Cerebrovascular accident
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A stroke or cerebrovascular accident (CVA) occurs when the blood supply to a part of the brain is suddenly interrupted by occlusion (an ischemic stroke- approximately 90% of strokes), by hemorrhage (a hemorrhagic stroke - less than 10% of strokes) or other causes. Ischemia is a reduction of blood flow most commonly due to occlusion (an obstruction). On the other hand, hemorrhagic stroke (or intracranial hemorrhage), occurs when a blood vessel in the brain bursts, spilling blood into the spaces surrounding the brain cells or when a cerebral aneurysm ruptures. A small proportion of strokes are watershed strokes caused by hypoperfusion (usually due to hypotension) or other vascular problems including vasculitis.
A stroke is a medical emergency. It generally presents with loss of function of the area of the body controlled by the affected part of the brain, e.g. hemiplegia, loss of speech or vision, impaired swallowing reflex or altered sensation. The immediate and long-term results lead to marked morbidity and mortality.
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Causes
Ischemic stroke
Ischemic stroke is usually caused by atherosclerosis (fatty lumps in the artery wall), embolism (obstruction of blood vessels by blood clots from elsewhere in the body), or microangiopathy (small artery disease, the occlusion of small cerebral vessels).
Risk factors (for atherosclerosis and small vessel disease) are age, hypertension (high blood pressure), diabetes mellitus, elevated cholesterol levels and cigarette smoking. High blood pressure is the most important modifiable risk factor of stroke. Atrial fibrillation and other arrhythmias can lead to clot formation in the heart, which embolize to the brain. Some forms of thrombophilia (increased coagulation tendency) have a predilection for arterial thrombosis and stroke; these include polycythemia vera and the rare paroxysmal nocturnal hemoglobinuria. Sickle cell anemia predisposes to strokes.
Hemorrhagic stroke
High blood pressure also predisposes to cerebral bleeding. Other causes include arteriovenous malformation (cerebral AVM), cerebral aneurysms, trauma and prematurity.
Watershed stroke
As opposed to hemorrhagic stroke or embolic (or other atherogenic) stroke, watershed strokes occur in parts of the brain that lie at the boundary between zones of arterial distribution from different arteries. When there is hypotension from any cause, these watershed areas are more susceptible to damage than other areas of the brain.
Signs and symptoms
The symptoms of stroke are usually easy to spot:
- sudden numbness or weakness, especially on one side of the body;
- reflexes can initially be decreased on the affected side, but are often livelier than on the other side
- the face is normally spared (as this is served by both hemispheres), but the corner of the mouth can be affected on the same side as the limb symptoms
- sudden confusion or aphasia (trouble speaking) or understanding speech;
- sudden trouble seeing in one eye (or rarely both);
- unequal pupils
- sudden trouble walking, dizziness, or loss of balance or coordination.
A subgroup loses consciousness as part of the initial presentation. This occurs more often in bleeding than in thrombosis.
A sudden-onset severe headache can denote subarachnoid hemorrhage, which is a stroke-like clinical entity. Some other forms of stroke can feature headaches.
If the symptoms resolve within an hour, or maximum 24 hours, the diagnosis is transient ischemic attack (TIA), and not a stroke. This syndrome may be a warning sign, and a proportion of patients develop strokes in the future. The chances of suffering a stroke can be reduced by using aspirin, which inhibits platelets from aggregating and forming obstructive clots.
Diagnosis
Stroke is diagnosed through several techniques: a neurological examination, blood tests, CT scans (without contrast enhancements) or MRI scans, Doppler ultrasound, and arteriography. The most important risk factors for stroke 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. Some risk factors for stroke apply only to women. Primary among these are pregnancy, childbirth, and the menopause and treatment thereof (HRT). Stroke seems to run in some families. Family members may have a genetic tendency for stroke or share a lifestyle that contributes to stroke.
Pathophysiology
Neurons and glia die when they no longer receive oxygen and nutrients from the blood or when they are damaged by sudden bleeding into or around the brain. These damaged cells can linger in a compromised state for several hours. With timely treatment, these cells can be saved.
Prevention
Prevention is an important public health concern. Identification of patients with treatable risk factors for stroke 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 had a stroke. Medication or drug therapy is the most common method of stroke prevention. Surgery such as Carotid endarterectomy can be used to remove significant narrowing of the neck (internal) carotid artery which supplies blood to the brain and this operation has been shown to be an effective way to prevent stroke in particular groups of patients.
Some brain damage that results from stroke may be secondary to the initial death of brain cells caused by the lack of blood flow to the brain tissue. This brain damage is a result of a toxic reaction to the primary damage. Researchers are studying the mechanisms of this toxic reaction and ways to prevent this secondary injury to the brain. Scientists hope to develop neuroprotective agents to prevent this damage. Another area of research involves experiments with vasodilators, medications that expand or dilate blood vessels and thus increase the blood flow to the brain. Basic research has also focused on the genetics of stroke and stroke risk factors. One area of research involving genetics is gene therapy. One promising area of stroke animal research involves hibernation. The dramatic decrease of blood flow to the brain in hibernating animals is extensive enough that it would kill a non-hibernating animal. If scientists can discover how animals hibernate without experiencing brain damage, then maybe they can discover ways to stop the brain damage associated with decreased blood flow in stroke patients. Other studies are looking at the role of hypothermia, or decreased body temperature, on metabolism and neuroprotection. Scientists are working to develop new and better ways to help the brain repair itself and restore important functions to the stroke patients. Some evidence suggests that transcranial magnetic stimulation (TMS), in which a small magnetic current is delivered to an area of the brain, may possibly increase brain plasticity and speed up recovery of function after stroke.
Treatment
Early assessment
It is important to identify that a patient is having a stroke as early as possible because recovery can be improved for patients treated earlier. The term "brain attack" is used to underline the urgency of early assessment and treatment similar in intensity to the management of a patient with a heart attack.
If a patient is suspected of having a stroke, emergency services should be contacted immediately, so he or she can be transported to the nearest hospital that can provide a rapid evaluation and treatment with the latest available therapies targeted to the type of stroke. The faster these therapies are started for hemorrhagic stroke (caused by bleeding into or around the brain) and ischemic stroke (due to a blood clot that blocks blood flow), the chances for recovery from each type improves greatly. Immediate decisions about medication and the need for surgery have been shown to improve outcome.
Only detailed physical examination and medical imaging provide information on the type of stroke (ischemic or hemorrhagic) and the extent, or whether the symptoms may be due to an unrelated condition.
Long-term studies show that patients treated in hospitals with a dedicated Stroke Team or Stroke Unit, and that have a specialized care program for stroke patients, have improved odds of recovery.
Ischemic stroke
As ischemic stroke is due to a thrombus (blood clot) occluding a cerebral artery, a patient is commenced on anticoagulant medication (aspirin and/or clopidogrel or warfarin, dependant on the cause) when this type of stroke has been demonstrated. As such treatment would be dangerous in hemorrhagic stroke, it is essential that this form of stroke is ruled out with medical imaging.
In increasing numbers of specialist centers, thrombolysis ("clot busting") is used to dissolve the putative clot. As this treatment is expensive, quite experimental, potentially dangerous and often contraindicated, the decision to thrombolyse can often only be made by an expert. There is also a time constraint: studies indicate that after three hours of symptom onset the damage to the brain is irreversible ("time is brain"), and that thrombolysis would provide no benefit. These various requirement prevent routine thrombolysis of ischemic stroke in most hospitals, especially out of working hours when no stroke expert may be available.
Whether thrombolysis is performed or not, the following investigations are required:
- Stroke symptoms are documented, often using scoring systems such as the National Institutes of Health Stroke Scale, the Cincinnati Stroke Scale, and the Los Angeles Prehospital Stroke Scale. The latter is used by emergency medical technicians (EMTs) to determine whether a patient needs transport to a stroke center.
- A CT scan is performed to rule out hemorrhagic stroke (or other specific forms of cerebral hemorrhage, such as subarachnoid hemorrhage)
- Blood tests, such as a full blood count, coagulation studies (PT/INR, APTT), electrolytes, renal function, liver function tests and glucose levels.
- In selected patients, specialized testing, such as a cerebral arteriogram, may be performed. Cerebral arteriography is used to both detect and to treat conditions that cause ischemic stroke.
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 stroke patient is receiving adequate oxygen and intravenous fluids. The patient may be positioned so that their 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 (50 to 325 mg daily), clopidogrel (75 mg daily), and combined aspirin and dipyridamole extended release (25/200 mg twice daily).
It is common for the blood pressure to be elevated immediately following a stroke. 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.
Hemorrhagic stroke
Patient's with bleeding into (intracerebral hemorrhage) or around the brain (subarachnoid hemorrhage), require neurosurgical evaluation. Neurosurgeons use specialized examinations for hemorrhagic stroke patients, such as the Hunt & Hess scale, that can help determine the appropriate treatment. Strategies to protect the brain during this type of stroke include blood sugar and blood pressure control, adequate oxygen and intravenous fluids, detection and treatment of the cause of bleeding, and constant surveillance (e.g. with the Glasgow Coma Scale) and immediate treatment for complications from bleeding into or around the brain.
Cerebral arteriography may be used to determine the cause for bleeding, since some causes may be surgically corrected to reduce the risk of future bleeding. Selected patients with subarachnoid hemorrhage due to a ruptured aneurysm require emergency surgery to "clip" the aneurysm off from the normal brain blood circulation, and they receive nimodipine, a drug shown to reduce incidence of vasospasm, a complication of this type of stroke.
Care and rehabilitation
Good nursing care is fundamental in maintaining skin care, feeding and hydration and positioning as well as the monitoring of vital signs such as temperature, pulse and blood pressure. Stroke rehabilitation begins almost immediately.
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 is multidisciplinary in the fact that it involves a team 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 rehabiliation medicine. Some teams may also include psychologists and social workers and pharmacists.
For most stroke patients, physical therapy is the cornerstone of the rehabilitation process. Another type of therapy involving relearning daily activities is occupational therapy (OT). OT involves exercise and training to help the stroke patient relearn everyday activities sometimes called the Activities of daily living (ADLs) such as eating, drinking and swallowing, dressing, bathing, cooking, reading and writing, and toileting. Speech and language therapy is appropriate for patients with problems understanding speech or written words, or problems forming speech.
Patients may have particular problems such as an inability to swallow or a swallow that is not safe such that swallowed material may pass into the lungs and cause an aspiration pneumonia. The swallow may improve with time but in the interim a nasogastric tube may be passed which enables liquid food to be given directly into the stomach. If after a week the swallow is still not safe then a PEG tube is passed and this can remain indefinitely.
The team have regular meetings at which the patient and family may be present to discuss the current situation and to set goals and to ensure effective communication. In most cases the desired goal is to enable the patient to return home to independent living though this is not always possible.
Stroke rehabilitation can last anything from a few days up to several months. Most return of function is seen in the first few days and weeks and then falls off. It is unusual that there is complete recovery but not impossible. Most patients will improve to some extent.
Prognosis
Although stroke is a disease of the brain, it can affect the entire body. Some of the disabilities that can result from stroke include paralysis, cognitive deficits, speech problems, emotional difficulties, pressure sores, pneumonia, continence problems, daily living problems, and pain. If the stroke is severe enough, coma or death can result. Depression is common but may respond to antidepressants.
See also
External links
- The original text for this article was taken from the National Institute of Neurological Disorders and Stroke public domain resource at this page (http://www.ninds.nih.gov/health_and_medical/disorders/stroke.htm)
- Cerebrovascular disease and risk of stroke (http://www.thedoctorslounge.net/medlounge/articles/stroke_risk/index.htm)de:Schlaganfall
fr:Accident vasculaire cérébral he:שבץ ms:Angin ahmar nl:Cerebrovasculair accident ja:脳血管障害 pl:Udar mózgu sv:Stroke zh:中風