A 72-year-old woman with a history of hypertension and diabetes mellitus presents with acute onset of severe headache, neck stiffness, and loss of consciousness. CT head reveals a hyperdense lesion in the pons with blood extending into the fourth ventricle. Which of the following is the most common cause of primary intracerebral hemorrhage in this age group?

## Most Common Cause of Primary ICH **Key Point:** Chronic hypertension remains the single most common cause of primary (non-traumatic) intracerebral hemorrhage globally, accounting for 50–60% of all ICH cases. ### Etiology of Primary ICH by Frequency | Cause | Frequency | Age Group | Typical Location | Mechanism | |-------|-----------|-----------|------------------|----------| | **Hypertension** | **50–60%** | Middle-aged & elderly | Deep (putamen, thalamus, pons, cerebellum) | Lipohyalinosis of penetrating arteries | | Cerebral amyloid angiopathy (CAA) | 10–20% | Elderly (>70 years) | Lobar (cortical) | Amyloid-β deposition in cortical vessels | | Anticoagulation | 10–15% | Elderly on warfarin/DOACs | Variable | Supratherapeutic INR or overdose | | Arteriovenous malformation | 5–10% | Young to middle-aged | Variable | Congenital vascular anomaly | | Aneurysm (non-ruptured into parenchyma) | 5% | Variable | Subarachnoid space | Saccular aneurysm rupture | | Coagulopathy/thrombocytopenia | 3–5% | Variable | Variable | Bleeding disorder | | Sympathomimetic drugs (cocaine, amphetamine) | 2–5% | Young adults | Variable | Acute hypertension, vasculitis | **High-Yield:** In a patient with **chronic hypertension and deep ICH** (putamen, thalamus, pons), hypertension is the presumed cause until proven otherwise. In contrast, **lobar hemorrhages in elderly patients without severe hypertension** suggest CAA. ### Pathophysiology of Hypertensive ICH 1. Chronic elevation of blood pressure → endothelial injury 2. Lipohyalinotic degeneration of small penetrating arteries (diameter 50–200 μm) 3. Formation of Charcot-Bouchard microaneurysms 4. Rupture → parenchymal hemorrhage, often with ventricular extension **Clinical Pearl:** The **location of ICH is a major clue to etiology**: - **Deep ICH** (putamen, thalamus, pons, cerebellum) → hypertension - **Lobar ICH** (cortical, subcortical white matter) → CAA (especially recurrent, elderly, no HTN) - **Subarachnoid** → aneurysm or AVM - **Subdural** → trauma or coagulopathy **Mnemonic:** **CHAMP** — Chronic hypertension (most common), History of anticoagulation, Amyloid angiopathy, Malformation (AVM), Platelet/coagulation disorders. [cite:Harrison 21e Ch 435; Robbins 10e Ch 28]