Ischemic Stroke

Definition

Ischemic stroke is a neurological condition caused by an interruption of blood flow to the brain, leading to cerebral infarction and acute neurological deficits.

Epidemiology

• Accounts for 80–85% of all strokes worldwide.
• Incidence increases with age; more common in men before age 75, then similar between sexes.
• Major risk factors: hypertension, diabetes, atrial fibrillation, smoking, hyperlipidemia, and obesity.
• Higher prevalence in low- and middle-income countries due to uncontrolled vascular risk factors.
• Significant cause of long-term disability and mortality.

Etiology

• Thrombotic stroke: in situ thrombosis of cerebral arteries, often due to atherosclerosis.
• Embolic stroke: emboli from the heart (atrial fibrillation, valvular disease) or large arteries.
• Small vessel disease (lacunar infarcts) due to chronic hypertension or diabetes.
• Other causes: arterial dissection, hypercoagulable states, vasculitis, drug-induced vascular events.
• Risk factors: age, hypertension, diabetes, dyslipidemia, smoking, prior TIA or stroke, atrial fibrillation.

Pathophysiology

• Occlusion of a cerebral artery leads to ischemia and infarction in brain tissue.
• Neuronal injury occurs due to energy failure, excitotoxicity, oxidative stress, and inflammation.
• Ischemic penumbra: surrounding tissue remains viable but at risk; salvageable with timely reperfusion.
• Cytotoxic and vasogenic edema develop in infarcted tissue.
• Secondary injury may occur due to reperfusion, hemorrhagic transformation, or increased intracranial pressure.