## Acute Intracerebral Hemorrhage on CT **Key Point:** Hyperdense (bright) collection within brain parenchyma is the most specific and earliest CT sign of acute ICH, distinguishing it from ischemic stroke in the hyperacute phase. ### CT Density Characteristics of Blood Over Time | Time Window | Appearance | Density (HU) | Pathophysiology | |--------------|-----------|--------------|------------------| | **Hyperacute (0–6 hrs)** | Hyperdense | 60–90 HU | Oxyhemoglobin in RBCs | | **Acute (6–24 hrs)** | Hyperdense | 50–80 HU | Deoxyhemoglobin formation | | **Early subacute (1–3 days)** | Hyperdense → isodense | 40–60 HU | Methemoglobin (periphery) | | **Late subacute (3–7 days)** | Isodense to hypodense | 20–40 HU | Hemosiderin deposition | | **Chronic (>7 days)** | Hypodense | <20 HU | Hemosiderin, gliosis, CSF | ### Why Hyperdensity is Specific for Acute ICH 1. **Immediate visibility:** Blood is hyperdense on non-contrast CT due to iron content in hemoglobin 2. **No delay:** Unlike ischemic stroke (requires 6–12 hours for cytotoxic edema to become visible), ICH is visible within minutes 3. **High specificity:** No other acute intracranial process produces this appearance in the hyperacute phase **High-Yield:** Non-contrast CT is the gold standard for acute ICH diagnosis because it detects blood within minutes, making it superior to MRI for hyperacute hemorrhage. ### Clinical Significance - Allows rapid differentiation from ischemic stroke (critical for thrombolysis eligibility) - Guides urgent management: ICH requires hemostasis, hypertension control, and reversal of anticoagulation - Identifies complications: intraventricular hemorrhage (IVH), subarachnoid extension, mass effect **Clinical Pearl:** A patient with acute stroke symptoms and a hyperdense lesion on CT is contraindicated for thrombolysis; focus shifts to ICH-specific management. 
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