AVC: Introdução e Tipos

A stroke is a sudden-onset neurological dysfunction caused by an interruption in cerebral blood flow. Neurons depend on continuous oxygen and glucose supply, so even brief interruptions can cause irreversible injury within minutes. This disruption leads to rapid loss of neuronal function and brain cell death.

Ischemic strokes occur when a blood vessel becomes blocked, cutting off oxygen and nutrients to brain tissue. Hemorrhagic strokes happen when a weakened blood vessel ruptures and bleeds into brain tissue. Ischemic strokes are more common and require different emergency treatments than hemorrhagic strokes.

Thrombotic strokes result from clot formation within cerebral vessels, often due to atherosclerosis and plaque rupture triggering the clotting cascade. Embolic strokes occur when a clot or debris, commonly from the heart, travels through the bloodstream and lodges in a cerebral artery, abruptly stopping blood flow.

Hemorrhagic strokes result from rupture of weakened intracranial vessels, causing bleeding in or around the brain. Accumulated blood increases increased intracranial pressure and compresses brain tissue. Two types include intracerebral hemorrhage, bleeding directly into brain tissue, and subarachnoid hemorrhage, typically from a ruptured aneurysm.

Chronic hypertension damages small cerebral arteries over time, weakening their walls and predisposing them to rupture. This arterial damage increases the risk of intracerebral hemorrhage, where blood bleeds directly into brain tissue, causing significant neurological dysfunction and potential permanent brain damage.

Atherosclerosis causes plaque buildup in cerebral arteries such as the middle cerebral artery. When atherosclerotic plaque ruptures, it triggers platelet aggregation and activation of the clotting cascade, forming an intravascular clot that obstructs blood flow and causes thrombotic ischemic stroke.

Neurons depend on continuous oxygen and glucose delivery to maintain energy production and ionic balance. When cerebral blood flow is interrupted, energy failure occurs within minutes, leading to ionic imbalance and rapid neuronal death. This is why immediate treatment is critical to minimize brain damage.