Stroke definition and causes
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Stroke Definition: Clinical and Modern Criteria
Stroke is defined as a sudden onset of neurological dysfunction caused by an acute injury to the central nervous system due to either infarction (blockage of blood flow) or hemorrhage (bleeding) in the brain, spinal cord, or retina 138. The updated definition of stroke incorporates both clinical symptoms and evidence from neuroimaging or pathology, recognizing that stroke can result from either ischemia (lack of blood flow) or bleeding, and includes both symptomatic and silent (asymptomatic) infarctions . Stroke is a leading cause of death and disability worldwide 1256+1 MORE.
Main Causes of Stroke: Ischemic and Hemorrhagic
Ischemic Stroke Causes
Ischemic strokes account for about 85% of all strokes and are primarily caused by:
- Small vessel disease (arteriolosclerosis)
- Large artery athero-thromboembolism (blockage from a clot or debris)
- Cardioembolism (clots originating from the heart) 1269
In younger patients, ischemic strokes can also result from extracranial artery dissection . The underlying process often involves atherosclerosis and microvascular dysfunction, especially in people with hypertension .
Hemorrhagic Stroke Causes
About 15% of strokes are due to intracerebral hemorrhage (bleeding within the brain) 126. The main causes include:
- Deep hemorrhages from hypertensive arteriopathy (damage to small blood vessels due to high blood pressure)
- Lobar hemorrhages from cerebral amyloid angiopathy or arteriolosclerosis
- Macrovascular lesions such as vascular malformations, aneurysms, or cavernomas, which are more common in younger patients 12
Key Risk Factors for Stroke
The most important modifiable risk factor for both ischemic and hemorrhagic stroke is hypertension (high blood pressure) 137. Other significant risk factors include:
- Age (risk increases after age 55)
- Atrial fibrillation (irregular heartbeat)
- Diabetes
- High cholesterol (hyperlipidemia)
- Smoking
- Physical inactivity
- Family history and genetic factors 357
Effective control of blood pressure can significantly reduce the risk of stroke .
Pathophysiology: How Stroke Develops
Stroke occurs when blood flow to part of the brain is interrupted, leading to reduced oxygen supply and cell death 59. In ischemic stroke, this is due to a blockage, while in hemorrhagic stroke, it is due to bleeding from a ruptured vessel. Cellular changes such as oxidative stress, inflammation, and disruption of the blood-brain barrier contribute to brain injury during stroke 579.
Conclusion
Stroke is a sudden neurological event caused by either blockage or bleeding in the central nervous system. The majority of strokes are ischemic, resulting from vessel blockage, while a smaller proportion are hemorrhagic, caused by bleeding. Hypertension is the most significant modifiable risk factor, and other factors like age, heart disease, diabetes, and lifestyle also play important roles. Understanding the definition and causes of stroke is essential for effective prevention, diagnosis, and treatment.
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