Ischemic stroke definition
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Understanding Ischemic Stroke: Definition and Key Insights
Definition of Ischemic Stroke
Ischemic stroke is a type of stroke characterized by the sudden loss of brain function due to a reduction in blood flow to the brain. This reduction in blood flow can be caused by the blockage of an artery or vein, leading to brain tissue ischemia, hypoxic necrosis, and brain softening . The condition is marked by a fixed focal neurologic deficit that lasts longer than 24 hours, distinguishing it from a transient ischemic attack, which lasts less than 24 hours.
Pathophysiology and Mechanisms
Blood Flow Interruption and Ischemic Cascade
The interruption of blood supply initiates a cascade of biochemical events known as the ischemic cascade, which ultimately leads to cell death and brain infarction . This cascade involves multiple processes, including oxidative stress, endoplasmic reticulum stress, and mitochondrial dysfunction, which contribute to the pathologic process of ischemic stroke.
Role of Autophagy
Autophagy, a cellular degradation process, is activated in various brain cell types during ischemic stroke. It plays a significant role in the pathologic process by interacting with necrosis and apoptosis, further influencing the outcome of the stroke.
Epidemiology and Risk Factors
Global Burden and Mortality
Ischemic stroke is a leading cause of death and disability worldwide, with a significant increase in the number of deaths from 2.04 million in 1990 to 3.29 million in 2019. This number is projected to rise to 4.90 million by 2030. The condition is particularly prevalent among older adults, with age being the strongest nonmodifiable risk factor.
Behavioral and Metabolic Risk Factors
Several risk factors contribute to the increased burden of ischemic stroke, including behavioral factors like smoking and high sodium diet, and metabolic factors such as high systolic blood pressure, high low-density lipoprotein cholesterol, kidney dysfunction, high fasting plasma glucose, and high body mass index (BMI).
Diagnostic and Classification Systems
TOAST Classification
The TOAST classification system categorizes ischemic stroke into five subtypes based on etiology: large-artery atherosclerosis, cardioembolism, small-vessel occlusion, stroke of other determined etiology, and stroke of undetermined etiology. This system aids in the diagnosis and management of stroke by providing a structured approach to identifying the underlying cause.
Conclusion
Ischemic stroke is a complex, multifactorial disorder resulting from the sudden reduction of blood flow to the brain. Understanding its definition, pathophysiology, risk factors, and classification systems is crucial for effective diagnosis, treatment, and prevention. As research continues to evolve, new insights into the mechanisms and management of ischemic stroke will further enhance our ability to combat this debilitating condition.
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