Stroke: Introduction and Types

A stroke is an acute neurological event caused by the sudden disruption of cerebral blood flow, leading to rapid loss of neuronal function. Neurons depend on continuous oxygen and glucose supply, so even brief interruptions can cause irreversible injury within minutes. Strokes are classified into ischemic and hemorrhagic types.

Ischemic Stroke

Ischemic strokes are most common and occur due to arterial occlusion, depriving brain tissue of oxygen and nutrients. This leads to energy failure, ionic imbalance, and neuronal death. They are subdivided into thrombotic and embolic types. Thrombotic strokes result from clot formation within vessels, often due to atherosclerosis and plaque rupture, which trigger platelet aggregation and coagulation, blocking arteries such as the middle cerebral artery. Embolic strokes occur when clots, commonly from cardiac sources such as atrial fibrillation, travel and lodge in cerebral vessels, abruptly stopping blood flow.

Hemorrhagic Stroke

Hemorrhagic strokes result from rupture of weakened intracranial vessels, causing bleeding in or around the brain. Chronic hypertension damages small arteries, predisposing them to rupture and intracerebral hemorrhage. Accumulated blood increases intracranial pressure and compresses brain tissue. Subarachnoid hemorrhage occurs when blood enters the subarachnoid space, usually from rupture of a berry aneurysm, causing meningeal irritation and rapid deterioration.

Clinical Importance

Recognizing stroke subtypes is critical, as ischemic and hemorrhagic strokes require different emergency treatments.