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) or by hemorrhage (a hemorrhagic stroke - approximately 10% of strokes). The former, ischemia, is a reduction of blood flow due to occlusion (an obstruction). The latter, 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 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.
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.
High blood pressure also predisposes to cerebral bleeding. Other causes include arteriovenous malformation (cerebral AVM), cerebral aneurysms, trauma and prematurity.
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);
- sudden trouble walking, dizziness, or loss of balance or coordination.
A subgroup loses conciousness 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 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.
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.
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 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.
It is important to identify that a patient is having a stroke as early as possible. Some suggest that we should rename stroke as a "brain attack" to underline the urgency of early assessment and treatment. Emergency services should be contacted so that the patient can be assessed by medical staff as quickly as possible. If the patient has had the stroke symptoms for less than 3 hours then they may need further assessment as they may be suitable for thrombolysis. This is "clot busting" treatment, useful only in those with ischemic stroke. The aim of the therapy is to minimise the size of the stroke and therefore minimise subsequent disability by restoring blood flow to the area of the brain affected as quickly as possible. It can however only be used in selected patients. The patient will need blood tests to be performed urgently as well as a CT scan of the head. If the scan shows no signs of bleeding (haemorrhage) then clot-busting therapy may be given depending on the judgment of the physician involved. Surgery may also be indicated in very selected cases to treat acute stroke.
If the CT scan shows the stroke to be ischaemic then Aspirin 75 mg to 300 mg is given. It is common for the blood pressure to be elevated following a stroke but many clinicians feel this is beneficial allowing better cerebral blood flow, though there is little hard evidence for this. Many clinicians do not treat mildly elevated blood pressures for the first few days at least. In the long term evidence has shown that particular antihypertensive medications reduce the long term risk 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 who have have 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.
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 and daily living problems, and pain. If the stroke is severe enough, coma or death can result. Depression is common but may respond to antidepressants.