- Stroke prevention: causes, risks and symptoms of a disease
- Risk Factors for Stroke
- Modifiable Risk Factors of a stroke
- Symptomatic Atherosclerosis in Other Circulations
- Patients at Highest Risk
- Warning Leak of Subarachnoid Hemorrhage
Stroke prevention: causes, risks and symptoms of a disease
Prevention of stroke is the most effective treatment to avoid death, disability, and suffering. In addition, successful preventive strategies eliminate the expenses of acute hospital care and rehabilitation and the economic costs of lost productivity. No treatment of stroke can be as successful as prevention of the stroke.
Prevention of stroke involves two different tactics. One involves interventions applied to large segments of the population, including health promotion and identification and management of common factors that increase the risk of either hemorrhagic or ischemic stroke.
These measures (eg, control of hypertension) may have limited benefit in individual persons, but their aggregate effects are substantial when prescribed to large populations. The second approach involves use of more expensive and potentially more dangerous therapies with smaller groups of people judged to be at the highest risk.
Primary prevention includes therapies to forestall vascular events, including stroke, in either large populations or small high-risk groups of asymptomatic people. Secondary prevention implies the use of treatments to prevent stroke or other vascular events in a person who already has symptoms, including those who may have had:
- A myocardial infarction
- Angina pectoris
- Amaurosis fugax
- Transient ischemic attack (TIA)
Thus, secondary prevention of stroke can include treatment of a spectrum of people to include those without neurological symptoms. In reality, the division into primary and secondary prevention is artificial because therapies for either situation basically are the same.
Risk Factors for Stroke
Stroke is a syndrome encompassing a heterogeneous group of vascular diseases that lead to ischemia or hemorrhage. Thus, the conditions or factors that predispose to or increase the risk of stroke are diverse.
Some factors are modifiable and others are not. Other risk factors for ischemic stroke include heart diseases predisposing to embolism.
While some conditions that lay the groundwork for ischemic stroke also lead to brain hemorrhage, additional risk factors may lead to intracranial bleeding.
Some conditions that lead to stroke are not modifiable. Advancing age is the single most important risk factor for stroke. Although stroke is much more common in elderly people than in children or young adults, it is an important disease in these latter groups.
Approximately 3% of ischemic strokes occur among people under the age of 45.
The causes of stroke vary by age. Atherosclerosis is the leading cause of stroke in the elderly while the differential diagnosis of stroke etiologies in younger people is much broader. The ratio of hemorrhagic stroke to ischemic stroke is higher in younger people than in the elderly.
The likelihood of stroke also differs between men and women. In each age group, the relative risk of stroke is higher in men than among women. Atherosclerosis, trauma, and X-linked diseases are more common in men. Strokes due to pregnancy, oral contraceptive use, migraine, and saccular aneurysms are more common in women.
The frequency of stroke also varies among different ethnic groups. The high risk of stroke in Blacks may be related to:
- Genetic predisposition
- High prevalence of arterial hypertension
- Economic or social factors.
At younger ages, Hispanic-Americans have higher rates of strokes than Whites, but this risk seems to reverse in elderly populations.Stroke is common in Asian populations, including Asian-Americans, and is a particularly prominent problem in China and Japan.
The conditions that promote stroke differ among ethnic groups. For example, sickle-cell disease is prominent in Blacks and diabetes mellitus is prevalent in Hispanic-Americans. The sites of atherosclerosis also differ. Atheromatous lesions are more common in intracranial locations among those of Asian or African background, but more common in extracranial locations among those of European ancestry.
A family history of stroke or other ischemic vascular disease, particularly at younger ages, portends an increased likelihood of stroke. A number of factors, including a genetic predisposition to atherosclerosis, can explain the increase in risk.
Intracranial saccular aneurysms, vascular malformations, and amyloid angiopathy are among the familial, nonatherosclerotic causes of stroke.
In addition, a family history of deep-vein thrombosis, pulmonary embolism, or spontaneous abortion may be associated with inherited procoagulant disorders. However, these genetic diseases are relatively uncommon causes of stroke in the population as a whole.
Modifiable Risk Factors of a stroke
The list of risk factors for hemorrhagic or ischemic stroke that can be controlled, modified, or treated is extensive). Hypertension is the premier manageable risk factor of either hemorrhagic or ischemic stroke.
Regardless of age, the presence of diastolic arterial hypertension greatly increases the likelihood of stroke. Among older people, isolated systolic arterial hypertension is an identified promoter of stroke. The relationship between hypertension and stroke is much closer than the association between an elevated blood pressure and coronary artery disease.
Diabetes mellitus promotes both atherosclerotic large and small artery disease of the brain.
Stroke is a common complication in both younger, insulin-dependent diabetic patients and older persons with type II diabetes. Diabetic patients may have more severe strokes, and hyperglycemia also may exacerbate the severity of the neurological impairments.
Hyperlipidemia (hypercholesterolemia) encourages early development of atherosclerosis. The relationship between elevated blood lipids and stroke is hard to establish because stroke occurs in older people and there are multiple causes of stroke.
Recent findings confirm the value of vigorous control of blood lipids by diet or medication in leading to the regression of atherosclerotic lesions in the carotid artery. While lowering blood lipids reduces the risk of ischemic stroke, overly low blood levels of cholesterol can be correlated with an increased risk of intracerebral hemorrhage.
Cessation of tobacco smoking is probably the single most cost-effective strategy to lower the risk of either hemorrhagic or ischemic stroke.
Smokers have an increased risk of atherosclerosis. While the relationship between smoking and cerebrovascular disease is not as obvious as the finding in heart disease, tobacco abuse is a strong risk factor in younger people and potentiates the risks associated with the use of oral contraceptives. In addition, smoking adds to the risk of intracranial hemorrhage. Other potential risk factors include:
- Use of oral contraceptives
- Lack of exercise.
Elevated blood levels of homocysteine may augment the development of atherosclerosis and associated thrombosis.
Symptomatic Atherosclerosis in Other Circulations
Evidence of atherosclerotic disease in other vascular territories identifies a person as being at high risk for stroke. Thus, patients who are automatically at high risk for ischemic stroke have a history of:
- Myocardial infarction
- Angina pectoris
- Abdominal aortic aneurysm
Conversely, those with ischemic stroke attributed to atherosclerotic disease are also at risk for cardiovascular events.
Patients at Highest Risk
People with the highest risk for stroke have a history of:
- Atrial fibrillation (AF)
- Asymptomatic stenosis of the carotid artery
- Amaurosis fugax
- A TIA
- A previous stroke.
Atrial fibrillation is the premier cardiac abnormality associated with ischemic stroke. It is the most important risk factor for stroke in patients older than 80, especially women. AF complicates a number of cardiac diseases, including:
- Coronary artery disease
- Rheumatic heart disease.
Those under the age of 60 who have AF and no other cardiac disorder (lone AF) appear to be at relatively low risk for stroke.
Thus, the importance of AF is as an abetting factor leading to the formation of thrombi in a patient with other heart disease. While people with chronic, sustained AF appear to be at greater risk than those with an intermittent arrhythmia, embolization can complicate intermittent or new onset AF.
The risk of embolism is relatively low during the first 2 to 3 days after the start of AF. The most important forecaster of embolism in a patient with AF is a history of stroke or previous embolism.
Asymptomatic Cervical Stenosis or Bruit
Severe asymptomatic stenosis of the extracranial internal carotid artery can be detected after a physician auscultates a cervical bruit or while the patient is being evaluated for:
- Other vascular disease
- Symptoms in the vertebrobasilar circulation
- Ischemia of the contralateral carotid artery.
The prevalence of severe asymptomatic stenosis increases with advancing age. The previously identified risk factors for atherosclerosis portend the likelihood of finding an asymptomatic carotid stenosis. The presence of a carotid stenosis forecasts an increased risk of:
- Myocardial infarction
- Vascular death
However, ischemic strokes are as likely to occur in the contralateral hemisphere or the brain stem as in the hemisphere perfused by the artery that has the stenosis.
The degree of risk of stroke correlates with the severity of the arterial narrowing; patients with high-grade stenosis are at the greatest risk.
Those with severely ulcerated plaques or stenotic lesions that are leading to progressive narrowing also are at higher risk. In general, the presence of a carotid stenosis does not predict an increased risk of stroke among patients who are having peripheral vascular or general surgical procedures.
The risk of stroke is high among patients with a carotid stenosis who undergo coronary artery bypass grafting or other cardiac operations, but the strokes may not be associated with the stenosis. Rather, these patients usually have more extensive aortic disease.
Transient Ischemic Attacks
Patients who have the greatest risk for a serious ischemic stroke are identified by:
- Amaurosis fugax
- Minor stroke.
Overall, the risk of a serious stroke within 1 year of a TIA is approximately 10%. The likelihood of a stroke is greatest during the first days and weeks after a TIA with an aggregate risk within 1 month being as high as 2% to 5%. The occurrence of one of these events should prompt rapid evaluation and urgent treatment.
The physician should determine if visual or neurologic symptoms are secondary to ischemia, if the symptoms reflect the carotid or vertebrobasilar circulation, and the likely cause of the vascular event before deciding about treatment.
Amaurosis fugax (transient monocular blindness) is an episode of painless visual loss in one eye which is secondary to retinal ischemia.
Amaurosis fugax usually is associated with atherosclerotic disease of the ipsilateral internal carotid artery. The attacks are discrete and brief, each lasting a few seconds to minutes. Occasionally, attacks are provoked by postural changes or exposure to bright light. While the classic description involves the complaint of a descending or ascending curtain covering part of the visual field of one eye, this symptom is relatively uncommon. Patients usually describe the symptoms as:
- Blurring of vision.
Occasionally, a patient describes a constriction in visual field with grayness moving from the periphery to the center. Other reported phenomena include:
- Bright lights.
A TIA is defined as a transient episode of focal neurologic dysfunction secondary to ischemia in one of the vascular territories of the brain. These events are discrete with a sudden onset and a relatively rapid resolution. Symptoms that wax or wane or that are relatively nondescript likely are not secondary to TIA.
The symptoms should reflect dysfunction of one part of the brain. Global phenomena, including confusion, wooziness, lightheadedness, or loss of consciousness, usually are not due to a TIA. The symptoms of TIA usually involve weakness, numbness, or incoordination and represent a loss of normal neurologic activity. Positive neurologic symptoms, such as scintillating visual phenomena, seizure activity, or involuntary movements, rarely are due to transient brain ischemia.
A migration or march of symptoms from one body part to another is uncommon with a TIA. The pattern of symptoms of a TIA in the vertebrobasilar circulation differs from those in the carotid territory.
Approximately 20% to 25% of patients have a headache with a TIA and this complaint is more common with events in the posterior circulation.
The evaluation of patients with amaurosis fugax or a TIA is similar to those with ischemic stroke. Because the risk of a potentially disabling stroke is greatest in the first days and weeks after the event, the evaluation should be done expeditiously and treatment started as soon as possible.
The selection of preventive therapy is based primarily on the presumed cause of the ischemic symptoms . The choices for management include:
- Antiplatelet agents
- Oral anticoagulants
- Carotid endarterectomy
- Other reconstructive vascular operations
The surgical procedures should be complemented by medical therapy, including the use of antiplatelet agents.
Warning Leak of Subarachnoid Hemorrhage
Subarachnoid hemorrhage (SAH) also can be preceded by warning symptoms. The symptoms usually are the result of a minor episode of bleeding and mimic those of SAH. The most common symptom is the sudden onset of an unusually severe headache often associated with:
The patient reports that this headache is different from previous headaches and often will seek medical attention. The patient’s examination often is normal and signs of meningeal irritation may be absent or subtle.
Computed tomography (CT) examination may be normal or show only a thin, focal collection of blood in a basal cistern. In this circumstance, examination of the cerebrospinal fluid (CSF) is important. If bloody CSF is obtained, evaluation and treatment for SAH is performed.