## Pathophysiology of Internal Capsule Stroke in Hypertension **Key Point:** Lipohyalinosis is the pathological hallmark of hypertensive small-vessel disease and is the most common cause of internal capsule infarction in patients with chronic, poorly controlled hypertension. ### Definition and Mechanism of Lipohyalinosis Lipohyalinosis is a degenerative process affecting small penetrating arteries (diameter <200 μm) in response to chronic hypertension: 1. **Hypertensive injury** → endothelial dysfunction 2. **Smooth muscle cell degeneration** → loss of structural integrity 3. **Lipid accumulation** in the vessel wall → weakening 4. **Microaneurysm formation** (Charcot-Bouchard aneurysms) → rupture or occlusion 5. **Lacunar infarction** in the distribution of affected penetrating arteries **High-Yield:** Lipohyalinosis is a **direct consequence of chronic hypertension** and is responsible for 50–60% of all lacunar infarcts, particularly in the internal capsule, basal ganglia, and pons. ### Comparison of Stroke Mechanisms in the Internal Capsule | Mechanism | Pathology | HTN Association | Frequency in IC | |---|---|---|---| | **Lipohyalinosis** | Small-vessel degenerative disease | Direct (chronic HTN) | **Most common (50–60%)** | | Atherosclerotic plaque rupture | Large-vessel atherosclerosis | Indirect (HTN is risk factor) | ~20–25% | | Cardioembolism | Thrombus from cardiac source | Indirect (HTN + AF) | ~15–20% | | Arterial dissection | Intimal tear + thrombosis | Not typical | <5% | **Clinical Pearl:** In an Indian patient with **20 years of poorly controlled hypertension**, the cumulative vascular injury from sustained elevated blood pressure makes lipohyalinosis virtually inevitable. This is the dominant pathology driving internal capsule infarction in this demographic. **Mnemonic:** **LIPO** = **L**ipohyalinosis **I**s the **P**rimary **O**ccluder in hypertensive lacunar stroke.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.