stroke.
Other heart problems, such as valve disease and cardiomyopathy are also associated with an increased risk of stroke.
Smoking
This is an established risk factor for stroke, mainly because it promotes atheroma, and increases the clotting ability of blood. Nicotine also causes arteries to constrict, and raises the pulse rate and blood pressure: all these factors combine to increase the workload of the heart and reduce blood flow to the brain.
It is very obvious that stopping smoking is a smart choice.
TIA
As already described, this is medical emergency. Without treatment of underlying causes, there is a 20% recurrence rate within 90 days. Commonly, the follow-up incident is a full-blown stroke, which could have been totally avoidable.
Diabetes
Poorly controlled diabetes increases the rate and severity of atherosclerosis, and promotes blood clotting. It is also associated with obesity and hypertension.
Blood disorders
In general, blood and coagulation disorders are not common primary causes for stroke or TIA, but should be considered in younger persons, ie under the age of 45.
Polycythaemia: This is a condition in which there is an excess of red blood cells : the ensuing hyperviscosity of the blood is a risk for clot formation.
Sickle cell anaemia: this genetically determined abnormality can result in excess clot formation, especially in small vessels.
Clotting disorders: Genetic deficiency of some clotting factors increase the risk of bleeding.
Others
Severe migraines may lead to a stroke in susceptible persons – this is a rare condition.
The use of oral contraceptives, especially in smokers, is associated with an increased risk of stroke.
Use of stimulants, like amphetamines and cocaine.
Diagnosis
A stroke is 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 some 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 is aimed at finding any obvious underlying causes for the stroke, and 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. It is vital to know whether or not the stroke is due to a bleed: if it is, the management is totally different.
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, and usually clearly separates stroke due to bleeds from those due to ischaemia. For best results, intravenous contrast material should not be administered. Further radiologic tests which may be required are decided upon by specialist radiologists.
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 and rehabilitation
The management of stroke has two distinct phases : immediate treatment, and longterm management.
Treatment in the immediate situation is aimed at:
Resuscitation
Diagnosing the type/cause of the stroke
Starting the appropriate treatment
Resuscitation follows the standard pattern of attending to Airways, Breathing, Circulation etc. Once stable, the next urgent step is to determine what type of stroke has occurred, because the treatment differs vastly.
The recognized types of stroke are:
Ischaemic: this may be due to:
(a) cerebral artery thrombosis (clots formed in the artery)
(b) cerebral embolism ( a clot or piece of atheroma from somewhere else in the body lodges in the cerebral artery)
85% are due to clots of some form, and these qualify for special treatment.
Haemhorragic: this means a bleed into tissues, usually due to a ruptured vessel
(c) Intracerebral bleed ( into the brain tissue)
(d) Subarachnoid bleed ( into the membranes around the brain)
It is also important to localise where in the brain the stoke has happened, and to assess the severity : both of these factors are relevant to the management and outcome of the stroke. The level of consciousness and severity are assessed clinically according to accepted criteria, eg on the Glasgow scale.
Immediate treatment
The most important factor here is time: any suspected stroke victim must receive emergency attention, preferably at an Emergency Casualty where they can be admitted.
Speed is necessary because clot-dissolving treatment will be successful only if used within 3 hours of the onset of symptoms. Also, reversible risk factors, such as extreme hypertension, if identified and treated early enough, can limit the extent of damage to the brain tissues.
Basic resuscitation, including attention to airways, fluid requirements etc must be given. In some cases, it may be necessary to insert a breathing tube, and use a ventilator. Once the patient is stable, appropriate investigation is begun to determine the type and cause of the stroke.
Most important is a non-contrast CT scan : this will identify whether or not the stroke is due to a bleed. There are other more sophisticated techniques available eg MRI scans, or even cerebral angiograms, and the choice of technique will be made by the specialist involved.
Further treatment will depend on the cause : eg if there is a bleed in the membranes or a ruptured brain artery (aneurysm) surgery may be needed. Whilst treatment is begun, bedridden patients are given physiotherapy to prevent lung complications and muscle contractures, and are also turned regularly to prevent bedsores and infections.
Specialised treatment
Once the site, severity and underlying contributing causes have been identified, specialised treatment aimed at dealing with these can be started. Any identified risk factors must be dealt with.
If the patient has a non-haemhorragic stroke and meets certain criteria, s/he may be a candidate for thrombolytic (clot-busting) therapy. Usually about 10% of patients will qualify for this treatment, which is administered only by specialists, preferably in a stroke unit, because of the significant risks involved.
Ischaemic stroke is most commonly due to the blocking off of a cerebral artery by a clot from elsewhere, so the source of this must be found and dealt with.
Cardiac problems
Many heart problems are possible sources of clots leading to stroke, and these must be identified and treated. A very useful investigation is an echocardiogram, which is a form of ultrasound. This can be done externally, with a probe placed on the chest wall, or internally, using a Trans Esophageal Echo (TEE).
The TEE consists of a specialised tiny probe which is inserted into the patient’s esophagus or stomach, much like “swallowing the camera” for a gastroscopy. This probe then lies directly behind the heart, and provides very clear and accurate information about heart function, as well as clear pictures of the chambers and valves.
Heart problems associated with stroke include:
Valve abnormalities
Endocarditis – infection of the abnormal valve
Rhythm disturbances - often associated with valve lesions, and predisposing to the formation of clots within the heart.
Heart problems associated with stroke require specialist treatment, and should thus be managed by a cardiologist. Eg. some rhythm disturbances will require anticoagulation with Warfarin, but this may pose a great risk (of brain bleeding) to a patient who has already had a stroke.
Carotid artery disease
Narrowing of the neck arteries (carotids) due to atheroma is a common cause of stroke. One or both arteries may be affected, and the narrowing may be partial or complete. Often, the patient’s symptoms will suggest carotid disease as a cause of the stroke, or s/he may have had previous Transient Ischeamic attacks (TIAs).
A simple ultrasound of the neck arteries will make the diagnosis, whilst an angiogram can provide incontrovertible proof of the degree of obstruction. Treatment of this condition is aimed at opening the narrowing and keeping it open, to restore proper blood flow to the brain.
Surgery can be done to widen the narrowed section : this is a risky procedure, and should only be done by experienced vascular surgeons.
An alternative nowadays is that of carotid Stenting. In this procedure, a catheter is threaded into the narrow section of the artery, and, when in position, a balloon is inflated to stretch open the narrowed part. Once dilated to normal size, a stent (a dilatable metal mesh tube) is inserted to keep the artery open.
This is the same procedure used for stents in the heart arteries. This procedure also has its risks, and is done only by cardiologists in a specially equipped catheterisation theatre.
Heamorrhagic stroke
The commonest cause for a bleed within the brain (Intracerebral) is uncontrolled hypertension: the obvious treatment is thus to lower and keep under control,the blood pressure.
Bleeding into the membranes around the brain (Subarachnoid bleeds) are usually due to rupture of small aneurysms (little blowouts of the artery wall, like a weak car tyre) near the base of the brain, or to bleeds from abnormal vessels on the surface of the brain’s membrane.
Once identified, surgery may be needed to stop the bleed and prevent recurrences. Investigations may show other abnormal arteries also needing to be sealed off before they rupture. Some success has been had with catheter embolisation, in which a catheter is threaded into the artery concerned, and the artery is then sealed from within – almost like glueing it shut from inside.
Both surgery and catheter ablation are risky procedures, and only undertaken by experienced specialists at well-equiped centres.
Other factors
Other unusual causes of stroke, such as vasculitis and neurofibromatosis will need managing, but may be less successful. Anticoagulants such as Warfarin are only of use when there is a clear indication, eg atrial fibrillation associated with stroke.
Modifiable risk factors must be dealt with, and carefully controlled:
If risk factors are not treated, many patients with an established stroke will have a second, usually fatal, stroke within a few months of the first one.
The important conditions which can be treated are:
TIAs
Hypertension
Diabetes
Cardiovascular disease of all types
Hypercholesterolaemia
Heart rhythm disturbances
Smoking
Use of oral contraceptives
Obesity
Sickle cell anaemia and migraines
Rehabilitation
Rehabilitation has two aims:
Restoring function to as near normal as possible (ie to pre-stroke abilities)
Preventing further strokes.
Restoring function begins immediately after admission at the time of the stroke. Physiotherapy, including passive exercise, is used to keep muscles supple. Also, as soon as the patient can cooperate, gentle exercise is begun to improve residual function, and possibly learn new techniques to make up for lost abilities.
Occupational and speech therapy are important, and should also be started as soon as possible. Recovery can be a very slow process, and many patients never return to their pre-stroke levels. Patients and their families must therefore be fully informed about the prospects in a realistic way.
An important aspect of rehabilitation is the psychological impact on the patient and the family. Apart from the expected, and normal, reaction to becoming suddenly physically disabled to some degree, stroke victims may be left with a range of emotional problems such as : uncontrollable crying, severe depression, inappropriate responses, lack of awareness of their physical disabilities, or even complete lack of awareness of the half of their body affected by the stroke.
This can be a management problem for caregivers, who are usually family members, so they have a double burden. – physical and psychological care. Support groups for stroke victims and their care-givers can be of value here. Community resources are important, and a social worker may be helpful in organizing access to these.
An often forgotten aspect of stroke management is the fact that some conditions or risk factors have a familial tendancy. If such factors are identified – eg hypercholesterolaemia – other family members should be informed, and encouraged to go for testing.
Preventing further strokes is accomplished by careful attention to underlying risk factors, as outlined in the section on treatment.
Prevention of stroke
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, keepingso 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 A.G. Hall (B.Soc.Sc.(SW), MB,Ch.B)
Last updated: 2008/02/08
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