Stroke is caused by a reduced or obstructed blood flow to part of the brain. The brain requires a continuous supply of oxygen and nutrients in order to function. Restriction of this blood supply to any area can cause sudden and serious damage to the brain. The reduced blood flow to the brain may be caused by a blockage in a vessel that supplies the brain or by bleeding in the brain.
As people age, the arteries narrow and harden, but the presence of certain medical conditions and some lifestyle factors can accelerate this process and increase the risk of stroke. Examples of these health conditions include diabetes, hypertension and high cholesterol and examples of lifestyle factors are alcohol consumption, drug abuse, poor diet, smoking and a low level of physical activity.Many cases of stroke are caused by blood clots that form in arteries that have become narrowed due to the presence of fatty deposits, a condition referred to as atherosclerosis.
Damage caused to a region of the brain during a stroke can affect parts of the body controlled by that brain area. There may be weakness or paralysis of the limbs or a loss of speech and facial muscle movement, for example. Some figures estimate that 75% of stroke survivors suffer from a disability that reduces their chances of getting or remaining fully employed. In addition, stroke has a severe impact on a person’s quality of life, as many cannot perform everyday activities. Stroke can also have an emotional impact, causing difficulties such as depression, anxiety and personality changes.
The two main forms of stroke are ischemic stroke and hemorrhagic stroke. Ischemic stroke is caused by a blockage in the artery (due to a blood clot, for example) that carries blood to the brain. In hemorrhagic stroke, a blood vessel ruptures and blood leaks into the brain causing brain damage and reducing the amount of blood and oxygen that reaches some parts of the brain. Another form of stroke is transient ischemic attack or mini-stroke, which describes a temporary blockage in a blood vessel that leads to the brain. This form of stroke does not cause permanent damage and symptoms usually resolve within 24 hours.
People who recover from stroke often face a range of problems after they leave hospital. Some of the effects of stroke are described below.
Some of the physical problems that affect a stroke sufferer include:
Weakness and paralysis - Weakness in the limbs is the most widely recognised effect of stroke. This weakness ranges in severity, with some people only suffering from very mild weakness and others finding one whole side of their body is affected. Paralysis may also occur, meaning a person loses the ability to move a body part altogether.
Spacticity - Muscles may be left stiff, tight and painful to use after a stroke.
Difficulty walking - A stroke sufferer may find their toes catch on the ground easily while they walk, a condition known of as “drop foot.”
Changes in sensation - A person’s sense of touch may be diminished, while sensitivity to pain may increase. Abnormal or unpleasant sensations may also be experienced such as burning, tingling, stinging or numbness.
Experts believe that cognitive loss occurs to some degree in all stroke survivors. The most common cognitive functions that are thought to be affected include memory, attention, and perception.
Memory - Short term memory problems commonly arise and it can take longer for survivors to remember new information.
Attention - Survivors may find it hard to choose when they need to pay attention and when they don’t. Focusing on a task may be difficult and it may become harder to concentrate, especially on several tasks at a time.
Perception- After a stroke, it may become difficult to process information or access a memory related to the information. This can affect a person’s ability to organize information in a way that they can understand.
Around 50% of stroke survivors develop depression after the event. Symptoms of depression vary in severity and duration. Some of these symptoms include feeling sad, difficulty concentrating or making decisions, loss of interest in daily activities and/or things that used to be of interest, anxiety, sleep disturbances, loss of appetite, suicidal thoughts, self harming, loss of libido, loss of confidence and a tendency to avoid people.
If stroke has caused damage to areas of the brain that are used in language, then communication may be affected. This can also be affected if muscles in the face or throat have been damaged. Around one third of survivors find their ability to communicate after a stroke is affected. The main conditions that cause communication difficulties after a stroke are aphasia, dysarthria, and dyspraxia.
Aphasia affects how a person speaks as well as their comprehension, reading and writing skills. Dysarthria causes weakness in the muscles required to speak, which can change the sound of the voice and cause slurring. Dyspraxia describes when the muscles fail to move in the order required to make the sounds needed for speech.
If the parts of the brain responsible for emotion are damaged by stroke then behavior, thought processes and emotions may be altered. Survivors of stroke may experience emotions such as anger, anxiety, bewilderment and frustration.
Fatigue is a common after effect of stroke and survivors may lack energy, strength and feel constantly tired. The fatigue experienced is unlike usual tiredness because it is not necessarily relieved by rest, nor is it related to recent activity.
Visual problems are also a common after effect of stroke, although they often resolve independently as the brain starts to recover. In cases where the brain does not recover, these problems can be quite difficult to get used to. The visual problems that arise depend on which brain parts are affected.
Central vision loss refers to a partial or complete loss of vision in both the eyes, while visual field loss refers to an inability to see properly either to the left or the right of the central vision field. There may also be eye movement problems and difficulty processing visual information may impair the ability to recognise faces or objects. Exercise can sometimes improve eye movement problems and an eye patch can sometimes be beneficial.
Stroke is the second leading cause of death across the globe, although the mortality rate is starting to decline. More than three quarters of people who suffer a stroke survive for a year and over half survive for more than five years.
The patient prognosis after an ischemic stroke is much more positive than after a hemorrhagic stroke. In addition to killing off brain cells, hemorrhagic stroke increases the risk of dangerous complications such as increased intracranial pressure or spasms in the brain vasculature.
Many people who survive a stroke recover their independence, although around one quarter are left living with minor disability and around 40% have more severe disabilities. Stroke outcome can be calculated using the National Institutes of Health stroke scale, which includes 11 factors ranging from facial movement through to consciousness level, to predict and assess how favorable the patient’s outlook is. If patients score less than 10, the outlook is generally favorable after one year, while a score of more than 20 suggests a less positive prognosis.