A 58-year-old man from Delhi presents with acute onset left-sided weakness and speech difficulty. CT brain shows no hemorrhage. Which is the most common cause of ischemic stroke in this patient?

Explanation

## Most Common Cause of Ischemic Stroke **Key Point:** Atherosclerotic disease of large cerebral arteries (particularly the carotid bifurcation, middle cerebral artery stem, and vertebral artery origins) accounts for approximately 50–60% of all ischemic strokes in most populations, including India. ## Epidemiology of Stroke Subtypes | Subtype | Frequency | Mechanism | Common Sites | |---------|-----------|-----------|---------------| | **Large artery atherosclerosis** | 50–60% | Plaque rupture, thrombosis, artery-to-artery embolism | Carotid bifurcation, MCA stem, vertebral origin | | Cardioemboli | 15–20% | Atrial fibrillation, valvular disease, post-MI thrombus | Random distribution, often multiple | | Small vessel lacunar | 15–20% | Lipohyalinosis of penetrating arteries | Deep gray matter, brainstem, internal capsule | | Other/cryptogenic | 10–15% | PFO, dissection, hypercoagulability | Variable | **High-Yield:** In the Indian population, atherosclerotic stroke is the dominant subtype due to high prevalence of hypertension, diabetes, and smoking. Large artery disease typically presents with acute focal deficits (hemiparesis, aphasia, hemianopia) and is often visible on imaging as territorial infarction. ## Clinical Pearl **Clinical Pearl:** The carotid bifurcation is the single most common site of atherosclerotic plaque formation in the cerebral circulation, making it the most frequent source of large artery ischemic stroke. Duplex ultrasound and CT/MR angiography are key diagnostic tools. ## Why Large Artery Atherosclerosis Dominates 1. High prevalence of vascular risk factors (HTN, DM, smoking) in the Indian population 2. Atherosclerotic plaques develop over decades and are the most common structural lesion in cerebral arteries 3. Plaque rupture and thrombosis or artery-to-artery embolism are the dominant mechanisms 4. Accounts for the majority of strokes in both developed and developing nations [cite:Harrison 21e Ch 297]