Stroke or cerebrovascular accident (CVA) is the clinical designation for a rapidly developing loss of brain function due to an interruption in the blood supply to all or part of the brain. This phenomenon can be caused by thrombosis, embolism, or haemorrhage.

Stroke is a medical emergency and can cause permanent neurological damage and death if not promptly diagnosed and treated. It is the third leading cause of death and the leading cause of adult disability in Europe and the United States. It is predicted that it will soon become the leading cause of death worldwide.

The symptoms of stroke, can be quite diverse, and patients with the same cause can have widely differing short and long term effects. Conversely, patients with the same clinical effects can in fact have different underlying causes.

The cause of stroke is an interruption in the blood supply, with a resulting depletion of oxygen and glucose in the affected area. This immediately reduces or abolishes neuronal function, and also initiates an ischemic cascade which causes neurons to die or be seriously damaged, further impairing brain function.

Risk factors include advanced age, hypertension (high blood pressure), previous stroke or TIA (transient ischaemic attack), diabetes mellitus, high cholesterol, cigarette smoking, atrial fibrillation, migraine with aura, and thrombophilia. In clinical practice, blood pressure is the most important modifiable risk factor; however many other risk factors, such as cigarette smoking cessation and treatment of atrial fibrillation with anticoagulant drugs, are important.

The traditional definition of stroke, devised by the World Health Organisation in the 1970s, is of a 'neurological deficit of cerebrovascular cause that persists beyond 24 hours or is interrupted by death within 24 hours'. This definition was largely devised for the purpose of research and the time frame of 24 hours appears purely arbitrarily chosen as a cut-off point. It divides stroke from TIA (or 'mini-stroke'), which is the same as above but completely resolves clinically within 24 hours. The division of the two into separate clinical entities is considered impractical and even unhelpful in practice by many doctors. The main reason for this is the fact that stroke and TIA are caused by the same disease process, and both persons who have suffered either are at a higher risk of a subsequent attack.

In recognition of this, and improved methods for the treatment, the term "brain attack" is being promoted in the Western World as a substitute for stroke or TIA. The new term makes an analogy with "heart attack" (myocardial infarction), because in both conditions, an interruption of blood supply causes death of tissue that is highly time dependent ('time is brain') and potentially life-threatening. Many hospitals have "brain attack" teams within their neurology departments specifically for swift treatment.


Types of Stroke

Strokes can be classified into two major categories: ischaemic and haemorrhagic. Ischaemia can be due to thrombosis, embolism, or systemic hypoperfusion. Haemorrhage can be due to intracerebral haemorrhage, subarachnoid haemorrhage, subdural haemorrhage, or epidural haemorrhage. ~80% of strokes are due to ischaemia.


Ischaemic Stroke

In an ischaemic stroke (approximately 80% of strokes), a blood vessel becomes occluded and the blood supply to part of the brain is totally or partially blocked. Ischaemic stroke is commonly divided into thrombotic, embolic, systemic hypoperfusion (Watershed or Border Zone Stroke), or venous thrombosis. Cocaine abuse doubles the risk of ischaemic strokes


Thrombotic stroke

In thrombotic stroke, a thrombus-forming process develops in the affected artery. The thrombus — a built-up clot — gradually narrows the lumen of the artery and impedes blood flow to distal tissue. These clots usually form around atherosclerotic plaques. Since blockage of the artery is gradual, onset of symptomatic thrombotic strokes is slower. A thrombus itself (even if non-occluding) can lead to an embolic stroke (see below) if the thrombus breaks off—at which point it is then called an "embolus."


Embolic Stroke

Embolic stroke refers to the blockage of arterial access to a part of the brain by an embolus—a traveling particle or debris in the arterial bloodstream originating from elsewhere. An embolus is most frequently a blood clot, but it can also be a plaque broken off from an atherosclerotic blood vessel or a number of other substances including fat (e.g., from bone marrow in a broken bone), air, and even cancerous cells. Another cause is bacterial emboli released in infectious endocarditis.

Because an embolus arises from elsewhere, local therapy only solves the problem temporarily. Thus, the source of the embolus must be identified. Because the embolic blockage is sudden in onset, symptoms usually are maximal at start. Also, symptoms may be transient as the embolus moves to a different location or dissipates altogether. Embolic stroke can be divided into four categories:

- those with known cardiac source
- those with potential cardiac or aortic source
- those with an arterial source
- those with unknown source


Systemic hypoperfusion (Watershed stroke)

Systemic hypoperfusion is the reduction of blood flow to all parts of the body. It is most commonly due to cardiac pump failure from cardiac arrest or arrhythmias, or from reduced cardiac output as a result of myocardial infarction, pulmonary embolism, pericardial effusion, or bleeding. Hypoxemia (low blood oxygen content) may precipitate the hypoperfusion. Because the reduction in blood flow is global, all parts of the brain may be affected, especially "watershed" areas --- border zone regions supplied by the major cerebral arteries. Blood flow to these areas does not necessarily stop, but instead it may lessen to the point where brain damage can occur. This phenomenon is also referred to as "last meadow" to point to the fact that in irrigation the last meadow receives the least amount of water.


Haemorrhagic Stroke

A haemorrhagic stroke, or cerebral haemorrhage, is a form of stroke that occurs when a blood vessel in the brain ruptures or bleeds. It interrupts the brain's blood supply because the bleeding vessel can no longer carry the blood to its target tissue. In addition, blood irritates brain tissue, disrupting the delicate chemical balance, and, if the bleeding continues, it can cause increased intracranial pressure which physically impinges on brain tissue and restricts blood flow into the brain. In this respect, haemorrhagic strokes are more dangerous than their more common counterpart, ischaemic strokes. There are two types of haemorrhagic stroke: intracerebral haemorrhage, and subarachnoid haemorrhage. Amphetamine abuse quintuples, and cocaine abuse doubles, the risk.


Signs and symptoms

The symptoms depend on the type of stroke and the area of the brain affected. Ischaemic strokes usually only affect regional areas of the brain perfused by the blocked artery. Haemorrhagic strokes can affect local areas, but often can also cause more global symptoms due to bleeding and increased intracranial pressure.

If the area of the brain affected contains one of the three prominent Central nervous system pathways—the spinothalamic tract, corticospinal tract, and dorsal column (medial lemniscus), symptoms may include:

- hemiplegia and muscle weakness of the face
- numbness
- reduction in sensory or vibratory sensation

In most cases, the symptoms affect only one side of the body. The defect in the brain is usually on the opposite side of the body (depending on which part of the brain is affected). However, the presence of any one of these symptoms does not necessarily suggest a stroke, since these pathways also travel in the spinal cord and any lesion there can also produce these symptoms.

In addition to the above central nervous system pathways, the brainstem also consists of the 12 cranial nerves. A stroke affecting the brainstem therefore can produce symptoms relating to deficits in these cranial nerves:

- altered smell, taste, hearing, or vision (total or partial)
- drooping of eyelid (ptosis) and weakness of ocular muscles
- decreased reflexes: gag, swallow, pupil reactivity to light
- decreased sensation and muscle weakness of the face
- balance problems and nystagmus
- altered breathing and heart rate
- weakness in sternocleidomastoid muscle with inability to turn head to one side
- weakness in tongue (inability to protrude and/or move from side to side)

If the cerebral cortex is involved, the central nervous system pathways can again be affected, but also can produce the following symptoms:

- aphasia (inability to speak or understand language from involvement of Broca's or Wernicke's area)
- apraxia (altered voluntary movements)
- visual field defect
- memory deficits (involvement of temporal lobe)
- hemineglect (involvement of parietal lobe)
- disorganized thinking, confusion, hypersexual gestures (with involvement of frontal lobe)

If the cerebellum is involved, the patient may have the following:

- trouble walking
- altered movement coordination
- vertigo and or disequilibrium

Loss of consciousness, headache, and vomiting usually occurs more often in haemorrhagic stroke than in thrombosis because of the increased intracranial pressure from the leaking blood compressing on the brain.

If symptoms are maximal at onset, the cause is more likely to be a subarachnoid haemorrhage or an embolic stroke.


Diagnosis

Stroke is diagnosed through several techniques: a neurological examination, CT scans (most often without contrast enhancements) or MRI scans, Doppler ultrasound, and arteriography. The diagnosis of stroke itself is clinical, with assistance from the imaging techniques. Imaging techniques also assist in determining the subtypes and cause of stroke. There is yet no commonly used blood test for the stroke diagnosis itself, though blood tests may be of help in finding out the likely cause of stroke

A systematic review found that facial paresis, arm drift, or abnormal speech are the best findings.


Treatment

Early assessment

Early recognition of the signs of stroke is generally regarded as important. Only detailed physical examination and medical imaging provide information on the presence, type, and extent of, and hence hospital attendance — even if the symptoms were brief — is advised.

Studies show that patients treated in hospitals with a dedicated team or unit and a specialized care program for patients have improved odds of recovery.


Treatment of Ischemic Stroke

As an ischemic stroke is due to a thrombus (blood clot) occluding a cerebral artery, a patient is given antiplatelet medication (aspirin, clopidogrel, dipyridamole), or anticoagulant medication (warfarin), dependent on the cause, when this type of stroke has been found. Hemorrhagic stroke must be ruled out with medical imaging, since this therapy would be harmful to patients with that type of stroke.

Whether thrombolysis is performed or not, the following investigations are required:

- Stroke symptoms are documented, often using special scoring systems
- A CT scan is performed to rule out hemorrhagic stroke
- Blood tests, such as a full blood count, coagulation studies, and tests of electrolytes, renal function, liver function tests and glucose levels are carried out.

Other immediate strategies to protect the brain during stroke include ensuring that blood sugar is as normal as possible (such as commencement of an insulin sliding scale in known diabetics), and that the patient is receiving adequate oxygen and intravenous fluids. The patient may be positioned so that his or her head is flat on the stretcher, rather than sitting up, since studies have shown that this increases blood flow to the brain. Additional therapies for ischemic stroke include aspirin, clopidogrel, and combined aspirin and dipyridamole extended release.

It is common for the blood pressure to be elevated immediately following an attack. Studies indicated that while high blood pressure causes stroke, it is actually beneficial in the emergency period to allow better blood flow to the brain.

If studies show carotid stenosis, and the patient has residual function in the affected side, carotid endarterectomy (surgical removal of the stenosis) may decrease the risk of recurrence if performed rapidly after an attack.

If the stroke has been the result of cardiac arrhythmia with cardiogenic emboli, treatment of the arrhythmia and anticoagulation with warfarin or high-dose aspirin may decrease the risk of recurrence.

Another intervention for acute ischemic stroke is removal of the offending thrombus directly (thrombectomy). This is accomplished by inserting a catheter into the femoral artery, directing it up into the cerebral circulation, and deploying a corkscrew-like device to ensnare the clot, which is then withdrawn from the body. A thrombectomy can take place up to 8 hours after onset of symptoms.

If the ischaemic stroke is due to an embolism anticoagulation can prevent recurrent attacks.


Treatment of Haemorrhagic Stroke

Patients with bleeding into (intracerebral hemorrhage) or around the brain (subarachnoid hemorrhage), require neurosurgical evaluation to detect and treat the cause of the bleeding. Anticoagulants and antithrombotics, key in treating ischemic stroke, can make bleeding worse and cannot be used in intracerebral hemorrhage. Patients are monitored and their blood pressure, blood sugar, and oxygenation are kept at optimum levels.


Care and rehabilitation

Stroke rehabilitation is the process by which patients with disabling strokes undergo treatment to help them return to normal life as much as possible by regaining and relearning the skills of everyday living. It also aims to help the survivor understand and adapt to difficulties, prevent secondary complications and educate family members to play a supporting role.

A rehabilitation team is usually multidisciplinary as it involves staff with different skills working together to help the patient. These include nursing staff, physiotherapy, occupational therapy, speech and language therapy, and usually a physician trained in rehabilitation medicine. Some teams may also include psychologists, social workers, and pharmacists since at least one third of the patients manifest post stroke depression.

Good nursing care is fundamental in maintaining skin care, feeding, hydration, positioning, and monitoring vital signs such as temperature, pulse, and blood pressure. Rehabilitation begins almost immediately.

For most patients, physotherapy and occupational therapy are the cornerstones of the rehabilitation process. Often, assistive technology such as a wheelchair, walkers, canes may be beneficial. Physiotherapy and occupational therapy have overlapping areas of working but their main attention fields are; physiotherapy involves re-learning functions as transferring, walking and other gross motor functions. Occupational therapy focusses on exercises and training to help relearn everyday activities known as the Activities of daily living (ADLs) such as eating, drinking, dressing, bathing, cooking, reading and writing, and toileting. Speech and language therapy is appropriate for patients with problems understanding speech or written words, problems forming speech and problems with eating (swallowing).

Patients may have particular problems, such as complete or partial inability to swallow, which can cause swallowed material to pass into the lungs and cause aspiration pneumonia. The condition may improve with time, but in the interim, a nasogastric tube may be inserted, enabling liquid food to be given directly into the stomach. If swallowing is still unsafe after a week, then a percutaneous endoscopic gastrostomy (PEG) tube is passed and this can remain indefinitely.

Stroke rehabilitation should be started as immediately as possible and can last anywhere from a few days to several months. Most return of function is seen in the first few days and weeks, and then improvement falls off after six months, with little chance of further improvement. However, patients have been known to continue to improve for years, regaining and strengthening abilities like writing, walking, running, and talking. Daily rehabilitation exercises should continue to be part of the stroke patient's routine. Complete recovery is unusual but not impossible and most patients will improve to some extent : a correct diet and exercise are known to help the brain to self-recover.


Prognosis

Disability affects 75% of survivors enough to decrease their employability. Stroke can affect patients physically, mentally, emotionally, or a combination of the three. The results of stroke vary widely depending on size and location of the lesion. Dysfunctions correspond to areas in the brain that have been damaged.

Some of the physical disabilities that can result include paralysis, numbness, pressure sores, pneumonia, incontinence, apraxia (inability to perform learned movements), difficulties carrying out daily activities, appetite loss, vision loss, and pain. If the stroke is severe enough, or in a certain location such as parts of the brainstem, coma or death can result.

Emotional problems can result from direct damage to emotional centers in the brain or from frustration and difficulty adapting to new limitations. Post-stroke emotional difficulties include anxiety, panic attacks, flat affect (failure to express emotions), mania, apathy, and psychosis.

30 to 50% of stroke survivors suffer post depression, which is characterized by lethargy, irritability, sleep disturbances, lowered self esteem, and withdrawal. Depression can reduce motivation and worsen outcome, but can be treated with antidepressants.

Emotional lability, another consequence, causes the patient to switch quickly between emotional highs and lows and to express emotions inappropriately, for instance with an excess of laughing or crying with little or no provocation. While these expressions of emotion usually correspond to the patient's actual emotions, a more severe form of emotional lability causes patients to laugh and cry pathologically, without regard to context or emotion. Some patients show the opposite of what they feel, for example crying when they are happy. Emotional lability occurs in about 20% of stroke patients.

Cognitive deficits resulting from stroke include perceptual disorders, speech problems, dementia, and problems with attention and memory. A sufferer may be unaware of his or her own disabilities, a condition called anosognosia. In a condition called hemispatial neglect, a patient is unable to attend to anything on the side of space opposite to the damaged hemisphere.

Up to 10% of all patients develop seizures, most commonly in the week subsequent to the event; the severity of the stroke increases the likelihood of a seizure.


Risk factors and prevention

Prevention of stroke can work at various levels including:

1. primary prevention - the reduction of risk factors across the board, by public health measures such as reducing smoking and the other behaviours that increase risk;
2. secondary prevention - actions taken to reduce the risk in those who already have disease or risk factors that may have been identified through screening; and
3. tertiary prevention - actions taken to reduce the risk of complications (including further strokes) in people who have already had a stroke.

The most important modifiable risk factors are hypertension, heart disease, diabetes, and cigarette smoking. Other risks include heavy alcohol consumption, high blood cholesterol levels, illicit drug use, and genetic or congenital conditions. Family members may have a genetic tendency for an attack or share a lifestyle that contributes to stroke. Having had a stroke in the past greatly increases one's risk of future occurrences.

One of the most significant risk factors is advanced age. 95% of strokes occur in people age 45 and older, and two-thirds occur in those over the age of 65. A person's risk of dying if he or she does have a stroke also increases with age. However, it can occur at any age, including in foetuses.

Sickle cell anemia, which can cause blood cells to clump up and block blood vessels, also increases risk. Stroke is the second leading killer of people under 20 who suffer from sickle-cell anemia.

Men are 1.25 times more likely to suffer strokes than women, yet 60% of deaths occur in women. Since women live longer, they are older on average when they have their strokes and thus more often killed. Some risk factors apply only to women. Primary among these are pregnancy, childbirth, menopause and the treatment thereof (HRT). Stroke seems to run in some families.

Prevention is an important public health concern. Identification of patients with treatable risk factors is paramount. Treatment of risk factors in patients who have already had strokes (secondary prevention) is also very important as they are at high risk of subsequent events compared with those who have never suffered one. Medication or drug therapy is the most common method of prevention. Aspirin (usually at a low dose of 75 mg) is recommended for the primary and secondary prevention of stroke. Treating hypertension, diabetes mellitus, smoking cessation, control of hypercholesterolemia, physical exercise, and avoidance of illicit drugs and excessive alcohol consumption are all recommended ways of reducing the risk of stroke.

In patients who have strokes due to abnormalities of the heart, such as atrial fibrillation, anticoagulation with medications such as warfarin is often necessary for prevention.

Procedures such as carotid endarterectomy or carotid angioplasty can be used to remove significant atherosclerotic narrowing (stenosis) of the carotid artery, which supplies blood to the brain. These procedures have been shown to prevent stroke in certain patients, especially where carotid stenosis leads to ischemic events such as transient iscahemic attack. (The value and role of carotid artery ultrasound scanning in screening has yet to be established.)


Epidemiology

Stroke will soon be the most common cause of death worldwide. It is the third leading cause of death in the Western world, after heart disease and cancer, and causes 10% of world-wide deaths.

The incidence of stroke increases exponentially from 30 years of age, and etiology varies by age.

For further help and information visit our Further Information and Support Groups page and click onThe Stroke Association link.