虚血性脳卒中1:はじめに

An ischemic stroke occurs when blood flow to a specific brain area is blocked, causing tissue damage. It differs from hemorrhagic stroke, which involves bleeding. Ischemic strokes are classified into thrombotic and embolic types based on their underlying mechanisms of clot formation and origin.

A thrombotic stroke develops when atherosclerotic plaque inside a cerebral artery gradually enlarges or ruptures. Plaque rupture exposes collagen and tissue factor, triggering platelet adhesion and activation of the coagulation cascade. The growing thrombus blocks the artery, stopping blood flow to brain tissue and causing neurological dysfunction.

An embolic stroke develops when a blood clot or other material forms elsewhere in the body and travels to the brain. Emboli often originate in the heart, especially in people with atrial fibrillation, or in large arteries such as the carotid arteries. These emboli lodge in brain arteries, disrupting blood supply and causing sudden neurological impairment.

Neurons depend on continuous oxygen and glucose supply for energy production. Even brief reductions in blood perfusion cause energy failure, ionic imbalance, and irreversible injury. This rapid cellular damage is why ischemic stroke is a medical emergency requiring immediate intervention to restore blood flow.

Major modifiable risk factors include smoking, hypertension, diabetes, obesity, high cholesterol, and chronic kidney disease. These factors contribute to vascular injury and atherosclerosis development. Controlling these conditions through lifestyle changes and medical management significantly reduces stroke risk and improves long-term outcomes.

The middle cerebral artery, internal carotid artery, and basilar artery are most commonly affected by ischemic stroke. These major vessels supply large brain areas, so their blockage produces abrupt and severe neurological deficits. Embolic strokes frequently obstruct the middle cerebral or posterior cerebral arteries.

Family history of stroke reflects shared genetic and environmental influences that increase ischemic stroke risk. Recognizing this non-modifiable risk factor is essential for implementing preventive strategies and monitoring for early warning signs. Individuals with family history should maintain awareness of modifiable risk factors and seek medical guidance.